CN117621044A - Control method and robot system - Google Patents

Abstract

The present invention provides a control method and a robot system with high position accuracy. The control method is a control method for determining the control position of the robot relative to the target position, which includes: a real reference position acquisition step to obtain the real reference position in an ideal coordinate system of more than three points; a first control reference position acquisition step to obtain the robot The first control reference position in the first robot control coordinate system when the control points are located at each real reference position; the first conversion function acquisition step is to obtain the first conversion function according to the real reference position and the first control reference position. The conversion function is used to convert the control position in the first robot control coordinate system into the target position in the ideal coordinate system; and the control position determination step uses the first conversion function to convert the control position in the first robot control coordinate system into the ideal coordinate system. The target position in the coordinate system, and determine the new control position based on the target position.

Description

Control method and robot system

Technical field

The invention relates to a control method and a robot system.

Background technique

For example, the robot system described in Patent Document 1 has a structure in which a plurality of work origins are set in a real coordinate system, measurement positions are acquired for each of the plurality of work origins based on images captured by a camera, and each work is measured based on the measurement positions. The position information of the origin is corrected to improve the robot's movement accuracy.

Patent Document 1: Japanese Patent Application Publication No. 2018-134695

Among the methods for determining the control position, in addition to the method of converting the target position in the real coordinate system into the robot control coordinate system to determine the control position as in Patent Document 1, there is also the method of directly specifying the control position on the robot such as direct teaching. Methods that control the coordinate system. Hereinafter, for convenience of explanation, the former method is also referred to as the first determination method, and the latter method is also referred to as the second determination method.

Here, after the control position in the first robot control coordinate system is determined, if the robot control coordinate system changes due to changes in mechanism parameters caused by maintenance, etc., the determined control position must be corrected to be equal to The value corresponding to the new robot control coordinate system. When the control position is determined using the first determination method, a new control position can be determined as long as the target position in the real coordinate system is converted into the second robot control coordinate system.

On the other hand, when the control position is determined using the second determination method, there is no target position in the real coordinate system corresponding to the control position. Therefore, it is impossible to control the second robot using the same method as the first determination method. Coordinate system transformation. Therefore, there is a possibility that the operation accuracy cannot be improved.

Contents of the invention

The control method of the present invention is a control method for determining the control position of the robot relative to the target position, and includes: a real reference position acquisition step to obtain the real reference position in an ideal coordinate system of more than three points; a first control reference position acquisition step, Obtaining the first control reference position in the first robot control coordinate system when the control point of the robot is located at each of the real reference positions; a first conversion function acquisition step, based on the real reference position and the first control reference Position acquisition first conversion function, the first conversion function represents the corresponding relationship between the control position in the first robot control coordinate system and the target position in the ideal coordinate system; and a control position determination step, The control position in the first robot control coordinate system is converted to the target position in the ideal coordinate system using the first conversion function, and the new control position is determined based on the target position.

The robot system of the present invention has a robot and a control device that controls the drive of the robot. The control device determines the control position of the robot relative to a target position. In the robot system, the control device acquires three or more points. the real reference position in the ideal coordinate system; obtain the first control reference position in the first robot control coordinate system when the control point of the robot is located at each of the real reference positions; based on the real reference position and the third A control reference position obtains a first conversion function that represents the corresponding relationship between the control position in the first robot control coordinate system and the target position in the ideal coordinate system; and, using the first conversion function The control position in the first robot control coordinate system is converted into the target position in the ideal coordinate system, and the new control position is determined based on the target position.

Description of drawings

FIG. 1 is a block diagram of a robot system according to a preferred embodiment.

FIG. 2 is a diagram showing how to use the stand.

FIG. 3 is a diagram showing a modification of the stand.

Fig. 4 is a block diagram of the control device.

FIG. 5 is a diagram showing errors in position control of the robot.

FIG. 6 is a flowchart showing a control method.

FIG. 7 is a diagram showing an example of robot operation.

FIG. 8 is a diagram showing a graph for controlling position determination.

FIG. 9 is a diagram showing a graph for controlling position determination.

FIG. 10 is a diagram showing a graph for controlling position determination.

Explanation of reference signs

10 robot system, 2 robot, 21 base, 22 robotic arm, 221 arm, 222 arm, 223 arm, 224 arm, 225 arm, 226 arm, 23 end effector, 3 control device, 31 processor, 310 control position determination Department, 32 memory, 33 interface circuit, 34 input device, 35 display unit, 5 stage, 51 positioning fixture, 53 positioning fixture, 531 base plate, 532 wall part, 54 positioning auxiliary tool, CD control position correction data, CP1 first control Reference position, CP11 first control reference position, CP12 first control reference position, CP13 first control reference position, CP14 first control reference position, CP2 second control reference position, CP21 second control reference position, CP22 second control reference position Position, CP23 second control reference position, CP24 second control reference position, G graphic, G1 graphic, G2 graphic, J1 joint, J2 joint, J3 joint, J4 joint, J5 joint, J6 joint, MP action program, RP real datum Position, RP1 real reference position, RP2 real reference position, RP3 real reference position, RP4 real reference position, S1 real reference position acquisition step, S2 first control reference position acquisition step, S3 first conversion function acquisition step, S4 target position, etc. Acquisition step, S5 first control position determination step, S6 robot control coordinate system confirmation step, S7 second control reference position acquisition step, S8 second conversion function acquisition step, S9 second control position determination step, S10 robot control step, TCP control points.

Detailed ways

Hereinafter, the control method and robot system of the present invention will be described in detail based on the embodiments shown in the drawings.

FIG. 1 is a block diagram of a robot system according to a preferred embodiment. FIG. 2 is a diagram showing how to use the stand. FIG. 3 is a diagram showing a modification of the stand. Fig. 4 is a block diagram of the control device. FIG. 5 is a diagram showing errors in position control of the robot. FIG. 6 is a flowchart showing a control method. FIG. 7 is a diagram showing an example of robot operation. 8 to 10 are diagrams respectively showing graphs for controlling position determination.

The robot system 1 shown in FIG. 1 includes a robot 2, a control device 3 for controlling the drive of the robot 2, and a gantry 5. In addition, FIG. 1 illustrates the three axes of the orthogonal coordinate system defining the three-dimensional space, that is, the X-axis, the Y-axis, and the Z-axis. The X-axis and Y-axis are horizontal axes, and the Z-axis is a vertical axis. Hereinafter, this three-dimensional space (real space) is also called an "ideal coordinate system."

As shown in Figure 1, Robot 2 is a six-axis vertical multi-jointed robot with six drive axes. The robot 2 has a base 21 , a robot arm 22 rotatably connected to the base 21 , and an end effector 23 attached to the front end of the robot arm 22 . In addition, the robot arm 22 is a robot arm in which a plurality of arms 221, 222, 223, 224, 225, and 226 are rotatably connected, and has six joints J1, J2, J3, J4, J5, and J6. Among these six joints J1 to J6, joints J2, J3, and J5 are bending joints respectively, and joints J1, J4, and J6 are torsion joints respectively.

Motors and encoders (not shown) are respectively provided at joints J1, J2, J3, J4, J5, and J6. While the robot system 1 is operating, the control device 3 executes servo control (feedback control) for each of the joints J1 to J6 so that the rotation angle of the joint indicated by the output of the encoder coincides with the control position. This allows the robot 2 to assume a desired posture.

The end effector 23 can be appropriately selected depending on the work to be performed by the robot 2 . In addition, the control point TCP of the robot 2 is set at the front end of the end effector 23 . The position of the control point TCP can be set arbitrarily. However, in order to determine the position of the control point TCP using the positioning jig 51 described below, it is preferable to set the control point TCP at the front end of the end effector 23 as in this embodiment.

The robot 2 has been described above, but the structure of the robot 2 is not particularly limited. For example, it may be a SCARA robot (horizontal multi-jointed robot), a dual-arm robot including two of the above-mentioned robotic arms 22, or the like. Alternatively, the robot may be a self-propelled robot in which the base 21 is not fixed.

The gantry 5 is used when acquiring the first conversion function and the second conversion function for reducing the position deviation of the robot 2 and is not used during the robot operation.

The position deviation of the robot 2 will be briefly explained. In the robot system 1 , the control device 3 controls the driving of the robot 2 based on a target position received from a host computer or the like (not shown). Specifically, the control device 3 calculates the position of the control point TCP based on design mechanism parameters such as the length of each arm 221 to 226, the origin of the rotation axis of each joint J1 to J6, and the parallelism and orthogonality of each joint J1 to J6. , and control the driving of robot 2 so that the control point TCP is consistent with the target position.

However, sometimes the actual mechanism parameters deviate from the designed mechanism parameters due to component deviations, assembly deviations, etc. In this way, when the actual mechanism parameters deviate, the calculated position of the control point TCP deviates from the actual position of the control point TCP. Therefore, even if the control point TCP is controlled to be consistent with the target position, the actual control point TCP will not deviation from the target position. It should be noted that this deviation is also referred to as “position control error” below.

Therefore, the robot system 1 is configured to obtain a conversion function that expresses the correspondence between the ideal coordinate system and the robot control coordinate system and is used to reduce errors in position control. Platform 5 is a prop used to obtain this conversion function. As shown in FIG. 1 , the stand 5 has four positioning clamps 51 . Each positioning jig 51 is a jig used when positioning the control point TCP. It should be noted that the number of positioning jigs 51 is not particularly limited as long as it is three or more.

In addition, a real reference position RP is set at the front end of the positioning jig 51 . It should be noted that the three-dimensional positional relationship between the real reference positions RP of each positioning jig 51 in the ideal coordinate system is measured in advance. Furthermore, as shown in FIG. 2 , by bringing the control point TCP of the robot 2 into contact with the real reference position RP, the control position in the robot control coordinate system at that time can be obtained as the control reference position corresponding to the real reference position RP.

It should be noted that the positioning jig is not particularly limited. For example, a positioning jig 53 as shown in FIG. 3 may also be used. The positioning jig 53 has a flat base plate 531 and an L-shaped wall portion 532 provided on the base plate 531 . The wall portion 532 is curved at a right angle, and a true reference position RP is set at a point where the curved portion of the wall portion 532 contacts the surface of the substrate 531 . On the other hand, a positioning auxiliary tool 54 is connected to the front end of the robot arm 22 . This positioning aid 54 has a rectangular parallelepiped shape, and a control point TCP is set at the vertex of its bottom surface.

By bringing the control point TCP into contact with the real reference position RP of the positioning jig 53, the control position of the robot control coordinate system at this time can be acquired as the control reference position corresponding to the real reference position RP. In addition, since the posture of the control point TCP of the robot 2 is uniquely determined even when the positioning jig 53 and the positioning auxiliary tool 54 are in contact with each other on three surfaces, the control posture of the robot control coordinate system at this time can be obtained as The control reference posture corresponding to the real posture at the real reference position RP.

It should be noted that instead of using the positioning fixtures 51 and 53 as described above, a three-dimensional measuring device may be used to obtain the real reference position and the control reference position of the robot control coordinate system. In this case, first, the control point TCP of the robot 2 is positioned using the control reference position of the robot control coordinate system. In this state, the three-dimensional position of the control point TCP in the ideal coordinate system is measured using a three-dimensional position measuring device. Set to the true reference position RP.

The control device 3 controls the driving of the robot 2 . As shown in FIG. 4 , the control device 3 is composed of, for example, a computer, and has a processor 31 , a memory 32 , an interface circuit 33 , an input device 34 connected to the interface circuit 33 , and a display unit 35 .

The processor 31 functions as a control position determination unit 310 that determines the control position of the robot 2 . The function of the control position determination unit 310 is realized by the processor 31 executing a computer program stored in the memory 32 . However, a part or all of the functions of the control position determination unit 310 may be implemented using hardware circuits.

The memory 32 stores the control position correction data CD and the operation program MP. In addition, the control position correction data CD includes a graph G, which will be described later, and first and second conversion functions A11, A12, and A2. In addition, the operation program MP is composed of a plurality of operation instructions for causing the robot 2 to operate.

Next, errors in position control of the robot 2 will be described based on FIG. 5 . The left side of FIG. 5 shows the control position in the robot control coordinate system, and the right side shows the position control error in the ideal coordinate system. The “robot control coordinate system” refers to a coordinate system expressing the position and posture of the robot 2 used in motion commands for controlling the robot 2 .

In the example shown in FIG. 5 , it is assumed that the control positions are set at intervals of 30 mm in the X direction and Y direction in the robot control coordinate system. The arrows drawn in the ideal coordinate system show errors in position control. That is, the starting point of the arrow is the target position, and the front side of the arrow is the control point TCP including the error. However, for ease of illustration, the length of the arrow is drawn with the error amount magnified 200 times.

In order to reduce errors in such position control, conventionally, a method has been used in which the target position in the ideal coordinate system is converted into a control position in the robot control coordinate system using a conversion coefficient or the like, and the robot 2 is controlled based on the control position. drive.

However, in such a method, problems described below arise. As mentioned above, since the actual mechanism parameters such as the length of each arm 221 to 226, the origin of the rotation axis of each joint J1 to J6, the parallelism and orthogonality of each joint J1 to J6 deviate from the designed mechanism parameters, the There is a deviation between the robot control coordinate system and the ideal coordinate system. In addition, when the joints J1 to J6 and the arms 221 to 226 are replaced, when the installation location of the robot 2 is changed, or when the end effector 23 is changed, the mechanism parameters may change due to ambient temperature or the like. In this way, when the mechanism parameters change, the robot control coordinate system also changes. Hereinafter, for convenience of explanation, the robot control coordinate system before the change is also called the first robot control coordinate system, and the robot control coordinate system after the change is also called the second robot control coordinate system.

Here, among the methods for determining the control position in the robot control coordinate system, in addition to the method of converting the target position in the ideal coordinate system into the control position in the robot control coordinate system, there is also the method of directly teaching in the robot control A method to directly set the control position in the coordinate system. It should be noted that, below, for convenience of explanation, the former method is also referred to as the first determination method, and the latter method is also referred to as the second determination method.

After the control position in the first robot control coordinate system is determined in this way, when the robot control coordinate system changes from the first robot control coordinate system to the second robot control coordinate system due to the above-mentioned various factors, if based on If the driving of the robot 2 is controlled with the original control position, that is, the control position in the first robot control coordinate system, position control errors will occur. Therefore, the control position in the first robot control coordinate system must be corrected to the control position in the second robot control coordinate system.

When the control position is determined using the first determination method, the control position has a target position in the ideal coordinate system. Therefore, if the target position is converted into a control position in the second robot control coordinate system, the third robot control position can be determined. The new control position in the second robot control coordinate system. On the other hand, when the control position is determined using the second determination method, the control position does not have a target position in the ideal coordinate system. Therefore, the control coordinates for the second robot cannot be determined using the same method as the first determination method. system conversion. Therefore, the robot system 1 is configured to determine a new control position in the second robot control coordinate system using the same method as the first determination method even when the control position is determined using the second determination method. As a result, position control errors can be effectively reduced. Hereinafter, a method of controlling the robot 2 by the control device 3 will be described.

As shown in Figure 6, the control method of the robot 2 includes the step of obtaining the real reference position S1, the step of obtaining the first control reference position S2, the step of obtaining the first conversion function S3, the step of obtaining the target position, etc. S4, and the step of determining the first control position S5. , robot control coordinate system confirmation step S6, second control reference position acquisition step S7, second conversion function acquisition step S8, second control position determination step S9, and robot control step S10. Hereinafter, these steps S1 to S10 will be described in sequence.

Real reference position acquisition step S1

In the real reference position acquisition step S1, the control position determination unit 310 acquires the real reference position RP in the ideal coordinate system at three or more points. As mentioned above, in this embodiment, the stand 5 has four positioning fixtures 51, and the real reference position RP is set at the front end. Therefore, in the present embodiment, as shown in FIG. 7 , the control position determination unit 310 acquires four real reference positions RP1, RP2, RP3, and RP4.

First control reference position acquisition step S2

In the first control reference position acquisition step S2, the control position determination unit 310 acquires the first control reference position CP1 in the first robot control coordinate system when the control point TCP is located at the real reference position RP. Specifically, first, the control position determination unit 310 positions the control point TCP at the true reference position RP1. Next, the control position determination unit 310 acquires the position of the control point TCP in the first robot control coordinate system when the control point TCP is located at the real reference position RP1, that is, the first control reference position CP11. The control position determination unit 310 also performs the same operation for the other real reference positions RP2, RP3, and RP4, and acquires the first control reference positions CP12, CP13, and CP14. Through the above operations, the control position determination unit 310 acquires four first control reference positions CP11, CP12, CP13, and CP14.

First conversion function acquisition step S3

In the first conversion function acquisition step S3, first, as shown in FIG. 8, the control position determination unit 310 sets a triangular figure G with three real reference positions RP as vertices in an ideal coordinate system. It should be noted that, as mentioned above, four real reference positions RP1 to RP4 are obtained in the real reference position acquisition step S1. Therefore, in this embodiment, the area surrounded by the four real reference positions RP1 to RP4 is divided. are two triangle figures G1 and G2. As the decomposition method, for example, any decomposition method such as Delaoni triangle decomposition can be used.

Next, as shown in FIG. 9 , the control position determination unit 310 obtains a first conversion function indicating the correspondence between the target position and the control position in each of the graphics G1 and G2. It should be noted that the control position determination unit 310 obtains the first conversion function A11 and the first conversion function A12 as the first conversion function. The first conversion function A11 converts the target position in the ideal coordinate system into the robot control coordinate system. A function of the control position. The first conversion function A12 is a function that converts the control position in the robot control coordinate system into the target position in the ideal coordinate system. The first conversion function A12 is the inverse conversion function of the first conversion function A11.

The first conversion function A11 in the graph G1 is obtained based on the difference between the vertices of the graph G1, that is, the real reference positions RP1, RP2, RP3 and their corresponding first control reference positions CP11, CP12, CP13. In addition, the first conversion function A11 in the graph G2 is obtained based on the difference between the vertices of the graph G2, that is, the real reference positions RP2, RP3, and RP4, and their corresponding first control reference positions CP12, CP13, and CP14. In addition, the first conversion function A12 can be obtained from the obtained first conversion function A11. The first conversion functions A11 and A12 can each be expressed by the following equations.

Pctrl=A11·Preal……(1)

Preal＝A12·Pctrl……(5)

Pctrl in the formula is the control position in the first robot control coordinate system, and Preal is the target position in the ideal coordinate system. In addition, Xctrl is the X coordinate of the control position in the first robot control coordinate system, and Yctrl is the Y coordinate of the control position in the first robot control coordinate system. In addition, Xreal is the X coordinate of the target position in the ideal coordinate system, and Yreal is the Y coordinate of the target position in the ideal coordinate system. In addition, A11 and A12 are the first conversion functions and are conversion expressions representing affine conversion. In addition, a11, a12, a21, a22, b1, and b2 are coefficients respectively, which are different according to the first conversion functions A11 and A12 and the graphics G1 and G2. By using such first conversion function A11, the target position Preal can be converted into the control position Pctrl easily and with high accuracy. In addition, by using the first conversion function A12, the control position Pctrl can be converted into the target position Preal easily and with high accuracy.

The conversion using such first conversion functions A11 and A12 is a coordinate conversion operation based on a method other than parallel movement and rotational movement.

It should be noted that the shape of the graph G does not need to be a triangle, and the first transformation function does not need to be an affine transformation. For example, the graph G may be a quadrilateral, and the first transformation function may be projection transformation. Alternatively, the polygons may be divided into a state in which a plurality of polygons are mixed, and the first conversion function may be changed for each graph G. In addition, the graphic G may be a three-dimensional graphic. The first conversion function may be configured as a conversion formula, or may be configured in another form such as a lookup table.

Target position, etc. acquisition step S4

In the target position and the like acquisition step S4, the control position determination unit 310 receives an input of the target position or the control position of the control point TCP. The target position can be input as a position in the ideal coordinate system by the operator using the input device 34, for example. In addition, the control position can be directly input by the operator as a position in the robot control coordinate system, for example, through direct teaching or the like. It should be noted that when the operator creates the operation program MP and describes the target position and the control position of the control point TCP in the operation instructions, the control position determination unit 310 may also acquire the operation instructions included in the operation program MP. Target position and control position to perform this step.

It should be noted that below, the following situation is taken as an example: as shown in Table 1 below, target positions Q1, Q2 and control position P3 are received, and the order of target position Q1, target position Q2, and control position P3 is The robot motion of one revolution is set as one cycle, and the cycle is repeated a specified number of times.

Table 1

First control position determination step S5

In the first control position determination step S5, the control position determination unit 310 performs the following processing on the target positions Q1 and Q2. The control position determination unit 310 first selects an object graphic including the target position Q1 from the graphics G1 and G2. Next, the control position determination unit 310 calculates the control position in the first robot control coordinate system relative to the target position Q1 using the first conversion function A11 corresponding to the selected object figure. If the target position Q1 is located within the graph G1, then the first conversion function A11 corresponding to the graph G1 is used to calculate the control position in the first robot control coordinate system relative to the target position Q1. In addition, if the target position Q1 is located within the graph G2, the control position in the first robot control coordinate system relative to the target position Q1 is calculated using the first conversion function A11 corresponding to the graph G2. In this case, for example, by using the above-mentioned equation (1) and inputting the coordinate value of the target position Q1 into Preal, Pctrl can be calculated as the control position relative to the target position Q1.

Similarly, the control position determination unit 310 first selects an object graphic including the target position Q2 from the graphics G1 and G2. Next, the control position determination unit 310 calculates the control position in the first robot control coordinate system relative to the target position Q2 using the first conversion function A11 corresponding to the selected object figure. If the target position Q2 is located within the graph G1, the first conversion function A11 corresponding to the graph G1 is used to calculate the control position in the first robot control coordinate system relative to the target position Q2. In addition, if the target position Q2 is located within the graph G2, the first conversion function A11 corresponding to the graph G2 is used to calculate the control position in the first robot control coordinate system relative to the target position Q2. In this case, for example, by using the above-mentioned equation (1) and inputting the coordinate value of the target position Q2 into Preal, Pctrl can be calculated as the control position relative to the target position Q2.

Through the above content, as shown in Table 2 below, the control positions P1 and P2 in the first robot control coordinate system of the target positions Q1 and Q2 are obtained.

Table 2

Next, the control position determination unit 310 uses the control positions P1 and P2 in the first robot control coordinate system of the target positions Q1 and Q2 calculated by the above method and the target position to obtain the control position P3 obtained in step S4 to create an action command. . It should be noted that when the motion program MP including the motion command is created in advance, this process can be executed by replacing the target position included in the motion command with the control position determined as described above.

Robot control coordinate system confirmation step S6

In the robot control coordinate system confirmation step S6, the control position determination unit 310 confirms whether the robot control coordinate system is still the first robot control coordinate system. When it is still the first robot control coordinate system, the control position determination unit 310 shifts to the robot control step S10. In contrast, when the robot control coordinate system changes from the first robot control coordinate system to the second robot control coordinate system, the control position determination unit 310 shifts to the second control reference position acquisition step S7.

Second control reference position acquisition step S7

In the second control reference position acquisition step S7, the control position determination unit 310 acquires the second control reference position CP2 in the second robot control coordinate system when the control point TCP is located at the real reference position RP. Specifically, first, the control position determination unit 310 positions the control point TCP at the true reference position RP1. Next, as shown in FIG. 10 , the control position determination unit 310 acquires the position of the control point TCP in the second robot control coordinate system when the control point TCP is located at the real reference position RP1, that is, the second control reference position CP21. The control position determination unit 310 also performs the same operation for the other real reference positions RP2, RP3, and RP4, and acquires the second control reference positions CP22, CP23, and CP24. Through the above operations, the control position determination unit 310 acquires four second control reference positions CP21, CP22, CP23, and CP24.

Second conversion function acquisition step S8

In the second conversion function acquisition step S8, as shown in FIG. 10, the control position determination unit 310 obtains the second conversion function A2 indicating the correspondence between the target position and the control position in each of the graphics G1 and G2. The second conversion function A2 in the graph G1 is obtained based on the difference between the vertices of the graph G1, that is, the real reference positions RP1, RP2, RP3 and their corresponding second control reference positions CP21, CP22, CP23. In addition, the second conversion function A2 in the graph G2 is obtained based on the difference between the vertices of the graph G2, that is, the real reference positions RP2, RP3, and RP4, and their corresponding second control reference positions CP22, CP23, and CP24. The second conversion function A2 can be expressed by the following equation.

Pctrl=A2·Preal……(9)

Pctrl in the formula is the control position in the second robot control coordinate system, and Preal is the target position in the ideal coordinate system. In addition, Xctrl is the X coordinate of the control position in the second robot control coordinate system, and Yctrl is the Y coordinate of the control position in the second robot control coordinate system. In addition, Xreal is the X coordinate of the target position in the ideal coordinate system, and Yreal is the Y coordinate of the target position in the ideal coordinate system. In addition, A2 is the second conversion function, and is a conversion expression expressing affine conversion. In addition, a11, a12, a21, a22, b1, and b2 are coefficients respectively, which are different according to the graphs G1 and G2. It should be noted that these coefficients may also be different from the coefficients used in the first conversion function A11. By using such second conversion function A2, the target position Preal can be converted into the control position Pctrl easily and with high accuracy.

Second control position determination step S9

In the second control position determination step S9, the control position in the second robot control coordinate system relative to the target positions Q1, Q2 and the control position P3 received in the target position acquisition step S4 is determined.

The control position determination unit 310 performs the following processing on the target positions Q1 and Q2. Similar to the first control position determination step S5 described above, the control position determination unit 310 calculates the control position P10 in the second robot control coordinate system relative to the target position Q1 using the second conversion function A2 corresponding to the graph G1. Similarly, the control position P20 in the second robot control coordinate system relative to the target position Q2 is calculated using the second conversion function A2 corresponding to the graph G2. The results are shown in Table 3 below.

table 3

In addition, the control position determination unit 310 performs the following processing on the control position P3. As mentioned above, the control position P3 is directly set in the first robot control coordinate system, and therefore does not have a target position in an ideal coordinate system. Therefore, the control position determination unit 310 first obtains the target position Q3 in the ideal coordinate system of the control position P3 using the first conversion function A12. In this case, for example, by using the above equation (5) and inputting the coordinate value of the control position P3 to Pctrl, Preal can be calculated as the target position Q3 in the ideal coordinate system.

Next, the control position specifying unit 310 selects an object graphic including the target position Q3 from the graphics G1 and G2. Next, the control position determination unit 310 calculates the control position P30 in the second robot control coordinate system relative to the target position Q3 using the second conversion function A2 corresponding to the selected object figure. In this case, by using the above equation (9) and inputting the coordinate value of the target position Q3 into Preal, Pctrl can be calculated as the control position P30. Thereby, the control position P30 in the second robot control coordinate system can be calculated with high accuracy. The results are shown in Table 4 below.

Table 4

Next, the control position determination unit 310 creates an action command using the control positions P10, P20, and P30 in the second robot control coordinate system calculated by the above method. It should be noted that when the motion program MP including the motion command is created in advance, this process can be executed by replacing the target position and the control position included in the motion command with the control position determined as described above. As described above, the target positions Q1 and Q2 and the control position P3 are replaced with new control positions P10, P20 and P30 in the second robot control coordinate system.

It should be noted that, in addition to the situation where the control position P3 in the first robot control coordinate system is directly converted to the new control position P30 in the second robot control coordinate system as described above, it is also envisaged that the control position P3 in the first robot control coordinate system is converted from the control position P3 in the second robot control coordinate system. A case where the control position P3 is relatively moved and converted to a new control position P30 in the second robot control coordinate system. Examples of the relative movement here include parallel movement in the X-axis direction and the Y-axis direction, rotational movement around the Z-axis, and the like. In this case, the control position determination unit 310 first obtains the target position Q3 in the ideal coordinate system of the control position P3 using the first conversion function A12. Next, the relative movement amount is added to the target position Q3 to obtain the target position Q3'. Here, the relative movement amount refers to the movement amount from a predetermined position, and adding the relative movement amount to the target position Q3 to obtain the target position Q3' means adding the movement to the coordinates (x3, y3, z3) of the target position Q3. Calculate the coordinates of the target position Q3' by measuring. Moreover, after that, the target position Q3' is converted into the control position P30 in the second robot control coordinate system using the second conversion function A2. In this way, by adding the relative movement amount instead of the control position P3 to the target position Q3, the control position P30 in the second robot control coordinate system can be calculated with high accuracy.

Robot control step S10

In the robot control step S10 , the control position determination unit 310 controls the driving of the robot 2 using the created latest motion program MP including the motion command. When one cycle of robot movement ends, the control position determination unit 310 determines whether the robot movement has reached a predetermined number of times. If it has been reached, the driving of the robot 2 will be stopped. If it has not been reached, it will return to the robot control coordinate system confirmation step S6. It should be noted that every time the robot control coordinate system confirmation step S6 is returned, the current robot control coordinate system becomes the first robot control coordinate system, and the changed robot control coordinates become the second robot control coordinate system.

According to the control method as described above, the target position Q3 in the ideal coordinate system is calculated for the control position P3 directly set in the first robot control coordinate system. Therefore, for the control position P3, the control position in the new robot control coordinate system can also be determined using the same method as the target positions Q1 and Q2. Therefore, the robot system 1 can effectively reduce errors in position accuracy using a simple method and can exhibit excellent operation accuracy.

In addition, when the control position P3 in the first robot control coordinate system is not converted to a new control position P30 in the second robot control coordinate system but is relatively moved, it is also preferable to convert the control position P3 in the ideal coordinate system to a new control position P30 in the second robot control coordinate system. The target position O3 plus the relative movement amount. This is to prevent that if the relative movement amount is added to the first robot control coordinate system, it will be different from the amount in the ideal coordinate system, so that the desired relative movement amount cannot be obtained. Specifically, the first conversion function A12 is used to find the target position Q3 in the ideal coordinate system of the control position P3. Next, the relative movement amount is added to the target position Q3 to obtain the target position Q3'. Moreover, after that, the first conversion function A11 is used to convert the target position Q3' into the control position P3' in the first robot control coordinate system. In this way, by adding the relative movement amount to the target position Q3 instead of the control position P3, the relative movement amount can be added with high accuracy.

The robot system 1 has been described above. As mentioned above, the control method of such a robot system 1 is to determine the control position of the robot 2 relative to the target position, including: the real reference position acquisition step S1, obtaining the real reference in the ideal coordinate system at more than three points position RP; the first control reference position acquisition step S2, obtains the first control reference position CP1 in the first robot control coordinate system when the control point TCP of the robot 2 is located at each real reference position RP; the first conversion function acquisition step S3, The first conversion function A12 is obtained based on the real reference position RP and the first control reference position CP1. The first conversion function A12 represents the corresponding relationship between the control position in the first robot control coordinate system and the target position in the ideal coordinate system; and as The second control position determination step S9 of the control position determination step uses the first conversion function A12 to convert the control position P3 in the first robot control coordinate system into the target position Q3 in the ideal coordinate system, and determines a new position based on the target position Q3. Control position P30. According to this control method, the control position P3 directly set in the first robot control coordinate system can also be determined in the new robot control coordinate system using the same method as the target positions Q1 and Q2 set in the ideal coordinate system. Control position P30. Therefore, the robot system 1 can effectively reduce errors in position accuracy using a simple method and can exhibit excellent operation accuracy.

In addition, as mentioned above, the control position P3 in the first robot control coordinate system is directly set in the first robot control coordinate system. In this way, for the control position P3 that does not have a target position in the ideal coordinate system, the control position P30 in the new robot control coordinate system can be determined using the same method as the target positions Q1 and Q2. Therefore, the calculation of the control position becomes easy.

In addition, as mentioned above, when the robot control coordinate system for setting the control position is changed from the first robot control coordinate system to the second robot control coordinate system, the second control reference position is included before the second control position determination step S9 Obtaining step S7, obtaining the second control reference position CP2 in the second robot control coordinate system when the control point TCP is located at the real reference position RP; and second conversion function obtaining step S8, based on the real reference position RP and the second control reference position CP2 obtains the second conversion function A2 that converts the target position in the ideal coordinate system to the control position in the second robot control coordinate system. In the second control position determination step S9, the first robot is converted to the target position using the first conversion function A12. After the control position P3 in the control coordinate system is converted to the target position Q3 in the ideal coordinate system, the second conversion function A2 is used to convert it into a new control position P30 in the second robot control coordinate system. Thereby, the control position P30 in the second robot control coordinate system can be calculated with high accuracy.

In addition, as mentioned above, in the first control position determination step S5 or the second control position determination step S9, the first conversion function A12 is used to convert the control position P3 in the first robot control coordinate system into the ideal coordinate system. Target position Q3, and add the relative movement amount to the target position Q3, and then use the first conversion function A11 to convert to the control position P3' in the first robot control coordinate system or use the second conversion function A2 to convert to the second robot control The new control position P30 in the coordinate system. This makes it possible to add the relative movement amount with high accuracy.

In addition, as mentioned above, in the first conversion function acquisition step S3, at least one graph G with three or more real reference positions RP as vertices is set in the ideal coordinate system, and the target position within the graph G is obtained. The first conversion functions A11 and A12 corresponding to the control position. As a result, the control position in the first robot control coordinate system can be calculated with high accuracy.

In addition, as mentioned above, the robot system 1 includes the robot 2 and the control device 3 that controls the driving of the robot 2. The control device 3 determines the control position of the robot 2 relative to the target position. In this robot system 1, the control device 3 obtains The real reference position RP in the ideal coordinate system, obtains the first control reference position CP1 in the first robot control coordinate system when the control point TCP of the robot 2 is located at the real reference position RP, based on the real reference position RP and the first control reference position CP1 obtains the first conversion function A12 that represents the correspondence between the control position in the first robot control coordinate system and the target position in the ideal coordinate system, and uses the first conversion function A12 to convert the control position P3 in the first robot control coordinate system. is the target position Q3 in the ideal coordinate system, and the new control position P30 is determined based on the target position Q3. According to this configuration, the control position P3 directly set in the first robot control coordinate system can be determined in the new robot control coordinate system using the same method as the target positions Q1 and Q2 set in the ideal coordinate system. Control position P30. Therefore, the robot system 1 can effectively reduce errors in position accuracy using a simple method and can exhibit excellent operation accuracy.

As mentioned above, the control method and the robot system of the present invention have been described based on the illustrated embodiments. However, the present invention is not limited thereto. The configuration of each part can be replaced with any configuration having the same function. In addition, other arbitrary structures may be added to the present invention.

Claims (6)

1. A control method characterized by determining a control position of a robot with respect to a target position, the control method comprising:

a real reference position obtaining step of obtaining real reference positions in an ideal coordinate system of three or more points;

a first control reference position obtaining step of obtaining a first control reference position in a first robot control coordinate system when a control point of the robot is located at each of the real reference positions;

a first conversion function obtaining step of obtaining a first conversion function based on the real reference position and the first control reference position, the first conversion function representing a correspondence between the control position in the first robot control coordinate system and the target position in the ideal coordinate system; and

a control position determining step of converting the control position in the first robot control coordinate system into the target position in the ideal coordinate system using the first conversion function, and determining a new control position based on the target position.

2. The control method according to claim 1, wherein,

the control position in the first robot control coordinate system is set directly in the first robot control coordinate system.

3. The control method according to claim 1, wherein,

when the robot control coordinate system for setting the control position is changed from the first robot control coordinate system to the second robot control coordinate system,

the control method includes, before the control position determining step:

a second control reference position acquisition step of acquiring a second control reference position in the second robot control coordinate system when the control point is located at the real reference position; and

a second conversion function obtaining step of obtaining a second conversion function based on the real reference position and the second control reference position, the second conversion function converting the target position in the ideal coordinate system to the control position in the second robot control coordinate system,

in the control position determining step, after converting the control position in the first robot control coordinate system to the target position in the ideal coordinate system using the first conversion function, the control position is converted to a new control position in the second robot control coordinate system using the second conversion function.

4. The control method according to claim 1, wherein,

in the control position determining step, a relative movement amount, which is a movement amount from a prescribed position, is added to the target position converted in the control position determining step, thereby determining a new control position.

5. The control method according to claim 1, wherein,

in the first conversion function obtaining step, at least one pattern having three or more of the real reference positions as vertices is set in the ideal coordinate system, and the first conversion function indicating the correspondence between the target position and the control position in the pattern is obtained.

6. A robot system comprising a robot and a control device for controlling driving of the robot, wherein the control device determines a control position of the robot with respect to a target position,

the control device

Acquiring real reference positions in an ideal coordinate system with more than three points;

acquiring a first control reference position in a first robot control coordinate system when the control point of the robot is positioned at each real reference position;

acquiring a first conversion function representing a correspondence relationship between the control position in the first robot control coordinate system and the target position in the ideal coordinate system based on the real reference position and the first control reference position; and, in addition, the processing unit,

the control position in the first robot control coordinate system is converted to the target position in the ideal coordinate system using the first conversion function, and a new control position is determined based on the target position.