JPH10312220A - Tracking control method between two servo systems - Google Patents

Abstract

(57) [Problem] To solve a problem that, in tracking control between two servo systems, a synchronization error in a portion where acceleration changes largely due to a response delay due to a speed loop of a slow system cannot be corrected. . SOLUTION: A speed command Xs' of a second servo system (fast response system) obtained by sampling a position detection signal Xs of a first servo system (slow response system) is multiplied by a correction coefficient K1. A first correction signal y1 (t) is obtained, and a second correction signal y2 (t) is obtained by multiplying a speed command f (t) of the first servo system by a correction coefficient K2. Correction signal y1
(T) and y2 (t) are added to correct the speed deviation of the second servo system, and the correction coefficient K3 is added to the differential value d (f (t)) / dt of the speed command of the first servo system. Multiply by 3
, And adds this to the speed command f (t) of the first servo system to correct the delay of the speed loop of the first servo system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of sampling a position detection signal of a first servo system having a closed circuit system of speed as a minor loop and subjecting the signal to digital arithmetic processing, and converting the signal to a closed loop control system of speed as a minor loop. The present invention relates to a tracking control method between two servo systems that causes the behavior of the second servo system to follow the behavior of the first servo system by using the position command signal of the second servo system.

[0002]

2. Description of the Related Art When a plurality of servo systems are controlled in synchronization, the following two methods are usually considered. One is to match the response characteristics of the servo system and output each other's commands synchronously. The other is to use the faster system for the servo system with difficult response characteristics. This is a method of controlling in synchronization with the system. The former is used for general control between servomotors, and accurate synchronous control is possible as long as the response characteristics are matched. However, in the latter case, after outputting the command to the slow system, the command to the fast system is calculated and output while observing the response, so there is a delay time at the time of observation, and how much faster the response of the fast system Also accurate synchronization (follow-up)
Was impossible.

Therefore, a first correction signal corresponding to a position detection signal of the first servo system and a second correction signal obtained from a speed command signal of the first servo system are generated, and these first correction signals are generated. A control method for improving synchronization accuracy between a slow system and a fast system, such as a system for correcting a speed deviation of a second servo system with a second correction signal (Japanese Patent Laid-Open No. 63-268011), has been proposed. FIG. 4 is a diagram showing a typical example of the control method disclosed in JP-A-63-268011. 4 is a first servo system (a system having a slow response), and a lower loop is a second servo system.
Servo system (system with fast response). Ks and Kz are proportional gains of the position loop, Gs and Gz are transfer functions, f (t)
Is a speed command, d (f (t)) / dt is a differential value of the speed command, ∫f (τ) dτ is a position command, Xs ′ and Xz ′ are speeds, Xs and Xz are positions, k is a constant, and K1 is A correction coefficient for the response, K2 is a correction coefficient for the command, and D is a sampling circuit.

In the control method shown in FIG. 4, a first correction signal y1 is obtained by multiplying a speed command Xs' of the second servo system obtained by sampling the position detection signal Xs of the first servo system by a correction coefficient K1. (T) and the speed command f of the first servo system.
(T) is multiplied by a correction coefficient K2 to obtain a second correction signal y2.
(T), and the first and second correction signals y1 (t), y2
(T) is added to correct the speed deviation of the second servo system.

[0005]

SUMMARY OF THE INVENTION As described above,
In the control method of -268011, the synchronization error correction for the ramp input is possible, but when the command speed and command acceleration of the slow system increase, the change in acceleration is large due to the response delay due to the speed loop of the slow system. There is a problem that the synchronization error in a portion, that is, a portion close to the step command cannot be corrected. An object of the present invention is to
It is an object of the present invention to provide a tracking control method between two servo systems capable of performing accurate synchronous control between controlled objects having different response characteristics by correcting a delay of a speed loop of a slow system in the control method of 3-268011.

[0006]

SUMMARY OF THE INVENTION To solve the above-mentioned problems, a first method according to the present invention of a tracking control method between two servo systems is described.
Is to correct the response delay of a slow system by adding differential compensation to the speed command signal of the first servo system. Second Embodiment of Tracking Control Method Between Two Servo Systems of the Present Invention
Is to correct the response delay of a slow system by adding differential compensation to the command signal for the position of the first servo system. The upper part of each figure is a first servo system (a system with a slow response), and the lower loop is a second servo system (a system with a fast response). Ks and Kz are proportional gains of the position loop, Gs and G
z is a transfer function, f (t) is a speed command, d (f (t)) /
dt is the differential value of the speed command, ∫f (τ) dτ is the position command,
Xs 'and Xz' are speeds, Xs and Xz are positions, k is a constant,
K1 is a correction coefficient for a response, K2 is a correction coefficient for a command, K3 is a differential compensation coefficient for a command, and D is a sampling circuit.

FIG. 2 corresponds to the first embodiment of the present invention, in which the speed command Xs' of the second servo system obtained by sampling the position detection signal Xs of the first servo system is multiplied by a correction coefficient K1. 1 and a second correction signal y2 (t) by multiplying a speed command f (t) of the first servo system by a correction coefficient K2 to obtain a first and second correction signal y1 (t). Signal y1 (t),
y2 (t) is added to correct the speed deviation of the second servo system, and the differential value d of the speed command of the first servo system is added.
(F (t)) / dt is multiplied by a correction coefficient K3 to obtain a third correction signal y3 (t), which is added to a speed command f (t) of the first servo system to obtain a first servo system. Is to correct the delay of the speed loop. The example of FIG. 3 corresponds to the second embodiment of the present invention. The first servo system speed command Xs 'obtained by sampling the position detection signal Xs of the first servo system is multiplied by a correction coefficient K1 to obtain the first servo system speed command Xs'. And a correction signal K2 is added to the position command Δf (τ) dτ of the first servo system.
, And a second correction signal y2 (t) is obtained. The first and second correction signals y1 (t) and y2 (t) are added to correct the speed deviation of the second servo system. A third correction signal y3 (t) is obtained by multiplying the differential value d (f (τ) dτ) / dt of the position command of the first servo system by a correction coefficient K3, and this is converted to the position command f of the first servo system. (Τ) is added to dτ to correct the delay of the speed loop of the first servo system.

Next, the example of FIG. 2 will be described in detail.
In this configuration, it is particularly important for the present method that the constant setting of K3 is added to the constant setting of K1 and K2 in the conventional method. In the prior art, the first servo system during the synchronization period and
In the second servo system, the case of the speed ramp input when the loop gain (Gs) of the minor loop of the closed circuit system of the slow system speed is approximated to infinity without considering the transient state has been described. In the present invention, the evaluation was performed by approximating a minor loop of a closed circuit system having a slow system speed as a first-order delay. However, at this time, the loop gain (Gz) of the minor loop of the closed circuit system having a high system speed is infinite. Here, the transfer function of the slow system has a second-order delay. However, by performing differential compensation by multiplying the speed command value of the slow system by K3, the second-order delay of the closed circuit of the position is treated as the first-order delay of the position. Can be. Thereby, the delay of the speed loop can be ignored.

[0009]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a servo system to which an embodiment of a tracking control method for two servo systems according to the present invention is applied. This system is applied to a synchronous tapping machine, and includes a servo motor 1, a tacho generator 2, a pulse generator 3, a servo drive 4, a D / A
The converter 5, the deviation counter 6, and the position command payout unit 7
Axis (spindle drive) servo system
1, tacho generator 12, pulse generator 13,
Servo drive 14, D / A converter 15, adder 27,
The deviation counter 16 and the multiplier 18 constitute a Z-axis (table driving axis) servo system.

The constant setting units 20, 21, and 22 are provided with corrections K1, K2, and K3, respectively.
A constant k is set to 6 by the microcomputer 8. The current value counter 9 samples the position detection signal Xs of the servo system for driving the spindle from the sampling signal 19,
The position signal Xs' is output. This position signal Xs' is multiplied by a constant k by a multiplier 18 to become a position command signal for a Z-axis servo system. This position command signal is multiplied by a correction coefficient K1 obtained by taking a difference from the previous read value by the synchronous speed correction calculator 23 to become a first correction signal y1 (t). Multiplier 17
Multiplies the position command signal αt ² of the S-axis drive servo system output from the position command issuing unit 7 by a constant k. After the output of the multiplier 17 is differentiated by the synchronous speed correction calculator 24, the output is multiplied by a correction coefficient K2 to obtain a second correction signal y2 (t). These first and second correction signals y1 (t), y2
(T) is added by the adder 27 to the output of the deviation counter 16. The synchronous speed correction computing unit 25 is provided with the position command payout unit 7.
Command signal αt of S-axis drive servo system output from
After differentiating ² , ² is multiplied by a correction coefficient K3 to obtain a third correction signal y3 (t). The third correction signal y3 (t) is added to the position command [alpha] t ^2.

Next, the effect of this embodiment will be described with reference to FIG. As shown in FIG. 5A, since the speeds of the S axis and the Z axis are generally different in synchronous tapping processing, the result of multiplying the position feedback value from the start point of the S axis by the synchronous speed constant k is the starting point of the Z axis. Compare with the position feedback value from. As shown in FIG. 5B, in the conventional example, when the synchronous tapping is performed, the synchronization error at the time of the change in the acceleration cannot be removed even if the correction coefficients K1 and K2 are optimally adjusted. In the embodiment of the present invention, since the delay of the S-axis speed loop can be corrected by differentially compensating the S-axis command signal by adjusting the correction coefficient K3, the synchronization error when the acceleration changes can be reduced.

The first correction signal y1 (t) mainly corrects the position observation of the slow system and the operation delay when creating a command for the fast system, and the second correction signal y2 (t) mainly corrects the slow system. Is corrected at the rise of the command, and the follow-up delay with respect to the change of the command acceleration of the slow system is corrected by the third correction signal y3 (t). Note that the correction coefficient K1,
K2 is determined by the observation delay, the delay due to the arithmetic processing, and the position loop gain of the Z axis, and the ratio of K1 and K2 is Z
It is determined by the position loop gain of the axis and S axis. The correction coefficient K3 is determined by the speed loop gain of the S axis.
The delay time due to the observation and calculation processing becomes constant due to the sampling time, and the correction coefficients K1 and K2 are set based on the position loop gain of the Z axis and the S axis, and the correction coefficient K3 is set based on the speed loop gain of the S axis. Thereby, accurate follow-up control of the Z axis and the S axis has become possible. As a result, tapping with higher speed and higher precision than before can be realized.

[0013]

As described above, the present invention corrects the delay of the speed loop of the slow system by adding differential compensation to the command signal of the first servo system of the slow response system of the prior art. Thus, there is an effect that accurate synchronization control between control objects having different response characteristics is possible.

[Brief description of the drawings]

FIG. 1 is a block diagram of a servo system to which a tracking control method between two servo systems according to the present invention is applied.

FIG. 2 is a first principle diagram of the present invention.

FIG. 3 is a second principle diagram of the present invention.

FIG. 4 is a diagram showing a typical example of a principle diagram of a conventional technique.

FIG. 5 is a timing chart showing a comparison of synchronization errors between the S-axis and the Z-axis with the conventional method when the present invention is implemented.

[Explanation of symbols]

 1, 11 S-axis servomotor, Z-axis servomotor 2, 12 Tach generator 3, 13 Pulse generator 4, 14 Servo drive 5, 15 D / A converter 6, 16 Deviation counter 7 Position command issuing unit 8 Microcomputer 9 Current value counter 17, 28 Multiplier 19 Sampling signal 20, 21, 22 Constant setting unit 23, 24, 25 Synchronous speed correction calculator 26 Synchronous speed payout unit 27 Adder

Claims (2)

[Claims] A second servo having a speed closed circuit control system as a minor loop is a signal obtained by sampling a position detection signal of a first servo system having a speed closed circuit control system as a minor loop and performing digital arithmetic processing. A tracking control method between two servo systems in which the behavior of a second servo system follows the behavior of a first servo system by using a position command signal of the first servo system, wherein a position detection signal of the first servo system is provided. Is multiplied by a first correction coefficient to generate a first correction signal, and a speed signal obtained from a speed command signal of the first servo system is multiplied by a second correction coefficient to generate a second correction signal. Follow-up control between two servo systems, in which a first correction signal and a second correction signal are added, and the added signal corrects a speed deviation of a speed control system of a second servo system. In the method, the speed of the first servo system Wherein the addition of differential compensation to the command signal, tracking control method between two servo systems. 2. A signal obtained by sampling a position detection signal of a first servo system having a closed loop control system of speed as a minor loop and performing digital arithmetic processing, and a second servo having a closed loop control system of speed as a minor loop. A tracking control method between two servo systems in which the behavior of a second servo system follows the behavior of a first servo system by using a position command signal of the first servo system, wherein a position detection signal of the first servo system is provided. Is multiplied by a first correction coefficient to generate a first correction signal, and a speed signal obtained from a speed command signal of the first servo system is multiplied by a second correction coefficient to generate a second correction signal. Follow-up control between two servo systems, in which a first correction signal and a second correction signal are added, and the added signal corrects a speed deviation of a speed control system of a second servo system. In the method, the position of the first servo system Wherein the addition of differential compensation to the command signal, tracking control method between two servo systems.