JP2005125427A - Robot controller and controlling method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device by which the contact with a contact object can be detected without using a sensor or the like and positional correction can be executed in a task coordinate system without applying excessive force to the contact object. <P>SOLUTION: A robot and an external shaft are controlled on the basis of commands from a high-order command part in a robot controller. The robot controller is characterized by having simulation parts 120, 220, which imitate real machine parts 110, 210 including the robot and the external shaft, state amount comparison parts 131, 231, which output a state amount comparison value by comparing the same state amount of the real machine parts 110, 210 and the simulation parts 120, 220, contact detection parts 132, 232, which detect the contact with the outside by comparing the state amount comparison value with a preset detection threshold, a correction amount calculation part 33, which calculates a positional correction amount for correcting the positions of the robot and the external shaft corresponding to the contact state amount of the contact detection parts 132, 232, and command correction parts 137, 237 which add the positional correction amount to the command from the high-order command part. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a motor and a robot using a motor as a drive source, and relates to a robot control device and a control method for detecting contact of a motor main body, a robot main body, an end effector, and the like with another object such as a workpiece and correcting the position. .

  Conventional robots are controlled by a position / speed control system for each joint axis of the robot. When performing playback playback of spot welding, seam welding or assembly work that involves contact with the workpiece in such a control system, if there is a positional deviation of the workpiece itself or a position where the robot grips the workpiece, In the conventional position / velocity control system shown in FIG. 11, a large torque is generated by the action of a gain and an integrator that are set large to increase positioning accuracy, and there is a risk of damaging the robot, the end effector, or the workpiece. . On the other hand, there may be a case where the working force is poor due to insufficient working force at the time of contact.

For example, in spot welding using a robot and an electric gun, let us consider a case where the workpiece is displaced from the teaching position due to a workpiece machining error or positioning error when the workpiece is conveyed on the line. If the displacement amount is large, there is a problem that the electrode tip of the electric gun cannot contact the teaching point on the workpiece surface, so that the current cannot be supplied, and the line is stopped due to poor welding. In addition, even when the displacement amount is small and the electrode and the workpiece are in contact with each other, if the workpiece is welded while being deformed, there is a problem that the welding quality is deteriorated or the workpiece or the electric gun is damaged. In addition, there is also a problem that the electrode gradually wears due to pressurization and welding heat at the time of spot welding, and unless the amount of wear is properly detected, the electrode and the workpiece do not come into contact with each other and cannot be energized.
Also, when welding multiple plates with different plate thicknesses, if the pressure applied to the workpiece by the upper and lower electrodes is equal, the nugget generated in the workpiece will reach the surface of the thin plate when the energization amount is large. As a result, spatter and chip welding occur, and when the energization amount is small, there is a problem that the nugget is small and the welding strength cannot be secured.
Furthermore, when the electrode or the core wire is welded to the workpiece when retracting from the welding end position, there is a problem that the workpiece or the welding jig is damaged or the line is stopped.

In addition, the gun arm of the electric gun is elastically deformed according to the applied pressure, and the position of the electrode moves from the position taught in advance. Unnecessary force is applied to the workpiece, the welding quality is lowered, the workpiece or the electric motor is There was also a problem of damaging the gun.
To solve this problem, a method for flexibly controlling the force in the work coordinate system without adding a special device to the robot is to reduce the rigidity of the servo system with respect to the gun pressurization direction of the work coordinate system and add a gun. There is a method of performing pressure and welding (see, for example, Patent Document 1).
In addition, as a method of performing force control by estimating external force, the disturbance to the motor of each axis of the joint coordinate system is estimated by a disturbance observer, and the estimated disturbance value is converted into the coordinate system using the Jacobian matrix. There is a method that can be converted into an external force estimated value (see, for example, Patent Document 2 and Patent Document 3).
Further, as a method for detecting the electrode wear amount, there are a method in which the total wear amount is obtained by blanking the electrode and divided into two, and a method in which the electrode wear amount is measured with an external measuring instrument (for example, Patent Document 4). Reference and patent document 5).

Further, as a method of spot welding a plurality of plates having different plate thicknesses, there is a method of moving the nugget position to the thick plate side by making the pressing force on the thin plate side larger than the pressing force on the thick plate side (for example, Patent Document 6 and Patent Document 7).
Further, as a method of detecting welding and stopping the robot, there are a method of detecting external force by a disturbance estimation observer and a method of detecting external force by current change (see, for example, Patent Document 8 and Patent Document 9).
Further, as a method for correcting the elastic deformation of the gun arm, there is a method in which the amount of displacement of the gun arm corresponding to the target pressure is read and the robot shaft is moved to determine whether the pressure has been reached based on the current value of the motor ( For example, see Patent Document 10).
JP 2000-005881 A Japanese Patent Laid-Open No. 11-058285 Japanese Patent No. 2819456 Japanese Patent Laid-Open No. 06-31274 Japanese Patent Laid-Open No. 06-031460 JP 09-277060 A Japanese Patent Laid-Open No. 10-249537 Japanese Patent Laid-Open No. 05-116094 JP 2001-170778 A JP 05-155036 A

However, in the conventional method in which softness (spring constant) is set in the tool coordinate system and the degree of adaptability to external force is specified for each direction in the space, the generated torque of the servo motor increases proportionally as the position deviation increases. Therefore, there is a problem that it is impossible to cope with a case where a positional deviation (movement distance) due to an external force is large. In addition, when the peripheral device or workpiece is removed and the contact state is released, the robot generates a force to return to the original position command location. It has problems such as damage.
In the conventional method of estimating the disturbance in the joint coordinate system with a disturbance observer and converting the estimated disturbance value into the estimated external force value in the work coordinate system by coordinate conversion using the Jacobian matrix, the detection time is obtained by using a filter. In addition, there is a problem that a delay occurs, and the influence of friction and gravity is large and an accurate external force estimation value cannot be obtained.

In addition, the method of determining the total wear amount by blanking the electrode and dividing it into two cannot cope with the case where the movable side electrode and the fixed side electrode do not wear evenly, and the electrode wear amount is measured by an external measuring instrument. This method has a problem that a separate measuring instrument is required and a place for arranging the measuring instrument is also required.
In addition, in the method of moving the nugget position to the thick plate side by increasing the pressure on the thin plate side than the thick plate side, in addition to driving the movable electrode, there is a separate drive source for moving the entire electric gun and the fixed electrode side up and down There is a problem that an electric gun having only a movable electrode drive source cannot be used.

In addition, in the method of detecting welding detection using a disturbance estimation observer or current change, there is a detection delay due to the use of a filter, etc., as described above, and the influence of friction and gravity is large and cannot be detected accurately. Have.
In the method of reading the displacement amount of the gun arm according to the target pressure and moving the robot shaft to determine whether the pressure has been reached based on the current value of the motor, the target pressure is reached from the actual start of pressurization. If the actual applied pressure by the motor and the target applied pressure are different, the pressure applied by the motor and the correction movement of the robot axis cannot be synchronized. Yes.

Accordingly, an object of the present invention is to detect contact with a contact object without using a sensor or the like, and to correct the position in a work coordinate system without applying excessive force to the contact object.
Also, in spot welding, the amount of electrode wear is accurately detected without the need for a measuring instrument, the elastic deformation of the gun arm is accurately corrected, and a plurality of plates having different plate thicknesses are welded with an electric gun that uses only a movable electrode drive source. For the purpose. Furthermore, it aims at detecting welding with high sensitivity.

The robot control device according to claim 1 of the present invention is a robot control device that controls a robot and an external axis based on a command from a higher-level command unit, and simulates an actual machine unit including the robot and the external shaft. A simulation unit, a state quantity comparison unit that compares the same state quantity of the actual machine unit and the simulation unit and outputs a state quantity comparison value, and compares the state quantity comparison value with a preset detection threshold value. A contact detection unit that detects contact with the outside, a correction amount calculation unit that calculates a position correction amount for correcting the positions of the robot and the external shaft according to the contact state amount of the contact detection unit, and the position A robot control apparatus comprising: a command correction unit that adds a correction amount to a command from the host command unit.

According to a second aspect of the present invention, the robot control device includes a correction amount storage unit that stores the position correction amount, and the command correction unit subtracts the position correction amount from the operation command at a next operation command. It is characterized by.

The robot control apparatus according to claim 3 of the present invention, wherein the correction amount calculation unit calculates a position correction amount of at least one of the robot and the external shaft based on a contact state amount from the contact detection unit. It is characterized by.

The robot control apparatus according to claim 4 of the present invention is characterized in that the correction amount calculation unit calculates a correction amount so that the contact state amount becomes a preset state amount.

In the robot control apparatus according to claim 5 of the present invention, the contact state amount is a detection position of the robot and the external shaft, and the correction amount calculation unit is configured to detect the robot and the robot based on the detection position and an operation command. The position correction amount to the external axis is calculated.

The robot controller according to claim 6 of the present invention is characterized in that the command correction unit includes a command adjustment unit that adjusts an operation command so that the robot and the external shaft come into contact with a contact target. It is.

The robot control apparatus according to claim 7 of the present invention is characterized in that the command correction unit includes a time adjustment unit that adjusts an operation command of the external shaft to the robot based on a preset time. Is.
The robot control apparatus according to claim 8 of the present invention, wherein the command correction unit is configured to detect contact between the robot and the work point of the end effector of the external shaft in contact with the contact object, and contact detection by the contact detection unit. The amount of bending of the contact object is set as a parameter.

According to a ninth aspect of the present invention, there is provided a robot control device comprising an operation pendant capable of inputting the detection threshold value, the bite amount, the advance time, and the deflection amount as parameters.

The robot control apparatus according to claim 10 of the present invention includes an operation pendant for operating the robot, and displays the state quantity in the form of continuous quantity or discrete quantity on the operation screen of the operation pendant, and can adjust the parameter. It is characterized by that.

In the robot control apparatus according to claim 11 of the present invention, the command correction unit uses the second action to obtain the position correction amount acquired at the first action point with respect to the action point in the same pressing direction on the contact object. The position of the action point after the point is corrected.

In the robot control device according to claim 12 of the present invention, the relational expression between the deformation amount of the structure of the external shaft generated by the force applied by the external shaft to the contact object is obtained in advance, and the contact detection is performed. The deformation amount corresponding to the state amount is used as a position correction amount for the robot.

According to a thirteenth aspect of the present invention, there is provided a robot control method for driving a motor based on a command from a motor control unit and controlling a robot having a drive mechanism unit connected to the motor and an external shaft. The robot and the external shaft have a mechanism unit and a motor control unit driven by a motor, simulate a motor model simulating the motor, a mechanism model unit simulating the mechanism unit, and the motor control unit. A simulation unit having a control model unit, and the motor control unit, the actual machine unit including the motor and the mechanism unit, and the simulation unit are arranged in parallel, and each receives an operation command from a higher-level command generation unit. The same state quantity of the actual machine part and the simulation part is compared, and the compared state quantity comparison value and a preset detection threshold value are Detecting a contact with the outside and compare, according to the state amount detected contact, it is characterized in that to correct the position of the robot and external axes.

According to a fourteenth aspect of the present invention, there is provided a robot control method for driving a motor based on a command from a motor control unit and controlling a robot having a drive mechanism unit connected to the motor and an external shaft. The robot and the external shaft have a mechanism unit and a motor control unit driven by a motor, and include a motor unit, a simulation unit for simulating an actual unit composed of the motor and the mechanism unit, and a playback operation. Sometimes, as a first step, contact detection is performed by moving the external shaft in advance with respect to the robot and bringing it into contact with a contact object, and comparing the state quantities of the simulation unit and the actual machine unit of the external shaft. The position correction amount for the contact object is calculated, and as the second step, the position correction of the contact object obtained in the first step is performed. It amounts to correct the position of the robot and external axes based, as a third step, is characterized in that subtracting the position correction amount obtained by correcting the second step to the next operation command from the operation command.

A robot control method according to a fifteenth aspect of the present invention is a robot control method for driving a motor based on a command from a motor control unit and controlling a robot having a drive mechanism unit connected to the motor and an external shaft. The robot and the external shaft have a mechanism unit and a motor control unit driven by a motor, and include a motor unit, a simulation unit for simulating an actual unit composed of the motor and the mechanism unit, and a playback operation. Sometimes, as a first step, the robot or the external shaft is brought into contact with an object to be contacted, the contact force is calculated by comparing the state quantities of the simulation unit and the actual machine unit, and based on the contact force, A position correction amount for the contact object is calculated, and as the second step, the robot and the robot are calculated based on the position correction amount obtained in the first step. The fix the position of the external axis, as a third step, is characterized in that subtracting the position correction amount obtained by correcting the second step to the next operation command from the operation command.

According to a sixteenth aspect of the present invention, there is provided a robot control method for driving a motor based on a command from a motor control unit and controlling a robot having a drive mechanism unit connected to the motor and an external shaft. The robot and the external shaft have a mechanism unit and a motor control unit driven by a motor, and include the motor control unit, a simulation unit for simulating an actual machine unit including the motor and the mechanism unit, and at the time of teaching work As a first step, the external shaft is moved in advance with respect to the robot to be brought into contact with a contact object, and contact detection is performed by comparing state quantities of the simulation unit and the actual machine unit of the external shaft. The position correction amount for the contact object is calculated, and the second step is based on the position correction amount of the contact object obtained in the first step. To correct the position of the robot and external axes, as a third step, it is characterized in that stored as teaching position of the current position of the modified robot and external axes.

According to a seventeenth aspect of the present invention, there is provided a robot control method for driving a motor based on a command from a motor control unit and controlling a robot having a drive mechanism unit connected to the motor and an external shaft. The robot and the external shaft have a mechanism unit and a motor control unit driven by a motor, and include the motor control unit, a simulation unit for simulating an actual machine unit including the motor and the mechanism unit, and at the time of teaching work As a first step, the contact force is calculated by bringing the robot or the external shaft into contact with a contact object, comparing the state quantities of the simulation unit and the actual machine unit, and the contact force based on the contact force. A position correction amount with respect to the object is calculated, and as the second step, the robot and the outside are calculated based on the position correction amount obtained in the first step. Fixed position of the shaft, as a third step, is characterized in that for storing the current position of the modified robot and the external axis as teaching position.

According to an eighteenth aspect of the present invention, there is provided a robot control method in which a motor is driven based on a command from a motor control unit, and a robot having a drive mechanism unit connected to the motor and an electric gun attached to the tip of the robot are spotted. In the control method of the robot for performing welding, the movable electrode shaft of the robot and the electric gun has a mechanism unit and a motor control unit driven by a motor, and an actual machine unit including the motor control unit, the motor, and the mechanism unit is provided. A simulation unit for simulating, and at the time of playback operation, as a first step, the movable electrode of the electric gun is operated with respect to the fixed electrode of the electric gun and brought into contact with the workpiece, and the movable electrode shaft of the electric gun is The position of the workpiece is corrected by detecting contact by comparing the state quantities of the simulation unit and the actual machine unit. The amount is calculated, and as the second step, the position of the movable electrode shaft of the robot and the electric gun is corrected based on the position correction amount of the workpiece obtained in the first step, and welding is performed as the third step. As a fourth step, the position correction amount corrected in the second step at the time of the next operation command is subtracted from the operation command.

According to a nineteenth aspect of the present invention, there is provided a robot control method in which a motor is driven on the basis of a command from a motor control unit, and is spotted by a robot having a drive mechanism unit connected to the motor and an electric gun attached to the tip of the robot. In the control method of the robot for performing welding, the movable electrode shaft of the robot and the electric gun has a mechanism unit and a motor control unit driven by a motor, and an actual machine unit including the motor control unit, the motor, and the mechanism unit is provided. A simulation unit for simulating, and at the time of teaching work, as a first step, the movable electrode of the electric gun is operated with respect to the fixed electrode of the electric gun and brought into contact with the work, and the movable electrode shaft of the electric gun is Position correction amount for the workpiece by detecting contact by comparing the state quantity of the simulation part and the actual machine part As a second step, the position of the movable electrode shaft of the robot and the electric gun is corrected based on the position correction amount of the workpiece obtained in the first step, and the corrected robot is determined as a third step. And the current position of the movable electrode shaft of the electric gun is stored as a teaching position.

According to a twentieth aspect of the present invention, there is provided a robot control method in which a motor is driven based on a command from a motor control unit, and a robot having a drive mechanism unit connected to the motor and an electric gun attached to the tip of the robot are spotted. In the method for controlling a robot for performing welding, the robot and the electric gun each include a mechanism unit and a motor control unit driven by a motor, and a simulation unit that simulates an actual machine unit including the motor control unit, the motor, and the mechanism unit As a first step, when the electrode is exchanged, the movable electrode of the electric gun and the tip of the fixed electrode are brought into contact with each other, and the contact force is calculated by comparing the state quantities of the simulation unit and the actual machine unit. Stops the movable electrode shaft when it becomes larger than a set threshold, and stops the movable electrode shaft In the process of storing as the reference position 1, and as the second step, the tip of the movable electrode and the fixed electrode are brought into contact during the playback operation, and the movable electrode shaft is stopped by the same contact detection method as in the first step, The process of memorizing the stop position of the movable electrode shaft as the total wear amount, and as the third step, the movable electrode of the electric gun is brought into contact with the work by moving the movable electrode of the electric gun in advance with respect to the fixed electrode of the electric gun, The movable electrode shaft is stopped by the same contact detection method, the stop position of the movable electrode shaft is stored as the reference position 2, and the wear amount of the movable electrode is calculated from the difference between the reference position 1 and the reference position 2. Then, the wear amount of the fixed electrode is calculated from the total wear amount and the wear amount of the movable electrode, and as the fourth step, the robot is based on the wear amounts of the movable electrode and the fixed electrode obtained in the third step. The position of the movable electrode shaft of the motor and the electric gun is corrected and welding is continued.

According to a twenty-first aspect of the present invention, there is provided a robot control method in which a motor is driven based on a command from a motor control unit, and a robot having a drive mechanism unit connected to the motor and an electric gun attached to the tip of the robot are spotted. In the method for controlling a robot for performing welding, the robot and the electric gun each include a mechanism unit and a motor control unit driven by a motor, and a simulation unit that simulates an actual machine unit including the motor control unit, the motor, and the mechanism unit And at the time of playback operation for welding a workpiece in which a plurality of plates having different thicknesses are stacked, as a first step, the movable electrode and the fixed electrode of the electric gun are brought into contact with the workpiece, and the simulation unit and the The contact force is calculated by comparing the state quantity of the actual machine part, and the contact force is calculated as the second step. In addition, the position correction amount for the workpiece is calculated so that the applied pressure of the electrode in the direction in which the nugget position is to be moved is small, and as the third step, based on the position correction amount obtained in the second step, the robot and The position of the movable electrode of the electric gun is corrected and welded.

According to a twenty-second aspect of the present invention, there is provided a robot control method in which a motor is driven based on a command from a motor control unit, and a robot having a drive mechanism unit connected to the motor and an electric gun attached to the tip of the robot are spotted. In the control method of the robot for performing welding, the robot and the external shaft have a mechanism unit and a motor control unit driven by a motor, and a simulation for simulating an actual machine unit including the motor control unit, the motor, and the mechanism unit And calculating the contact force between the robot or the external shaft and the contact object by comparing the state quantities of the simulation unit and the actual machine unit as a first step at the end of welding. As the second step, the contact force obtained in the first step is compared with a preset detection threshold, and the third step Then, when the contact force is larger than the detection threshold, the robot and the external shaft are stopped, a preset welding release operation is performed, or a signal is output to the outside. It is what.

According to a twenty-third aspect of the present invention, there is provided a robot control method in which a motor is driven based on a command from a motor control unit, and a robot having a drive mechanism unit connected to the motor and an electric gun attached to the tip of the robot are spotted. In the control method of the robot for performing welding, the movable electrode shaft of the robot and the electric gun has a mechanism unit and a motor control unit driven by a motor, and an actual machine unit including the motor control unit, the motor, and the mechanism unit is provided. A simulation unit for simulating, and as a first step before a playback operation or teaching operation, as a first step, a force generated by the movable electrode shaft of the electric gun and a fixed electrode side and a movable electrode side of the electric gun generated by the force The relational expression with the amount of bending of the arm is obtained, and the second step is performed at the time of pressurization during playback operation or teaching work. The amount of bending of the arm on the fixed electrode side and the movable electrode side is obtained from the applied pressure detected by comparing the state quantity of the simulation unit and the actual machine unit of the movable electrode shaft of the electric gun and the relational expression, As a third step, a position correction amount of the robot is obtained from the deflection amount, and as a fourth step, the robot is operated by the position correction amount, and the positions of the movable electrode and the fixed electrode are maintained. .

As described above, according to the robot and the external axis control device of the first aspect, the actual machine unit and the simulation unit are arranged in parallel, and the same command is input from the higher-level command generation unit, and the actual machine unit and the simulation are performed. Compare the internal state quantity of the part to create an internal state quantity comparison value, compare it with the preset detection threshold value, and correct the position of the contact detection and robot and external shaft to work the contact object Even when the position is shifted in the coordinate system, it is possible to detect contact with high sensitivity by simple processing and absorb the position shift by the robot and the external shaft.
According to the robot control device of the second aspect, the position correction amount is stored, and the position correction amount is subtracted from the operation command during the next operation, so that the position correction is performed with the operation command generated by the host. The present position can be matched so that excessive force is not generated.
According to the robot control apparatus of claim 3 and 4, the position correction amount is calculated based on the detected force and torque state quantity, and the position is controlled by controlling the force so as to become a preset force and torque. Absorbing the deviation, it is possible to obtain any pressure state while maintaining the contact state.

According to the robot control device of claim 5, by calculating the position correction amount to the robot and the external axis based on the detected position and the operation command, the contact detection with high sensitivity can be performed with simple processing. And the position shift can be absorbed by the external shaft.
According to the robot control device of the sixth aspect, by providing operation commands for the robot and the external shaft within the contact object by a preset amount of biting, the robot is moved in the direction of the contact object from the target position. Corresponding to the case of displacement, contact can be made.
According to the robot control apparatus of the seventh aspect, the external axis is brought into contact with the contact target first by advancing the operation command of the external axis to the robot for a preset advance time, and only the external axis is contacted The amount of positional deviation of the object can be detected.

According to the robot control device according to claim 8, even when the rigidity of the contact object is low by setting, as a parameter, an amount by which the contact object bends until it is detected by the contact detection unit, The position of the deflection amount is also corrected, and the object to be contacted can be contacted at the position of the operation command.
According to the robot control device according to claim 9 and 10, from the operation screen of the operation pendant attached to the control device, the detection threshold value, the bite amount, the advance time, and the deflection amount are input as parameters, By displaying the state quantity before and after contact in the form of continuous quantity or discrete quantity and adjusting the parameters, the operator can grasp the detection state intuitively and quantitatively, and can easily adjust the parameters. .

According to the robot control device of claim 11, the position correction amount acquired at the first action point is calculated for the action point after the second action point with respect to the action point in the same pressing direction on the contact object. By correcting the position, it is possible to perform the position correction by reducing the calculation load that has been executed every time the contact is made.
According to the control apparatus for a robot that performs spot welding according to claim 12, the relational expression between the force and torque applied to the object to be contacted by the external shaft and the deformation amount of the structure of the external shaft generated thereby is obtained in advance. By obtaining the amount of deformation according to the force and torque state amount detected for contact as a position correction amount to the robot, the robot can be operated in conjunction with the force and torque on the work object of the external shaft, The working position can be maintained. Moreover, unnecessary force is not applied to the work object.

According to the robot control method of the thirteenth aspect, the real machine unit and the simulation unit are arranged in parallel, the same command is input from the host command generation unit, and the internal state quantities of the real machine unit and the simulation unit are compared. The internal state quantity comparison value was created, and the contact object was misaligned in the work coordinate system by comparing the contact detection and the position of the robot and the external shaft with the detection threshold value set in advance. Even in this case, it is possible to detect the contact with high sensitivity by a simple process and to absorb the positional deviation by the robot and the external shaft.
According to the robot control method according to claim 14, as a first step, in the playback operation, the external shaft is moved in advance with respect to the robot to contact a contact object, and the simulation unit and the actual unit The position correction amount for the contact target object is calculated by detecting contact by comparing the state amounts of the robot, and as a second step, the robot's position is calculated based on the position correction amount of the contact target object obtained in the first step. Even when the contact object is misaligned in the work coordinate system by correcting the position and subtracting the position correction amount corrected in the second step from the operation command as the third step in the next operation command. It is possible to detect contact with high sensitivity by simple processing and absorb the positional deviation with the robot and external axis, and the motion command generated by the host at the next motion command and the current position corrected. The position can be matched so that excessive force is not generated.

According to the robot control method of claim 15, as a first step during the playback operation, the robot or the external shaft is brought into contact with the contact object, and the state quantities of the simulation unit and the actual machine unit are compared. Then, the contact force is calculated, the position correction amount for the contact object is calculated based on the contact force, and the position of the robot is calculated based on the position correction amount obtained in the first step as the second step. As a third step, by subtracting the position correction amount corrected in the second step at the time of the next operation command from the operation command, the position shift is absorbed, and any pressure state is maintained while maintaining the contact state. Can be obtained.
According to the robot control method of the sixteenth aspect, at the time of teaching work, as the first step, the external shaft is moved in advance with respect to the robot to contact a contact object, and the simulation unit and the actual machine unit The position of the robot is calculated based on the position correction amount of the contact object obtained in the first step as a second step by calculating a position correction amount for the contact object by comparing the state quantity and detecting the contact. As a third step, the corrected current position of the robot is stored as a teaching position, so that even when the operator cannot visually check, it is possible to easily teach while maintaining the contact state with the workpiece.

According to the method for controlling a robot for spot welding according to claim 17, as teaching process, the robot or the external shaft is brought into contact with a contact object as a first step, and the state quantities of the simulation unit and the actual machine unit are determined. The contact force is calculated by comparing the contact force, the position correction amount for the contact object is calculated based on the contact force, and the robot is based on the position correction amount obtained in the first step as the second step. In the third step, the current position of the corrected robot is stored as a teaching position, and teaching is performed while maintaining a contact state with the workpiece with a preset force even in a situation where the operator cannot visually check the position. can do.
According to the method for controlling a robot that performs spot welding according to claim 18, as a first step, in the playback operation, the electric gun is moved in advance with respect to the robot to contact the workpiece, and the simulation unit and the The position of the robot is calculated based on the position correction amount of the workpiece obtained in the first step as a second step by detecting the contact by comparing the state quantities of the actual machine and calculating the position correction amount for the workpiece. As a third step, welding was performed, and as a fourth step, the workpiece was misaligned by subtracting the position correction amount corrected in the second step at the next operation command from the operation command. Even in such a case, the position shift can be absorbed and pressurized and welded without applying excessive force to the workpiece.

According to the method for controlling a robot for spot welding according to claim 19, as a first step during teaching work, the electric gun is moved in advance with respect to the robot and brought into contact with the work, and the simulation unit and the actual machine The position correction amount for the workpiece is calculated by detecting contact by comparing the state quantities of the parts, and the position of the robot is corrected based on the position correction amount of the workpiece obtained in the first step as the second step. Then, as a third step, by storing the corrected current position of the robot as a teaching position, it is possible to easily press the spot of the movable electrode and the fixed electrode while maintaining the contact state with the workpiece even when the operator cannot visually check Can teach points.
According to the robot control method for spot welding according to claim 20, as a first step, the movable electrode and the tip of the fixed electrode are brought into contact with each other at the time of electrode replacement, and the stop position of the movable electrode shaft is stored as the reference position 1. As the second step, the movable electrode and the tip of the fixed electrode are brought into contact with each other during the playback operation, and the stop position of the movable electrode shaft is stored as the total wear amount, and as the third step, the movable electrode is fixed. The movable electrode shaft is stopped by moving the electrode in advance to contact the workpiece, and the stop position of the movable electrode shaft is stored as the reference position 2. The amount of wear of the movable electrode is determined from the difference between the reference position 1 and the reference position 2. The amount of wear of the fixed electrode is calculated from the amount of wear of the total electrode and the amount of wear of the movable electrode. As the fourth step, the robot and the motor are electrically operated based on the amount of wear of the movable electrode and the fixed electrode obtained in the third step. By correcting the position of the movable electrode shaft and continuing welding, it is possible to cope with the case where the electrodes on the movable and fixed sides do not wear evenly. Welding can be continued.

According to the method for controlling a robot for spot welding according to claim 21, as a first step during a playback operation of welding a workpiece in which a plurality of plates having different thicknesses are overlapped, the movable electrode of the electric gun and The fixed electrode is brought into contact with the workpiece, the contact force is calculated by comparing the state quantities of the simulation unit and the actual machine unit, and as a second step, the nugget position is moved based on the contact force. A position correction amount for the workpiece is calculated so that the pressure applied to the electrode is reduced, and welding is performed as a third step by correcting the positions of the robot and the electric gun based on the position correction amount obtained in the second step. Therefore, welding can be performed by moving the nugget position to the thick plate side by increasing the pressing force on the thin plate side rather than the thick plate side. It is possible to cope with an electric gun that has only.
According to the method for controlling a robot for performing spot welding according to claim 22, when spot welding is finished, as a first step, by comparing state quantities of the simulation unit and the actual machine unit, the robot or the external shaft The contact force with the workpiece is calculated, and as the second step, the contact force obtained in the first step is compared with a preset detection threshold, and as the third step, the contact force is detected as the detection threshold. If the value is larger than the value, stop the robot and the external shaft, perform a preset welding release operation, or output a signal to the outside, so that there is no detection delay, and the influence of friction and gravity is reduced. Without receiving it, it is possible to detect the welding with high sensitivity and take an avoidance action.

According to the method for controlling a robot for spot welding according to claim 23, the force generated by the movable electrode shaft of the electric gun and the electric gun generated by the force as the first step before the playback operation or the teaching operation. The relationship between the fixed electrode side and the arm deflection amount on the movable electrode side is obtained, and when performing pressurization during playback operation or teaching work, as a second step, the simulation unit of the movable electrode shaft of the electric gun The amount of bending of the arm on the fixed electrode side and the movable electrode side is obtained from the applied pressure detected by comparing the state quantity of the actual machine part and the relational expression, and as a third step, the position of the robot is corrected from the amount of bending. As a fourth step, the robot is operated with the position correction amount, and the positions of the movable electrode and the fixed electrode are maintained. Against in conjunction with the occurrence of pressure can operate the robot, it is possible to perform a spot welding while maintaining the welding position. Further, unnecessary force is not applied to the workpiece, and the welding quality can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

A first basic configuration of the present invention will be described with reference to FIGS. 1, 2 and 18. FIG. Here, for simplification of explanation, the motor of the external shaft driven by the present control device is assumed to be one shaft.
In FIG. 1, the control of the robot and the external axis can be divided into a robot axis control system 10 that controls the robot and an external axis control system 20 that controls the external axis. Here, the external axis is an axis driven by a motor other than the robot axis, and is in contact with the robot or disposed in the vicinity of the robot.
The robot axis control system 10 includes an actual machine unit 110 and a simulation unit 120 as shown in FIG. The actual machine unit 110 includes a mechanism unit 112, a motor 113 connected to the mechanism unit 112, and a motor control unit 111 that controls the motor 113. The simulation unit 120 includes a mechanism model unit 122 that simulates the dynamic system of the mechanism unit 112, a motor model unit 123 that simulates the dynamic system of the motor 113, and a control model unit 122 that simulates the motor control unit 111. It is configured.
In the control device that controls the motor, the actual machine unit 110 and the simulation unit 120 are arranged in parallel, and each receives the same command from the higher-level command generation unit 50. The actual machine unit 110 and the simulation unit 120 output torque commands for controlling the mechanism unit 112 and the mechanism unit model 122 to the motor 113 and the motor model 123, respectively, according to the input commands.

Here, the calculation for obtaining the torque command by the simulation unit 120 can solve the following formulas 1 to 3 when the mechanism unit 112 is a rigid body model, and since the calculation amount is small, there is no burden on the CPU of the control device. If a multitasking CPU is used, the calculation can be performed in parallel with the control of the actual machine.

Tref = J * Kv * (Kp * (θref−θfb) −Vfb) (Formula 1)
Where Tref: torque command J: motor rotor inertia + mechanism inertia (including reduction gear)
Kv: Speed loop gain
Kp: Position loop gain θref: Position command θfb from position command generator 50: Position feedback Vfb: Speed feedback

Vfb-= Σ (dt * Tref / J) (Formula 2)
here,
dt: Calculation cycle time Σ: Integration

θfb = Σ (dt * Vfb) (Formula 3)

Here, the external axis control system 20 also includes an actual machine unit 210 and a simulation unit 220, as in the robot axis control system 10, as shown in FIG. 2 (b). Therefore, here, the robot axis control system 10 will be described.
Since the simulation unit 120 reflects the motor motion characteristics including the delay of the servo system of the actual unit 110 and the characteristics of the mechanism, the internal state quantities (position command, position feedback, position position) of the actual unit 110 and the simulation unit 120 are reflected. Deviation, speed command, speed feedback, speed deviation, etc.) are almost the same.
Therefore, the collision between the load connected to the motor 113 and an external peripheral device acts only on the internal state quantity of the actual machine unit 110 and does not change the internal state quantity of the simulation unit 120. This difference makes it possible to detect a collision with an external peripheral device. Here, since the same command as that of the actual machine unit 110 is input to the simulation unit 120, even if the operation command changes rapidly including a high frequency component like a step waveform, the simulation unit 120 and the actual machine unit 110 Since the internal state quantity shows the same response, the change of the internal state quantity due to the command can be canceled by comparing the internal state quantities of both, and does not affect the sensitivity of collision detection.

In the state quantity comparison unit 131, the same state quantity (for example, position deviation, speed feedback, torque command, etc.) of the motor control unit 111 and the control model unit 121 in the actual machine unit 110 and the simulation unit 120, or the above A state quantity comparison value is created by comparing the same state quantity (for example, position feedback) of the mechanism unit 113 and the mechanism model part 122. Here, the state quantity comparison value is created by an instantaneous value of the state quantity, an accumulated value of the state quantity at fixed time intervals, or a differential value of the state quantity.
The contact detection unit 132 detects a collision between the load connected to the motor 113 and the outside by comparing the state quantity comparison value with a detection threshold set in advance according to the work content, and the collision is detected. A contact state amount is generated at the point of time.
As shown in FIG. 1, the correction amount calculation unit 33 creates a robot axis position correction amount and an external axis position correction amount based on the contact state amounts from the robot axis control system 10 and the external axis control system 20. To do. Here, according to the contact state amount detected by the robot axis control system 10, it is possible to select whether to correct the position of only the robot axis or the external axis. The same applies to the case detected by the external axis control system 20, and the position of the robot axis and the external axis is corrected by combining the contact state quantities detected by the robot axis control system 10 and the external axis control system 20. An amount may be created.

The robot axis position correction amount and the external axis position correction amount are stored in the correction amount storage unit 34, and are simultaneously added to the position commands of the robot axis control system 10 and the external axis control system 20, respectively. As a result, when the robot axis or the external axis comes into contact with the contact object, the position of the robot axis or the external axis is corrected according to the amount of the contact state without applying excessive force to the contact object. You can continue working. Moreover, you may make it pressurize a contact target with the preset applied pressure, keeping a contact state after a contact.

The first specific example of the present invention will be described below.
In this embodiment, as shown in FIGS. 3, 20 and 23, a spot welding application using a robot 401 using an electric gun 402 will be described as an example. When the workpiece 405, which is the welding object, is transported on the line, the workpiece 405 is displaced from the pre-registered teaching position in the opening and closing direction of the electric gun 402 due to processing errors or positioning errors of the workpiece 405. Consider the correction method (equalizing function).
In the playback operation, the movable electrode 403 and the fixed electrode 404 of the electric gun 402 arranged at the hand of the robot 401 move to the teaching points registered in advance on the surface of the workpiece 405. However, if the displacement amount of the electric gun 402 in the opening / closing direction is large, the electric gun 402 cannot be energized, resulting in poor welding and line stoppage, or due to the action of a gain or integrator that is set large to increase positioning accuracy. There is a possibility that a large torque is generated and the work 405 and the electric gun 402 are damaged. Further, even if the positional deviation amount is small, welding is performed while the workpiece 405 is deformed, so that the welding quality is deteriorated. Therefore, it is necessary to detect the positional deviation of the workpiece 405 with the robot 401 and the electric gun 402 and correct the position in real time.

In the following, a method of detecting and correcting the positional deviation by the robot 401 and the electric gun 402 with respect to the positional deviation of the workpiece 405 will be described.
A normal state in which the workpiece 405 is not misaligned is shown in FIGS.
When the workpiece 405 is very thin, the teaching points on the movable electrode side and the fixed electrode side intersect at point A. To this teaching point A, the movable electrode 403 and the fixed electrode 404 start to descend and rise simultaneously from the pre-registered small opening position of (a). In FIG. 4B, the movable electrode 403 and the fixed electrode 404 reach the teaching point A at the same time, come into contact with the workpiece 405, and the workpiece 405 can be welded by performing the main pressurization. In FIG. 4C, the movement to the small opening position is performed by the opening command.

Next, a state in which the workpiece 405 is misaligned is shown in FIGS.
(1) Detection of positional deviation As shown in FIG. 4D, there is a positional deviation amount α from the teaching position to the movable electrode side. The movable electrode 403 and the fixed electrode 404 start to descend and rise simultaneously from the small opening position.
As shown in FIG. 4 (e), the movable electrode 403 contacts the workpiece 405 at a point B that is higher than the teaching position by α before the fixed electrode 404. The fixed electrode reaches the teaching position, but does not come into contact with the workpiece 405 due to a positional deviation.
Here, the contact between the workpiece 405 and the movable electrode 403 is detected by comparing the internal state quantities of the actual machine unit 210 and the simulation unit 220 of the gun axis control system 20, as shown in FIG. Here, an actual machine torque command and a model torque command, which are outputs of the motor control unit 211 and the control model unit 221, are used as the internal state quantities. In the state quantity comparison unit 231, the actual machine torque command of the actual machine unit 210 is suddenly changed by the contact, so a difference between the actual machine torque command and the model torque command is created as a state quantity comparison value.

The contact detection unit 232 compares the state quantity comparison value with a detection threshold value set in advance according to the work content, so that the mechanism unit 212 (here, the movable electrode 403) connected to the motor 213 and the workpiece 405 are connected. When the collision is detected, a gun shaft contact force is generated as a contact state amount. The gun shaft contact force can be obtained by converting the state quantity comparison value, which is a difference between torque commands, into a force unit system according to the configuration of the reduction gear.
Here, the process in which the workpiece 405 is displaced from the teaching position to the movable electrode side to obtain the contact force of the gun axis control system 20 has been described, but the same applies when the workpiece 405 is displaced from the teaching position to the fixed electrode side. It is. However, the process of converting the state quantity comparison value, which is the difference in torque command for each axis of the robot, into a force unit system is different.

The contact detection unit 132 of the robot axis control system 10 obtains a micro displacement relational expression between a joint coordinate system generally called a Jacobian and a work coordinate system, and uses the inverse matrix of the transposed value to obtain the above-mentioned in a plurality of joint coordinate systems. The robot axis contact force (force) in the work coordinate system can be calculated from the state quantity comparison value (torque). Here, by making one axis of the work coordinate system coincide with the opening / closing direction of the electric gun 402, the contact force acting in the opening / closing direction can be calculated.
In the state of FIG. 4 (e), the contact force of the gun axis control system 20 is F, but the contact force of the robot axis control system 10 is zero.

(2) Correction amount calculation In the correction amount calculation unit 33, the movable electrode 403 and the fixed electrode 404 are moved to the workpiece 405 with a preset target contact force _FREF based on the gun axis contact force and the robot axis contact force. The robot axis position correction amount and the gun axis position correction amount are created so as to make contact evenly.

(2-1) Impedance control In the impedance control unit 331, since the contact force of the gun axis control system 20 is F and the target contact force is F _REF , the difference value _FFREF is substituted into (Expression 4). Thus, the position correction amount X in the work coordinate system of the gun axis control system 20 can be obtained.

In (Expression 4), substituting the following expressions for speed and acceleration,

Further, the position correction amount X in the work coordinate system of the robot axis can be similarly obtained. Since the contact force of the robot axis is 0, the position correction amount X is calculated so as to come into contact with the workpiece 405 and contact with the target contact force _FREF by the calculation of Expression 4.
Further, the position correction amounts of the robot axis and the external axis may be created by combining the contact forces detected by the robot axis and the gun axis.

(2-2) Coordinate conversion Since the position correction amount X in the work coordinate system of the robot axis and the gun axis is obtained, it is necessary to convert the value into a value in the joint coordinate system coordinate system of the robot axis and the gun axis. In the coordinate conversion unit 332, with respect to the robot axis, the position correction amount X in the work coordinate system can be converted into the position correction value θ _ROBOT in the joint coordinate system by using the aforementioned Jacobian inverse matrix. Similarly, the gun axis is converted into a position correction value θ _GUN in the joint coordinate system according to the configuration of the speed reducer.
The robot axis position correction amount θ _ROBOT and the gun axis position correction amount θ _GUN are stored in the correction amount storage unit 34 and simultaneously added to the position commands of the robot axis control system 10 and the gun axis control system 20, respectively. As a result, the movable electrode 403 and the fixed electrode 404 can contact the workpiece 405 with the target pressure F _REF as shown in FIG.

(3) Pressurization control At the time of the main pressurization after the contact, the contact object is pressurized with another preset target pressurization while maintaining the contact state. This is because when there is a gap between the workpieces 405, it is necessary to crush the gap between the workpieces by applying pressure with a target pressure larger than that at the time of contact.

(4) Command correction When a release command to the small opening position or a command to move to the next teaching point comes after the completion of the main pressurization, the robot axis position correction amount stored in the correction amount storage unit 34 and It is necessary to correct only the external axis position correction amount. This is because a command to move to the teaching position A is received from the higher order command generation unit, and the current position is changed to the point B which has been displaced by the above processing. Therefore, if the next small opening position or the next teaching point is moved as it is, a command for moving from the teaching position A to the small opening position comes from the higher order command generation unit. There is a risk of damaging the workpiece 405 by performing an operation of pressing against the workpiece 405. For this reason, the robot axis position correction amount and the external axis position correction amount stored in the correction amount storage unit 34 are subtracted from the instruction for moving from the teaching position A to the small opening position sent from the higher order command generation unit. There is a need to.
As another method, before the release command is issued, the host command generation unit may be requested in advance to recreate the current position at a position changed by the correction amount.
By these methods, a command to move from the current position changed by the correction amount to the small opening position or the next teaching point is sent from the higher order command generation unit.

As described above, even when the workpiece is misaligned, the contact between the workpiece and the electrode can be detected with high sensitivity, and the workpiece can be pressurized with a preset target force.
In addition, as shown in FIG. 22, the movable electrode and the fixed electrode are brought into contact with the workpiece during teaching work, the workpiece position is obtained, and the robot axis and the external axis are operated according to the workpiece position, and stored as the teaching position. You may do it.

A second specific embodiment of the present invention will be described below with reference to FIGS. 4, 6, and 19. FIG.
In this embodiment, the process of position correction after contact detection in the first embodiment is different. In the first embodiment, the force at the time of contact detection is obtained and the position is corrected by impedance control. However, in this embodiment, the positional deviation amount α of the workpiece 405 is calculated from the position detected by the contact and the previously taught position. The position is corrected by this positional shift amount α.
Hereinafter, a method for detecting and correcting the positional deviation amount α of the workpiece 405 will be described. Here, as in the first embodiment, consider a case where there is a positional shift amount α from the teaching position to the movable electrode side as shown in FIG.

(1) The positional deviation detection movable electrode 403 and the fixed electrode 404 start to descend and rise simultaneously from the small opening position. As shown in FIG. 4 (e), the movable electrode 403 contacts the workpiece 405 at a point B that is higher than the teaching position by α before the fixed electrode 404. The fixed electrode 404 reaches the teaching position, but does not come into contact with the workpiece 405 due to a positional shift.
Here, the contact between the workpiece 405 and the movable electrode 403 is detected by comparing the internal state quantities of the actual machine unit 210 and the simulation unit 220 of the gun axis control system 20, as shown in FIG. Here, a differential value of the difference between the actual machine torque command and the model torque command is created as the state quantity comparison value. Here, the reason for using the differential value is to capture a sudden change in the difference value. Further, before creating the differential value, a signal having a frequency higher than the frequency generated at the time of collision may be deleted by a filter or the like.

The contact detection unit 232 can detect a collision between the movable electrode 403 and the workpiece 405 by comparing the state quantity comparison value with a detection threshold set in advance according to the work content, and detects a collision. When it is done, gun shaft contact detection information is output.
Similarly, in the contact detection unit 132 of the robot axis control system 10, the collision between the fixed electrode 404 and the workpiece 405 is made by comparing the state quantity comparison value obtained by the state quantity comparison unit 131 with the detection threshold value. When a collision is detected, robot axis contact detection information is output.
The contact determination unit 334 in the correction amount calculation unit 33 determines which of the movable electrode 403 and the fixed electrode 404 has previously contacted the workpiece 405 from the gun axis contact detection information and the robot axis contact detection information. Here, the gun shaft contact detection information is input to the contact determination unit 334 first. At this time, the robot axis contact detection information is not input. Therefore, it can be seen that the workpiece 405 is displaced toward the movable electrode. Here, when the gun axis contact detection information and the robot axis contact detection information are input simultaneously, it is determined that the workpiece 405 is not displaced.

(2) Correction amount calculation (2-1) Calculation of positional deviation amount α The gun shaft contact detection information is sent to the correction amount calculation unit 335. The correction amount calculation unit 335 takes in a contact detection position and a position command which are position responses of the motor 213 of the actual machine unit 210 at the time when the gun axis contact detection information is input. At this time, the positional deviation amount α _GUN in the joint coordinate system can be obtained by the following equation.

Position shift amount α _GUN = contact detection position−position command (Formula 6)

Since the obtained positional deviation amount α _GUN is a motor angle of the joint coordinate system, the coordinate conversion unit 332 converts the positional deviation amount α _GUN into a positional deviation amount α of the work coordinate system according to the configuration of the reduction gear. To do. For example, when the speed reducer is a ball screw, it can be converted into a position in the work coordinate system by multiplying the angle of the joint coordinate system by the pitch of the ball screw.
Similarly, even when the fixed electrode 403 has previously contacted the workpiece 405, when the robot axis contact detection information is output to the correction amount calculation unit 335, contact detection that is a position response of the motor 113 of the actual machine unit 110 is detected. Capture position and position command. Thereby, a positional shift amount α _ROBOT in the joint coordinate system of each axis of the robot is obtained. Next, in the robot axis control system 10 as well, by using the aforementioned Jacobian, it is possible to convert the positional deviation amount α _ROBOT in the joint coordinate system into the positional deviation amount α in the work coordinate system.

(2-2) Coordinate conversion When the movable electrode 403 contacts the workpiece 405 prior to the fixed electrode 404 to determine the positional deviation amount α, the gun shaft position correction amount θ _GUN is the same as the positional deviation amount α. However, the position correction amount θ _ROBOT of the robot axis is not obtained. Therefore, it is necessary to obtain the robot axis position correction amount θ _ROBOT from the positional deviation amount α obtained by detecting the contact of the gun axis. For this purpose, the positional deviation amount α in the work coordinate system can be converted into the position correction amount θ _ROBOT in the joint coordinate system by using the aforementioned Jacobian inverse matrix in the coordinate conversion unit 332.
Here, as shown in FIG. 4 (e), since the movable electrode 403 is already in contact with the workpiece 405, only the fixed electrode 404 needs to be corrected. Therefore, the robot axis position correction amount θ _ROBOT and the gun axis position correction amount θ _GUN are stored in the correction amount storage unit 34, and the robot axis control system 10 and the position correction amount θ _ROBOT are added. However, since the position of the movable electrode 403 also rises when the fixed electrode 404 rises by the positional deviation amount α, it is necessary to lower the position of the movable electrode 403 by the positional deviation amount α in accordance with the operation of the fixed electrode 404. is there.
Through the above processing, the movable electrode 403 and the fixed electrode 404 can come into contact with the workpiece 405 as shown in FIG.

(3) Pressurization control At the time of the main pressurization after the contact, the method of Example 1 is used to pressurize the contact target with another preset target pressurization while maintaining the contact state.

Subsequent (4) command correction processing is the same as that in the first embodiment, and is therefore omitted.
As described above, even when the workpiece is misaligned, the contact between the workpiece and the electrode can be detected with high sensitivity, and the workpiece can be pressurized with a preset target force.

Hereinafter, a third specific example of the present invention will be described with reference to FIGS.
In the present embodiment, the command method to the movable electrode when contact detection is performed in the second embodiment is different. In the second embodiment, the movable electrode and the fixed electrode are simultaneously moved from the small opening position to the teaching position on the workpiece surface. However, in this embodiment, the operation of the movable electrode is started early with respect to the fixed electrode. Thus, the movable electrode is brought into contact with the workpiece before the fixed electrode. This is because the motor capacity and friction of the robot that drives the fixed electrode are larger than the external shaft motor that drives the movable electrode, and detection with the movable electrode is more accurate.
Hereinafter, a method for detecting and correcting the positional deviation amount α of the workpiece 405 will be described. Here, a case is considered where there is a positional deviation of the workpiece 405 from the teaching position to the fixed electrode side.
As shown in FIG. 7, time adjustment units 135 and 235 are provided in the robot axis control system 10 and the gun axis control system 20. In addition, a command adjusting unit 236 is provided in the gun axis control system 20.
In the time adjustment units 135 and 235, only the advance time set in advance by performing phase advance compensation, the gun axis operation command for the robot axis is advanced, or only in the advance time set in advance using a buffer, Processing to delay the movement command of the robot axis relative to the gun axis is performed. Thus, when moving from the small opening position to the target position on the workpiece surface, the movable electrode 403 starts operating first, and after the advance time has elapsed, the fixed electrode 404 starts operating.

The command adjustment unit 236 adds a preset command adjustment amount to the operation command from the higher-level command generation unit. The command adjustment amount is for giving the target position of the movable electrode 403 closer to the fixed electrode than the workpiece surface. When the workpiece 405 is displaced toward the fixed electrode, the movable electrode 403 does not come into contact with the workpiece 405 even if the movable electrode 403 reaches the teaching position only by moving the movable electrode 403 to the target position on the workpiece surface. For this reason, the second teaching position in consideration of the amount of displacement of the workpiece is generated on the fixed electrode side with respect to the workpiece surface. Here, the command adjustment amount is set to a value larger than the assumed positional deviation amount α.
Further, when the correction amount is calculated after the contact of the movable electrode 403 is detected, it is necessary to obtain the positional deviation amount α not from the second teaching position but from the previously taught teaching position and the contact detecting position. This is to obtain the amount of deviation from the teaching position of the workpiece that should be.
The contact detection method, correction amount calculation, pressurization control, and command correction processing are the same as those in the first and second embodiments, and will be omitted.
In the following, a method of detecting and correcting the positional deviation by the robot 401 and the electric gun 402 with respect to the positional deviation of the workpiece 405 will be described.

A normal state in which the workpiece 405 is not misaligned is shown in FIGS.
As shown in FIG. 8A, the second target position C is created from the teaching position A of the movable electrode 403 with a command adjustment amount larger than the positional deviation amount α assumed by the command adjustment unit 236.
The movable electrode 403 moves from the small opening position to the second teaching position C, and the fixed electrode 404 moves from the small opening position to the teaching position A. At this time, in the time adjustment units 135 and 235, the position command is advanced by a preset time adjustment amount (several tens to several hundreds ms) of the movable electrode before the fixed electrode.
Here, since there is no positional deviation, the movable electrode 403 contacts the workpiece 405 at the teaching position A without reaching the second teaching position C, as shown in FIG. Detected by 20 contact detectors 232. After the contact is detected, the positional deviation amount α (here, 0) is calculated, the position correction amount (here, 0) of the robot axis is calculated, and the robot axis operates.
After the fixed electrode 404 and the movable electrode 403 come into contact with the workpiece 405, the main pressurization is executed and the workpiece 405 is welded. As shown in FIG. 8C, the movement to the small opening position is performed by the opening command.

Next, a state in which the workpiece 405 is misaligned is shown in FIGS.
As shown in FIG. 8D, there is a positional shift amount α from the teaching position to the fixed electrode side. The movable electrode 403 starts to descend from the small opening position earlier than the fixed electrode 404 by a time adjustment amount, and then the fixed electrode 404 starts to rise from the small opening position.
As shown in FIG. 8E, the movable electrode 403 comes into contact with the workpiece 405 at a point B that is α on the fixed electrode side from the teaching position A before the fixed electrode 404. At this time, the fixed electrode 404 is moving toward the teaching position A. The contact between the movable electrode 403 and the workpiece 405 is detected by the contact detection unit 232 of the gun axis control system 20, and the position correction amount of the robot axis is calculated. Here, the robot axis and gun axis commands are corrected so as to reach the contact detection position B, and the fixed electrode and the movable electrode can be brought into contact with the workpiece as shown in FIG. 8 (f).
After the fixed electrode 404 and the movable electrode 403 come into contact with the workpiece 405, the main pressurization is executed and the workpiece 405 is welded. As shown in FIG. 8 (c), when the movement to the small opening position or the next teaching position is performed by the opening command, it is necessary to correct the robot axis command as in the first embodiment. is there.

As described above, the movable electrode is moved in advance with respect to the fixed electrode, and the second target position of the movable electrode is generated from the fixed electrode by the work, so that the movable electrode is brought into contact with the work before the fixed electrode. By obtaining and correcting the deviation amount α, the fixed electrode and the movable electrode can be brought into contact with the workpiece.
Further, as shown in FIGS. 21 and 24, during the teaching operation, the external axis (movable electrode) is moved in advance with respect to the robot axis (fixed electrode), brought into contact with the workpiece, the workpiece position is obtained, and the workpiece position is obtained. The teaching axis may be stored by operating the robot axis and the external axis according to the above.

A fourth specific example of the present invention will be described below with reference to FIG.
In the present embodiment, the timing for obtaining the positional shift amount α is different from that in the second embodiment. In the second embodiment, the positional shift amount α is obtained every time the movable electrode and the fixed electrode are brought into contact with the workpiece at the teaching position. In this embodiment, welding points in the same pressure direction on the workpiece are welded. In doing so, the difference is that the positional deviation amount α acquired at the first welding point is used after the second welding point. This can reduce the arithmetic processing by using the fact that the positional deviation amount α of the welding point with respect to the teaching point of the same workpiece becomes the same.

The process of detecting the contact between the movable electrode 403 and the fixed electrode 404 and the workpiece 405 is the same as that in the second embodiment, and is therefore omitted. For this reason, the following description will be made after contact with the workpiece is detected by the gun axis control system or the robot axis control system.
As shown in FIG. 9, a second correction amount storage unit 341 that stores a positional deviation amount α that is an output from the correction amount calculation unit 335 is provided. When welding the first teaching point on the same plane on the workpiece, the positional deviation amount α output from the correction amount calculation unit 335 passes through the coordinate conversion unit 332 of the correction amount calculation unit 33 and is stored in the correction amount. Sent to the unit 34 and added to the position command as a robot axis position correction amount. Here, the positional deviation amount α is stored in the second correction amount storage unit 341. Next, when the teaching point after the second welding point in the same pressurizing direction on the workpiece is welded, the stored positional deviation amount α is sent to the coordinate conversion unit 332 to create a second correction amount. The second correction amount is added to the position command, and a correction operation is performed. At this time, the robot axis position correction amount, which is the output of the correction amount storage unit 34, is set to zero.

Here, when the workpiece 405 is thin and has low rigidity, even if the movable electrode 403 or the fixed electrode 404 comes into contact with the workpiece 405, it cannot be detected immediately, but the workpiece 405 is bent and welded, resulting in a decrease in welding quality. There is a case. In this case, the corrected position can be made coincident with the teaching position by adding the workpiece deflection amount preset in the work coordinate system to the positional deviation amount α to compensate. At this time, a plurality of workpiece deflection amounts can be stored in accordance with the teaching points of the workpiece 405. In addition, when the positional deviation amount α is obtained and compensated every time, the work deflection amount may be input to the correction amount calculation unit 335 and added to the positional deviation amount α.
Further, for example, after welding the plane A, when the plane B having a different inclination from the plane A is welded, and the plane A or a plane having the same inclination as the plane A is welded again, the positional deviation obtained in the plane A is changed. By using the quantity α _A again, the calculation processing can be reduced.

Further, although not shown, the positional deviation amount α obtained for the first time may be sent to the higher order command generation unit, and the position command itself may be changed to be used as the position commands for the robot axis control system 10 and the gun axis control system 20. .
As described above, the position deviation amount obtained at the first time is stored at the welding point in the same pressurizing direction of the workpiece, and the correction amount is obtained from the stored value after the next time, thereby eliminating the contact detection process and reducing the calculation load. be able to.

Hereinafter, a fifth specific embodiment of the present invention will be described with reference to FIG.
In this embodiment, in the fourth embodiment, the detection threshold value input to the contact detection units 132 and 232 from the operation screen of the operation pendant 406 connected to the control device 400 that drives the robot 401 The time adjustment amount input to the time adjustment unit 235, the command adjustment amount input to the command adjustment unit 236, and the workpiece deflection amount input to the second correction amount storage unit 341 are used as parameters. The state quantity comparison value is input and displayed on the operation screen to facilitate parameter adjustment.
As shown in FIG. 10A, the value of the parameter is input from the operation screen of the operation pendant 406. For example, as shown in FIG. 10B, the gun axis detection threshold value, the robot axis detection threshold value, the gun axis detection force, and the robot axis detection force input to the contact detection units 132 and 232 are Is displayed so that it can be observed continuously as time. While observing the detection threshold value and the detection force of each axis, the operator adjusts the detection threshold value so that no erroneous detection occurs during the operation from the small opening position to the main pressurization.

As described above, since the parameter and the state quantity are displayed as continuous change amounts, the operator can make an intuitive and quantitative determination, and the adjustment work can be easily performed.

Hereinafter, a sixth specific embodiment of the present invention will be described with reference to FIGS. 11, 12, and 25. FIG.
In this embodiment, the method for controlling the applied pressure is different from that in the first embodiment. In the first embodiment, the contact force is separately obtained for the robot axis and the gun axis, and each is controlled so as to have the target contact force F _REF . However, in this embodiment, the contact between the robot axis and the gun axis is controlled. The difference is that the force difference is controlled to increase intentionally. This is because the difference in contact force acting on the top and bottom of the workpiece is used to move the nugget position generated inside the workpiece to the side where the contact force is smaller than the center of the workpiece. To do.
Process (1) for detecting contact between movable electrode 403 and fixed electrode 404 and workpiece 405, (2-2) coordinate conversion for correction amount calculation, and pressure control after contact with workpiece is detected (3) In addition, since the command correction process (4) is the same as that in the first embodiment, a description thereof will be omitted. Therefore, here, (2-1) Impedance control for correction amount calculation in the gun axis control system or the robot axis control system will be described.
Here, an example of a workpiece in which the movable electrode 403 side is a thin plate and the fixed electrode 404 side is a thick plate is described.

(2-1) Impedance Control for Correction Amount Calculation As shown in FIG. 11, in the correction amount calculation unit 33, the gun axis contact force, the robot axis contact force, a preset target contact force F _REF, and a target pressure force Based on the difference ΔF, the robot axis position correction amount and the gun axis position correction amount are created so that the movable electrode 403 and the workpiece 405 are in contact with F _REF + ΔF and the fixed electrode 404 and the workpiece 405 are in contact with F _REF −ΔF. . By operating the robot axis and the gun axis with the position correction amount, the contact resistance between the tip of the fixed electrode 404 and the workpiece 405 becomes larger than the contact resistance between the tip of the movable electrode 403 and the workpiece 405, and the nugget is removed. It can be moved to the thick plate side.

Next, the operation of this embodiment will be described with reference to FIG. As in the first embodiment, the target pressing force F _up between the movable electrode 403 and the workpiece 405 and the target pressing force F _down between the fixed electrode 404 and the workpiece 405 are made the same, which is sufficient to ensure the welding strength. Generate a nugget of size. As a result, as shown in FIG. 12 (a), the nugget is generated at the contact portion between the thin plate and the thick plate inside the workpiece 405, and the nugget on the thin plate side reaches the surface of the thin plate, causing spatter and chip welding. May end up. Conversely, when the energization amount is decreased to make each nugget smaller, the nugget on the thin plate side does not reach the surface of the thin plate as shown in FIG. 12 (b), but the welding strength is insufficient.
For this reason, the robot axis and the gun axis are controlled so that the difference in the target pressure F _REF between the movable electrode 403 and the fixed electrode 404 and the workpiece 405 becomes the preset pressure difference ΔF. As a result, as shown in FIG. 12 (c), the nugget is generated closer to the thick plate inside the workpiece 405, so that a sufficiently large nugget is generated while preventing the occurrence of spatter and chip welding, It is possible to weld with securing the welding strength.

Hereinafter, a seventh specific embodiment of the present invention will be described with reference to FIGS.
In this embodiment, the position shift detection target is different from that in the second embodiment. In the second embodiment, the correction method (equalizing function) when the workpiece 405 is displaced in the opening / closing direction of the electric gun 402 from the pre-registered teaching position has been considered. However, in this embodiment, the workpiece displacement is not detected. In the absence, there is a difference in a method corresponding to a correction method of positional deviation due to electrode wear. In this method, welding is continued by detecting the wear amount of the electrode and correcting the positions of the movable electrode and the fixed electrode by the wear amount.
Since the principle of detecting the contact between the movable electrode 403 and the fixed electrode 404 and the workpiece 405 is the same as the process (1) of the second embodiment, a method for detecting the amount of electrode wear will be described here.

(1) Storage of reference position 1 after electrode replacement As shown in FIG. 13A, when the wear electrode is replaced with a new electrode, the movable electrode 403 of the electric gun and the tip of the fixed electrode 404 are brought into contact with each other. At this time, as shown in FIG. 14, the state quantity comparison unit 231 uses state quantities (for example, speed feedback value (hereinafter referred to as speed FB), torque command, etc.) of the simulation unit and the actual machine unit of the movable electrode shaft of the electric gun. The contact detection unit 232 calculates the contact force of the movable electrode 403 with the fixed electrode 404, and when the contact determination unit 334 exceeds a preset threshold value, issues a stop command to the actual unit 210. The movable electrode shaft is stopped by feeding. The stop position X ₁ of the said movable electrode shaft, and stored in the reference position storage section 35 as the reference position 1.

(2) Measurement of total wear amount during playback operation As shown in FIG. 13B, the total wear amount ΔL of the movable electrode 403 and the fixed electrode 404 is measured during the playback operation. It can be selected whether this measurement is performed after welding a preset number of hit points or after a preset time has elapsed. The total wear amount is measured during the air cut operation before starting welding.
Wherein an electric gun of the movable electrode 403 into contact with the tip of the fixed electrode 404, similarly to (1), said movable electrode shaft is stopped, as in the stop position X ₂ the movable electrode shaft, the reference position storage unit Remember to 35. At this point, the total wear amount ΔL is the is the sum of the amount of wear of the electrode in the movable electrode 403 and the fixed electrode 404, the correction amount calculation unit 335, at the reference position 2 from X ₁ is the reference position 1 by subtracting the certain X _2, it can be calculated the total wear amount [Delta] L.

(3) Measurement of reference position 2 during playback operation The amount of wear of the movable electrode 403 is measured in the process of moving to the welding point taught in advance. The target positions of the movable electrode 403 and the fixed electrode are shifted to the inside of the work as shown in the third embodiment.
The movable electrode 403 of the electric gun is moved in advance with respect to the fixed electrode 404 of the electric gun and brought into contact with the workpiece 405, and the state quantities of the simulation unit and the actual machine unit of the movable electrode shaft of the electric gun are compared. The contact force is calculated by the above, and the movable electrode shaft is stopped when it becomes larger than a preset threshold value. At this time, when there is no wear, the contact is made at the position taught in advance as shown in FIG. 13 (c), but when there is wear, only ΔL ₁ from the original taught position as shown in FIG. 13 (d). Contact at the lowered position. This ΔL ₁ is the amount of wear of the movable electrode 403 and can be detected by the correction amount calculation unit 335 as the amount of movement of the movable electrode 403.
Finally, the correction amount calculation unit 335, the by subtracting the wear amount [Delta] L ₁ of the movable electrode 403 from the total wear amount [Delta] L, can be calculated wear amount [Delta] L ₂ of the fixed electrode.

(4) the position correction based on the wear amount [Delta] L ₂ of wear amount [Delta] L ₁ and the fixed electrode 404 of the movable electrode 403 obtained in (3), the position of the movable electrode shaft of the robot and the electric gun fixed in real time And can continue welding. The position correction method is the same as (2) correction amount calculation in the second embodiment, and is therefore omitted here.

Hereinafter, an eighth specific embodiment of the present invention will be described with reference to FIGS. 15 and 27. FIG.
In this embodiment, (4) welding detection processing is added after the command correction in the second embodiment. Specifically, in the second embodiment, when an opening command to the small opening position or a movement command to the next teaching point comes after the end of this pressurization, the robot axis stored in the correction amount storage unit 34 is stored. After correcting the position correction amount and the external axis position correction amount, the opening operation and the movement to the next teaching point were performed. In this embodiment, electrode welding is detected during the opening operation or movement to the next teaching point.
Since the process (1) from the detection of the contact between the movable electrode 403 and the fixed electrode 404 and the workpiece 405 to the command correction (4) is the same as that in the second embodiment, the description thereof is omitted. Therefore, here, (5) welding detection will be described in the gun axis control system or the robot axis control system.

(5) Welding detection The process of detecting the welding of the movable electrode 403 or the fixed electrode 404 and the workpiece 405 is the same as (1) of the second embodiment, and the actual parts of the robot axis control system 10 and the gun axis control system 20 The welding is detected by comparing the internal state quantities of 110 and 210 with the simulation units 120 and 220. Since the robot axis control system 10 and the gun axis control system 20 have the same detection method, only the gun axis control system 20 will be described here.
As the internal state quantity, for example, an actual machine torque command and a model torque command that are outputs of the motor control unit 211 and the control model unit 221 are used. In the state quantity comparison unit 231, the actual machine torque command of the actual machine unit 210 undergoes abrupt fluctuation due to electrode welding, so a difference between the actual machine torque command and the model torque command is created as a state quantity comparison value.

The contact detection unit 232 compares the state quantity comparison value with the welding detection threshold value set in advance according to the work content, so that the mechanism unit 212 (here, the movable electrode 403) connected to the motor 213 and the workpiece When welding with 405 is detected, gun shaft welding detection information is output when the welding is detected. Similarly, the contact detection unit 132 of the robot axis control system 10 also welds the fixed electrode 404 and the workpiece 405 by comparing the state quantity comparison value obtained by the state quantity comparison unit 131 with the detection threshold value. When the welding is detected, the robot axis welding detection information is output.
The contact determination unit 334 in the correction amount calculation unit 33 determines whether the movable electrode 403 or the fixed electrode 404 is welded to the workpiece 405 from the gun axis welding detection information and the robot axis welding detection information. When one of the welding detection information is input to the contact determination unit 334, a welding detection signal is output from the contact determination unit 334 to the welding process selection unit 336. In the welding process selection unit 336, the robot axis control system 10 and the actual machine units 110 and 210 of the gun axis control system 20 are caused to stop the robot and the movable electrode axis, or perform a preset welding release operation. Either a release operation command is output or a command for outputting a welding occurrence signal to an external device is selected. Here, the welding release operation command will be described as an example.

As the welding release operation command, for example, a method of rotating the electric gun 402 around the electrode tip and re-energizing during the rotation to melt the electrode and the workpiece 405 is selected.
By adding these operation signals to the command correction units 137 and 237, the electric gun 402 can be rotated.
In this way, welding can be continued without stopping the line by performing the operation of detecting welding and automatically outputting a release command to release welding.

The ninth specific embodiment of the present invention will be described below with reference to FIGS. 16, 17 and 28. FIG.
In this embodiment, a deflection correction process for the gun arm portion of the electric gun 402 is added to the second embodiment. Specifically, in the second embodiment, a relational expression between the pressure applied to the electric gun and the amount of deflection of the gun arm is measured in advance before actual work, and the amount of deflection corresponding to the pressure applied during pressurization during actual work. Thus, the robot 401 is caused to perform a correction operation. Here, a C-type gun will be described as an example of the electric gun 402, but the same applies to an X-type gun. Further, the deflection amount ΔX is a value in the opening / closing direction of the movable electrode 403.

As shown in FIG. 16 (a), the gun arm portion of the electric gun 402 is greatly deformed by the applied pressure from the movable electrode shaft, and the positions of the movable electrode and the fixed electrode are deviated from the original teaching positions. The amount of deviation is corrected by the robot. Hereinafter, the correction method will be described.
(1) Relational expression creation between pressure force and deflection amount An operator creates a relational expression between pressure force and deflection amount regarding the gun arm portion of the electric gun before actual work. The movable electrode of the electric gun is brought into contact with the fixed electrode, and the applied pressure is obtained from the torque generated by the motor of the movable electrode shaft. Further, the position is obtained from a position detector such as an encoder connected to the motor. By obtaining these pieces of information with a plurality of pressures, a graph as shown in FIG. 16B can be obtained, and the following relational expression of the bending coefficient can be derived.

Deflection amount ΔX = Deflection coefficient × Pressure force F (Expression 7)

(2) Detection of applied pressure When performing a pressurizing operation during playback operation or teaching operation, as shown in FIG. 17, the internal state quantities of the actual unit 210 and the simulation unit 220 of the gun axis control system 20 are changed. By comparing with the amount comparison unit 231, the applied pressure (gun axis contact force) applied to the workpiece 405 by the movable electrode 403 is obtained.
The contact detection unit 232 compares the state quantity comparison value with a detection threshold value set in advance according to the work content, so that the mechanism unit 212 (here, the movable electrode 403) connected to the motor 213 and the workpiece 405 are connected. When the collision is detected, a gun shaft contact force is generated as a contact state amount. The gun shaft contact force can be obtained by converting the state quantity comparison value, which is a difference between torque commands, into a force unit system according to the configuration of the reduction gear. Alternatively, the deflection amount ΔX may be obtained from the target applied pressure.

(3) Calculation of deflection amount The deflection amount calculation unit 337 of the correction amount calculation unit 33 calculates the deflection amount ΔX of the gun arm portion in the work coordinate system from the obtained pressure and the deflection coefficient.

(4) Calculation of the robot position correction amount Since the deflection amount ΔX in the work coordinate system of the robot axis is obtained, it is necessary to convert the value into a value in the joint coordinate system coordinate system of the robot axis. In the coordinate conversion unit 332, with respect to the robot axis, the deflection amount ΔX of the work coordinate system can be converted into the position correction value θ _ROBOT of the joint coordinate system by using the aforementioned Jacobian inverse matrix. The robot axis position correction amount θ _ROBOT is stored in the correction amount storage unit 34 and simultaneously added to the position command of the robot axis control system 10.
As a result, the robot 401 performs a correction operation in synchronization with the pressure applied by the electric gun 405. As shown in FIG. 16C, the position of the movable electrode 403 and the fixed electrode 404 is maintained at the teaching position. The pressurizing operation can be executed without deforming 405.
In addition, the position of the movable electrode 403 and the fixed electrode 404 can be kept at the teaching position by performing the correcting operation of the robot in accordance with the detected applied pressure even during the decompression after the pressurization.

The present invention relates to a control device and a control method for a robot in which a motor main body, a robot main body, an end effector, or the like detects contact with another object such as a workpiece and corrects the position in a motor and a robot using a motor as a drive source. It is valid.

First basic configuration diagram of the present invention The figure which expanded the 1st basic composition of the present invention Mechanism diagram showing a first specific embodiment of the present invention Operational diagram in the first specific embodiment of the present invention The figure showing the 1st specific Example of this invention The figure showing the 2nd specific Example of this invention The figure showing the 3rd specific Example of this invention Operational diagram in the third specific embodiment of the present invention The figure showing the 4th specific Example of this invention The figure showing the 5th specific Example of this invention The figure showing the 6th specific Example of this invention Operational diagram in the sixth specific embodiment of the present invention The figure showing the 7th specific Example of this invention Operational diagram in the seventh specific embodiment of the present invention The figure showing the 8th specific Example of this invention. Operational diagram in the ninth specific embodiment of the present invention The figure showing the 9th specific Example of this invention. The flowchart showing the 1st basic composition of the present invention. Flowchart representing a second specific embodiment of the present invention. The flowchart showing the 1st specific Example of this invention. Flowchart representing the third specific embodiment of the present invention. The flowchart showing the 1st specific Example of this invention. The flowchart showing the 1st specific Example of this invention. Flowchart representing the third specific embodiment of the present invention. Flowchart representing the sixth specific embodiment of the present invention. Flowchart representing the seventh specific embodiment of the present invention. Flowchart representing the eighth specific embodiment of the present invention. Flowchart representing the ninth specific embodiment of the present invention. Diagram showing conventional control method

Explanation of symbols

10: Robot axis control system 110, 210: Real machine unit 111, 211: Motor control unit 112, 212: Mechanism unit 113, 213: Motor 120, 220: Simulation unit 121, 221: Control model unit 122, 222: Mechanism model unit 123, 223: Motor models 131, 231: State quantity comparison unit 132, 232: Contact detection unit 135, 235: Time adjustment unit 236: Command adjustment unit 137, 237: Command correction unit 20: External axis (gun axis) control system 33: Correction amount calculation unit 331: Impedance control unit 332: Coordinate conversion unit 334: Contact determination unit 335: Correction amount calculation unit 336: Welding process selection unit 337: Deflection amount calculation unit 34: Correction amount storage unit 341: No. 2 correction amount storage unit 35: reference position storage unit 400: control device 401: robot 402: electric gun 403: movable electrode 404: fixed Electrode 405: Work 406: Operation pendant

Claims (23)

In the robot control device that controls the robot and the external axis based on the command from the host command unit,
A simulation unit simulating a real unit including the robot and the external shaft;
A state quantity comparison unit that compares the same state quantities of the real machine unit and the simulation unit and outputs a state quantity comparison value;
A contact detection unit that detects contact with the outside by comparing the state quantity comparison value with a preset detection threshold;
A correction amount calculation unit that calculates a position correction amount for correcting the position of the robot and the external shaft according to the contact state amount of the contact detection unit;
A robot control apparatus comprising: a command correction unit that adds the position correction amount to a command from the host command unit. The robot control apparatus according to claim 1, further comprising a correction amount storage unit that stores the position correction amount, wherein the command correction unit subtracts the position correction amount from the operation command at a next operation command. . 3. The robot control according to claim 1, wherein the correction amount calculation unit calculates a position correction amount of at least one of the robot and the external shaft based on a contact state amount from the contact detection unit. apparatus. 4. The robot control device according to claim 1, wherein the correction amount calculation unit calculates a correction amount so that the contact state amount becomes a preset state amount. The contact state amount is a detection position of the robot and the external axis, and the correction amount calculation unit calculates a position correction amount to the robot and the external axis based on the detection position and an operation command. 5. The robot control apparatus according to claim 1, wherein the robot control apparatus is a robot. The robot control apparatus according to claim 1, wherein the command correction unit includes a command adjustment unit that adjusts an operation command so that the robot and the external shaft come into contact with a contact object. The robot control device according to claim 1, wherein the command correction unit includes a time adjustment unit that adjusts an operation command of the external axis for the robot based on a preset time. The command correction unit sets, as a parameter, an amount by which the work point of the end effector of the robot and the external shaft comes into contact with the contact object and the contact object bends until contact is detected by the contact detection unit. 8. The robot control apparatus according to claim 1, wherein the control apparatus is a robot. The robot control device according to claim 1, further comprising an operation pendant capable of inputting the detection threshold value, the biting amount, the advance time, and the deflection amount as parameters. 10. An operation pendant for operating a robot is provided, the state quantity is displayed in a form of a continuous quantity or a discrete quantity on an operation screen of the operation pendant, and parameters can be adjusted. Control device for Nobi robot. The command correction unit corrects the position correction amount acquired at the first action point with respect to the action point in the same pressure direction on the contact object with respect to the position of the action point after the second action point. 11. The robot control device according to claim 1, wherein the control device is a robot. A relational expression with the deformation amount of the structure of the external shaft generated by the force applied to the contact object by the external shaft is obtained in advance, and the deformation amount according to the state amount detected by the contact is determined as a position to the robot. 12. The robot control apparatus according to claim 1, wherein the correction amount is a correction amount. In a robot control method for driving a motor based on a command from a motor control unit and controlling a robot having a drive mechanism unit connected to the motor and an external shaft,
The robot and the external shaft have a mechanism unit and a motor control unit driven by a motor,
A simulation unit including a motor model simulating the motor, a mechanism model unit simulating the mechanism unit, and a control model unit simulating the motor control unit;
The actual machine unit including the motor control unit and the motor and the mechanism unit and the simulation unit are arranged in parallel, and each inputs an operation command from a higher-level command generation unit,
Compare the same state quantity of the actual machine part and the simulation part,
Detecting the contact with the outside by comparing the compared state quantity comparison value with a preset detection threshold;
A robot control method comprising correcting the positions of a robot and an external axis in accordance with a state quantity detected by contact. In a robot control method for driving a motor based on a command from a motor control unit and controlling a robot having a drive mechanism unit connected to the motor and an external shaft,
The robot and the external shaft have a mechanism unit and a motor control unit driven by a motor, and include a simulation unit that simulates an actual machine unit including the motor control unit, the motor, and the mechanism unit,
At the time of playback operation, as a first step, the external shaft is moved in advance with respect to the robot to be brought into contact with a contact object, and contact is made by comparing the state quantities of the simulation unit and the actual machine unit of the external shaft. Detecting and calculating a position correction amount for the contact object;
As a second step, the positions of the robot and the external shaft are corrected based on the position correction amount of the contact object obtained in the first step,
As a third step, a robot control method comprising subtracting the position correction amount corrected in the second step from the operation command at the time of the next operation command. In a robot control method for driving a motor based on a command from a motor control unit and controlling a robot having a drive mechanism unit connected to the motor and an external shaft,
The robot and the external shaft have a mechanism unit and a motor control unit driven by a motor, and include a simulation unit that simulates an actual machine unit including the motor control unit, the motor, and the mechanism unit,
During the playback operation, as a first step, the contact force is calculated by bringing the robot or the external shaft into contact with the contact object, comparing the state quantities of the simulation unit and the actual machine unit, and calculating the contact force. Based on the position correction amount for the contact object based on,
As a second step, the positions of the robot and the external shaft are corrected based on the position correction amount obtained in the first step,
As a third step, a robot control method comprising subtracting the position correction amount corrected in the second step from the operation command at the time of the next operation command. In a robot control method for driving a motor based on a command from a motor control unit and controlling a robot having a drive mechanism unit connected to the motor and an external shaft,
The robot and the external shaft have a mechanism unit and a motor control unit driven by a motor, and include a simulation unit that simulates an actual machine unit including the motor control unit, the motor, and the mechanism unit,
At the time of teaching work, as a first step, contact detection is performed by moving the external shaft in advance with respect to the robot and bringing it into contact with a contact object, and comparing the state quantities of the simulation unit and the actual machine unit of the external shaft. And calculating a position correction amount for the contact object,
As a second step, the positions of the robot and the external shaft are corrected based on the position correction amount of the contact object obtained in the first step,
As a third step, a robot control method characterized by storing the corrected current position of the robot and the external axis as a teaching position. In a robot control method for driving a motor based on a command from a motor control unit and controlling a robot having a drive mechanism unit connected to the motor and an external shaft,
The robot and the external shaft have a mechanism unit and a motor control unit driven by a motor, and include a simulation unit that simulates an actual machine unit including the motor control unit, the motor, and the mechanism unit,
During teaching work, as a first step, the contact force is calculated by bringing the robot or the external shaft into contact with an object to be contacted, and comparing the state quantities of the simulation unit and the actual machine unit. To calculate a position correction amount for the contact object,
As a second step, the positions of the robot and the external shaft are corrected based on the position correction amount obtained in the first step,
As a third step, a robot control method characterized by storing the corrected robot and the current position of the external axis as a teaching position. In a control method of a robot that drives a motor based on a command of a motor control unit and performs spot welding with a robot having a drive mechanism unit connected to the motor and an electric gun attached to the tip of the robot,
The movable electrode shaft of the robot and the electric gun has a mechanism unit and a motor control unit driven by a motor, and includes a simulation unit for simulating an actual machine unit composed of the motor control unit, the motor, and the mechanism unit,
At the time of playback operation, as a first step, the movable electrode of the electric gun is operated with respect to the fixed electrode of the electric gun and brought into contact with the workpiece, and the simulation unit and the actual machine unit of the movable electrode shaft of the electric gun are operated. By detecting the contact by comparing the state quantity, the position correction amount for the workpiece is calculated,
As a second step, the position of the movable electrode shaft of the robot and the electric gun is corrected based on the position correction amount of the workpiece obtained in the first step,
As a third step, welding is performed,
As a fourth step, a robot control method comprising subtracting the position correction amount corrected in the second step from the operation command at the time of the next operation command. In a control method of a robot that drives a motor based on a command of a motor control unit and performs spot welding with a robot having a drive mechanism unit connected to the motor and an electric gun attached to the tip of the robot,
The movable electrode shaft of the robot and the electric gun has a mechanism unit and a motor control unit driven by a motor, and includes a simulation unit for simulating an actual machine unit composed of the motor control unit, the motor, and the mechanism unit,
During teaching work, as a first step, the movable electrode of the electric gun is operated with respect to the fixed electrode of the electric gun and brought into contact with the workpiece, and the simulation unit and the actual machine unit of the movable electrode shaft of the electric gun are operated. By detecting the contact by comparing the state quantity, the position correction amount for the workpiece is calculated,
As a second step, the position of the movable electrode shaft of the robot and the electric gun is corrected based on the position correction amount of the workpiece obtained in the first step,
As a third step, a welding robot control method characterized by storing the corrected robot and the current position of the movable electrode shaft of the electric gun as a teaching position. In a control method of a robot that drives a motor based on a command of a motor control unit and performs spot welding with a robot having a drive mechanism unit connected to the motor and an electric gun attached to the tip of the robot,
The robot and the electric gun have a mechanism unit and a motor control unit driven by a motor, and include a simulation unit that simulates an actual machine unit including the motor control unit, the motor, and the mechanism unit,
As a first step, when the electrode is replaced, the movable electrode of the electric gun and the tip of the fixed electrode are brought into contact with each other, and the contact force is calculated by comparing the state quantities of the simulation unit and the actual machine unit. A step of stopping the movable electrode shaft when it becomes larger than a threshold value, and storing the stop position of the movable electrode shaft as a reference position 1;
As a second step, the movable electrode and the tip of the fixed electrode are brought into contact with each other during the playback operation, the movable electrode shaft is stopped by the same contact detection method as in the first step, and the stop position of the movable electrode shaft is completely worn. The process of memorizing as quantity,
As a third step, the movable electrode of the electric gun is moved in advance with respect to the fixed electrode of the electric gun and brought into contact with the workpiece, and the movable electrode shaft is stopped by the same contact detection method as in the first step, and the movable The stop position of the electrode shaft is stored as a reference position 2, the wear amount of the movable electrode is calculated from the difference between the reference position 1 and the reference position 2, and the fixed amount is calculated from the total wear amount and the wear amount of the movable electrode. Calculate the wear amount of the electrode,
As a fourth step, a robot control method characterized in that welding is continued by correcting the positions of the movable electrode shafts of the robot and the electric gun based on the wear amounts of the movable electrode and the fixed electrode obtained in the third step. . In a control method of a robot that drives a motor based on a command of a motor control unit and performs spot welding with a robot having a drive mechanism unit connected to the motor and an electric gun attached to the tip of the robot,
The robot and the electric gun have a mechanism unit and a motor control unit driven by a motor, and include a simulation unit that simulates an actual machine unit including the motor control unit, the motor, and the mechanism unit,
At the time of a playback operation for welding a workpiece in which a plurality of plates with different plate thicknesses are overlapped, as a first step, the movable electrode and the fixed electrode of the electric gun are brought into contact with the workpiece, and the state of the simulation unit and the actual machine unit Calculate contact force by comparing the amount,
As a second step, based on the contact force, a position correction amount for the workpiece is calculated so that the applied pressure of the electrode in the direction in which the nugget position is to be moved is reduced,
As a third step, a robot control method characterized in that welding is performed by correcting the positions of the movable electrodes of the robot and the electric gun based on the position correction amount obtained in the second step. In a control method of a robot that drives a motor based on a command of a motor control unit and performs spot welding with a robot having a drive mechanism unit connected to the motor and an electric gun attached to the tip of the robot,
The robot and the external shaft have a mechanism unit and a motor control unit driven by a motor, and include a simulation unit that simulates an actual machine unit including the motor control unit, the motor, and the mechanism unit,
At the end of welding, as a first step, by comparing the state quantities of the simulation unit and the actual machine unit, the contact force between the robot or the external shaft and the contact object is calculated,
As the second step, the contact force obtained in the first step is compared with a preset detection threshold value,
As a third step, when the contact force is larger than the detection threshold, the robot and the external shaft are stopped, a preset welding release operation is performed, or a signal is output to the outside. A method for controlling a robot characterized by the above. In a control method of a robot that drives a motor based on a command of a motor control unit and performs spot welding with a robot having a drive mechanism unit connected to the motor and an electric gun attached to the tip of the robot,
The movable electrode shaft of the robot and the electric gun has a mechanism unit and a motor control unit driven by a motor, and includes a simulation unit for simulating an actual machine unit composed of the motor control unit, the motor, and the mechanism unit,
Before playback operation or teaching work, as a first step, a relational expression between the force generated by the movable electrode shaft of the electric gun and the amount of deflection of the arm on the fixed electrode side and the movable electrode side of the electric gun caused by the force Seeking
During pressurization during playback operation or teaching operation, as a second step, the pressure detected by comparing the state quantities of the simulation unit and the actual unit of the movable electrode shaft of the electric gun and the relational expression The amount of bending of the arm on the fixed electrode side and the movable electrode side is obtained,
As a third step, a position correction amount of the robot is obtained from the deflection amount,
As a fourth step, a control method for a welding robot, wherein the robot is operated with the position correction amount to maintain the positions of the movable electrode and the fixed electrode.