JPS62229412A - Positioning device - Google Patents

Abstract

PURPOSE:To control a motor to a target position in a minimum time and to improve the accuracy of positioning a motor by executing a feed forward control, storing a following delay time at acceleration according as a load is great or not and correcting a speed pattern at deceleration with the aid of said amount. CONSTITUTION:A deviation arithmetic part 22 obtains a deviation (N-n) between an integrated value N in a command value pulse counter 14 and an integrated value (n) in a feedback pulse counter 20. Accordingly, since the differentiated value B of the speed pattern A based on the command value is added to the deviation (N-n), so-called feed forward control is executed. Moreover at acceleration, an acceleration delay is improved, and the speed is almost linearly accelerated. If the inertia of a load is great to deteriorate trackability at that time, a subtraction pattern arithmetic part 32 obtains and stores the following delay amount (x). Then a deceleration start point (a) ahead of the speed pattern A at deceleration is obtained, and the speed pattern A is corrected so that it can be the prescribed deceleration pattern C corresponding to the following delay amount (x) at the point (a).

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is directed to a servo motor that outputs a speed pattern corresponding to a target position as a command pulse and performs closed loop control using the deviation between this command pulse and a feedback pulse. This is similar to the positioning device applied to

(Background of the Invention) As a method for controlling the positioning of a servo motor, the deviation between a command pulse and a feedback pulse (hereinafter referred to as F/B pulse) from a position detector attached to the motor is determined.
So-called closed-loop control, which controls the deviation to zero, is widely known. In this case, the optimal speed pattern corresponding to the amount of movement to the target position is stored in advance,
A method has been proposed in which a speed pattern for a target position is read in correspondence with a command value, and a command pulse is determined according to this speed pattern.

However, depending on the inertia of the rotating part of the motor and the magnitude of the load, the amount of delay in following the command pulse by the motor always changes.

For this reason, if the speed pattern for the target position is uniquely determined, the motor cannot be accurately positioned at one mark position.

FIG. 3 is a speed profile diagram showing this follow-up delay, in which A is a pre-stored trapezoidal speed pattern, B is a trapezoidal speed pattern stored in advance,
shows the actual speed pattern. As described above, during acceleration, an acceleration delay corresponding to the shaded region S1 occurs, and during deceleration, a deceleration delay corresponding to the region S2 occurs. Therefore, there was a problem that accurate positioning could not be performed.

(Object of the invention) The present invention was made in view of such circumstances,
A positioning device that not only improves the motor's ability to follow pre-stored speed patterns, but also reduces positioning time by decelerating the motor at an optimal speed pattern even when the load changes, and enables high-precision positioning at the target position. The purpose is to provide

(Structure of the Invention) According to the invention, the object is to include a speed pattern setting section that outputs an operating speed pattern as a command value pulse based on a command value indicating a target position of the motor, and a feedback pulse indicating the amount of movement of the motor. and a positioning device that controls the motor based on a deviation between the command value pulse and the command value pulse, and calculates an acceleration follow-up delay amount of the motor with respect to the speed pattern to steplessly determine an optimal deceleration start point, and adjusts the speed pattern. The motor is provided with a deceleration pattern calculating section for correcting, a differential calculating section for differentiating the speed pattern, and an adding section for calculating the sum of the differential value and the deviation, and controlling the motor so that the sum becomes zero. This is achieved by a unique positioning device.

(Embodiment) FIG. 1 is a control system diagram of an embodiment of the present invention, and FIG. 2 is a speed profile diagram thereof.

In FIG. 1, reference numeral 10 is an 11-mark position command section for inputting a command value indicating a target position, and 12 is a speed pattern setting section which stores, for example, a trapezoidal speed pattern A shown in FIG. 2. In this speed pattern A, a plurality of patterns are stored in the form of a map or function in correspondence to the amount of movement indicated by the command value. Therefore, this speed pattern setting section 12 selects one speed pattern A corresponding to the command value and outputs it as a command pulse. Reference numeral 14 denotes a command value pulse counter, which calculates an integrated value N of command value pulses output by the speed pattern setting section 12.

Reference numeral 16 denotes a motor, and the amount of rotation or movement of this motor 16 is detected by a position detector 18 such as a rotary encoder and output as an F/B pulse. This F/B pulse is integrated in the F/B pulse counter 20, and this F/B pulse is
The stitching value n of the /B pulse is sequentially determined. A deviation (N-n) between the integrated value N of the command value pulse counter 14 and the integrated value n of the F/B pulse counter 20 is determined by the deviation calculating section 22.

On the other hand, the speed pattern A is also input to the differential calculation section 24, where the rate of change of the speed pattern A is determined as a differential value B. The sum (N-n)+B of this differential value B and the deviation (N-n) is obtained by the output calculation section 26, this sum is converted into an analog signal by the D/A converter 28, and the servo driver 30 Based on this analog signal, motor 1
Drive 6.

32 is a deceleration pattern calculation unit, which calculates the follow-up delay lx of the actual speed pattern B shown in Fig. 52, steplessly determines the optimum deceleration starting point a, and corrects the speed pattern A according to the command value. do. This calculation unit 32 sequentially calculates and stores the follow-up delay amount X as a function of time x (t) at very short time intervals determined by, for example, clock pulses,
The deceleration pattern C can be obtained by subtracting the follow-up delay amount x(tl-t) from the speed pattern A, assuming that the follow-up delay amount during deceleration is x(L+-t).

Here, tl is the time at which the target position is reached by speed pattern A (point b in FIG. 2). In this way, during deceleration, the speed pattern A is corrected by the follow-up delay amount X. Various algorithms are possible for modifying this speed pattern A, and the optimal algorithm may be appropriately adopted depending on the purpose.

Therefore, the differential value B of the speed pattern A based on the command value is added to the deviation (N - n ), so so-called feedforward control is performed, and the acceleration delay is improved during acceleration, as shown in the second figure. Accelerates almost linearly. At this time, if the inertia of the load is large and the followability becomes poor, the follow-up delay amount X is determined by the subtraction pattern calculation section 32 and stored. Then, a deceleration start point a that precedes the speed pattern A during deceleration is determined, and the speed pattern A is corrected from this point a so that it becomes a predetermined deceleration pattern C in accordance with the follow-up delay amount X. Therefore, the followability of speed control is improved, and positioning accuracy is significantly improved.

In this embodiment, since the speed pattern setting section 12 stores the trapezoidal speed pattern A, the number of speed patterns to be stored can be reduced. However, the present invention is not limited to this, and various patterns such as an exponential function can be set, and it is desirable to set a speed pattern that allows movement to a predetermined movement position in the shortest time and most stably. The present invention can also be applied to a case where the amount of movement is small and the speed is decelerated before reaching a constant rotational speed range, and the present invention naturally includes this.

The present invention includes the speed pattern setting section 12 and each calculation section 22.
．． 24.26 and the counter 14.2° can of course be constructed by a CPU (digital arithmetic unit), and in this case, the speed pattern A is stored in advance in a FROM or the like.

(Effects of the Invention) As described above, the present invention calculates the differential value of the speed pattern set corresponding to the command value and adds this to the deviation (N-n) to drive the motor. Feedforward control improves the followability of the remoter.
．． do. Furthermore, since the amount of follow-up delay during acceleration due to the magnitude of the load is stored and this is used to correct the speed pattern during deceleration, the motor can be controlled to the target position in the shortest possible time, improving motor positioning accuracy.

[Brief explanation of drawings]

FIG. 1 is a control system diagram of an embodiment of the present invention, FIG. 2 is a speed profile diagram thereof, and FIG. 3 is a speed profile diagram of a conventional device. DESCRIPTION OF SYMBOLS 10... Target position command part, 12... Speed pattern setting part, 16... Motor, 18... Position detector, 24... Differential calculation part, 26... Output calculation part, 32. ...Subtraction pattern calculation section.

Claims (1)

[Scope of Claims] A speed pattern setting unit that outputs an operating speed pattern as a command value pulse based on a command value indicating a target position of the motor, the deviation between a feedback pulse indicating the amount of movement of the motor and the command value pulse. a positioning device that controls the motor based on the speed pattern, comprising: a deceleration pattern calculation unit that calculates an acceleration follow-up delay amount of the motor with respect to the speed pattern, steplessly determines an optimal deceleration start point, and corrects the speed pattern; A positioning device comprising: a differential calculation unit that differentiates a speed pattern; and an output calculation unit that calculates the sum of the differential value and the deviation; and controls a motor so that the sum becomes zero.