JPH02197285A - Digital control system for synchronous motor - Google Patents

Abstract

PURPOSE:To operate a synchronous motor smoothly by operating the difference between previous and current speed command values, then obtaining the number of times of the speed control loop operation where a speed command is executed during the same time interval and calculating the distributed value of speed command value. CONSTITUTION:Moving amount of a synchronous motor SM1 is counted based on the output from an incremental rotary encoder RE2 coupled with the SM1, then it is fed to a CPU10. The CPU10 receives a speed command N0 from a host CPU9 and controls an inverter circuit 13 to drive the SM1. Then a difference N between previous speed command value N0-1 and current command value N0 is obtained. The number of times of operation, M, of a speed operating loop executed during such interval as the difference N is zero is determined based on the difference of a counter 3 thus determining the distributed value n0 of the variation of speed command according to a formula n0=N/M. By such arrangement, smooth rotation is realized, without requiring modification of program, even if the time interval of the variation of speed command signal is not constant.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a digital control system for synchronous motors used in machine tools, industrial robots, and the like.

(Prior Art) A conventional digital control device for a synchronous motor is configured as shown in FIG.

In Fig. 1, 1 is a synchronous motor (S M
), 2 is an incremental rotary encoder (RE
) outputs two-phase square wave signals A and B having an electrical phase difference of 90 degrees from each other, and is directly connected to the synchronous motor] in order to convert the rotation angle of the rotor on the synchronous motor into the amount of movement. Ru. 3 is a two-phase output signal A of the incremental rotary encoder 2;

4 is an absolute rotary encoder (C
S) outputs three-phase square wave signals PIJ, Pv, and PW having an electrical phase difference of 120 degrees, and the synchronous motor 1
is directly connected to the synchronous motor 1 to detect the position of the rotor. 5 is a first current detection circuit (CT) that detects the current flowing in the U phase of the synchronous motor 1, and 6 is a second current detection circuit (CT2) that detects the current flowing in the V phase of the synchronous motor 1.
, 7 are the analog signal IU of the first current detection circuit 5 and the second
A multiplexer 8 switches the analog signal 7 of the current detection circuit 6, and 8 an A/D converter (8) that converts the analog signal selected by the multiplexer 7 into a digital signal.
analog signal/digital signal conversion circuit), and 9 is an upper C that outputs a speed command signal that determines the rotation speed of the synchronous motor 1.
A PU (central processing unit) 10 receives output signals from the host CPU 9, the counter circuit 3, the absolute rotary encoder 4, and the A/D converter 8, and calculates a pulse width modulation signal for the synchronous motor 1. U, 1
1 is a ROM (R
ead 0nly Memory), 12 is CPU10
R A M (Random Acce) used when calculating the pulse width modulation signal of the synchronous motor 1 in
ssMemory), 13 is an inverter circuit controlled by the pulse width modulation output signal of cputo.

This digital control is carried out by the CPU1. O is the speed command value N from the host CPU 9. (Fig. 4 (3)) is read at the timing shown in Fig. 4 (2) (Fig. 5 (a)), and the speed command value N is obtained. is different from the speed command value N-1 read last time by the counter circuit 3, the deviation ΔN of the speed command is calculated as follows (
Figure 5 (a)).

ΔN=No-N, -1 The CPU 10 then determines the distribution value n of the speed command value.

(Figure 4 (4)) is calculated as follows (Figure 5 (1)).

(tsu)′).

no=no+(ΔN/4) Next, the CPU 1.0 calculates the speed feedback value by dividing the difference between the previous value and the current value of the counter circuit 3 by a fixed time (Fig. 5 (1)), and calculates the speed command. Value N.

The distribution value n. The speed deviation value is calculated from the difference between (force)), the current command value of each phase is calculated from the rotor position of the synchronous motor 1 from the absolute rotary encoder 4 and the speed control loop calculation result (Fig. 5 (g)), A/D converter 8
A pulse width modulation output signal is calculated from the current value from and the current command value of each phase (Fig. 5 (ri)).

(Problem to be solved by the invention) In the above conventional example, the speed command value N from the CPU 9.

If the time interval at which the speed command value changes (Fig. 4 (3)) is not constant, the synchronous motor 1 cannot be driven smoothly, and if the time interval at which the speed command value changes is changed, the distribution of the speed command value It was necessary to change the calculation program at that time.

The present invention has been made in view of the above-mentioned drawbacks of the conventional example, and an object of the present invention is to provide a digital control system for a synchronous motor that can be smoothly driven.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides
an incremental rotary encoder that outputs a two-phase square wave signal having a phase difference of 0 degrees and converts the rotation angle of a rotor of a synchronous motor into a movement amount;
A counter circuit receives the two-phase output signal of the rotary encoder and measures the amount of movement of the synchronous motor, and outputs a three-phase square wave signal having an electrical phase difference of 120 degrees, An absolute rotary encoder that detects the position of the rotor, a current detection circuit that detects the current flowing through the synchronous motor, and the output signal of the current detection circuit is input, and the analog signal of this current detection circuit is converted into a digital signal. inputs an A/D converter that determines the rotation speed of the synchronous motor, a speed command signal that determines the rotation speed of the synchronous motor, the counter circuit, the absolute 1 to rotary encoder, and the output signals of the A/D converter,
A digital control device for a synchronous motor includes a CPU that calculates a pulse width modulation signal of the synchronous motor, and an inverter circuit controlled by the pulse width modulation output signal of the CPU; From the time interval of the speed control loop calculation, which calculates the speed feedback value by dividing the difference between the current value and the current value by a fixed time, and then performs proportional, integral, and differential control from the difference between the speed command signal and the speed feedback value. When the time interval at which the speed command signal changes becomes longer, the number of times the speed control loop calculation is executed by the CPU is measured, and the speed command value is equalized by the number of times the speed control loop calculation is performed. This is a digital control method for a synchronous motor, characterized in that the speed command value is divided into minutes and used as a speed command value for a speed control loop calculation executed by the CPU.

(Function) The present invention simultaneously calculates the deviation ΔN between the previous speed command and the current speed command, and measures the number M of times the speed control loop calculation was executed during the time when the speed command value did not change. Distribution value n of command value. By calculating this, we have developed a digital control system for synchronous motors that smoothly drives the synchronous motor without changing the speed command value distribution calculation program even when the time interval at which the speed command signal changes is not constant. can be provided.

(Embodiment) Hereinafter, an embodiment of the present invention will be described with reference to the timing diagram of FIG. 2 and the flowchart of FIG. 3 for a digital control device for a synchronous motor shown in FIG.

CPtJ], O is the speed command value No. from the host CPU 9
(Fig. 2 (3)) is read at the timing shown in Fig. 2 (2) (Fig. 3 (A)), and the speed command value N is obtained. When the speed command value N-1 is different from the previously read speed command value N-1, the deviation ΔN of the speed command is calculated as follows (Fig. 3 (a)).

ΔN=No-N-.

At the same time, in the present invention, the CPU 10 measures the number M of executions of the speed control loop calculation during the time when the speed command value from the host CPU 9 did not change (Fig. 3 (e)). (See Figure 5 (a)).

That is, CPtJlo is the distribution value n of the speed command value.

(Figure 2 (4)) is calculated as follows (Figure 3 (4))
.

(tsu)″).

no=no+(ΔN/M) The CPUIO then calculates the speed feedback value by dividing the difference between the previous value and the current value of the counter circuit 3 by a fixed time (Fig. 3 (1)), and calculates the speed command value N. .

The speed deviation value is calculated from the difference between the distribution value n0 of Calculate the current command value of each phase from the rotor position of the synchronous motor 1 from the absolute rotary encoder 4 and the speed control loop calculation result. /D converter 8
A pulse width modulation output signal is calculated from the current value from the current value and the current command value for each phase (see FIG. 3).

In the timing diagram of FIG. 2, the speed command value N from the host CPU 9. The number of times M that the speed control loop calculation was executed from timing (1) during the time (T) when (3) did not change is calculated as N 2 ++ in the case of rotation.

In addition, in the timing diagram of FIG. 4, the upper CPU 9
Speed command value N from. (3) remains unchanged (T
), the number M of executions from timing (1) of the speed control loop calculation is calculated as rr 4 ++.

(Effects of the Invention) = As explained, the present invention simultaneously calculates the deviation ΔN between the previous speed command and the current speed command, and executes the speed control loop calculation during the time when the speed command value does not change. The number of times M that has been performed is measured, and the distribution value n of the speed command value is determined. By calculating this, we have developed a digital control system for synchronous motors that smoothly drives the synchronous motor without changing the speed command value distribution calculation program even when the time interval at which the speed command signal changes is not constant. can be provided.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a digital control device for a synchronous motor in which the present invention is implemented, Fig. 2 is a timing diagram of an embodiment of the present invention, Fig. 3 is a flow chart of the present invention, and Fig. 4 is a diagram of a conventional example. Timing diagram FIG. 5 is a flowchart of a conventional example. 1... Synchronous motor (SM), 2... Incremental rotary encoder (RE), 3 Counter circuit, 4... Absolute rotary encoder (CS), =11- 5... First current detection Circuit (CT,), 6...
2nd current detection circuit (c T2), 7 multiplexer, 8... A/D converter, 9... Upper CPU, 1O-CPU, 11-= ROM, 12-
RAM, 13... Inverter circuit. Patent applicant Matsushita Electric Industrial Co., Ltd.

Claims (1)

[Claims] An incremental rotary encoder that outputs two-phase square wave signals electrically having a phase difference of 90 degrees and converts the rotation angle of a rotor of a synchronous motor into a movement amount; A counter circuit receives the two-phase output signal of the rotary encoder and measures the amount of movement of the synchronous motor, and outputs a three-phase square wave signal having an electrical phase difference of 120 degrees, An absolute rotary encoder that detects the rotor position,
a current detection circuit that detects a current flowing through the synchronous motor; an A/D converter that receives an output signal of the current detection circuit and converts an analog signal of the current detection circuit into a digital signal; and a rotation speed of the synchronous motor. a CPU which receives as input a speed command signal for determining a speed command signal and output signals of the counter circuit, the absolute rotary encoder, and the A/D converter and calculates a pulse width modulation signal of the synchronous motor; It is equipped with a digital control device for a synchronous motor consisting of an inverter circuit controlled by a modulated output signal, and the CPU calculates a speed feedback value by dividing the difference between the previous value and the current value of the counter circuit by a fixed time. , further executed by the CPU when the time interval at which the speed command signal changes is longer than the time interval of speed control loop calculations that execute proportional, integral, and differential control based on the difference between the speed command signal and the speed feedback value. The speed command value of the speed control loop calculation executed by the CPU is calculated by measuring the number of times the speed control loop calculation has been executed, and equally dividing the speed command value by the number of times the speed control loop calculation has been performed. A digital control method for a synchronous motor, characterized by: