JPH07175521A - Controller for servomotor - Google Patents

Abstract

PURPOSE:To make an accurate positioning stop when a controlled object is moved from a stop position to a specific target position, and positioned and stopped on the basis of a stop signal halfway in movement toward the infinite target position. CONSTITUTION:This controller is provided with a target position command switching part 21 which performs switching from a 1st target position command signal Prf1 for movement toward the infinite target position to a 2nd target position command signal Prf2 set on the basis of the stop position of the stop signal Pst as a start point in response to the input of the stop signal Pst. Further, the device is provided with a correction signal output part 22 where position deviation g at the moment when the stop signal Pst is received is set as a position command correction value Pepsilon and an arithmetic part 23 which corrects the command signal Prf2 on the basis of the value. An arithmetic part 24 finds the position deviation epsilon from a target position command signal and a position feedback signal Pfb and an arithmetic part 25 multiplies the position deviation epsilon by a position loop gain Kp and outputs a speed command signal Sv.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo motor control device in a positioning control system using a servo motor such as NC machine tools and industrial robots.

[0002]

2. Description of the Related Art For example, a positioning control system for an industrial robot generally employs feedback control for outputting a speed command signal based on a target position command and a position feedback signal to a servo driver. Here, as the operation of the robot arm, the robot is moved toward an infinite target position, and when a stop signal is received from the limit switch on the way, the robot is moved from the stop position toward a predetermined target position for positioning. It may stop.

FIG. 3 shows a conventional controller 1 in such a case.
It is a figure which shows the software-like structure of with a processing block.
Here, the first target position command signal Prf1 toward the infinite target position is output from the position command generator 2, and the second target position command signal Prf2 set starting from the stop position by the stop signal is the position. It is designed to be output from the command generation unit 3.

Then, when the stop signal Pst from the limit switch is input, the switching unit 4 changes the first target position command signal Prf1 to the second target position command signal Prf2.
It is designed to switch to. The calculation unit 5 calculates the target position command signal Prf1 (Prf2) and the feedback signal Pf.
b is subtracted to obtain the position deviation ε, and the calculation unit 6 outputs the speed command signal Sv obtained by multiplying the position deviation ε by the position loop gain Kp to a servo driver (not shown). .

[0005]

However, in the above-mentioned prior art, the stop signal Pst from the limit switch is used.
Since the position deviation ε exists at the moment when is input,
Even if control is performed to stop the arm of the robot at the second target position that is set starting from the stop position by the stop signal, the actual stop position of the arm of the robot is
The position will deviate from the target position by the position deviation ε.

In this case, the amount of deviation (positional deviation ε) is not constant, but varies greatly depending on the size of the load and the size of the position loop gain Kp. Therefore, in the conventional robot, for example, when the stop signal from the limit switch is received while moving the robot arm toward the infinite target position, the robot arm moves from the stop position toward the predetermined target position. It is difficult to accurately stop the positioning when the positioning is stopped.

The present invention has been made in view of the above circumstances, and an object thereof is to set a predetermined target position from a stop position based on a stop signal during the movement of a controlled object toward an infinite target position. An object of the present invention is to provide a servo motor control device capable of performing accurate positioning stop in the case where the position is stopped by moving it toward the position.

[0008]

A servomotor control apparatus according to the present invention is configured to output a target position command to a first target position toward an infinite target position based on an input of a stop signal from a controlled object side. A command is switched to a second target position command set starting from a stop position by the stop signal, and the second target position command is set in accordance with a position deviation at the time of inputting the stop signal. This is characterized in that a target position command correction means for correction is provided.

[0009]

According to the above means, when the stop signal is input during the movement to the first target position, the second target position command is switched to. At this time, the target position command correction means The second target position command set starting from the stop position by the stop signal is corrected according to the position deviation at the time of inputting the stop signal. Therefore, even if there is a position deviation at the time when the stop signal is input, the second target position command is corrected by the position deviation, and the final stop position is set to the second target. It is possible to match the position.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to drive an arm of an industrial robot will be described below with reference to FIGS.
Will be described with reference to. First, FIG. 2 schematically shows the overall configuration of a robot arm positioning control system. Here, the servo motor 11 for driving the robot arm to be controlled is driven by a known servo driver 12. It has become. The servo driver 12
Controls the speed and current of the servomotor 11 according to the speed command signal from the control device 13 according to the present embodiment.

The position of the servo motor 11 and thus of the arm is detected by a position detector 14 such as a pulse generator, and the detection signal is given to a counter 15 of the controller 13. Counter 1
5 counts the pulses of the position detector 14 to generate the current position and outputs the position feedback signal Pfb.

The control device 13 according to the present embodiment is mainly composed of a microcomputer 16 and includes the counter 15 and a D / A converter 17 described above.
And so on. As will be described later in detail, the microcomputer 16 directly outputs the digital speed command signal Sv or an analog signal via the D / A converter 17 based on the preset target position command and the position feedback signal Pfb. The data is output to the servo driver 12 as Sva.

At this time, the control device 13 first moves the arm toward an infinite target position (first target position), and the stop signal Pst from the limit switch 18 is input to the microcomputer 16 as an interrupt during the movement. Based on this, control is performed so that the stop position is moved toward a predetermined target position (second target position) and the positioning is stopped.

Now, FIG. 1 shows the microcomputer 16 of the controller 13.
It is a figure which shows the software-like structure of this with a processing block. Here, the first target position command signal Prf1 toward the infinite target position is output from the position command generator 19.
The second target position command signal Prf2 set starting from the stop position by the stop signal Pst is the position command generator 20.
It is supposed to be output from.

The target position command switching unit 21 first outputs the first target position command signal Prf1 and then the limit switch 1
When the stop signal Pst from 8 is input, the output signal is switched from the first target position command signal Prf1 to the second target position command signal Prf2. And
At this time, the microcomputer 16 is configured to set the position deviation ε at that moment to the correction signal output unit 22 as the position command correction value Pε at the moment when the stop signal Pst from the limit switch 18 is received by the interrupt processing. There is. The calculation unit 23 subtracts the position command correction value Pε from the second target position command signal Prf2 to obtain the target position command correction signal Prf2.
It is designed to be output as ´. Therefore, the correction signal output unit 22, the calculation unit 23, and the like constitute the target position command correction unit.

In the calculation unit 24, the target position command signal Prf
1 (before stop signal) or target position command correction signal Prf2 '
From (after the stop signal), the position feedback signal Pf
b is subtracted to obtain the position deviation ε, and the computing unit 25 multiplies the position deviation ε by the position loop gain Kp to obtain the speed command signal Sv, and the speed command signal Sv is output to the servo driver 12. It is.

Next, the operation of the above configuration will be described.
When the servo motor 11 (arm) is moving toward the first target position (first target position command signal Prf1), the current position PF1 is given by expressed. PF1 = Prf1-ε1 (1)

When the stop signal Pst is input from the limit switch 18, the target position command switching unit 21 outputs the output signal from the first target position command signal Prf1 to the second target position command as described above. It is switched to the signal Prf2 side. At this time, since the position deviation ε immediately after receiving the stop signal Pst is set to ε1, the servo motor 11
From the side, the position command required to move to the second target position is Prf2 + ε1.

When the servomotor 11 (arm) is moving toward the second target position, the target position command signal is corrected to Prf2 '(= Prf2-ε1) by the arithmetic unit 23, and therefore the current position PF2 is obtained. Is expressed by the following equation, where ε2 is the position deviation at that time. PF2 = (Prf2 + ε1) −ε1-ε2 (2)

Since the final control is such that ε2 → 0, the position deviation ε at the time when the stop signal Pst is input.
1 exists and the position deviation ε1 varies greatly depending on the magnitude of the load and the magnitude of the position loop gain Kp, the final stop position is matched with the second target position. It is possible to make it.

As described above, according to the present embodiment, the second target position command signal Prf2 is supplied to the position deviation ε when the stop signal is input.
Since the target position command correction means for correcting according to 1 is provided, the actual stop position of the arm of the robot may deviate from the target position by the position deviation ε when the stop signal Pst is input. Unlike what was there, the stop signal P
Even if there is a position deviation ε1 when st is input, the final stop position can be made to coincide with the second target position, and accurate positioning stop can be performed. It is possible to obtain an excellent effect.

The present invention is not limited to the above-described embodiment, and is not limited to the positioning control of the arm of the robot, but can be applied to the positioning control of various devices using a servo motor. The invention can be appropriately modified and implemented within a range that does not deviate.

[0023]

As is apparent from the above description, according to the servo motor control device of the present invention, the target position command correction for correcting the second target position command according to the position deviation at the time of inputting the stop signal is performed. Since the means is provided, based on the stop signal during the movement of the controlled object toward the infinite target position,
Even when the positioning is stopped by moving from the stop position toward the predetermined target position, the excellent practical effect that the accurate positioning stop can be performed is achieved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a software configuration of a control device according to an embodiment of the present invention.

FIG. 2 is a block diagram schematically showing the overall configuration of a positioning control system.

FIG. 3 is a view corresponding to FIG. 1 showing a conventional example.

[Explanation of reference numerals] In the drawings, 11 is a servo motor, 12 is a servo driver,
13 is a control device, 14 is a position detector, 15 is a counter,
Reference numeral 16 is a microcomputer, 17 is a D / A converter, 18 is a limit switch, 19 and 20 are position command generators, 21 is a switching unit, 22 is a correction signal output unit, and 23, 24 and 25 are arithmetic units.

Claims (1)

[Claims] 1. A speed command signal based on a target position command and a position feedback signal is output to a servo driver which controls a servo motor which is a drive source of a control target, and the target position command is controlled by the control. Based on the input of the stop signal from the target side, the first target position command toward the infinite target position is switched to the second target position command set starting from the stop position by the stop signal. The servo motor control device according to any one of the preceding claims, further comprising target position command correction means for correcting the second target position command according to the position deviation when the stop signal is input.