JPS627380A - Controller for synchronous motor - Google Patents

Abstract

PURPOSE:To improve the precision of a position on stop, by keeping 120 deg. electrical conduction system when the rotating state of a motor is indicated with the output of a working condition discriminating means, and by changing the system to 180 deg. electrical conduction system when the stopping state is indicated. CONSTITUTION:By a working condition discriminating means 33, whether a synchronous motor 21 is stopping or rotating in the working state is discriminated. When rotating 'rotating' is indicated by the output of the working condition discriminating means 33, then the product of 6 signals obtained by obtaining the product of one signal among 3 signals of a commutation coder 23 and the negation of other one signal, and the pulse width output of a PWM section 30 is obtained by a phase switching circuit 31, and as the result, phase to which the voltage of the windings of the synchronous motor 21 is applied by the obtained six signals is switched. (120 deg. electrical conduction system) When 'stopping' is indicated by the output of the working condition discriminating means 33, than phase based on 6 signals obtained by obtaining the product of 6 signals of the 3 signals of the commutation coder 23 and the respective negations, and he pulse width output of the PWM section 30 is switched. (180 deg. electrical conduction system) As the result, torque generated on stop can be increased and positional precision can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a control device for a synchronous motor that drives a 1'lC machine tool or an industrial robot.

BACKGROUND OF THE INVENTION In recent years, control devices for synchronous motors, such as those used to drive industrial robots, are required to have high positioning accuracy and low speed fluctuation rate.

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

FIG. 3 shows the configuration of a conventional synchronous motor control device. In FIG. 3, 1 is a controlled synchronous motor. Reference numeral 2 designates an incremental encoder which is connected to the synchronous motor 1 and outputs two signals (2a, 2b) consisting of a number of pulses proportional to its rotation angle, as shown in FIG.
The phase difference between the two signals is 90 degrees, and one of the two signals advances in the rotation direction of the synchronous motor 1. 3 is a commission encoder, which is used to switch the voltage applied to each phase stator winding of the synchronous motor 1, as shown in FIG.
3b, 3a3 signals are generated once per rotation. Reference numeral 4 denotes a Norms converter that divides the two signal outputs of the incremental encoder 2 into signals for different rotational directions. 6 to pulse converter 4
This is an up/down counter used to obtain the absolute position of the synchronous motor 1 by counting pulse signals for each rotational direction, which are the outputs of the synchronous motor 1. 6 is a microcomputer that reads the target position and target speed 6a of the synchronous motor 1 given from the host system or other control equipment, and calculates a speed command value from the current position 5a of the synchronous motor 1 obtained by the up/down counter 5. Outputs 6b.

7l-j-D/A converter converts the speed command value of the microcomputer 6 into an analog signal 7a.

A speed conversion circuit 8 obtains a voltage signal 8a proportional to the rotational speed of the synchronous motor 1 from the output of the incremental encoder 2. , 9 is an operational amplifier that amplifies the difference between the outputs of the D/A converter 7 and the speed conversion circuit 8. 10 is a PWM circuit with a constant width proportional to the output 9& of the operational amplifier 9. It outputs a periodic pulse 10a and a rotational direction signal 10b. 11 is a phase switching circuit, and a commission encoder 3
11a as shown in FIG. 6 obtained by obtaining the logical product of one of the three signals and the negation of the other signal.

111>, 11c, 11d, 11e, 111a signals and P
The circuit has a configuration as shown in FIG. 7, in which the logic product with the output pulse of the WM circuit 10 is taken. 12 is part of the driver,
By turning on and off switching elements consisting of six transistors as shown in FIG. 8 using pulses for each phase of the synchronous motor 1 obtained by the phase switching circuit 11, and changing the pulse width, each phase winding is changed. Change the voltage applied to.

The operation of the synchronous motor control device configured as described above will be described below.

First, the microcomputer 6 reads the target position 6a.
and the current position 5a of the synchronous motor 1, which is the output of the up-down counter 6, and calculate the speed command 6b according to the difference.
/A output to converter 7. Next, the operational amplifier 9 converts the output of the incremental encoder 2 into the speed conversion circuit 8.
is converted into a speed feedback value 8a, and the difference with the speed command ratio cuff a of the D/A converter 7 is amplified to obtain a pulse width command value 9.
get a. In the PWM circuit 10, the pulse width command value 9a is
A signal '412a is output which outputs WM-modulated pulses 10a and signals 10b for each rotational direction, and turns on and off the switching elements of the driver part 12 from the outputs 3a, 3b, and 3c of the community encoder 3 in the phase switching circuit 11. ,
12b, 12a, 12d.

Make 12e and 12f. Finally, by changing the width of the pulse applied to the switching element by the driver part 12, the voltage applied to each phase winding of the synchronous motor 1 is changed, and the rotation speed is changed. It is designed to stop.

Problems to be Solved by the Invention However, with the above configuration, only two voltages are applied to the stator winding of the synchronous motor even during a stop state, just like when it is rotating, and the torque generated by the rotor is However, there was a problem in that the positional accuracy at the time of stopping was poor due to the small amount of the

In view of the above-mentioned problems, the present invention provides a control device for a synchronous motor that improves positional accuracy when stopped.

In order to solve the above-mentioned problem, the synchronous motor control device of the present invention includes an operating state determining means for determining whether the operating state of the synchronous motor is stopped or rotating; This device includes a phase switching device that changes the output depending on the output of the state determining device.

Effect: With the above-described configuration, the present invention calculates the product of one of the three signals of the second detector and the negation of the other signal when the output of the operating state determining means indicates rotation. The phase to which the voltage is applied to the stator winding of the synchronous motor is switched using the 6 signals obtained by this (120 degree energization method). By performing phase switching (18a degree energization method) using 3 signals and 6 negative signals of each, sufficient torque is generated to keep the position stopped at the time of stop.

Embodiment Hereinafter, a control device for a synchronous motor according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows the configuration of a synchronous motor control device in a first embodiment of the present invention. In Figure 1, 21
is a controlled synchronous motor; 22 is a first detector, e.g. an incremental encoder; 23 is a second detector;
For example, Al with the Comiti John encoder. 24U pulse K conversion 5.25 is an up/down counter and constitutes position detection means. 26 is a microcomputer,
27 is a D/A converter, 28 is a speed conversion circuit, 29 is an operational amplifier, 3o is a PWM circuit, and these are the synchronous motor 2.
This is a control means for controlling 1. 32 is a part of the driver, and the above structure is the same as that shown in FIG. 3. Reference numeral 33 indicates an operating state determining means for determining whether the operating state of the synchronous motor 21 is stopped or rotating, for example, determined by processing within the microcomputer 26 and output. 31 is an operating state determining means 33
When the output of is rotating, take the product of the 6 signals obtained by taking the product of one of the three signals of the community encoder 23 and the negation of the other one signal and the pulse width output of the PWM section 3o. 12, when the output of the operating state determining means 33 is stopped, the product of the three signals of the community encoder 23, the six signals of their negatives, and the pulse width output of the PWM section 30 is calculated. This is a phase switching circuit with the following configuration.

The operation of the synchronous motor control device configured as described above will be described below.

The mass microcomputer 26 receives a target position 26a that is given from a host system or another microcomputer, or is stored in its own storage means, and a current position 25a of the synchronous motor 21 that is the output of the up/down counter 25.
and the speed command 26b obtained from the difference.
output to the /A converter 27. The above processing is shown in the flowchart of FIG. Next, the arithmetic amplifier 29 converts the output of the incremental encoder 22 into the speed feedback value 28a and the D/
The difference from the speed command output 27a of the A converter 27 is amplified to obtain a pulse width command 29a. In the PWM circuit 3o, the pulse width command value 29a is converted into a triangular wave 30a as shown in FIG.
PWM modulated pulse sob by comparing with
Then, a direction signal 30c indicating whether the pulse width command 29a is a positive number or a negative number is output. The operating state determining means 33 determines the operating state of the synchronous motor 21 during calculation within the microcomputer 26 and outputs the result. When the output of the operating state determining means 33 indicates that the rotation is in progress, the three signals 23a of the community encoder 23 are output as shown in FIG. 10, as in the conventional example.
, 23b, 23a and the direction signal 300, and the e signal 31a, 3 obtained by taking the AND of the negation of one of the signals and the other signal and the pulse width output 3ob.
1b, 31a.

Obtain 31d, sle, and 31f. Operating state determining means 3
When the output of 3 indicates that the output is stopped, the 3 signals 23a, 23b,
23c and the direction signal 36c, these three signals, the six negative signals of each, and the pulse width output 30
31 a , 31 b , obtained by the logical product of b
31a, 31d, 31e.

Get slf. Finally, the driver part 32 changes the pulse width of the six signal outputs of the phase switching circuit 31 that turns all six switching elements on and off, thereby changing the 120-degree energization method while the synchronous motor 21 is rotating, and Time is 1
The 80 degree energization method is used to rotate the synchronous motor 21 at a constant speed and to stop it at any desired position.

As described above, according to this embodiment, the operating state of the synchronous motor controlled by a microcomputer is determined, and the phase switching can be switched between the 120-degree energization method and the 180-degree energization method based on the output, without significantly changing the circuit configuration. It becomes possible to increase the generated torque and improve position accuracy.

In the first embodiment, the microcomputer 26 is used as the operating state determining means, but if the speed feedback value is zero, the synchronous motor is stopped; otherwise, it is determined that the synchronous motor is rotating. good.

Effects of the Invention As described above, the present invention provides an operating state determining means for determining whether the operating state of the synchronous motor is rotating or stopping, and a 120-degree energizing w type when the output indicates rotating, and a 120-degree energization W type when the motor is stopped. By providing a phase switching means that switches the current through 180 degrees, the positional accuracy at the time of stopping can be adjusted from north to south.

[BRIEF DESCRIPTION OF THE DRAWINGS] Figure 1f1 is a configuration diagram of a control device for a synchronous motor in the ninth embodiment of the present invention, Figure 2 is a flowchart of calculations performed in the microcomputer section of Figure 1, and Figure 3. is a configuration diagram of a conventional synchronous motor control device, FIG. 4 is an output waveform diagram of an incremental encoder, which is the first detector, and FIG. 5 is an output waveform diagram of a commissural encoder, which is the second detector. , FIG. 6 is a waveform diagram of input and output signals of a conventional phase switching circuit, FIG. 7 is a circuit diagram of a conventional phase switching circuit, and FIG.
The figure is a main circuit diagram of a part of the driver, FIG. 9 is an input/output waveform diagram of the PWM circuit, and FIG. 10 is an input/output waveform diagram of the phase switching circuit in an embodiment of the present invention when the synchronous motor is rotating. 1st
FIG. 1 is an input/output waveform diagram of a phase switching circuit according to an embodiment of the present invention when the synchronous motor is stopped, and FIG. 12 is a circuit diagram of the phase switching circuit according to an embodiment of the present invention. 21-... Synchronous motor, 22... Incremental encoder, 23... Commiciency encoder, 24... Pulse converter, 26...
...Up/down counter, 26...Microcomputer, 27...D/A converter, 2
8...Speed W conversion! , 29... operational amplifier, 3o... PWM circuit, 31...-
・Phase switching circuit, 32... Driver part, 33.
...Operation status determination means. Name of agent: Patent attorney Toshio Nakao and 1 other person25
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Figure; 1f1

Claims (1)

[Claims] a synchronous motor; a first detector connected to the synchronous motor and outputting two signals with a phase difference of 90 degrees and a number proportional to the rotation angle of the synchronous motor; a position detection means for calculating the absolute position of the electric motor;
Speed detecting means for detecting the rotational speed of the synchronous motor from the output of the first detector, and stopping the synchronous motor at a pre-stored position or an arbitrary position from the position detecting means and the speed detecting means. a control means connected to the synchronous motor for performing control calculations to obtain the width of a pulse voltage applied to the windings of the synchronous motor and outputting a pulse signal having the width; a second detector that outputs three signals whose phases are shifted by 120 degrees, in which 1/2 of one rotation of the synchronous motor is "1" and the remaining 1/2 is "0"; an operating state determining means for determining and outputting whether the operating state is stopped or rotating; and when the output of the operating state determining means indicates that the synchronous motor is rotating, the second detector 3;
6 signals are obtained by multiplying one signal by the negation of another signal, and when the output of the operating state determining means indicates that the synchronous motor is stopped, the second detector 3 a phase switching means that obtains the signal output and six negative signals of each, and calculates the product of the pulse signal output obtained by the control means and the six outputs; and six signals controlled by the six outputs of the phase switching means. A control device for a synchronous motor, comprising: a switching element that rotates the synchronous motor by applying a pulsed voltage to each winding of the synchronous motor by the switching element; and a drive section comprising a DC power source.