JPS63283490A - Speed controller for servomotor - Google Patents

Abstract

PURPOSE:To secure the stabilized operation of a feedback system at all times during the operation of a servo-system, by a method wherein an integration gain is set to a large value when the output of error between an actual speed signal and a speed commanding signal is within the range of a stationary error. CONSTITUTION:An adding circuit 1 operates an error between the actual speed TSA of a servomotor 3 and a speed command Vcmd and the result of the operation is outputted to a compensating circuit 2 as the deviation of speed. The control gain G of the compensating circuit 2 is set by the formula G=Kp+Ki/S. Here, a proportional gain is shown by a notation Kp and the integration gain is shown by the notation Ki. When a difference between a stationary error and the absolute value of the error is positive, the integration gain Ki is determined so as to be a predetermined gain. However, when the difference is negative, the integration gain Ki is set so as to be larger than the predetermined gain. According to this method, the responding property of the title device may be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a speed control device for a servo motor in a digital servo system.

(Prior Art) In a typical digital servo system, a torque command for a servo motor is set based on an error between a command speed and an actual speed, and for this purpose, a pulse coder or the like is used as a speed detection means.

In order to accurately control the speed and position of the servo motor from the above error signal, proportional operation and integral operation are normally performed.
An I compensation circuit is required, and if the integral gain is increased,
In general, minute deviations can be corrected with good response. However, whether or not the speed deviation is within the steady-state error range is determined by the operating speed of the system, which is not uniform, so the conventional method was to increase the integral gain just before the mechanical system stops. (Problem to be Solved by the Invention) In other words, in the past, the integral gain during normal operation could not be set very large, and special measures were taken only during stoppage. However, if the integral gain during normal operation is small, when the deviation becomes large, it can cause fluctuations in the mechanical system's operation, such as overshoot in the control system, and the stable operation of the feedback system is lost. .

The present invention has been made in view of the above points, and is a servo system that secures stable operation of the feedback system during the operation of the servo system by setting the integral gain large only when the deviation is minute within the steady error range. It is an object of the present invention to provide a speed control device for a motor.

(Means for Solving the Problems) According to the present invention, in a servo motor speed control device that controls the speed of a servo motor using discrete speed command signals, an actual speed signal and a speed command fed back from the servo motor are provided. a calculation means for outputting a speed error with respect to the signal; and a torque for forming a torque command to the servo motor by setting an integral gain larger than a predetermined gain when the absolute value of the error output of the calculation means is within a steady error range. It is possible to provide a speed control device for a servo motor characterized by comprising a command means.

(Function) The servo motor speed control device of the present invention operates by setting the integral gain to a large value when the error output between the actual speed signal and the speed command signal during operation of the servo system is within a set steady error range. It can be used to increase the rigidity of mechanical systems.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing a speed control device according to an embodiment of the present invention, in which a speed command Vcmd is supplied to a compensation circuit 2 having a predetermined control gain via an addition circuit 1, and a torque to a servo motor 3 is This is converted into a command T, and the servo motor 3 is driven and controlled at the command speed Vcmd.

The adder circuit 1 receives the actual speed TS from the servo motor 3.
A is fed back, and the error with respect to the speed command Vcmd is calculated here, and it is output to the compensation circuit 2 as a speed deviation.

The compensation circuit 2 controls the servo motor 3 based on the speed deviation.
It is used to set the power such as a predetermined drive current, and its control gain G is G = K p + K i
/s is set. Here, Kp is a proportional gain, Ki is an integral gain, and this integral gain Ki is defined by a function having a negative slope within a steady-state error range, which will be described next.

Figure 2 shows the magnitude of the integral gain Ki as the steady-state error RANG.
It is a flowchart which shows the triangular wave-like function defined within the E range, and the control algorithm in that case.

That is, as shown in FIG. 3(b), the actual speed signal TSA from the servo motor 3 is constantly fed back to the addition circuit 1 via speed detection means such as a pulse coder, and first the error ERROR (= V c + nd - TS^) is calculated (step a). When the difference between the steady-state error R^NGE and the absolute value of the error ERROR is defined as Xl (step b), the sign of this xl is determined (step c)
, if positive, the integral gain Ki is set to a predetermined gain of 1 (step d), and an integral operation is performed (step e).
. However, when xl is negative, that is, when the absolute value of the error output is within a predetermined steady-state error range, the error ERR
The absolute value of OR is calculated as x2 (step f), and the corresponding integral gain Ki is calculated as X5 = K1 + X2
*Calculated from the GAIN formula. In step g), the integral gain Ki is set to a predetermined gain greater than 1, and then in step h, an integral operation is performed.

In Fig. 3, the magnitude of the integral gain Ki is not defined by a triangular waveform function within the steady error range as shown in Fig. 2(a), but by a rectangular function, that is, a predetermined gain within the steady error range. An example is shown in which the integral gain is set to a constant value of 2 greater than 1, and in the flowchart showing the control algorithm in this case, a step called KixK2 may be inserted in place of steps f, g, and h.

In the servo motor speed control device configured as described above, PI control is performed using the speed command Vcmd.
When forming the torque command for the servo motor 3, the integral gain Ki of the compensation circuit 2 can be set large when the error is within the steady error range, and set small when the error is above the steady error range. Regardless of system characteristics and operating speed, responsiveness to minute errors can be improved without reducing stiffness during operation. Moreover, compared to the conventional system that increases the integral gain only when stopping, the integral gain during normal operation is increased when the deviation becomes large, so control is performed when the deviation becomes large. Even if there is an overshoot in the system, no fluctuations will occur in the mechanical system operation.

The most preferred embodiment of the present invention has been described above in some detail. However, how to define the magnitude of the integral gain Ki within the steady-state error range is determined by appropriate design according to the characteristics of the digital servo system. Modifications to detailed parts of the structure of the invention, various modifications as long as they do not go against the spirit of the invention as described in the claims, or combinations thereof may be made. It is clear that it can be done.

(Effects of the Invention) As explained above, according to the present invention, the integral gain is set large when the error output between the actual speed signal and the speed command signal during operation of the servo system is within the set steady error range. Since the rigidity of the mechanical system during operation is increased, it is possible to provide a servo motor speed control device that ensures stable operation of the feedback system during operation of the servo system.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2(a) is an explanatory diagram showing an example of setting the integral gain in the same embodiment, and FIG. 2(b) is a block diagram showing an example of setting the integral gain in the same embodiment. FIG. 3 is a flowchart showing the control algorithm of FIG. 3, which is an explanatory diagram of the operation of another embodiment. 1... Addition circuit, 2... Compensation circuit, 3... Servo motor.

Claims (3)

[Claims] (1) In a servo motor speed control device that controls the speed of a servo motor using discrete speed command signals, the calculation means outputs a speed error between the actual speed signal fed back from the servo motor and the speed command signal; A servo motor characterized by comprising: torque command means for setting an integral gain larger than a predetermined gain to form a torque command to the servo motor when the absolute value of the error output of the calculation means is within a steady error range. speed control device. (2) The servo motor according to claim 1, wherein the torque command means has an integral gain defined by a function having a negative slope within the steady-state error range. speed control device. (3) The speed control of the servo motor according to claim (1), wherein the torque command means has an integral gain set to a constant value larger than a predetermined gain within the steady-state error range. Device.