JPS61246807A - Runaway detecting method - Google Patents

Abstract

PURPOSE:To detect surely runaway of a servo control system by providing an integration device integrating a position deviation and a comparator comparing its integration output with a setting value. CONSTITUTION:An output of a counter 4 representing the present position and an output of a counter 5 representing a command position are subtracted by a subtractor 6 and its output is fed back to a control circuit 1 as a position error. In the control system, a speed signal obtained by differentiating the output of the counter 4 by a differentiation circuit 7 and an integration value of the position deviation integration the output of the subtractor 6 by an integration circuit 8 are inputted to the control circuit 1 as a feedback signal. In the servo control system as above, if an abnormality is caused in the feedback signal of an encoder or the like, the system causes runaway. Thus, the integration output of the position deviation integration circuit 8 is compared with a predetermined setting value and when the output exceeds the setting value, a runaway detection circuit 10 gives an output of a runaway detection signal.

Description

[Detailed Description of the Invention] [Summary] A servo control system includes an integrator that integrates a position deviation value and a comparator that compares the integrated output with a certain set value, and the integrated output is equal to the set value. By exceeding the limit, runaway of the servo system is detected, and as a result,
Runaway can be reliably detected.

[Industrial Application Field] The present invention relates to a runaway detection method in a servo control system.

In a closed-loop servo system, if an abnormality occurs in the feedback signal, the system will run out of control. Therefore, it is necessary to immediately detect the occurrence of runaway and stop it.

The present invention relates to a method that can reliably detect runaway in a servo system.

[Prior Art] FIG. 2 is a block diagram showing an example of a servo control system for controlling a robot or the like.

In FIG. 2, 1 is a control circuit, 2 is a motor to be controlled, and 3 is an encoder as a feedback element.

The position increment pulses which are the output of the encoder 3 are fed into a counter (CTRI) 4 whose output will indicate the current position.

In this control system, control commands are input in the form of commanded speed pulses. The instruction speed pulse is the counter (CTR2) 5
Therefore, the output of the counter 5 indicates the command position.

The output of the counter 5 and the output of the counter 4 are input to a subtracter 6 and subtracted therefrom.

The output of the subtracter 6 indicates the position error and is input to the control circuit 1 as a feedback signal.

In this control system, the output of a differentiating circuit (d/dt) 7 that differentiates the output of the counter 4, that is, the speed, is input to the control circuit 1 as a feedback signal.

Furthermore, in this control system, the output of the integrating circuit (f) 8 that integrates the output of the subtracter 6, that is, the integrated value of the positional deviation, is also input to the control circuit 1 as a feedback output.

The control circuit 1 minimizes the difference between the commanded speed and the actual speed and supplies current to the motor so that the positional deviation becomes zero. If the positional deviation becomes zero, the current value given to the motor becomes zero, so the robot In controlling an arm or the like, it is known that feedback of the integral value of the positional deviation is effective in bringing the positional deviation to zero against gravity.

In the servo control system as described above, if an abnormality occurs in the feedback signal of the encoder or the like, the system will run out of control.

Conventionally, as a method for detecting this runaway, an overcurrent detector (Dll!Tl) 9 was provided for the motor current, and runaway was detected by the occurrence of this overcurrent.

[Problems to be Solved by the Invention] In the conventional runaway detection method using overcurrent detection as described above, runaway cannot always be completely detected.

That is, if the motor runs out of control and hits an obstacle, an overcurrent will flow through the motor, but it cannot be detected if the motor runs out of control in one direction with a constant current.

The present invention aims to solve these problems and provide a detection method that can reliably detect runaway in the servo system.

[Means for Solving the Problems] FIG. 1 is a block diagram showing the principle of the runaway detection method of the present invention.

In FIG. 1, the same reference numerals as in FIG. 2 indicate the same objects.

Reference numeral 10 denotes a runaway detection circuit (DET2), which compares the output of the deviation integration circuit (negative 8) with a certain set value, and outputs a runaway detection signal when it exceeds this set value.

FIG. 1 is a block diagram for explaining the present invention in detail, but the servo control system shown here is just an example, and
The present invention is not limited to this.

In a control system without a position error integrator, a separate integration circuit is provided and its output is input to the runaway detection circuit.

[Function] In the servo control system shown in FIG. 1, if there is an abnormality in the feedback signal, a deviation will definitely occur and a runaway will begin.

Due to an abnormality in the feedback signal, even if the deviation does not change, the integrated value increases over time and when it exceeds a certain value, runaway can be detected.

If it is not an abnormality in the feedback signal but an abnormality in the drive system, the deviation will definitely increase if the motor runs out of control. Therefore, since the integrated value of the deviation also increases, runaway can be detected.

[Effects of the Invention] As explained above, according to the present invention, all kinds of runaways due to feedback signal abnormalities, drive system abnormalities, etc. can be reliably detected with a relatively simple configuration, and it is possible to detect it in practice. The effect is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the principle of the present invention, and FIG. 2 is a block diagram of a conventional example. In the drawing, 1 is a control circuit, 2 is a motor, 3 is an encoder, 4 is a counter (CTRL), 5 is a counter (CTR2), 6 is a subtracter, and 7 is a differential circuit (d/
dt), 8 is an integration circuit (negative, 9 is an overcurrent detector (D
10 indicates a runaway detection circuit (DET2), respectively. Mine 1 close

Claims (1)

[Claims] A servo control system comprising: an integrator (8) that integrates positional deviation; and a detection circuit (10) that compares the integrated output of the integrator (8) with a predetermined set value. . A runaway detection method, characterized in that runaway of the servo control system is detected when the integral output exceeds the set value.