JPH0215311A - Backlash correcting device for position control device - Google Patents

Abstract

PURPOSE:To move a machine position in a track close to a command position by discriminating the inversion of a direction by using a position control model and switching a backlash correcting variable to two steps. CONSTITUTION:Even when a command position P0 generated from a command position generator 1 is inverted at a point T0 of time, a correcting position Pc obtained by adding a backlash correcting variable outputted from a backlash correcting device 15 to the position P0 is equal to the position P0 and the position Pc is set up to a position obtained by adding a backlash correcting variable BL2 to the position P0 from a point T0' of time when a machine position inversion timing estimater 12 discriminates the timing of the inversion of a machine position PM. Consequently, a motor 7 shortens the backlash, and from the time T1' ending the backlash shortening, the correcting variable BL2 is changed to a backlash correcting variable BL1. Although a machine 9 is stopped during the period between T0' and T1', the machine 9 starts to be driven from the time T1' and is moved with the delay of practical backlash from a motor position PF.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a backlash correction device for a position control device that drives a servo motor to control the contour of a machine tool to cut and grind a workpiece.

[Conventional technology]

Conventional backlash correction devices of this type employ a method in which, after the command position is reversed, only a position corresponding to the backlash is added to the command position.

FIG. 3 shows a block diagram of a conventional backlash correction device. In the figure, (1) is a command position generator that generates a command position, (2) is a command position PO1 (3) of the output from this generator (1) is a direction discriminator of command position (2), and (4) is a command position generator that generates a command position.
) is the backlash correction amount BL% (5) is the command device (
Correction position P where backlash correction amount (4) is added to 2)
C1 (6) is the position loop gain, (A) is the amplifier motor, (8) is the motor position P2, (9) is the amplifier motor (7
), (10) is this machine position PM.

Next, the operation will be explained. FIG. 4 is a timing chart of an example in which the direction of the ramp-shaped command position is actually reversed in the block diagram of FIG. 3.

In other words, the command position P. The time T. When reversed at , the correction position PC, which was equal to the command position Pa, becomes the position to which the backlash correction amount BL is added from this point on. Also, the motor position Pr starts to reverse from this point, but the machine position PM remains at the time T because it enters backlash. It stops after the point. Then, the mechanical position PM starts to move for the first time at time T1 when the motor position P is separated from the mechanical position PM by the amount of backlash. Then machine position P
M moves away from the motor position P by the backlash correction amount BL.

(Problem to be Solved by the Invention) Since the conventional backlash correction device is configured as described above, there is no particular problem in correction during positioning and stopping, but when the device is in motion, the trajectory differs from the commanded shape. There was a problem with driving the .

The present invention was made to solve the above-mentioned problems, and an object of the present invention is to obtain a backlash correction device for a position control device that can drive a machine position along a trajectory close to a commanded position.

[Means to solve the problem]

The backlash correction device according to the present invention is a position control device that drives a servo motor by position loop control according to a command position to move a machine tool and perform contour control. Then, a means for determining the timing at which the motor reverses, and a command position at which the motor can move with the acceleration that can be generated starting from this timing are added to the original command position, and then when the movement equivalent to backlash ends, the command position is set to reverse. It is equipped with means for returning the original command position to the position corresponding to the rush.

[Effect]

In this invention, the timing at which the machine position, which is followed by the delay of the position loop gain, reverses is delayed from the command position reversal, but since this timing can be estimated, the error is sufficiently close to the command position. can be made smaller. Further, the backlash correction can be performed in two stages, and first a position command can be issued for the amplifier motor to reduce backlash as quickly as possible.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure shows a block diagram of a backlash correction device for a position control device according to the present invention. In the figure, (1) is a command position generator that generates a command position, and (2) is this generator (1).
), (11) is a position control model equipped with a position loop gain (6), (3) is a direction discriminator connected to the output side of this position control model (11), (
12) is a combination of the position control model (11) and the direction discriminator (3).
), and (13) is a control device that switches the backlash correction amount into two stages based on the output of the timing estimator (12). (4) is the correction amount BL+ corresponding to the actual backlash, (14)
is a backlash correction amount BL2 for quickly reducing backlash, (15) is a backlash correction device including the above-mentioned control device (13), backlash correction amount BLI, and BL2, and (5) is a backlash correction amount at the command position (2). Correction position Pc with backlash correction amount added, (6) is position loop gain, (7) is amplifier motor, (8) is motor position P
2, (9) is a machine tool driven by an amplifier motor (7), and (10) is this machine position P2.

Next, the operation of this invention will be explained. FIG. 2 is a timing chart of an example in which the direction of the ramp-shaped command position is actually reversed in the block diagram of FIG. 1. In other words, even if the commanded position Po is reversed at time T0, the corrected position pc is equal to the commanded position P0, and the machine position reversal timing estimator (
12), the time T at which the timing at which the machine position PM would have reversed was determined. Therefore, the correction position PC becomes the position to which the backlash correction amount BL2 is added. This results in
The motor (7) fills up the backlash as fast as possible, and changes the amount of backlash correction to BL at the time TI° when the backlash is filled. In addition, the time To' and T
, ゛, the machine stops, but from time T1° the machine starts moving and moves behind the motor position P by the actual backlash.

Note that in the above embodiment, the first backlash correction amount BL
, is given in a step shape, or in other cases such as a ramp shape, the same effect as described above can be obtained as long as the backlash can be reduced as quickly as possible.

〔Effect of the invention〕

As explained above, according to the present invention, direction reversal is determined using a position control model without measuring the actual machine position, and high precision is achieved by simply switching the backlash correction amount between two levels. Moreover, an inexpensive backlash correction device can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a backlash correction device according to an embodiment of the present invention, FIG. 2 is a timing chart diagram for explaining the invention in detail, and FIG. 3 is a block diagram of a conventional backlash correction device. FIG. 4 is a timing chart for explaining the conventional operation. (11)...Position control model, (12)...Machine position reversal timing estimator, (13)...Backlash correction amount switching device, (15)...Backlash correction device. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Diagram Diagram / Procedural Amendment (Voluntary)

Claims (1)

[Claims] In a position control device that drives a servo motor by position loop control according to a command position to move a machine tool and perform contour control, means for inputting a command position into a position loop control model and determining the timing at which the motor reverses;
From the above timing, first a command position that can be moved by the acceleration that the motor can generate is added to the original command position, and then, when the movement equivalent to the backlash ends, the original command position is returned to the position equivalent to the backlash. A backlash correction device for a position control device, comprising: