JPH02228289A - Driver for synchronous motor - Google Patents

Abstract

PURPOSE:To shorten a period of a rectangular wave drive and to suppress a torque ripple and a reactive current by calculating the pole position of a motor based on the states of pole sensors and an encoder at the time of detection of an edge to generate a sine wave drive signal. CONSTITUTION:An encoder which outputs a signal responsive to a rotating angle of a motor 1, pole sensors 7a-7c which output pulselike detection signals in response to a positional relation to the poles of the motor 1, edge detecting means 4 for detecting the edges of the detection signals of the sensors 7a-7c, and control means 5 for calculating the pole position of the motor 1 based on the states of the sensors 7a-7c and the encoder at the time of detection of the edge and generating a sine wave drive signal are provided. Synchronization with the pole position of the motor is performed in a short time by using the detection signals of the sensors. Thus, a torque ripple and a reactive current can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a synchronous motor drive device incorporating a pole sensor.

<Conventional technology> Conventionally, the method for driving a synchronous motor is to first drive it with a square wave voltage when the power is turned on, and then switch the square wave drive to sine wave drive to drive the motor. It is being In the case of a drive device using this method, synchronization with the magnetic pole position of the rotor is required, and a Z-phase signal from an encoder attached to the electric motor is used as a means for this purpose.

In other words, in this type of synchronous motor drive device, first the rough initial position of the magnetic pole is read with a pole sensor and square wave drive is performed, then when the motor rotates by an appropriate angle and the encoder outputs a Z-phase signal. This Z-phase signal is used to accurately synchronize the magnetic pole positions and switch from rectangular wave drive to sine wave drive.

<Problems to be Solved by the Invention> However, in this type of system, the Z-phase signal is output only once per encoder rotation, so when switching from rectangular wave drive to sine wave drive, the electric motor is It can rotate up to 360 degrees. For this reason, rectangular wave driving is performed for a fairly long period of time, and as a result, the torque ripple of the motor becomes large, and there is a problem that the reactive current with respect to the torque flowing through the motor cannot be ignored.

This invention was made with a focus on the above problem, and by using the detection signal from the pole sensor to synchronize with the magnetic pole position of the motor in a short period of time, it suppresses the generation of torque ripple and reactive current. The purpose of this invention is to provide a novel synchronous motor drive device.

<Means for Solving the Problems> In order to achieve the above object, the synchronous motor drive device according to the present invention has a positional relationship between an encoder that outputs a signal according to the rotation angle of the motor and the magnetic poles of the motor. a pole sensor that outputs a pulse-like detection signal in accordance with the detection signal, an edge detection means that detects an edge of the detection signal from the pole sensor, and a magnetic pole position of the motor is calculated based on the states of the pole sensor and encoder when the edge is detected. and control means for generating a sine wave drive signal.

When the synchronous motor is driven by a rectangular wave, the pole sensor outputs a pulse-like detection signal that changes depending on the positional relationship with the magnetic poles of the motor, and the edges of this detection signal are detected by the edge detection means. Ru. In the case of a 3-phase n-pole synchronous motor,
Since the portion where the detection signal changes, that is, the edge appears 30 times per rotation of the rotor, the timing of calculating the magnetic pole position by the control means is 3n times faster than in the conventional method, and a large amount of torque ripple occurs. The period of rectangular wave driving can be shortened to 1/3 n.

<Embodiment> FIG. 1 shows a schematic configuration of a synchronous motor drive device according to an embodiment of the present invention.

In the figure, an electric motor 1 is equipped with an incremental encoder (not shown), and is driven by a power section 2 in a rectangular wave or a sine wave.

The encoder serially outputs pulses corresponding to the rotation angle of the electric motor 1 as A-phase signals and B-phase signals, and the counter 3 counts the output of this encoder.

As shown in FIG. 2, the motor 1 of this embodiment is a three-phase, two-pole synchronous motor, with each phase coil 6a to 6 of the stator.
Pole sensors 7a to 7C are provided at positions C, respectively. These pole sensors 7a to 7C are arranged according to the positional relationship with the magnetic poles N and S of the rotor 8 as shown in FIGS.
As shown in the figure, pulse-like detection signals P, ~Pc with a phase shift of 120' in electrical angle are output.

In the case of a three-phase n-pole synchronous motor, the detection signals P8 to P
The rising and falling portions where C changes, ie edges 9 and 10, appear 3n times per revolution of the rotor 8.

These edges 9 and 10 are detected by an edge detecting section 4 composed of a logic circuit, and the count value of the counter 3 at the time of detecting the edge is notified to and held by the CPU 5 of the microcomputer.

By executing the control procedure shown in FIG. 5, the CPU 5 generates a drive signal for driving the electric motor 1 in a rectangular wave or a sine wave, and supplies it to the power unit 2.

In step 1 of FIG. 5 (indicated by rsTIJ in the figure), the CPU 5 controls each of the pole sensors 7a to 7a for each sampling period.
The states of detection signals P and PC of 7c are read.

FIG. 3(4) shows the states of the detection signals P1 to PC of each of the pole sensors 7a to 7C in decimal notation. As shown in FIG. 4, each data has a 3-bit structure, and each bit corresponds to the level of the detection signals P, -Pc.

In other words, when detecting an edge, for example, the detection signal PC
If the detection signal P is at the "H" level, the Oth bit will be "1", and if the detection signal P is at the "LOW" level, the first bit will be "1".
If the detection signal P is at the "LOW" level, the third bit becomes "0" and becomes "1" in decimal notation (as shown in FIG. 3 (4)).

Returning to FIG. 5, step 2 is to detect the detection signals P, -P of each of the pole sensors 7a to 7c at the time of the current sample. The state of each pole sensor 7a~ at the time of the previous sample is
It is determined whether or not there has been a change from the state of the detection signals P, .about.Pc of 7c by comparing each data of the 3-bit configuration. If the determination is "NO°', the process proceeds from step 2 to step 3, and the CPU 5 detects the approximate position of the magnetic pole of the rotor 8 based on the information read in step 1. Next, in step 4, the CPU 5 For each phase coil 6a to 6c of the stator, determine a rectangular wave voltage input cover turn suitable for the magnetic pole position to rotate the rotor 8 in a desired direction, and in the next step 5, drive the electric if with a rectangular wave. A drive signal is generated and applied to the power section 2.

In step 2 above, each pole sensor 7a to 7C
When it is determined that the state of the detection signals P1 to PC has changed, the process proceeds from step 2 to step 6, where the CPU 5 reads the current count value of the counter 3 and compares that value with the count value held at the time of edge detection. to detect the accurate magnetic pole position of the rotor 8. Next, in step 7, the CPU 5 determines the sine wave voltage input cover turns for each phase coil 6a to 6c of the stator, and in the next step 8, the CPU 5 determines the drive signal for driving the motor l in a sine wave (see FIG. , 11a=11c) is generated and applied to the power part 2.

<Effects of the Invention> As described above, the present invention detects the edge of the detection signal from the pole sensor, calculates the magnetic pole position of the motor based on the states of the pole sensor and encoder at the time of edge detection, and generates a sine wave drive signal. Since I made it to generate
Compared to conventional drive systems, the period of rectangular wave drive can be shortened, and the torque ripple of the motor and the reactive current with respect to the torque flowing through the motor can be reduced, achieving the remarkable effects of achieving the objectives of the invention.

[Brief explanation of the drawing]

FIG. 1 is a block diagram schematically showing a drive device for a synchronous motor according to an embodiment of the present invention, FIG. 2 is an explanatory diagram showing the internal configuration of the synchronous motor and the arrangement of pole sensors, and FIG.
FIG. 4 is an explanatory diagram showing the detection signal of each pole sensor, FIG. 4 is an explanatory diagram showing the data structure showing the state of the detection signal of each pole sensor, and FIG. 5 is a flowchart showing the control procedure of the CPU. ■...Electric motor 4...Edge detection section 5.
...CPU 7a-7c...Pole sensor

Claims (1)

[Scope of Claim] A synchronous motor drive device that drives a motor with a square wave and then synchronizes the magnetic pole position to switch from square wave drive to sine wave drive, which outputs a signal according to the rotation angle of the motor. a pole sensor that outputs a pulse-like detection signal according to the positional relationship with the magnetic poles of the motor; edge detection means that detects an edge of a detection signal from the pole sensor; and the pole sensor and encoder when detecting an edge. 1. A synchronous motor drive device comprising: control means for calculating a magnetic pole position of the motor based on each state of the motor and generating a sine wave drive signal.