JP2797330B2 - Variable gain integral proportional compensator - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an integral proportional compensator for a servo control system.

[Conventional technology]

FIG. 3 (a) shows a speed pattern of a mechanism for repeating a high-speed forward movement after a constant-speed forward movement, for example, a servomotor (accordingly, a scanning unit) for driving a scanning mechanism of a copying machine. Indicates the scanning mechanism. In FIG. 4, 1 is a wire, 2 is a pulley, 3 is a mirror, 4 is a coupling, 5 is a servo motor, and 6 is a control device. To improve the transient response of the servo motor 5, for example, It has an integral proportional compensator having the configuration shown in FIG. In FIG. 1, reference numeral 10 denotes an A / D converter, which converts a step-like speed command (analog signal) r into a digital value speed command (signal) R. Numeral 11 denotes an integral proportional compensator, which has an integrator 12 and a proportional amplifier 13, and its output is
It is supplied to a motor drive unit (current amplifier) 16 through a D / A converter 15. A pulse generator 17 detects the rotation angle of the servo motor 5. Reference numeral 18 denotes a speed detector which detects the rotation speed of the servo motor 5 by taking in the output of the pulse generator 17 and outputs a speed feedback signal f.
Create The speed feedback signal f is matched with the speed command signal R sent from the A / D converter 10 in the integral proportional compensator 11, and the deviation ε is input to the integrator 12.

Before starting the copy operation, the mirror 3 has moved to the reference position (home position) and stopped. The control device 6 receives the step-like speed command, rotates the servo motor 5, moves the mirror 3 from this home position to the end of the document at a constant speed, and returns to the home position without stopping. When the number of copies increases, this cycle operation is repeated, and the speed (initial speed fo) of the servo motor 5 at the start of the cycle operation includes f00, f01, f02 in FIG. 3 (b).
Variations occur as shown by. The integral proportional compensator 11
The output U of the integrator 12 continues to increase until the actual speed f of the servo motor 5 coincides with the speed command value r, as indicated by the dotted line in FIG. When it comes
It starts to decrease and finally settles to the steady-state value Uis, but the integrator 12
Since the gain Ki is constant, the above initial speed (negative value)
As fo increases, the maximum value of the output U of integrator 12 correspondingly increases.

For this reason, when the initial speed fo of the servomotor 5 increases, the overshoot at the start of the forward movement increases as shown by the waveforms ABC, and it takes time to settle, and the copy image at the start of the copy operation takes a long time. It has an adverse effect. In FIG. 3B, a waveform A is a waveform at the start of the first copy operation, and B and C are waveforms at the start of a plurality of cycle operations.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problem, and provides a variable gain integral proportional compensator that can obtain a transient response characteristic that is not affected by the variation even when the operation initial value of the controlled object varies. The purpose is to:

[Means for solving the problem]

The present invention has been made to solve the above problems,
In the integral proportional compensator of a servo control system having a predetermined gain integrator for integrating a deviation between a command value and a feedback value from a controlled object and a proportional amplifier having the feedback value as an input, the deviation reaches a predetermined value. Up to this point, the configuration is such that the gain of the integrator is lower than the predetermined gain.

[Action]

In the present invention, the gain of the integrator is maintained at a low value until the response of the control target to the step-like command value reaches a predetermined level. Therefore, even if the initial value of the control target varies, the transient response The characteristics are hardly affected by the variation.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a servo motor control device.
5 in that the integral proportional compensator 20 has a gain adjustment unit 14.

The gain adjuster 14 receives the speed command r (= R) and the speed feedback signal f, and obtains the gain Ki of the integrator 12.
(A) If α · r> f, switch to Ko, and (b) If α · rf, switch to K1 (> Ko), but to 0α1.

The output Ui of the integrator 12, the output Up of the proportional amplifier 13, and the output U of the integral proportional compensator 20 are represented by the following equations, respectively.

Ui = Uin−1 + Ki · T · (rn−fn) (1) Upn = Kp · fn (2) Un = Uin−Upn (3) where Ki: gain of the integrator 12 T: sampling Period n: Number of samplings The operation of this embodiment will be described with reference to the transient response waveform diagram of FIG. 2, (a) shows the relationship between the speed command and the actual speed f of the servomotor 5, (b) shows the output waveform of the gain adjustment unit 14, and (c) shows the output waveform of the integrator 12. Show.

When the step-like speed command r is given without the gain adjusting unit 14, the output Ui of the integrator 12 is provided as described above.
Continues to increase until the actual speed f of the servomotor 5 matches the value of the speed command r as shown by the dotted line in FIG. 2 (c), and when the deviation ε becomes a negative value, it starts decreasing. After a while, it calms down to the steady value Uis. At this time, the servo motor 5 shows a transient state shown by a dotted line in FIG. The value of Ui at the time of transition is larger as the initial speed (negative value) fo of the servo motor 5 is larger, which causes the servo motor 5 to overshoot.

In the present embodiment, the actual speed f of the servomotor 5 is α ·
r until the time t = to, that is, the servo motor 5
Until the speed reaches a predetermined speed attainment with respect to the speed command r, the gain Ki of the integrator 12 is set to a small value Ko to suppress an increase in the output of the integrator 12, and after increasing to α · r, the gain becomes Since Ki is switched to a large value K1, the value of Ui−Uis is reduced as shown by the solid line in FIG.
The speed f of the servo motor 5 can be increased to the value of the speed command r without overshooting the servo motor 5 as shown in FIG.

Therefore, even if the initial speed fo when the mirror 3 returns to the home position and moves forward again greatly differs from the initial speed at the start of the previous forward movement, the transient response time until the speed settles is substantially Thus, good image quality can be obtained at the start of each copy operation.

In the above embodiment, the gain Ki of the integrator 12 is switched stepwise. However, as shown in FIG. 2 (d), the gain Ki is continuously changed until the actual speed f of the servomotor 5 reaches r. You may make it change.

〔The invention's effect〕

As described above, the present invention is configured to keep the gain of the integrator at a low value until the responsiveness of the control target to the step-like command value reaches a predetermined level. Therefore, the initial value of the control target varies. However, it is possible to prevent the transient response characteristic from being affected by the variation.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 (a) is a waveform diagram showing a relationship between a speed command and an actual speed of a servomotor, and FIG. 2 (b). FIG. 2C is a diagram showing an output waveform of the gain adjusting unit in the embodiment, FIG. 2C is a diagram showing an output waveform of the integrator, and FIG. 2D is another output waveform of the gain adjusting unit in the embodiment. FIG. 3A is a diagram showing a speed pattern of a servo motor for driving a copier scanner by a control device having a conventional integral proportional compensator, and FIG.
FIG. 4B is a diagram for explaining the problem of the conventional example, FIG. 4 is a diagram showing the configuration of the scanner section, and FIG. 5 is a block diagram of the conventional integral proportional compensator. 12: Integrator, 13: Proportional amplifier, 14: Gain adjustment unit.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G05D 3/12

Claims (2)

(57) [Claims] An integrator having a predetermined gain for integrating a deviation between a digital speed command value and a digital feedback value from a control target; and a proportional amplifier receiving the digital feedback value as an input. In the integral proportional compensator of the servo control system, which takes an output difference and uses it as an input signal of a driving source to be controlled via at least a D / A converter and an amplifier, the gain of the integrator until the deviation reaches a predetermined value. Is a lower value than the predetermined gain. 2. A variable gain integral proportional compensator wherein the gain of the integrator increases to the predetermined gain in proportion to the deviation until the deviation reaches a predetermined value.