JPS63198590A - Digital control device of synchronous motor - Google Patents

Abstract

PURPOSE:To accomplish digital control of a high-precision synchronous motor, by cutting down the operating time of CPU when the synchronous motor is running at a high speed. CONSTITUTION:When a synchronous motor 1 is running at a low speed, a CPU 10 operates the speed feedback value by dividing the difference between the preceding value and the last value of a counter circuit 3 by a definite time. However, when the synchronous motor 1 is running at a high speed, let the output signal of a first A/D converter 15 be the speed feedback value so that the speed deviation value is operated from the difference between the speed control value at a higher-level CPU 9 and the speed feedback value. The current command value is operated from the rotor position of the synchronous motor 1 from an absolute rotary encoder 4 and the speed deviation value. The pulse width modulation output signal is operated from the current value at a second A/D converter 8 and the current command value.

Description

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

2. Description of the Related Art A conventional digital control device for a synchronous floating rock is constructed as shown in FIG.

In Fig. 2, 1 is a synchronous motor, and 2 is a synchronous motor that outputs two-phase square wave signals electrically having a phase difference of 90 degrees and converts the rotation angle of the rotor of the synchronous motor 1 into a moving amount. 1 is an incremental rotary encoder directly connected to 1, 3 is a counter circuit that receives the two-phase output signal of the incremental rotary encoder 2, and measures the amount of movement of the synchronous motor 1; 4 is an electrically connected phase difference of 120 degrees. Outputs a three-phase square wave signal with synchronous motor 1
6 is an absolute rotary encoder directly connected to the synchronous motor 1 that detects the position of the rotor of the synchronous motor 1.
a first current detection circuit that detects the current flowing in the U phase of 6;
7 is a second current detection circuit that detects the current flowing in the V phase of the synchronous motor 1; 7 is a multiplexer that switches between the analog signal of the first current detection circuit 5 and the analog signal of the second current detection circuit 6; and 8 is a multiplexer. A second A/D converter (analog signal/digital signal conversion circuit) converts the analog signal selected at 7 into a digital signal, and a host CPU 9 outputs a speed command signal that determines the rotation speed of the synchronous motor 1. The central processing unit (central processing unit) 1o receives the output signals of the upper CPU 9, the counter circuit 3, the absolute rotary encoder 4, and the second A/D converter 8, and calculates the pulse width modulation signal of the synchronous motor 1. C.P.
U and 11 are R O in which a program for calculating the pulse width modulation signal of the synchronous motor 1 is stored in the CPU 1o.
M (Read Only Memory), 12 is R A M (Random Memory) used when calculating the pulse width modulation signal of the synchronous motor 1 in the CPU 10
13 is an inverter circuit controlled by the pulse width modulation output signal of the CPU 10.

The CPU 10 calculates a speed feedback value by dividing the difference between the previous value and the current value of the counter circuit 3 by a fixed time, calculates a speed deviation value from the difference between the speed command value from the host CPU 9 and the speed feedback value, and calculates the absolute value. A current command cooling value is calculated from the position and speed deviation value of the rotor of the synchronous motor 1 from the rotary encoder 4, and a pulse width modulation output signal is calculated from the current value and current command value from the second A/D converter 8. are doing.

Problems to be Solved by the Invention In the conventional example described above, since the speed feedback value is obtained by dividing the amount of movement of the synchronous motor by a fixed time, there is a drawback that the calculation time of the CPU becomes long during high-speed rotation.

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 highly accurate digital control device for a synchronous motor.

Means for Solving the Problems To achieve this objective, the present invention provides
An incremental rotary encoder that outputs a two-phase square wave signal with a phase difference of 0 degrees and converts the rotation angle of the rotor of a synchronous motor into a movement amount, and inputs the two-phase output signal of the incremental rotary encoder. and an F/V circuit (frequency/four-pressure conversion circuit) that converts the rotational speed of the synchronous motor into speed, and an output signal of the F/V circuit as input, and converts the analog signal of the F/V circuit into a digital signal. The first A/D converter (analog signal
a counter circuit that receives the two-phase output signal of the incremental rotary encoder and measures the amount of movement of the synchronous motor;
an absolute rotary encoder that outputs a three-phase square wave signal having an electrical phase difference of 120 degrees and detects the position of the rotor of the synchronous motor; and a current detection circuit that detects the current flowing through the synchronous motor. , a second A/D converter that receives the output signal of the current detection circuit and converts the analog signal of the current detection circuit into a digital signal; a speed command signal that determines the rotation speed of the synchronous motor; 1 A/D converter, the counter circuit, and the absolute rotary encoder (!: A CPU (central CPU) which receives output signals from each of the second A/D converter and calculates a pulse width modulation signal of the synchronous motor. It consists of an arithmetic processing unit) and an inverter circuit controlled by the pulse width modulated output signal of the CPU.

Operation The present invention can provide a highly accurate digital control device for a synchronous motor with the above-described configuration.

EXAMPLE Hereinafter, an example of the present invention will be explained in detail based on FIG. However, the same reference numerals as in FIG. 2 indicate the same parts.

In FIG. 1, 14 inputs the two-phase output signal of the incremental rotary encoder 2, and the synchronous motor 1
A first F/V circuit (frequency/voltage conversion circuit) 16 receives the output signal of the F/V circuit 14 and converts the analog signal of the F/V circuit 14 into a digital signal. A/D converter (analog signal/digital signal conversion circuit), 10 is the upper CPU 9 and counter circuit 3
This is a CPU that calculates the pulse width modulation signal.

When the synchronous motor 1 is rotating at a low speed, the CPU 10 calculates a speed feedback value by dividing the difference between the previous value and the current value of the counter circuit 3 by a fixed time, and when the synchronous motor 1 is rotating at a high speed, the CPU 10 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. The output signal of the /D converter 16 is used as a speed feedback value, and a speed deviation value is calculated from the difference between the speed command value from the host CPU 9 and the speed feedback value, and the position of the rotor of the synchronous motor 1 from the absolute rotary encoder 4 is calculated. A current command value is calculated from the speed deviation value, and a pulse width modulation output signal is calculated from the current value from the second A/D converter 8 and the current command value.

As described in detail, the present invention can achieve highly accurate digital control of a synchronous motor by shortening the CPU calculation time when the synchronous motor rotates at high speed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a digital control device for a synchronous motor according to an embodiment of the present invention, and FIG. 2 is a 1072 diagram of a conventional digital control device for a synchronous motor. 1...Synchronization'lf motive, 2...Incremental rotary encoder, 3...Counter circuit, 4...Affnryuto rotary encoder, 6... ...First current detection circuit, 6...
...Second current detection circuit, 7...Multiplexer, 8...Second A/D converter, 9
......Upper CPU, 10...CPU, 1
1...ROM1 1 2...RAM
, 13...In/<-evening circuit, 14...
...F/V converter, 16...1st A/
D converter.

Claims (1)

[Claims] an incremental rotary encoder that outputs two-phase square wave signals electrically having a phase difference of 90 degrees from each other and converts the rotation angle of the rotor of the synchronous motor into a movement amount; an F/V circuit (frequency/voltage conversion circuit) that receives an output signal and converts the rotational speed of the synchronous motor into speed;
a first A/D converter (analog signal/digital signal conversion circuit) that receives the output signal of the circuit and converts the analog signal of the F/V circuit into a digital signal; and a two-phase output of the incremental rotary encoder. A counter circuit receives a signal 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 to detect the position of the rotor of the synchronous motor. an absolute rotary encoder, a current detection circuit that detects a current flowing through the synchronous motor,
a second A that receives the output signal of the current detection circuit as an input and converts the analog signal of the current detection circuit into a digital signal;
/D converter, a speed command signal that determines the rotation speed of the synchronous motor, and output signals of each of the first A/D converter, the counter circuit, the absolute rotary encoder, and the second A/D converter. A CP that takes as input and calculates a pulse width modulation signal of the synchronous motor.
A digital control device for a synchronous motor, comprising a central processing unit (U) and an inverter circuit controlled by a pulse width modulated output signal of the CPU.