JPH04209001A - Safety device for servo controller - Google Patents

Abstract

PURPOSE:To stably detect abnormality regardless of a decrease in the speed of a moving body by switching and setting the maximum permissible value of an error by a maximum permissible value setting means depending upon the speed of the moving body. CONSTITUTION:An alternation device 10 connects a switch 11 to the side of a buffer 8a in stationary mode unless a command position signal 1 varies and a comparator 9 compares an error from a differentiator 7 with the maximum permissible value in the stationary mode. When the signal 1 begins to vary, the alternation device connects the switch 11 to the side of a buffer 8b in operation and the comparator 9 compares the error from the differentiator 7 with the maximum permissible value in the operation. The alternation device 10 switches the switch 11 back to the side of the buffer 8a a time, determined by considering the delay of the feedback of the servo controller, after the signal 1 comes to have no variation.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a safety device for a servo control device that issues a stop signal for a movable body depending on the magnitude of the error value between the measured position and the predicted position of a movable body. It is something.

[Conventional technology]

FIG. 2 is a block circuit diagram of the main parts of a conventional servo control device and its safety device.

In the figure, (11 is a command position signal, (2) is an adder, (3)
is a servo amplifier connected to the adder (2), (4) is a motor connected to the servo amplifier (3), and (5) is an ABS coupled to the motor (4) and outputs an actual position signal (5a).
(absolute position) encoder, (6) is the command position signal (
1) is a predictor that predicts the actual position, (7) is a differentiator that outputs the error (7a) between the predicted position and the actual position, (8)
is a buffer that stores the maximum allowable value of error (7a), (9
) is a comparator that compares the error (7a) with the maximum allowable value stored in the buffer (8) and outputs an abnormality signal (9a).

Note that the configuration of the predictor (6) is that the command position signal (
1) is input, AB as a feedback signal
The time until the actual position signal (5a) is returned from the S encoder (5) and the predicted position at which the movable body is predicted to move corresponding to the time are stored in advance for each time, and the actual position is calculated. The corresponding predicted position is output as a position command signal (6a) in accordance with the return time of the signal (5a).

The safety device of the conventional servo control device is configured as described above, and the predicted position command signal (6a) and the actual position signal (5a) output from the ABS encoder (5) are connected to the difference device (
The comparator (9) compares the error (7a) between each signal (6a) and (5a) with the maximum allowable error value stored in the buffer (8), and calculates the error (7a). If is larger, an abnormality signal (9a) is output and the servo control device is stopped.

[Problems to be Solved by the Invention] In the conventional safety device of the servo control device as described above, the maximum allowable value is always constant, so if the maximum allowable value is set for operation at maximum speed, The abnormality detection speed of the system became slow and the servo control device could not be stopped immediately when an abnormality occurred.

This invention was made in order to solve the above-mentioned problems, and it is a servo control device that increases the abnormality detection sensitivity when the servo device is running at low speed, and that can stop the servo control device as soon as possible when an abnormality occurs. The purpose is to provide a safety device for control equipment.

[Means for Solving the Problems 1] A safety device for a servo control device according to the present invention includes an encoder that outputs a number of pulse signals according to the amount of movement of a movable body, and a count value of the pulse signal that is output by the actual body of the movable body. a counter that outputs a position signal; an actual position predictor that stores in advance a predicted position every predetermined time after inputting a movement position command for the movable body and retrieves the predicted position every predetermined time; monitoring means for monitoring the error between the actual position of the object and the predicted position from the actual position predictor, and a maximum permissible value setting means for setting the maximum permissible error value according to the moving speed of the movable body; A comparator is provided which issues a signal to stop the movable body when the maximum value is exceeded.

[Operation] According to the present invention, since the maximum allowable value setting means switches and sets the maximum allowable error value depending on the speed of the movable body, the abnormality detection sensitivity can be improved even when the movable body is operating at low speed. will no longer decrease.

[Embodiment] FIG. 1 is a block circuit diagram showing an embodiment of the present invention, and parts similar to those of the conventional device are designated by the same reference numerals.

In the figure, (8a) is a buffer that stores the maximum allowable value when the command position signal does not change, that is, when it is stationary, and (8b) stores the maximum allowable value when the command position signal changes, that is, when it is in operation. Buffer, (10) is a switch that outputs a signal for switching the switch according to the command position signal (1),
(11) is a switch that is switched by a switch (10).

The buffer (8b) during operation stores the conventional maximum allowable value, and the buffer (8a) when at rest stores the maximum allowable value, which is smaller than that during operation, which corresponds to the standstill.

Next, the operation of this embodiment will be explained.

When the command position signal (1) is not changing, the switch (11) is set by the switch (lO) to the stationary buffer (
A comparator (9) connected to the side 8a) compares the error from the difference device (7) with the maximum allowable value when stationary. In addition, when the command position signal (1) starts to change, the switch (10) switches the switch (11) to the operating buffer (8b) side, and also the difference device (error from the moon and the operating tolerance). The maximum value is compared with the comparator (9).The command position signal (
The switch (10
) switches the switch (11) to the stationary buffer (8a) side. However, if the command position signal changes after the above time, the switch (11) is not switched.

Further, in the above embodiment, the state is divided into two states, the rest state and the operating state, but it goes without saying that the effect can be further improved by determining several allowable maximum values.

[Effects of the Invention] As described above, according to the present invention, the maximum permissible error value corresponding to the speed of the movable body is set, and the maximum permissible value corresponding to the speed is determined between the actual position and the predicted position. Since the configuration is such that the error is compared, abnormality detection can be performed stably regardless of a decrease in the speed of the movable body, which has the effect of improving the safety of the device.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram showing an embodiment of a safety device for a servo control device according to the present invention, and FIG. 2 is a block circuit diagram of a conventional safety device for a servo control device. In the figure, (4) motor, (5) ABS (absolute position) encoder, (5a) real position signal, (6) real position predictor, (8a) buffer when stationary, (8b) Buffer during operation, (9) is a comparator, and (10) is a switch. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] an encoder that outputs a number of pulse signals corresponding to the amount of movement of the movable body; a counter that outputs the counted value of the pulse signals as an actual position signal of the movable body; a real position predictor that stores predicted positions in advance and extracts the predicted positions at predetermined time intervals; and a monitor that monitors the error between the actual position from the counter and the predicted position from the real position predictor at each time. means, maximum allowable value setting means for setting the maximum allowable error value according to the moving speed of the movable body, and a comparator that issues a stop signal for the movable body when the error exceeds the maximum allowable value. Safety device for servo control equipment.