JPH04101694A - Synchronous motor controller - Google Patents

Abstract

PURPOSE:To reduce the size and to shorten the processing time by detecting the current flowing through an inverter circuit and determining a current command value based on the difference between the detected current value and a target current value thereby employing only one current detector. CONSTITUTION:A current control means 10 amplifies the difference between a target current value Ic fed from a host system or a speed amplifier and a current value If fed back from a current detector and a current command value is fed to a multiplying means 9. The multiplying means 9 multiplies the output from the current control means 10 by three signals, obtained by converting the output from a position detector 2 according to a ROM table in a sine wave generating means 8, and provides the products to PWM circuits 5, 6, 7, respectively. Switching transistor in an inverter circuit 3 is then turned ON/OFF by the PWM signal and current flows through each phase coil of a synchronous motor 1 thus rotating the synchronous motor 1. Since only one current detector is required, the size of controller is reduced and since multiplication is required only one time, processing time of microcomputor is shortened in current control.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a control device for a synchronous motor used to drive industrial machines, NC machine tools, and the like.

(Prior art) In recent years, control devices for synchronous motors used to drive industrial robots and NC machine tools have been digitally controlled using microcomputers, and have become smaller and smaller through the use of custom ICs.
Efforts are being made to improve performance.

An example of a conventional synchronous motor control device will be described below with reference to the drawings.

FIG. 6 is a block diagram of a conventional synchronous motor control device. In FIG. 6, 21 is a controlled synchronous motor, and 22 is a position detector that detects its absolute position within one rotation. 23
．． 24 is a current detector that detects the phase current of the synchronous motor 1. 25 is an inverter circuit that flows a predetermined current to each phase of the synchronous motor 21, and 26, 27, and 28 are inverter circuits 2.
Synchronous motor 1 is turned on and off by switching element 5.
This is a PWM circuit that changes the current flowing through the circuit.

Reference numeral 29 denotes a sine wave generating means consisting of a table in which two-phase sine wave data with a phase shift of 120° as shown in FIG. 7 is written in a ROM. 30 is a multiplier for multiplying the target value of the current flowing through the synchronous motor 21 by a two-phase sine wave obtained from the sine wave generating means 29; 31, 32, and 33 are the output of the multiplier 30 and the current detector 23. This current control means calculates and outputs a human power signal for the PWM circuits 26, 27, and 28 from the output of 24.

Regarding the synchronous motor control device configured as above,
The operation will be explained below.

First, the current target value 1c obtained from the host system or speed amplifier and the output of the position detector 22 are transferred to the sine wave generating means 29.
The two signals converted using the ROM table are multiplied by the multiplier 30, and current command values for the U phase and W phase are calculated. Further, the current command value of the ■phase is calculated by taking the sum of the current command values of the U phase and W phase and inverting the sign thereof. next,
In the current control means 31, 32, 33, the difference between the current command value for each phase and the current feedback value obtained from the current detector 23, 24 is taken, amplified, and sent to the PWM circuit 26, 27, .
Output to 28. At this time, the output of the current detector 23 becomes the U-phase current feedback value FU, the output of the current detector 24 becomes the W-phase current feedback value IN, and the current foot bank value Ifν of the ■phase is Ifv--1fu −Ifw. Then, the current command value is PWM-modulated by the PWM circuits 26, 27, and 28, and the switching elements of the inverter circuit 25 are turned on and off. Thus, current flows through the synchronous motor 21, causing the synchronous motor 21 to rotate.

(For example, "Basics and Applications of Brushless Servo Motors J2
See pages 1-28, General Electronic Publishing. ) (Problem to be Solved by the Invention) However, the above configuration requires at least two current detectors and three current control means, so there is a problem that miniaturization is difficult. Further, in the case of digital control in which the above processing is performed by a microcomputer, there is a problem in that the current control routine must be performed three times, which slows down the processing time and makes stable motor control difficult.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a synchronous motor control device that is compact and capable of stable control.

(Means for Solving the Problems) In order to solve the above problems, the synchronous motor control device of the present invention includes a synchronous motor, a position detector for detecting the rotational position of the synchronous motor, and a three-phase An inverter circuit that flows current through the coil, one current detector that detects the current flowing through the inverter circuit, and three PWs that generate signals that control the switching elements of the inverter circuit on and off.
M circuit, current control means that calculates a current command value from the target value of the current flowing through the synchronous motor and the output of the current detector, and sine wave generation means that generates sine waves whose phases differ by 120 degrees from the output of the position detector. and a multiplier for multiplying the output of the current control means and three-phase sine wave data, which is the output of the sine wave generation means, and outputting the result to three PWM circuits.

(Function) With the above configuration, the present invention detects the current value flowing through the inverter circuit and determines the current command value based on the deviation from the current target value, so only one current detector is required.
In addition to being miniaturized, the current control routine only needs to be performed once when digitally controlled by a microcomputer, reducing processing time and stably controlling the motor.

(Example) Hereinafter, a synchronous motor control device according to an example of the present invention will be described with reference to the drawings.

FIG. 1 shows the configuration of a synchronous motor control device.

In FIG. 1, 1 is a synchronous motor, and 2 is a position detector that detects the absolute position of the synchronous motor 1 within one rotation. 3 is an inverter circuit, as shown in Fig. 3, it consists of six switching transistors Q1 to Q6, and by turning these switching transistors on and off, current flows through the three-phase coils of the synchronous motor 1. It is composed of 4 is the current flowing through the coils of each phase (,
This is one current detector that detects the combined current flowing through the inverter circuit 3. 5.6.7 is P provided for each phase
It is a WM circuit, and as shown in Figure 4, it is a triangular wave generator (
Qo, c) 11 and comparator (Qc,, ) 12
As shown in FIG. 5, the input voltage V i n
The pulse voltage ■ is higher than the triangular wave voltage V c m p. It is configured to output uL. 8
As shown in FIG. 2, sine wave generating means consists of a table in which three-phase sine wave data with a phase shift of 120° is written in the ROM, and 9 indicates the current command value output from the current control means 10 and the sine wave data. A multiplication means 10 multiplies the three-phase sine wave data obtained from the wave generation means 8, and 10 amplifies the difference between the current target value and the output of the current detector 2, and outputs a current command value to the multiplication means 9. This is a current control means for outputting.

Next, the operation of the synchronous motor control device configured as above will be explained.

First, the current control means 10 calculates and amplifies the difference between the current target value rc obtained from the host system or speed amplifier and the feedback current value I from the current detector, and the current command value is sent to the multiplication means 9. Output. The multiplication means 9 multiplies the output of the current control means 10 and three signals obtained by converting the output of the position detector 2 using the Fi'OM table of the sine wave generation means 8, and outputs the results to the PWM circuits 5.6.7. do.

Then, the switching transistor of the inverter circuit 3 is controlled on/off by the PWM modulated signal in the PWM circuit 5.6.7, current flows through the coils of each phase of the synchronous motor 1, and the synchronous motor 1 rotates.

As described above, according to this embodiment, since only one current detector 4 is required, miniaturization is possible, and since the current control means is placed before the multiplication means 9, only one multiplication is required.
Processing time when current control is performed by a microcomputer is shortened, allowing stable motor control.

(Effects of the Invention) As described above, according to the synchronous motor control device of the present invention, only one current detector detects the current value flowing through the inverter circuit.
Since only one unit is required, miniaturization is possible, and since the current control means is placed before the means for multiplying with three-phase sine wave data, only one multiplication is required, and the processing when current control is performed by a microcomputer is possible. The time is reduced to about one-third, and the effect is that stable motor control is possible.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a synchronous motor control device according to an embodiment of the present invention, FIG. 2 is a graph showing the contents of a table of the sine wave generating means, FIG. 3 is a schematic block diagram of the inverter circuit, and FIG. Figure 5 is a diagram of the configuration of the PMW circuit, Figure 5 is a waveform diagram explaining the operation of the PMW circuit, Figure 6 is a configuration diagram of a conventional synchronous motor control device, and Figure 7 is a table of the sine wave generating means. This is a graph showing the contents. sine wave generating means; multiplication means; current control means;

Claims (1)

[Claims] (1) a synchronous motor, a position detector that detects the rotational position of the synchronous motor, an inverter circuit that flows current through the three-phase coils of the synchronous motor, and one current detector that detects the current flowing through the inverter circuit; Three PWMs that create signals that control on/off of switching elements in inverter circuits
a circuit, a current control means for calculating a current command value from a target value of the current flowing through the synchronous motor and the output of the current detector, and a sine wave generating means for generating sine waves having a phase different by 120 degrees from the output of the position detector. , the output of the current control means and the three-phase sine wave data that is the output of the sine wave generation means are multiplied to obtain 3.
A synchronous motor control device comprising: multiplication means for outputting to two PWM circuits.