JPH03158905A - Servo-controller - Google Patents

Abstract

PURPOSE:To obviate a transient error by providing a correction computing element for operating the position correction quantity by a motor position stored at the time when a machine is operating in the positive and the negative directions, and a motor position detected by a motor position detector, and also, adding this position correction quantity to a command position. CONSTITUTION:A storage device 10 stores a positive direction function and a negative direction function at the time when a machine is operating in the positive direction, and at the time when the machine is operating in the negative direction, respectively. At the time when a command position PCMD moves in the positive direction, including the time for actuating the machine and the time for inverting the direction, a motor position PPGM of a positive direction function is outputted, and an output of a negative direction function is also the same. Subsequently, a correction computing element 11 derives the correction quantity PCMP 15 by the expression of PCMP=PPGM-PPG by an actual motor position PPG of the motor and the motor position PPGM of the stored positive direction function or negative direction function. In such a way, an error caused by the error cause existing between the machine position and the motor position is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a servo control device, and is particularly useful when applied to feed servo control of a motor for a feed axis of an NC-controlled machine tool.

<Prior Art> FIG. 3 is a block diagram showing a servo control device for a feed shaft motor of an NC-controlled machine tool according to the prior art. As shown in the figure, in this servo control device, a position signal P1No of a machine tool 2 and a command position signal P detected by a position detector 1 such as an inductosin. . 0, and the calculator 3 calculates and outputs a speed command according to the deviation between the two. The speed of the motor 4 can be obtained by a differentiator 6 that differentiates a motor position signal PPC outputted from a motor position detector vii5 such as a positive concoder that detects the motor position and a motor position detector 5. Of course, the motor speed can also be similarly detected by a tachogenerator that directly detects it. Then, compare the speed command and the motor speed,
A calculator 8 calculates and outputs a current command according to the deviation between the two. Further, the motor current flowing through the motor 4 detected by the current detector 8 is compared with the current command, and the motor current is controlled by the current controller 9 according to the deviation between the two. Thus, the motor 4 is driven by the current controller 9 and drives the machine tool 2 to the commanded position.

<Problem to be solved by the invention> There is mechanical play or distortion between the motor 4 and the machine tool 2.
The motor position and S machine position do not necessarily match. That is, for example, as shown in FIG. 2, when the machine position signal PIND and the motor position signal PPo move in the positive direction, a positive direction [PINo-PPG] function I (hereinafter referred to as the positive direction function) is created.
There is a correlation shown by , which moves in the negative direction (time is in the negative direction [PI
There is a correlation represented by the N[) 'PG) function (hereinafter referred to as a negative direction function). Therefore, when the machine is stopped, the machine position and the motor position are shown by the area (■) surrounded by the positive direction function (■) and the negative direction function (■).

In the servo control device according to the prior art, the command position signal P. Since the speed command of the motor 4 is calculated using the HD and the machine position signal PINO, a tracking error occurs because the speed command of the motor 4 does not match the speed at which the machine tool 2 should move when the machine tool 2 is started or when the direction is reversed. Ta. For example, the fourth
As shown in the figure, the feed axis is at the starting point 10. of the X-axis and Y-axis. In the two-axis linear command 12 at the end point 11, the following error is
Since the two axes are different, an error occurs with respect to the two-axis linear command 12, as in the actual movement 13 of the machine tool 2. Further, as shown in FIG. 5, in the circle command 14 of the XYZ axes, a movement 15 with a tracking error occurred when the Y axis changed from the positive direction to the negative direction.

SUMMARY OF THE INVENTION In view of the above-mentioned prior art, an object of the present invention is to provide a servo control device that can eliminate errors that are not caused by error causes that exist between a machine position and a motor position.

Means for Solving the Problems> The configuration of the present invention that achieves the above object includes a position loop that calculates a speed command based on a command position given as a function of time and a machine position detected by a position detector; A servo control device comprising a speed loop that calculates a current command for the motor by comparing the speed command with a motor speed of a motor that drives the machine, and drives the motor with the current of the current command. , a motor position detector that detects the position of the motor, and a motor position detector that detects the position of the motor; a memory device that stores the motor position and the motor position; and a position correction amount is calculated based on the motor position stored when the machine is moving in the positive direction or the negative direction, and the motor position detected by the motor position detector. The present invention is characterized in that it also includes a correction calculator that adds the position correction amount to the command position.

Function> In the present invention having the above configuration, the memory device stores in advance a positive direction function when the machine is moving in the positive direction, and a negative direction function when the machine is moving in the negative direction.

Command position PCM in the forward direction, including when starting the 4J machine and when reversing direction. When moves, the motor position PP61 of the positive direction function
．． Output l. The same applies to the output of the negative direction function. The correction calculator calculates the actual motor position PP6 and the motor position Ppa of the stored positive direction function or negative direction function.
The correction amount P is determined by h. 1.1215 is calculated using the formula P = P - P. Wk Correction amount P when starting up or reversing the machine. , 2 is the commanded position P of the machine. M. If the motor is rotated extra in order to move according to the direction, the movement immediately becomes upward according to the positive direction function or the negative direction function.

When the movement follows a positive direction function or a negative direction function P = P Because it is Po,,P-0 This results in the same movement as conventional servo control.

Embodiments Hereinafter, embodiments of the present invention will be described in detail based on the drawings. Note that parts that are the same as those in the prior art are given the same numbers and redundant explanations will be omitted.

FIG. 1 is a block diagram showing an embodiment of the present invention. As shown in the figure, the memory 10 stores a positive direction function (2) and a negative direction function (2).

In this embodiment, in order to store the positive direction function (2), the command position P. . 0 in the positive direction, and after a certain period of time has passed since the start of the change in the positive direction, the relationship between the machine position PIIIQ and the motor position PPG becomes a positive direction function I, so this is stored in the memory 10. . The memorization work for the negative direction function (2) is also performed in the same manner. When the command position P is changing in the positive direction, the memory 10 stores the value of the motor position PPG of the positive direction function I, and also stores the command position P. M. When is changing in the negative direction, the value of the negative direction function (■) is output as the reference motor position PPGM.

The correction calculator 11 receives the command position P. 1. When lo is changing in the positive or negative direction, P = P - P, and the command position P. oMP- when FID does not change
The position correction amount P becomes 0. Output M2.

According to this embodiment, the command position Pc1. In a stopped state where lI is not changing, it is similar to a conventional servo control device.

Furthermore, when the servo is continuously moving in the positive or negative direction, PPG-PPGM from the original definition, so P = 0, which is the same as in the conventional servo control device.

On the other hand, when the machine tool 2 starts up or reverses direction, Ppa"pan becomes Ppa"pan, and the value of PCMP becomes the amount of motor position correction that should be made by turning extra in order to move according to the positive direction function I or the negative direction function ■. Therefore, PPG = PPGM immediately.

<Effects of the Invention> As specifically explained above in conjunction with the embodiments, according to the present invention, the problem that exists between the machine position and the motor position when the feed axis is started or when the direction is reversed, which occurs in conventional servo control devices, It is possible to eliminate transient errors caused by errors caused by backlash or distortion in the mechanical system.

[Brief Description of the Drawings] Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a graph showing the relationship between machine position and motor position, and Fig. 3 shows a servo control device according to the prior art. Block diagram, 4th
FIG. 5 is an explanatory diagram of the XY two-axis linear movement, and FIG. 5 is a diagram illustrating the XYZ-axis circular axis movement. In the drawing, 1 is the position detector, 2 is the machine tool, 4 is the motor, 5 is the motor position detector, PINO is the position signal, PCHD is the command position signal, PCHp is the correction amount, PPG" PGl, l is the motor position be.

Claims (1)

[Claims] A position loop that calculates a speed command based on a command position given as a function of time and a machine position detected by a position detector; and a position loop that calculates a speed command based on a command position given as a function of time and a machine position detected by a position detector; a speed loop that compares and calculates a current command for the motor, and a servo control device that drives the motor with the current of the current command, a motor position detector that detects the position of the motor; a memory device that stores the machine position and motor position when the machine is moving in one direction, that is, the positive direction, and the machine position and the motor position when the machine is moving in the opposite direction, that is, the negative direction; A correction calculator that calculates a position correction amount based on the motor position stored when the machine is moving in the negative direction and the motor position detected by the motor position detector, and adds this position correction amount to the command position. A servo control device comprising: