JPH02214908A - Robot controller - Google Patents

Abstract

PURPOSE:To automatically restore the movement of a robot to its original position within a fixed range in a servo OFF state by outputting directly an error signal if the command value given from a monitor means is small when a servo ON state is set and moving the robot back to a position set right before a servo OFF state is set. CONSTITUTION:No reset signal 21 is produced even in a servo OFF state and a speed command per unit time is always calculated by an integrator 14. A comparator 24 compares the error (speed command) value per unit time which is calculated by the integrator right before a servo ON state with the reference value 23. If the speed command value is smaller than the value 23, a cut-off command 22 is turned off and a switch 15 is connected. Thus a robot is restored to the position set before the servo OFF state. In the case the speed command value is larger than the value 23, the speed command value is not outputted and reset for the generation of an alarm. As a result, the comparatively small movements of the robot can be automatically restored within a fixed range in the servo OFF state.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control device for a robot, and more particularly to means for controlling an initial position when a servo mechanism is re-driven.

[Conventional technology]

First, the configuration of the robot control device will be explained based on FIG. 3. Figure 3 is an overall configuration diagram showing the outline of the robot control device.
2) is a ROM in which a control program for the CPU (1) is stored, and (3) is a RAM used to store data calculated by the CPU (1).

(4) is a program meso that stores the program and position data for the robot user to make the robot do the desired work, and (5) is the speed command (speed command per unit time) calculated by CPt11 (1). This is a shared memory in which movement commands) are written.

In addition, (6) is a CPU (hereinafter referred to as rcpH2J) that drives and controls the servo system, and (7) and (8) are CPUs that drive and control the servo system.
2 (6) and corresponds to ROM (2) and RAM (3) in CPU 1 (1), respectively, and (9) are installed in CPLI 2 (6) and the robot body (IO). Servo interface (hereinafter referred to as “servo I/F J”) that connects the motor of each axis
).

The basic operation of the robot control device having the above configuration is performed as follows.

First, CPU 1 (1) has program memory (4
) and reads the movement target position from the CPU 2 every unit time according to the control program written in the ROM (2).
The speed command for (6) is sequentially written into the shared memory (5). Then, CPU 2 (6) executes cpu 1(t
) is read from the shared memory (5), and the servo 1 is executed based on the control program written in the ROM (7) and the control data in the RAM (8).
A predetermined signal is sent to the robot body (1o
) to drive the servo motor in the robot body (10) to cause the robot to perform a predetermined operation.

Next, the control method of the conventional robot control device will be explained in detail based on the configuration diagram shown in FIG. 4. In the same figure, (4) is the program memory in FIG.
11) is a target position buffer that exists in RAM (2) in FIG. 3 and stores the target position of movement of the robot;
(12) is a speed command calculation device that calculates a speed command for each axis at the next point in time from the target position stored in the target position buffer (11), and stores it in the speed command buffer (13); is a speed command buffer existing in the shared memory (5) in FIG. 3, (14) is an integrator that accumulates the difference between the speed command and a feedback value output from a differentiator (20), which will be described later, and (15) is an integrator Output disconnector, (16
) is the servo amplifier, (17) is the servo motor, (18)
is an encoder, (19) is a counter that counts the pulses output from the encoder (18), and (20) is the above-mentioned differentiator, which converts the value of the counter (19) into the amount of movement per unit time. ing.

Therefore, the servo ON in the conventional robot control device
The operation is performed by converting the difference between the speed command written in the speed command buffer (13) and the feedback value calculated by the differentiator (20) into a speed command per unit time in the integrator (14). This is done by outputting the signal to the servo amplifier (16). At this time, the output disconnector (15)
is connected and ready to perform a predetermined operation.

Under such conditions, the servo amplifier (16) drives the servo motor (17) to move the robot to a predetermined position. The current position is then fed back, and the feedback signal is transmitted by the encoder (18) to the servo motor (
The rotation of 17) is converted into a pulse signal, and after the pulse signal is converted into a rotation angle by a counter (19), a differentiator (20)
is converted into speed.

Now, when the servo is switched from ON to OFF, a disconnection command (22) is output to the output disconnector (15) and the command to the servo amplifier (16) is set to O.
The servo motor (17) is prevented from rotating, and a reset signal (21) is input to the integrator (14) so that the output is always zero. By setting the output of the integrator (14) to 0, if the robot is moved while the servo is OFF, a feedback value is returned to the integrator, and an integral that attempts to return the posture of the robot body (10) to its original position. This is to prevent the occurrence of an unexpected operation in which the output disconnector (15) attempts to return to the position immediately before the servo is turned off the moment the output disconnector (15) is connected when the servo is turned on when the output from the device (14) is generated.

[Problem to be solved by the invention]

However, as mentioned above, in the conventional robot control device, the output of the integrator (14) is always 0 while the servo is OFF, so when the servo is turned on, it is not possible to restore it to the position immediately before the servo was turned off. In order to restore the posture of the rear robot body to its original position, it was necessary to issue a movement command or manually return it.

This invention was made to solve the above problems,
An object of the present invention is to obtain a robot control device that can automatically restore the robot's movement within a certain range while the servo is off to its original position.

[Means for Solving the Problems] A robot control device of the present invention includes a monitoring device that constantly monitors an error between a position command value and a feedback value of the current position, and a monitoring device that monitors the error based on an error signal output by the monitoring device. a comparator that compares the value with a preset reference to determine the magnitude of the error value; selection means that corrects the error when the output signal of the comparator is large; and resets the error when the output signal is small; It is equipped with the following.

[Effect]

According to this invention, if the command value from the monitoring means is small when the servo is turned on, the selection output means directly outputs the error signal and returns the robot to the position immediately before the servo was turned off.If the command value is large, the selection output means outputs the error signal. Reset without output.

〔Example〕

Hereinafter, the features of the present invention will be mainly explained based on the embodiment shown in FIGS. 1 and 2, with the same or corresponding parts as those in the prior art being designated by the same reference numerals. FIG. 1 is a configuration diagram corresponding to FIG. 4 showing the control method of the robot of this embodiment. In the same figure,
(23) is the integrator (14) for the servo amplifier (16).
) is a reference value set in advance to determine whether to output an error signal or to reset without outputting an error signal and generate an alarm;
A comparator (25) is a signal for generating an alarm.

Therefore, in this embodiment, the reset signal (21) is not generated even when the servo is turned off, and the integrator (14) is always activated.
The speed command per unit time is calculated by , and when the servo is turned on, the process shown in the flowchart shown in FIG. 2 is performed. Next, the process immediately after the servo is turned on will be explained based on FIGS. 1 and 2. First, the comparator (24) compares the error (speed command) value per unit time immediately before the servo is turned on calculated by the integrator (14) with the reference value (23), and the speed command value is determined as the reference value. In step 101), if the speed command value is within the reference value (23) and smaller than the reference value, the disconnection command (22) is turned OFF and the disconnection device (15) is connected to servo the robot. It is restored to the position before it was turned off (step 102). Conversely, if the speed command value of the integrator (14) exceeds the reference value (23), the speed command value is reset without being output and an alarm is generated (step 103). Next, it is determined whether or not the alarm has been reset (step 104), and if it has been reset, a reset signal (21) is output to the integrator (14) to reset it, and the output of the integrator (14) becomes 0. (Step 105). Thereafter, the disconnection command (22) is turned OFF and the disconnector (15) is connected (step 102).
The posture of the robot body (10) is not restored to the position immediately before the servo was turned off.

〔Effect of the invention〕

As described above, according to the robot control device of the present invention, the servo O
The configuration is such that relatively small movements of the robot within a certain range during FF are automatically restored, so even if the robot moves beyond the control range while the servo is OFF, the servo amplifier cannot be commanded to move or the robot can be returned manually. No need to return to position.

[Brief explanation of the drawing]

FIG. 1 is a control block diagram of a robot control device according to an embodiment of the present invention, FIG. 2 is a flowchart showing processing immediately after servo ON, FIG. 3 is a block diagram showing an outline of the robot control device, and FIG. The figure is a control block diagram of a conventional robot control device. (1) is CPU i, (2) is ROM for CPU i,
(3) is RAM for CPU i, (4) is program memory, (5) is CP memory (6) is CPII
2. (7) is ROM for CPU Z, (8) is C
RAM for PII Z, (9) is servo I/F. (10) is the robot body, (11) is the target position buffer, (12) is the speed command calculation device, (13) is the speed command buffer, (14) is the integrator, (15) is the output disconnector, (16) is the ) is the servo amplifier, (17) is the servo motor,
(18) is an encoder, (19) is a counter, (20)
is a differentiator, (21) is a reset signal, (22) is a disconnection command, (23) is a reference value, (24) is a comparator, (25)
is the alarm output signal. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] In a robot control device equipped with means for detecting the current position of the robot, a monitoring means constantly monitors an error between a position command value and a feedback value of the current position, and the error value is determined based on an error signal output by the monitoring means. a comparator that compares the error value with a preset reference value to determine the magnitude of the error value, and corrects the error when the output signal of the comparator is large;
A control device for a robot, comprising: selection means for resetting the error when the error is small.