JPH05265563A - Controller for robot - Google Patents

Abstract

PURPOSE:To improve the locus accuracy of the final working point of a robot by using a positioning controller provided with a realizable gain. CONSTITUTION:A command generator 1 calculates the rotating quantity of a motor 7 so that the final working point of the robot can plot a desired locus. A correction value calculator 10 calculates the correction value of the amount of travel by which the actual operation of the robot is delayed to a command value. A coefficient selector 11 selects an appropriate coefficient corresponding to the operating direction of a robot arm. The positioning controller 12 inputs two inputs the correction value from the correction value calculator 10 and the command value from the command value generator 1, and outputs the sum of the result that the output of a deviation quantity calculator 3 is multiplied by a gain Gp and the correction value, as a velocity command to a velocity controller, 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for industrial robots such as welding and cutting, which is applicable to applications requiring high trajectory accuracy.

[0002]

2. Description of the Related Art Conventionally, in order to improve the trajectory accuracy of a robot, modern control theory is used to increase the gain Gp of the position control device to increase the amount of rotation of the motor by the output of the command generator and the actual motor. I was using a method to bring the rotation amount of the.

FIG. 6 shows a block diagram of a main part of a conventional structure. The output of the command generator 1 is input to the conventional position controller 2. This input is connected to the deviation amount calculation device 3 of the position control device 2, and the deviation amount calculation device 3 obtains the difference between the integrated value of the output of the command generation device 1 and the integrated value of the output of the position detection device 8. The conventional position control device 2 gives a value obtained by multiplying this value by the gain Gp to the speed control device 4 as an output. The speed controller 4 outputs the current controller 5 to the current controller 5.
Generates a PWM output from the output of the current detection device 9 and the current command value of the speed control device 4, and controls the servo amplifier 6. The motor 7 for each axis of the robot rotates according to the output of the servo amplifier 6, and the rotation amount is detected by the position detection device 8 and input to the position control device 2 and the speed control device 4, respectively.

[0004]

In order to increase the gain Gp of the position control device 2, it is necessary to increase the gains of the speed control device 4 and the current control device 5. For that purpose, modern control theory calculations are required. At the same time, it is necessary to speed up the sampling period of speed and current, increase the resolution of the position detection device 8 and the current detection device 9, reduce the dead time, and increase the PWM carrier frequency. In addition, at the same time as increasing the calculation speed of the CPU that performs processing, it is necessary to increase the responsiveness of peripheral power elements. Therefore, there is a problem that a configuration for obtaining a desired gain is impossible, or even if possible, it is expensive.

The present invention solves the above problems, and provides a robot controller capable of improving the trajectory accuracy of the final action point of the robot by using a position controller having a realizable gain. It is intended.

[0006]

In order to achieve the above object, the present invention is a controller for a robot that stores teaching contents and operates the robot according to the teaching contents. A command generator that calculates the amount of rotation of each axis motor of the robot per fixed time so that the point draws a desired trajectory at a desired speed, and it is attached to the motor of each axis of the robot and detects the amount of rotation of the motor Position detection device, a deviation amount calculation device that calculates the difference between the integrated value of the output from the command generation device and the integrated value of the output from the position detection device, and the output of the command generation device in the past The output of the command generator to be output is multiplied by a coefficient Kmng depending on how many times before the output or how many times before the output, and the integrated value and the current output of the command generator. And a value multiplied by a coefficient Kmng accordingly, and a value obtained by multiplying this total value by a gain Gm is calculated as a correction value of the movement amount for the delay of the actual robot operation with respect to the command value. And a device.

Further, according to the present invention, the correction value calculating device calculates the correction value by discriminating whether the arm of the robot operates in a direction against gravity, in the direction of gravity, or in the horizontal direction. A coefficient selecting device for obtaining a coefficient Kmng to be used for the calculation is output to the correction value calculating device. Further, the first input to which the output of the command generating device and the output of the correction value calculating device are input. And a second input input from the correction value calculation device, which is obtained by multiplying the output of the deviation amount calculation device operated by the first input input from the command generation device with a gain Gp, and a second input input from the correction value calculation device. The position control device that outputs the sum of the above to the speed control device as a speed command is provided.

[0008]

According to the present invention having the above-described structure, the command generator determines the rotation amount of the motor for each axis of the robot per given time so that the final action point of the robot draws a desired trajectory at a desired speed according to the teaching content. The correction value calculation device calculates the correction value according to the output of the past command generation device and the output of the command generation device that is expected to be output in the future, depending on how many outputs before or how many outputs ahead. A value obtained by multiplying the coefficient Kmng by multiplication and an integrated value and a value obtained by multiplying the current output of the command generator by a coefficient Kmng accordingly, and multiplying the total value by a gain Gm with respect to the command value Is calculated as a correction value of the movement amount for the delay of the operation. At this time, the coefficient Km is given by the coefficient selecting device. The coefficient selection device determines whether the robot arm operates in a direction against gravity, in the direction of gravity, or in the horizontal direction, and when the correction value calculation device calculates the correction value. The coefficient Kmng to be used is calculated and output to the correction value calculation device.

The position control device has a first input to which the output of the command generation device is input and a second input to which the output of the correction value calculation device is input, and the deviation amount operated by the first input. The sum of the output of the calculation device multiplied by the gain Gp and the second input input from the correction value calculation device is output to the speed control device as a speed command. This speed control device obtains the current rotation speed of the motor from the differential value of the output of the position detection device, and outputs a value obtained by multiplying the difference from the commanded speed by the gain Gv to the current control device as a current command, and outputs the current The controller obtains the difference between the commanded current value and the current flowing through the motor, forms a PWM output from the value obtained by multiplying the gain Gi, and outputs the PWM output to the servo amplifier. In this way, the position control device
Since the speed command for the speed control device is formed from the first input and the second input, the position control device, the speed control device,
It is possible to improve the locus accuracy without increasing the gain of the current control device.

The position detecting device detects the rotation amount of the motor attached to the motor of each axis of the robot and outputs it to the deviation amount calculating device, and the deviation amount calculating device determines the integrated value of the output from the command generating device. And the difference between the integrated values of the output from the position detection device is calculated.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a robot controller according to an embodiment of the present invention. Command generator 1
Calculates the amount of rotation of the motor 7 for each axis of the robot per given time so that the final action point of the robot draws a desired trajectory at a desired speed in accordance with the teaching content, and calculates the latest command value as a correction value calculation device. 10 and outputs to the position control device 12 a command value one before the latest command value. Further, the command generation device 1 outputs to the coefficient selection device 11 a signal indicating whether the operation of the arm corresponding to the latest command value operates in a direction against gravity, in the gravity direction, or in the horizontal direction. ..

In this embodiment, the coefficient selecting device 11 is
As shown in FIG. 2, the coefficient Kmng corresponding to each axis is obtained by tracing back from the latest command value (n = + 1) to the command value five times before (n = -4), and outputs it to the correction value calculation device 10. ..
Here, the subscript m indicates the axis number of the robot. n indicates the order of command values, and when n = + 1 is the latest command value,
When n = 0, the command value is output to the position control device 12 this time. Similarly, n = -1 is the command value previously output to the position control device 12, n = -2 is two times before, n = -3 is three times before, and n = -4 is four times before. The command value output to 12 is shown. g indicates the movement direction of the arm. Therefore
36 coefficients Kmng are output from the correction value calculation device 10.

The correction value calculation device 10 is a second control device of the position control device 12.
The correction value Am input to the input of is calculated as in (Equation 1).

[0014]

## EQU1 ## Am = Gm × (Km, + 1, g × θm, + 1 + Km, 0, g × θm, 0 + Km, -1, g × θm, -1 + Km, -2, g × θm, -2 + Km,- 3, g × θm, −3 + Km, −4, g × θm, −4) where Am represents a correction value. Gm represents the gain determined for each axis. θmn is a command value output by the command generator 1. The subscript m is the robot axis number, and n is the order of command values. Therefore, the correction value calculation device 10 has a function of storing the latest command value for each axis and the command values for the past five times.

The output of the command generation device 1 is input to the deviation amount calculation device 3 through the first input of the position control device 12, and the difference between the integrated value of the command value and the integrated value of the output of the position detection device 8 is calculated. The gain Gp is multiplied. This value is added to the correction value Am that is the second input, and the added value is output as a command to the speed control device 4. Thereafter, the motor 7 is rotated and the robot arm is moved in the same manner as in the conventional case. To move.

That is, the speed control device 4 obtains the current rotation speed of the motor 7 from the differential value of the output of the position detection device 8, and the value obtained by multiplying the difference from the commanded speed by the gain Gv is used as the current command. Output to the controller 5 and the current controller 5
Calculates the difference between the commanded current value and the current flowing through the motor 7, multiplies the gain Gi to form a PWM output, and outputs the PWM output to the servo amplifier 6. The servo amplifier 6 supplies a current to the motor 7 according to the PWM output to rotate the motor 7.

FIG. 3 is a block diagram of a main part of a configuration in which this embodiment is realized by using a computer. Unit A13 is
The command generation device 1, the correction value calculation device 10, and the coefficient selection device 11 are configured. The CPU-A18 calculates the command value according to the procedure described in the ROM-A20. At this time, at the same time, the motion direction of the arm of the robot is obtained in the process of solving the forward kinematics problem shown in the procedure described above. The FPU 19, which represents a floating point arithmetic unit, is required to perform a large amount of floating point arithmetic when executing this arithmetic operation. Km shown in FIG.
The ng table is stored in the ROM-A 20, and the value Kmng is determined from the command value, the arm movement direction and the axis number. The past command value required for calculating the correction value is stored in the RAM-A21. CPU-A18 is ROM-A
Read coefficient Kmng and gain Gm from 20, RAM-
The command value is read from A21, and the correction value Am is calculated according to the calculation of (Equation 1).

The unit B14 constitutes the position control device 12 and the deviation amount calculation device 3. The dual port RAM 25 stores the first input and the second input input to the position controller 12. Each input is assigned to the addresses A and B of the dual port RAM 25. CPU-B22 is R
The speed command value is calculated according to the procedure stored in OM-B23. The CPU-B22 adds the command value input at the address A to the command counter in the RAM-B24 and integrates it. Further, the counter 29 in the unit C15 is read via the bus arbitration circuit 28, and the output from the rotary encoder 17 constituting the position detecting device 8 is added to the position counter in the RAM-B24 and integrated. The value obtained by subtracting the value of the position counter from the value of the command counter is stored in the deviation counter in the RAM-B24. The correction value Am read from the address B is added to the value obtained by multiplying the value of the deviation counter by the gain Gm, and this value is written in the RAM-C27 of the unit C15 as a speed command.

The unit C15 constitutes the speed controller 4 and the current controller 5. CPU-C26 has no ROM and CP
The program stored in the ROM-B23 by the U-B22 is written into the RAM-C27 via the bus arbitration circuit 28, and the program operates according to the program. The rotation speed of the motor 7 is detected from the amount of change in the value of the counter 29 within a fixed time. The current command value is obtained from the difference between the value and the speed command value. CT16 mounted as current detector 9
Is converted into a digital value by the A / D converter 31, and the current value flowing through the motor 7 is detected. The value obtained from the value and the current command value is input to the PWM generator 30, and the servo amplifier 6 is operated by the output, and the motor 7 is rotated to operate the arm of the robot.

FIG. 4 shows the correction value A in the correction value calculation device 10.
7 is a flowchart showing a procedure for obtaining m. In step A, the coefficient Kmng according to the arm movement direction
From ROM-A20. In step B,
The calculation of (Equation 1) is executed to obtain the correction value Am. In step C, the address B of the dual port RAM 25 is written.

FIG. 5 is a flow chart showing the operation procedure of the position control device 12. In step D, the command value input to the address A of the dual port RAM 25 is added to the command counter in the RAM-B24. In step E, the output of the rotary encoder 17 is counted
It is read from 29 and added to the position counter in RAM-B24. At step F, the value obtained by subtracting the value of the position counter from the value of the command counter is stored in the deviation counter in the RAM-B24. At step G, the value obtained by multiplying the value of the deviation counter by the gain Gm is added to the address B of the dual port RAM 25.
The correction value Am read from the address is added, and the added value is output to the speed control device 4. This process is repeated during the operation of the robot.

[0022]

As described above, according to the robot controller of the present invention, it is possible to improve the trajectory accuracy without increasing the gains of the position controller, the speed controller, and the current controller, and the cutting is performed. The robot can be adapted to applications that require high trajectory accuracy, such as
It is possible to provide a cutting device that is inexpensive and versatile.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a robot controller according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining a table to be referred to when a constant calculation device in a robot control device according to an embodiment of the present invention obtains a value Kmng.

FIG. 3 is a block diagram of a main part of a configuration in which a robot control device according to an embodiment of the present invention is realized using a computer.

FIG. 4 is a flowchart showing a procedure for obtaining a correction value in the robot controller according to the embodiment of the present invention.

FIG. 5 is a flowchart showing an operation procedure in the position control device of the robot control device according to the embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of a conventional robot controller.

[Explanation of symbols]

 1 command generation device 3 deviation amount calculation device 4 speed control device 5 current control device 6 servo amplifier 7 motor 8 position detection device 10 correction value calculation device 11 coefficient selection device 12 position control device

Claims (3)

[Claims] 1. A controller for a robot, which stores teaching contents and operates a robot according to the teaching contents, wherein the robot has a final action point draw a desired locus at a desired speed in accordance with the teaching contents. Command generator that calculates the amount of rotation of the motor of each axis per unit time, a position detector that is attached to the motor of each axis of the robot to detect the amount of rotation of the motor, and the integration of the output from the command generator. How many times each for the deviation amount calculation device that calculates the difference between the value and the integrated value of the output from the position detection device, and the output of the past command generation device and the output of the command generation device that is expected to be output in the future by performing the preceding calculation. Add the value obtained by multiplying and integrating the coefficient Kmng according to the previous output or the number of times of the output and the value obtained by multiplying the current output of the command generator by the coefficient Kmng accordingly A control device for a robot, comprising a correction value calculation device for calculating a value obtained by multiplying a value by a gain Gm as a correction value for a movement amount corresponding to a delay in actual robot operation with respect to a command value. 2. The correction value calculation device calculates the correction value by determining whether the arm of the robot moves in a direction against gravity, moves in the direction of gravity, or moves in the horizontal direction. 2. The controller of the robot according to claim 1, further comprising a coefficient selecting device which calculates a coefficient Kmng to be used and outputs it to a correction value calculating device. 3. A first input to which the output of the command generator is input and a second input to which the output of the correction command generator is input, and the operation is performed by the first input input from the command generator. The control of the robot according to claim 1, further comprising a position control device that uses a sum of a deviation amount calculation device multiplied by an output gain Gp and a second input input from the correction command generation device as a speed command. apparatus.