JP2007052590A - Numerical controller and numerical control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a numerical controller which can safely stop without applying any large impact to any motor or machine system when a movable body stops by reducing over-travel amounts from the boundary of a movement inhibition region, and to provide a numerical control method. <P>SOLUTION: This numerical controller is provided with a soft limit setting means 57 for setting the movement forbidden position of a movable body 74; a deceleration setting means 58 for setting set deceleration; and a movement forbidden position intrusion disabling means 59 for generating a third speed command by reducing a first speed command so that a set deceleration stop distance when the speed of the first speed command is decelerated by the set deceleration speed to stop the movable body can be made smaller than a movable distance as a difference between the forbidden position of a movable forbidden region and the current position. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a numerical controller that controls the speed of a movable body.

Conventionally, in numerical control that controls the drive of machine tools, etc., a movement prohibition area has been set in order to prevent the movable body to be controlled from interfering with other components due to program errors or operator operation errors. When it is detected that the movable body has entered the movement prohibited area, a warning is issued and the movable body is controlled to be brought to an emergency stop. As a method for detecting the intrusion into the movement prohibited area, a movable upper limit value and a lower limit value are set by parameters, and the current position signal of the movable body from a position detector such as an encoder is compared with the movable upper limit value and the lower limit value. In particular, soft limit means for detecting intrusion into the movement prohibited area has been proposed.

Unlike the position control, the soft limit means at the time of speed control does not change the target position of the movable body and does not manage the command position, so it is difficult to stop within the movable region. As one of the soft limit means at the time of speed control, according to Patent Document 1, as shown in FIG. 4, when the moving movable body exceeds the movable region in accordance with the speed command signal V, as shown in FIG. A soft limit alarm SA is generated, and the speed command signal V is immediately cut off for an emergency stop (FIG. 4B). However, if the speed command signal V is cut off and the speed command signal V is set to 0, a large impact is given to the motor or the mechanical system at the time of stoppage. Therefore, as shown in FIGS. 4 (C) and 4 (D), the speed command signal Soft limit means has been proposed in which V is cut off and at the same time the current command signal I to the motor is reduced to decelerate and stop to stop the motor with a small impact.
Japanese Patent Laid-Open No. 5-250022 (pages 2, 3 and 4)

  Unlike the position control, the conventional soft limit means during speed control does not change the target position of the movable body and does not manage the command position, so it is difficult to stop within the movable area. When the vehicle exceeds the movable region, it is decelerated and stopped, so the amount of the deceleration stop distance of the movable body is the overtravel amount. Further, since a process for controlling the current output to the movable body is required as means for decelerating and stopping, there is a problem that the control system becomes complicated and the calculation load increases.

  The present invention has been made in view of such problems, and when moving the movable body according to the speed command value in the speed control mode, it is determined whether or not the moving movable body reaches the movement prohibition region, If it is determined that the movement prohibited area has been reached, the speed command value is changed to a decelerated speed command value to decelerate the movable body, and the amount of overtravel from the boundary of the movement prohibited area is small. It is an object of the present invention to provide a numerical control device and a control method thereof that can be stopped safely without giving a large impact to the system.

  In order to solve the above problem, the present invention is configured as follows.

The invention according to claim 1 is a program analysis unit that analyzes an application program at regular control times and generates a position command in the position control mode and a first speed command in the speed control mode; Position control means for generating a second speed command from the difference from the motor position, and speed control means for generating a torque command from the difference between the speed command and the speed using the sum of the first speed command and the second speed command as a speed command A motor drive means for generating a current command from the torque command and generating a voltage command from the difference between the current command and the current to drive the motor; a current detection means for detecting the current; and a position coupled to the motor A position speed converting means for converting a motor position generated by the detector into a motor speed; and a soft limit setting means for setting a movement prohibition position of the movable body, and driving the motor. Then, in the numerical control apparatus for moving the movable body, a deceleration setting means for setting a predetermined deceleration, and a deceleration stop distance when the command speed of the first speed command is decelerated and stopped at the predetermined deceleration A movement prohibition position intrusion unit that changes the first speed command so as to be equal to a movable distance that is a difference between the movement prohibition position and the current motor position, and generates a third speed command. The sum of the second speed command and the third speed command is used as the speed command.
The invention according to claim 2 is the numerical controller according to claim 1, wherein the deceleration stop distance is a distance when the motor speed is decelerated at the predetermined deceleration and stopped. To do.
According to a third aspect of the present invention, in the numerical control apparatus according to the first aspect, the movement prohibition position impenetrable means has a predetermined speed from the third speed command when the deceleration stop distance is larger than the movable distance. The minute speed is subtracted to obtain a new third speed command.
According to a fourth aspect of the present invention, in the numerical control apparatus according to the first aspect, the motor position is obtained by integrating the speed command.
According to a fifth aspect of the present invention, in the numerical control apparatus according to the first aspect, the motor position is obtained by integrating a motor speed generated by the speed detector.
According to a sixth aspect of the present invention, there is provided program analysis means for analyzing an application program at regular control times and generating a position command in the position control mode, and generating a first speed command in the speed control mode, and the position command Control means for generating a second speed command from the difference between the motor speed and the motor position, and a speed control for generating a torque command from the difference between the speed command and the speed, using the sum of the first speed command and the second speed command as a speed command. A motor driving means for generating a current command from the torque command and generating a voltage command from the difference between the current command and the current to drive the motor; a current detecting means for detecting the current; and a position coupled to the motor A position speed conversion means for converting the motor position generated by the detector into a motor speed, and a soft limit setting means for setting a movement prohibition position of the movable body, In the numerical control method of moving and moving the movable body, before operation, the step of setting the movement prohibition position of the movable body as a soft limit, the step of setting a predetermined deceleration, and at the time of operation, every control time A step of calculating a deceleration stop distance when the command speed of the first speed command is decelerated at the predetermined deceleration and stopped, and a movable distance that is a difference between the movement prohibited position and the current motor position And a step of generating a third speed command by changing the first speed command so that the deceleration stop distance becomes equal to the movable distance, and the second speed command and the third speed command. The sum of the speed command and the speed command is used as the speed command.
A seventh aspect of the present invention is the numerical control method according to the sixth aspect, wherein the deceleration stop distance is a deceleration stop distance when the motor speed is decelerated at the predetermined deceleration and stopped. It is what.
The invention according to claim 8 is the numerical control method according to claim 6, wherein a predetermined minute speed is subtracted from the third speed command to obtain a new third speed command.
A ninth aspect of the present invention is the numerical control method according to the sixth aspect, wherein the motor position is obtained by integrating the speed command.
A tenth aspect of the present invention is the numerical control method according to the sixth aspect, wherein the motor position is obtained by integrating the motor speed generated by the speed detector.

  According to the present invention, in the numerical control device that moves the movable body according to the speed command value given by the user application program, the position of the movable body is estimated from the speed command value, and a predetermined reduction is performed from the estimated position of the movable body. It is determined whether or not it can be stopped at the boundary of the movement prohibited area according to the speed, and when it is determined that it cannot be stopped, the movable body can be stopped near the boundary of the movement prohibited area by decreasing the speed command value. Therefore, the amount of overtravel from the boundary of the movement prohibited area is small, and it can be stopped safely without giving a large impact to the motor or the mechanical system when stopping.

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

  FIG. 1 is a hardware configuration diagram of a motion system according to the present invention. In FIG. 1, 1 is a controller for controlling a connected control device, 2n (n = 1, 2,...) Is a servo for controlling the rotational drive of the connected servo motor in accordance with a command output from the controller 1. Drive, 3n is a servo motor, 4 is a controller and servo drive, a motion network connecting the servo drive and the servo motor, 5 is a CPU that outputs various calculation results, and a fixed cycle generation circuit that outputs a fixed cycle signal at a set cycle And a CPU unit having an interrupt circuit for inputting an interrupt signal to the CPU and inputting an interrupt signal to the CPU, 6 is a user application program 7 described by the user, a soft limit program 8 in which soft limit processing is described, various control parameters, etc. RAM, 9 for each operator An input device for inputting the control parameters and the like. The controller 1 naturally includes a functional block for originally functioning as a controller and a functional block for executing communication processing, but is not shown because it is not directly related to the description of the present invention. In this embodiment, the soft limit position PS and the deceleration DC are set in advance by the operator using the input device 9.

  FIG. 2 is a block diagram showing the functional configuration of the numerical control apparatus of the present invention with a single axis. In FIG. 2, 51 periodically analyzes the application program and generates a position command in the position control mode, and generates a first speed command in the speed control mode. A position control means 52 subtracts the motor position from the position command for each control time to generate a position deviation, and further performs a PID control process on the position deviation to generate a second speed command. 53 is a speed control means, which subtracts the motor speed from the speed command for each control time to generate a speed deviation, and further performs a PID control process on the speed deviation to generate a torque command. The motor drive means 54 converts the torque command into a current command at each control time, then subtracts the current from the current command to generate a current deviation, and then generates a voltage command by PID processing the current deviation. Then, the voltage command is amplified to drive the motor. Reference numeral 55 denotes a current detector that detects a motor current and generates a current signal. Reference numeral 56 denotes a position / velocity conversion means for generating a speed by dividing the position difference before and after the latest control time by the control time. Reference numeral 57 denotes a soft limit setting means for setting the position of the movement prohibition area with a parameter. Normally, it is set inside the movable range of the hard limit switch. 58 is a deceleration setting means for setting a value smaller than the maximum deceleration determined by the maximum torque of the motor or the movable body. 59 is a movement prohibition position impenetrable means, and the set deceleration stop distance when the vehicle is stopped by decelerating from the speed of the first speed command at the set deceleration is the difference between the prohibition position and the current position of the movable prohibition area. The first speed command is changed so as to be smaller than the movable distance, and a third speed command is generated.

  FIG. 3 is a flowchart showing the numerical control method of the numerical control apparatus of the present invention. In step ST1, the movement prohibition area of the movable body is set with a soft limit parameter, and in step ST2, a set deceleration that is smaller than the maximum deceleration determined from the motor maximum torque, the movable body, or the like is set. These are all initial settings or are set by the operator from the programming panel each time. Next, in the flowchart with scheduled interruption for each control time, in step ST3, the set deceleration stop distance when decelerating from the speed of the first speed command with the set deceleration is calculated, and in step ST4, the current position is subtracted from the soft limit position. Calculate the stoppable distance. Next, in step ST5, the set deceleration stop distance is compared with the stoppable distance. If the set deceleration stop distance is large, the process moves to step ST5, and if it is small, the process ends and waits for the next control time. In step ST5, the first speed command is changed to the third speed command and the next control time is awaited.

FIG. 4 shows a case where the motor position is estimated by integrating the speed command and the soft limit process is performed. In FIG. 4, in the software limit program 8 activated by a software interrupt that occurs every dt command cycle, the movable distance of the servo motor 3n and the deceleration stop distance are obtained, the distances are compared, and the software limit position is reached. It is a flowchart which shows the process sequence until it stops at a predetermined deceleration when it judges. FIG. 5 shows a timing chart until it is determined that the moving servo motor 3n reaches the soft limit position in accordance with the speed command value programmed by the user application program 6 and the vehicle is decelerated and stopped. First, the software limit program 8 is activated by a software interrupt, and it is checked in S1001 in FIG. 4 whether or not the soft limit alarm flag is ON. If not, the speed commanded by the user application program 6 in S1002 From the command value V and a predetermined deceleration DC, a deceleration stop distance DL required until the servo motor 3n decelerates to a stop is obtained as follows.

DL = V2 / (2 · DC) (1)
Next, in S1003, when the time of the current command cycle is T _i (i is arbitrary) as shown in FIG. 5A, the position PN (that is, the next time) of the servo motor 3n moving according to the speed command V The position of the command cycle at time T _{i + 1} ) is estimated. Here, assuming that the estimated current position is PC, the estimated next position PN is estimated by integrating the speed command as in the following equation.

PN = PC + V · dt (2)
Since the estimated next position PN is used as the estimated current position PC in S1003 at time T _{i + 1} , the estimated current value PC is updated with the estimated next position PN.

In step S1004, a movable distance AL at which the servo motor 3n at time T _{i + 1} can move to the soft limit position PS is obtained. The movable distance AL is a difference value between a predetermined soft limit position PS and the estimated next position PN obtained in S1002.

AL = PS-PN (3)
Next, in S1005, the deceleration stop distance DL obtained in S1002 and S1004 is compared with the movable distance AL. If the deceleration stop distance DL is larger than the movable distance AL, the soft limit position is set by decelerating and stopping at the deceleration DC. Therefore, when the servo motor 3n is moved at the speed command value V in the current command cycle, it is determined that the soft limit position PS is reached. If it is determined that the soft limit position PS is reached, the speed command value V is decelerated by the deceleration DC as shown in FIG. 5C in S1006, and the speed command value V is updated as in the following equation. .

V = V−DC · dt (4)
The part where the present invention is different from Patent Document 1 is not to stop when the movable body exceeds the soft limit position, but to monitor the estimated position of the movable body in the next command cycle and the movable distance to the soft limit position, If it is determined that if the movable body is moved with the speed command value V of the command cycle this time, it is impossible to stop at the soft limit position with the specified deceleration, the speed command value V is decreased with the specified deceleration. It is a part that is used as means for stopping at the soft limit position by updating with the speed command value.

Next, in S1007, it is determined whether the deceleration stop is completed with the speed command value V of the current command cycle. If the deceleration stop is completed, the soft limit alarm flag is turned OFF, and the deceleration stop is not completed. As shown in FIG. 5B, the software limit alarm flag is turned ON and the software limit program 8 is terminated.
If the soft limit alarm flag is ON, it is determined that deceleration stop has not been completed in the next command cycle S1001, and the speed command value V is updated again in S1006.

  After the end of the soft limit program 8, the speed command value V is transmitted to the lower servo drive 2m. A series of these processing flows is performed every dt command cycle.

  To obtain the current motor position, a speed detector can be coupled to the motor and the motor speed generated by the speed detector can be integrated over time.

FIG. 7 shows a conventional technique, and FIG. 8 shows a simulation of the operation of the present invention. The conditions are as follows: Movable conversion total mass M = 10 kg, motor maximum thrust Fmax = 500 N, set deceleration DCC = 30 m / s ² , motor induced voltage constant Ke = 13.3 Vs / m, speed control proportional gain Kv = 10000 Ns / m , Speed control integration time constant Tvi = 20 ms, thrust filter Tf = 0.2 ms, constant speed command V = 0.5 m / s, soft limit setting Xlim = 0.085 m, acceleration time Tac = 50 ms. In FIG. 7, the vehicle travels at a constant speed command V = 0.5 m / s until the motor position reaches the soft limit position. When the motor limit position is reached, the speed command V = 0 m / s, and the vehicle decelerates at the maximum deceleration. As the current reaches the maximum current, the speed control loop is fully saturated and the speed deviation over the soft limit is accumulated in the speed control integral and then back to the soft limit position for release. Come. In FIG. 8, when the motor speed approaches the soft limit position, the speed command is reduced to a value that can be decelerated and stopped at the soft limit position, so that the soft limit position is not excessively exceeded. (Circled part in FIGS. 7 and 8)

In this way, when it is determined that it is not possible to stop at the soft limit position with a predetermined deceleration after obtaining and comparing the speed command value and the movable distance and deceleration distance from the deceleration to the soft limit position for each command cycle Because the command speed can be reduced according to the deceleration and stopped near the boundary of the soft limit position, the amount of overtravel from the soft limit position is small, and a large impact is given to the motor and mechanical system when stopping. And can be safely stopped.
In addition, a complicated control system such as current control is not required to decelerate and stop, and it can be decelerated and stopped only by simple calculations, so it can be stopped without the addition of hardware such as a current control circuit or an increase in calculation load. Can be made.

  It can be applied to applications such as motion controllers that control motors by speed commands.

Motion system configuration diagram showing an embodiment of the present invention The block diagram which shows the function structure of this invention The flowchart which shows the control method of this invention Soft limit processing flowchart Soft limit processing timing chart of the present invention Conventional software limit processing timing chart Conventional simulation Simulation of the present invention

Explanation of symbols

1 Controller 2n (n = 1, 2,...) Servo drive 3n (n = 1, 2,...) Servo motor 4 Motion network 5 CPU unit 6 RAM
7 User application program 8 Soft limit program 9 Input device 51 Program analysis means 52 Position control means 53 Speed control means 54 Motor drive means 55 Current detection means 56 Position speed conversion means 57 Soft limit setting means 58 Deceleration setting means 59 Movement prohibited position Non-invasive means 73 Position detector 74 Movable body

Claims (10)

Analyzing the application program at regular control times and generating a position command in the position control mode and a first speed command in the speed control mode, and a second speed based on the difference between the position command and the motor position. A position control means for generating a command, a speed control means for generating a torque command from the difference between the speed command and the speed, and a current command from the torque command. A motor driving means for generating a voltage command from the current command and a difference between the current and driving the motor; a current detecting means for detecting the current; and a motor position generated by a position detector coupled to the motor. A position speed converting means for converting to a speed and a soft limit setting means for setting a movement prohibition position of the movable body, and the motor is driven to move the movable body. In that numerical control device,
Deceleration setting means for setting a predetermined deceleration;
The decelerating stop distance when the command speed of the first speed command is decelerated and stopped at the predetermined deceleration is equal to the movable distance that is the difference between the movement prohibited position and the current motor position. A movement prohibition position impenetrable means for changing one speed command and generating a third speed command;
With
A numerical control apparatus characterized in that a sum of the second speed command and the third speed command is used as the speed command.   The numerical control apparatus according to claim 1, wherein the deceleration stop distance is a distance when the motor speed is decelerated at the predetermined deceleration and stopped.   The movement prohibition position impenetrable means subtracts a predetermined minute speed from the third speed command when the deceleration stop distance is greater than the movable distance, thereby obtaining a new third speed command. Item 2. The numerical control device according to Item 1.   The numerical controller according to claim 1, wherein the motor position is obtained by integrating the speed command.   The numerical controller according to claim 1, wherein the motor position is obtained by integrating a motor speed generated by the speed detector. Analyzing the application program every fixed control time and generating a position command in the position control mode, generating a first speed command in the speed control mode, and a second from the difference between the position command and the motor position. Position control means for generating a speed command, speed control means for generating a torque command from the difference between the speed command and the speed, using the sum of the first speed command and the second speed command as a speed command, and a current command from the torque command The motor position is generated by a motor drive means for generating a voltage command from the current command and the difference between the current and driving the motor, a current detection means for detecting the current, and a position detector coupled to the motor. A position speed conversion means for converting to a speed, and a soft limit setting means for setting a movement prohibition position of the movable body, and the movable body is moved by driving the motor. In the numerical control method,
Before operation, setting the movement prohibition position of the movable body as a soft limit;
Setting a predetermined deceleration;
Calculating a deceleration stop distance when the command speed of the first speed command is decelerated at the predetermined deceleration and stopped for each control time during operation;
Calculating a movable distance that is a difference between the movement prohibited position and the current motor position;
Generating a third speed command by changing the first speed command so that the deceleration stop distance becomes equal to the movable distance;
With
A numerical control method characterized in that a sum of the second speed command and the third speed command is used as the speed command.   7. The numerical control method according to claim 6, wherein the deceleration stop distance is a deceleration stop distance when the motor speed is decelerated at the predetermined deceleration and stopped.   The numerical control method according to claim 6, wherein a predetermined minute speed is subtracted from the third speed command to obtain a new third speed command.   The numerical control method according to claim 6, wherein the motor position is obtained by integrating the speed command.   The numerical control method according to claim 6, wherein the motor position is obtained by integrating a motor speed generated by the speed detector.

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