JPS61109482A - Motor controller - Google Patents

Abstract

PURPOSE:To always obtain a desired rotating speed by regulating the duty of a rotating direction designation signal in accordance with the detected output of the rotating speed of a motor. CONSTITUTION:A signal generator 221 generates a pulse signal having the period of (m) times of a ripple period of a motor torque. This pulse signal is pulse-width-modulated by a pulse width modulator 222, and applied as a rotating direction designation signal to a motor 21. The modulation factor of the modulator 222 is controlled in accordance with the detected output of a speed detector 26 for detecting the rotating speed of the motor 21. In other words, the pulse width of the input pulse signal and hence the duty of the input pulse signal is altered in accordance with the rotating speed error signal to follow the rotating speed of the motor 21 to the predetermined speed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a motor control device that controls the rotational speed of a motor.

[Technical background of the invention and its problems]

FIG. 3 shows a device for controlling the rotational speed of a capstan motor in a magnetic recording/reproducing device.

The illustrated device detects the rotational speed of a capstan motor 11 with a speed detector 12, samples this detection output with a sampling circuit 13, and obtains the reference rotation period difference. According to this error output, the motor drive signal is pulse width modulated in the /4' pulse width modulation circuit 14, and this modulated output is smoothed in the smoothing circuit 15 to control the rotational speed of the capstan motor 11, which is a DC motor. be.

However, in the case of such a control system, when used in a direct P live system set, the motor drive voltage becomes an extremely low level during slow playback, making it extremely difficult to override the current. Especially when slowing down the slow playback speed, You will not be able to apply it at all. Therefore, if the device shown in FIG. 3 is used in a direct drive type set, the slow playback speed will be significantly limited.

In order to solve this problem, as shown in FIG. A device that controls the duty of a signal according to a slow playback speed has been considered.

With this control method, the servo can be applied even if the slow playback speed becomes slow. However, since the circuit is under open-loop control, the rotational speed of the cazostan motor 11 is greatly influenced by its motor characteristics and motor load characteristics. As a result, the desired slow playback speed may not be obtained, or in some cases, the motor 11 may not start at all.

[Purpose of the invention]

This invention was made to deal with the above-mentioned circumstances, and it is possible to control the rotation speed even when driving the motor at low speed, and it is possible to always maintain the desired rotation speed without being affected by the motor characteristics or motor load characteristics. The object of the present invention is to provide a motor control device that can be obtained.

[Summary of the invention]

This invention controls multiple rotational speeds by setting the driving voltage of the motor to a constant voltage and adjusting the duty of the motor rotational direction designation signal according to the detection output of the rotational speed of the motor.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.゛) FIG. 1 is a circuit diagram showing the configuration of an embodiment of the present invention.

In FIG. 1, a cazostan motor 21 is a DC motor whose rotation direction is designated by the duty of a rotation direction designation signal applied from a rotation direction designation signal generation circuit 22 to a terminal 23. As shown in FIG.

The driving voltage of this motor 21 is a constant voltage applied from a constant voltage generating circuit 24 to a terminal 25.

The rotation direction designation signal generation circuit 22 includes a signal generation circuit 221 that generates a pulse signal having a period m (m is a natural number) times the ripple period of the motor torque. The /4 pulse signal from the signal generation circuit 221 is transmitted to the pulse width modulation circuit 221.
The signal is /IP pulse width modulated at 22 and given to the motor 21 as a rotation direction designation signal.

- The modulation degree of the f pulse width modulation circuit 222 is controlled according to the detection output of the speed detector 26 that detects the rotational speed of the motor 2. That is, the detection output of the rotational speed detector 26 is transmitted to the sampling circuit 2 of the rotational direction designation signal generation circuit 22.
23, and a one-difference signal indicating the deviation from the reference rotation period is obtained. According to this error signal, the f-pulse width modulation circuit 222 changes the pulse width of the input/f-pulse signal, in other words, the duty of the input pulse signal, and causes the rotational speed of the motor 21 to follow a predetermined speed. Here, the sampling signal of the sampling circuit 223 is given from the frequency dividing circuit 224. This frequency dividing circuit 224 divides the frequency of the /f pulse signal outputted from the signal generating circuit 221 by n (n is a natural number) to obtain a sampling signal having a period n times that of the rotation direction designation signal.

Here, the operation of the rotation direction designation signal generation circuit 22 can be realized by software using a microcomputer. In this way, the rotational speed of the motor 21 can be controlled at low cost.

An example of software control is shown in FIG. 2. Let us now assume that the rotation direction designation signal is high level for forward rotation and low level for reverse rotation. First, the number t of pulses constituting one period of the rotation direction designation signal is set to 6 so that one period of the rotation direction designation signal of the motor 21 is m times the ripple period of the motor torque. In this case, the duty is 50%, that is,
If the high-level pulse number is set to i, motor 2 will only vibrate but will not rotate.

On the other hand, if it is set to a number greater than 1, the motor 21 rotates in the forward rotation direction, and the greater the number of /f pulses in the -.level, the faster the motor rotation speed becomes. Conversely, when the value is less than 1, the motor 21 rotates in the reverse direction and the high level /f
The smaller the number of ruses, the faster the rotational speed of the motor 2 becomes.

Here, control of the rotational speed of the motor 21 will be explained by taking normal rotation slow playback as an example. In Stella 7'S in FIG. 2, the number of high-level pulses required to obtain the desired slow playback speed is set. After setting this number of pulses, generation of high level pulses is started in step S2. In the next step, the number of pulses of the rotation speed detection output is counted every time a pulse is generated in step S. Step 3 above
1 *8.0 processing is the next Stella f S 4 Te, the number of high level nolus is determined by Stella fS1,
This continues until it is confirmed that the output is equal to the output duty of the output.

When it is confirmed that the duty has been output, Stella f
Shifting to Ss, generation of low level pulses is started this time. Then, in the next step S6, the number of /4 pulses of the rotational speed detection output is counted in the same manner as in step S=. The above processing of step 81s86 is performed in step S7.
This continues until it is confirmed that one cycle of /f pulses has been output.

The above processing of steps aS to S7 is executed over n cycles of the rotation direction designation signal under the supervision of steps aS and S. When the processing for n cycles is completed, step S,
of the rotational speed detection output in step ss eS)
9. Compare the Luss number F with the reference number f. If the deviation (F
-f) is ±W (where W is the rotational speed tolerance deviation,
If it is within the range of
1 @ K s'), step S1 is busy maintaining the pulse number t set in step S1. If F - f
) In the case of 10w, the slow playback speed is faster than the target value, so move to step fS, and set the number of pulses of high level/l/ to 1.
The rotational speed of the motor 21 is lowered by reducing the number of rotational speeds of the motor 21. On the contrary, F-
If f (-w), increase the rotation speed of motor 2 by increasing the number of high-level pulses by one. The slow playback speed is set to the target value by repeating the above operations during the slow playback mode under the supervision of step StS.

According to this embodiment described in detail above, the rotation speed of the motor 2 is set directly to the target by controlling the duty of the capstan motor 210 rotation direction designation signal according to the rotation speed of the motor 2. Because of this configuration, even when the motor 21 is driven at a low speed such as during slow playback, the surno can be applied. Moreover, according to such a configuration, a desired motor rotation speed can always be obtained without being influenced by motor characteristics or motor load characteristics.

In addition, by setting the cycle of the motor 210 rotation direction designation signal to a natural number multiple of the IJ and 76L cycles of the motor torque, the rotation speed of the motor 21 is determined not only when viewed on average over a long period of time, but also when the motor torque There is no variation with the ripple period of the rotation direction designation signal or the period of the rotation direction designation signal. That is, since the torque of the motor 21 changes depending on the phase of the rotor and stator, the rotational speed changes for each pull and pull. However, by setting the periodicity of the rotation direction designation signal to a natural number multiple of the ripple period of the motor torque, changes in the rotation speed due to the ripple period of the motor torque are averaged, and the rotation speed of the motor 21 can be stabilized. It will be done.

In addition, since the sampling period of the rotation speed detection output is set to a natural number multiple of the period of the rotation direction designation signal, the rotation speed of the motor 21 can be accurately measured, and as a result, the rotation of the motor 2 Speed stabilization can be improved. That is, in each cycle of the rotation direction designation signal of the motor 21, the high level period of the signal is as follows:
A starting force is applied to the motor 21 in the forward direction, and a starting force is applied to the motor 2 in the reverse direction during the low level period. During normal slow playback, the rotational speed of the motor 21 gradually increases during the high level period of the rotational direction designation signal, and the brake operates and the rotational speed gradually decreases during the low level period. As a result, the period of the rotation speed detection output becomes shorter and shorter during the high level period of the rotation direction designation signal, and gradually becomes longer during the low level period of the rotation direction designation signal.

Therefore, if the sampling timing of the rotation speed detection output is arbitrarily selected with respect to the period of the rotation direction designation signal, the rotation speed detection output cannot be measured accurately. Therefore, by setting the sampling period of the rotation speed detection output to a natural number multiple of the period of the rotation direction designation signal, the rotation speed of the motor 21 can be accurately measured and the rotation speed can be stabilized. That's why.

〔Effect of the invention〕

According to this invention, the motor control device is capable of not only controlling the speed even when the motor is operated at low speed, but also being able to always obtain the desired rotational speed without being affected by the motor characteristics or motor load characteristics. can be provided.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the configuration of an embodiment of the present invention, and FIG.
The figure is a flowchart showing an example of the operation when the process of FIG. 1 is performed by microcomputer software.
FIG. 3 is a circuit diagram showing an example of a conventional motor control device, and FIG. 4 is a circuit diagram showing another example. 21... Capstan motor, 22... Rotation direction designation signal generation circuit, 23.25... Terminal, 24... Constant voltage generation circuit, 26... Speed detector, 221... Signal generation Circuit, 222... Mother pulse width modulation circuit, 223...
... Sampling circuit, 224... Frequency dividing circuit.

Claims (3)

[Claims] (1) A motor to which a rotational direction designation signal is given as a pulse width modulation signal, a constant voltage generation means for supplying a constant voltage as the driving voltage of this motor, a rotational speed detection means for detecting the rotational speed of the motor, and this rotation. A motor control device comprising pulse width modulation means for sampling the detection output of the speed detection means and pulse width modulating the rotation direction designation signal so that the sampled value becomes a predetermined value. (2) The motor control device according to claim 1, wherein the sampling period of the rotation speed detection output is set to be a natural number multiple of the period of the rotation direction designation signal. (3) The motor control device according to claim 1, wherein the period of the rotation direction designation signal is set to be a natural number multiple of the ripple period of the torque of the motor.