JPS60144802A - Speed controller - Google Patents

Abstract

PURPOSE:To improve the responsiveness of a speed control system and also to improve the processing efficiency by inputting the detected value of a current which flows through an electric motor to a variable frequency oscillator, and using its output as the oscillation source for a counter which generates a pulse width signal. CONSTITUTION:When the output signal CQUT1 of a current detector 14 rises, the signal CQUT1 is inputted to an oscillator 10, whose oscillation frequency (signal QSC3) therefore increases. The oscillator 10 serves as the oscillation source for the counter 11, so it operates to reduce the current by decreasing the pulse width data of the counter when the signal QSC3 rises. Namely, the pulse width of current detection is increased and decreased directly by the counter. A control logical device 16 is therefore dedicated to only speed detection, so the responsiveness of the speed control system is improved extremely and the processing efficiency is also improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a speed control device for an electric motor that performs pulse width modulation driving.

Conventional configurations and their problems In recent years, there has been remarkable progress in speed control devices that drive motors using pulse width modulation, detect the motor's rotational speed and flowing current, and control the speed of the motor. .

A conventional speed control device will be explained below.

Fig. 1 is a configuration diagram of a conventional speed control device, where 1 is an oscillator that oscillates at a constant frequency, and 2 is a counter that divides the set count value in the direction of decreasing by the output of the oscillator 1, and the counter output is During counting, it outputs “1” output,
After counting is completed, it outputs °゛0''0''. Reference numeral 3 denotes a drive device composed of transistors and the like that performs power conversion based on the output of the counter 2 and drives the motor. 4 is a motor; 5 is a current detection device that detects the current flowing through the motor; 6 is a speed detection device that detects the rotational speed of the motor; the outputs of the current detection device 5 and the speed detection device 6 are input to a control logic device 7. be done. The control logic device T calculates pulse width data to be set in the p counter 2 based on the outputs of the current detection device 5 and the speed detection device 6, and controls the speed of the motor by setting the counter 2. 8 is an oscillator that generates a constant frequency, and is input to the control logic device 7. 9 is a speed command device, which gives a speed command to the control logic device.

Regarding the speed control device configured as above, the following is the first part.
The operation will be explained using FIG.

Figure 2 is a timing chart of the waveforms of each part in Figure 1, where the QS01 signal is the output of oscillator 1, the QS02 signal is the output of oscillator 8, the CQUT signal is the output of counter 2,
The T signal is the output of the current sensing device. It is now assumed that a speed command is given to the control logic device by the speed command device 9, and the electric motor 4 is rotating at a constant speed. The control logic device γ outputs the speed command value, in synchronization with the rising edge of the QSC2 signal.
The electric power to be supplied to the electric motor 4 is calculated from the detected current value and the detected speed value, and pulse width data is set in the counter 2.

The CQUT signal becomes “1” when the pulse width data is set.
From this point on, the count value of counter 2, that is, the pulse width data, is counted in the direction of decreasing by the QS01 signal, and the CQUT signal is
It is held at ``1''.

When the count value of counter 2 becomes “0”, the CQUT signal becomes 0.
It becomes ゛′. The drive device 3 performs power conversion based on the CQUT signal, supplies power to the electric motor 4, and the electric motor 4 rotates according to the applied power. If you increase the pulse width data set in the slack counter 2, the pulse width of the CQUT signal will become wider, and the rotation speed of the motor 4 will increase, and if you make the pulse width data smaller, the pulse width of the CQUT signal will become narrower.
The rotation speed of the electric motor 4 decreases. If the IQUT signal rises for some reason in FIG. 2, the control logic device 7 reduces the pulse width data set in the counter 2, and
1. Reduce the power applied to the motor to maintain constant rotation speed. In the opposite case, if the IQUT signal falls, the pulse width data will be widened to maintain constant speed rotation. Although not shown here, when the output of the current detection device exceeds the set rotation speed, the pulse width is narrowed, and when the output falls below the set rotation speed, the pulse width is widened. It will keep the rotation speed high.

As explained above, in the speed control device shown in FIG. The electric motor 4 rotates in accordance with the speed command value. However, in the above conventional configuration, the current flowing through the electric motor 4 is detected by the current detection device 5,
Since the pulse width data was input to the control logic device 7 and then the control logic device 7 set the pulse width data to the counter 2 according to the detected value, the speed detected by the control logic device 7 was determined by the time required for the calculation of the control logic device 7. This has the problem that the system becomes slow (delayed by one hour in FIG. 2), and the responsiveness of the system becomes extremely poor.

The control logic unit 7 is also a microprocessor and peripheral L.
When configured as an SI (large-scale integrated circuit; the same applies hereinafter) and perform digital processing, the current detection device 5 requires an analog-to-digital conversion circuit, which increases complexity and costs, and further increases the need for a microprocessor. Since a considerable portion of the operation is spent on the above processing, there is also the problem that other processing by the microprocessor is restricted.

OBJECTS OF THE INVENTION The present invention solves the above-mentioned conventional problems, and provides a speed control system that has a simple configuration that speeds up the response of a speed control system, and that is more stable and efficient.

Structure of the Invention In order to achieve the above object, the present invention comprises a first oscillator whose oscillation frequency can be varied, a counter which can count the output of the first oscillator and generate an arbitrary pulse width signal. , a drive device that drives a motor using a pulse width modulated signal from the counter output, a current detection device that detects the current of the motor, a speed detection device that detects the rotational speed of the motor, and a current detection value and speed detection. and a second oscillator that generates a constant frequency for providing timing for setting the pulse width data to the control logic device. By varying the frequency of the first oscillator with the feedback value of the current detection device, the response of the speed control system can be significantly increased, the configuration is simple, the cost is low, and the processing efficiency can be further improved. This is what I did.

DESCRIPTION OF THE EMBODIMENTS 6) a of one embodiment of the present invention will be described below using the drawings from FIG. 3 onwards. FIG. 3 is a configuration diagram of a speed control device in an embodiment of the present invention. In FIG. 3, 11 is a counter, 12 is a drive device, 13 is an electric motor, 15 is a speed detection device, 16 is a control logic device, 17 is an oscillator, and 18 is a speed command device, which are the conventional ones shown in FIG. This is the same configuration as the example. 14 is a current detection device, 10 is an oscillator, and the output of the current detection device 14 is connected to the oscillator 10. If the current detection value is large, the oscillation frequency of the oscillator 10 becomes high, and if the current detection value is small, the oscillation frequency is low. Become. Also, the output of the oscillator 1Q is connected to the counter 11,
As a result, the pulse width data set in the counter 2 is subtracted.

The operation of the speed control device of this embodiment configured as described above will be described below. FIG. 4 is a timing chart of waveforms of various parts in FIG. 3. The QS03 signal is the output of the oscillator 10, the QSC4 signal is the output of the oscillator 17, and the C
The output of the QU and TI multiplication signal counter 11 and the IQUT1 signal are the outputs of the current detection device 14. It is now assumed that a speed command is given to the control logic unit N16 by the speed command device 18, and the electric motor 13 is rotating at a constant speed. Next, if the IQUT+ signal rises for some reason, IQU
Since the T1 signal is input to the oscillator 1o, the oscillation frequency (QSC3 signal) of the oscillator 1Q becomes high. (In the conventional configuration (Fig. 1), when the QUT signal rises by 2, the control logic device 7 inputs the IQUT in synchronization with the rising edge of the output of the oscillator 8, and causes the current to decrease. However, in the present invention, the frequency of the QSC3 signal is increased, and the same effect as when the pulse width data value is set to a small value is obtained. In other words, in the conventional example, in order to shorten (lengthen) the output pulse width data of the counter, the frequency of the oscillator connected to the counter is kept constant, and the control logic device shortens (lengthens) the pulse width data value according to the current detection value. In contrast, in the configuration according to the embodiment, the frequency of the oscillator connected to the counter becomes higher (lower) depending on the current detection value in order to make the output pulse width data of the counter less than (longer).
It works to bring about exactly the same effect. In this embodiment, the control logic device 16 is connected to the output of the oscillator 17 (QS
C4 signal), the power to be supplied to the motor 13 is calculated from the speed command value and the detected speed value, and the counter 1
Set the pulse width data to 1. The electric motor 13 maintains constant speed rotation according to the command value of the speed command value 18 in the same way as the operation of the conventional example except that the current detection operation does not go through the control logic device 16. As described above, this embodiment According to the above, the control logic device 16 is not concerned with current detection at all, and the oscillation frequency of the oscillator 10 is increased or decreased according to the detected current value, and this is taken into account in the pulse width, so that the burden on the control logic device is lightened. (T in FIG. 2 becomes T' in FIG. 4) The response of the speed control system is significantly improved.

Hereinafter, a speed control device using the invention described above will be explained using FIG. 6. 19 is an oscillator, 2° is a counter,
21 is a drive device, 22 is an electric motor, 23 is a current detection device,
25 is a speed detection device, 26 is a control logic device, 27 is an oscillator, and 28 is a speed command device, which have the same configuration as in FIG. 3.

24 is a phase shift device that advances the phase, and the current detection device 1
If the phase is not advanced when feeding back the output of 4,
This prevents the control system from becoming unstable depending on the type of electric motor 13 or the load condition. By making the amount of phase shift variable, a stable speed control system can be achieved no matter what motor is connected or the load changes.

Effects of the Invention - As is clear from the description of the embodiments above, according to the present invention, the current flowing through the motor is detected by a current detection device,
The detected value is not input to the control logic device, but is input to an oscillator whose oscillation frequency can be varied, and the frequency of the oscillator is increased or decreased.
Since the output of the oscillator is used as the oscillation source for the counter that generates the pulse width signal, the pulse width is increased or decreased by current detection directly by the counter. In other words, whereas conventional control logic devices had to monitor both speed detection and current detection, the present invention allows them to concentrate solely on speed detection, greatly improving the responsiveness of the speed control system. and processing efficiency will be improved. Conventionally, the control logic unit is a microprocessor and peripheral
When configured with SI, the current detection device required an analog-to-digital conversion circuit, but the present invention requires only an analog signal, which simplifies the circuit and reduces costs accordingly. Therefore, it is possible to realize a speed control device that can obtain excellent effects.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a conventional speed control device, FIG. 2 is a timing chart of waveforms of each part in FIG. 1, FIG. 3 is a configuration diagram of a speed control device in an embodiment of the present invention, and FIG. FIG. 6 is a timing chart of waveforms of each part, and is a configuration diagram of a speed control device in another embodiment of the present invention. 1.10.19...Oscillator, 2,11.20.
...Counter, 3,12.21...Drive device, 4°13.22...Electric motor, 5,14.2
3...Current detection device, 6,15.25...
Speed detection device, Otsu 16.26... Control logic device, 8
, 17.27... Oscillator, 9.18. ．． 2B・
Speed command device, 24... Phase shift device.

Claims (2)

[Claims] (1) A first oscillator whose oscillation frequency can be varied, a counter that counts the output of the first oscillator and generates an arbitrary pulse width signal, and a motor using a pulse width modulation signal generated by the output of this counter. A drive device that drives the motor, a current detection device that detects the current of the motor, a speed detection device that detects the rotational speed of the motor, and a current detection value and a speed detection value obtained from the current detection device and the speed detection device. a control logic device for setting pulse width data in the counter; and a second oscillator for generating a constant frequency to provide timing for setting the pulse width data to the control logic device; A speed control device characterized in that speed control is performed by varying the frequency of a first oscillator. (2) Using a first oscillator that can vary the oscillation frequency, a counter that can count the output of the first oscillator and generate an arbitrary pulse width signal, and a pulse width modulation signal based on the output of this counter. a drive device that drives the motor, a current detection device that detects the current of the motor, a phase shift device that advances the phase of the output of the current detection device, a speed detection device that detects the rotational speed of the motor, and the current detection device. and a control logic device that sets pulse width data in the counter based on the current detection value and speed detection value obtained from the speed detection device, and a second control logic device that generates a constant frequency to give the control logic device the timing of setting the pulse width data. oscillator, the feedback value of the current detection device is input to the phase shift device to advance the phase, and the frequency of the first oscillator is varied by the output of the phase shift device to perform speed control. Characteristic speed control device.