JPS639274Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to the improvement of a speed control device for an electric motor, and its purpose is to provide a speed control device that has a large gain in the signal output of the control system and has stable control characteristics. Our goal is to provide the following.

A conventional device to be improved by the present invention will be explained with reference to FIGS. 1 and 2. In FIG. 1, 1 is an electric motor, and 2 is a frequency generator connected to the electric motor 1, which generates a voltage having a frequency corresponding to the rotational speed of the electric motor 1 and having periodicity approximately every half cycle. 3 is a waveform shaping circuit that shapes the output of the frequency generator 2, and its output drives a monostable multivibrator (MM) 4. A reference oscillator 5 generates a pulse voltage having a frequency (reference frequency) corresponding to the reference speed of the motor. A phase comparator 6 compares the phases of the output of the reference oscillator 5 and the output of the waveform shaping circuit 3, and its output is added to the output of the MM 4 in an adder 7. The output of the adder 7 is smoothed and amplified by a smoothing amplification circuit 8 to control a speed control circuit 9 of the electric motor 1. 10 is a power source.

In FIG. 2, a is the waveform of the output voltage of the reference oscillator 5, b is the waveform of the output voltage of the waveform shaping circuit 3,
c is the waveform of the output voltage of the phase comparator 6 which compares the phases of the rising edges of the pulse waveforms a and b. d is the waveform of the output voltage of MM4 that is triggered by the rising edge of b, and its output time (H time) T _M is MM
It is set to be shorter than the period T of b by the external capacitor and resistor 4. e is c
This is the output waveform of the adder 7 obtained by adding d and d.

By the way, in the above conventional device, when trying to increase the gain of the signal output of the control system, the adder 7
The ripple of the output becomes large and the amplifier saturates. In order to reduce this ripple, a delay occurs in the control operation to increase the time constant of the smoothing amplification circuit 8, making the control characteristics unstable.

The present invention is intended to solve the above problems. The embodiment will be described below with reference to FIGS. 3 and 4. As shown in FIG. 3, the device of the present invention is characterized by adding the part shown in the dotted line frame to the conventional device shown in FIG. 1, and the other parts 1 to 10 are the same as in FIG. . Yes, the first
The monostable multivibrator (MM) 4 shown in the figure becomes a third monostable multivibrator (3rd MM) 4 in the apparatus of the present invention shown in FIG. The output of the waveform shaping circuit 3 is driven to the first monostable multivibrator (1st MM) 11 and the second monostable multivibrator (2nd MM) 12 within the dotted line frame,
The outputs of the first MM11 and the second MM12 are input to the OR circuit 13, and the output of the OR circuit 13 is input to the OR circuit 13.
Drives 3MM4.

In FIG. 4, a is the waveform of the output voltage of the reference oscillator 5, and has twice the frequency of the conventional a in FIG. b is the waveform of the output voltage of the waveform shaping circuit 3. c is the output waveform of the first MM11 that operates on the rising edge of b, and d is the output waveform of the second MM12 that operates on the falling edge of b.
In the output waveform, the output times of c and d are set to be shorter than the period of the pulse frequency of the frequency generator 2. e is the output of the OR circuit 13, and is a pulse waveform of the OR of c and d. f is the rising edge of a and e
The output of the phase comparator 6, which compares the phase with the rising edge of , has a frequency twice that of c in FIG. 2, indicating that the gain of the phase synchronization control loop is twice as high. g is the first wave operated by the rise of e.
This is the output waveform of 3MM4. h is the output waveform of the adder 7 which is the sum of f and g.

As described above, the ripple frequency of the control signal h of the present invention is twice that of the conventional control signal e shown in FIG. 2, and if the same ripple as that of the device shown in FIG. Not only can the time constant be made smaller, but also the gain of the speed control loop by the third MM4 can be increased, which, together with the increase in the gain of the phase synchronization control loop mentioned above, is an excellent method for improving the characteristics of the control system. have an effect.

[Brief explanation of the drawing]

Figure 1: A block diagram showing the configuration of a conventional speed control device, Figure 2: An explanatory diagram of the operation of the device in Figure 1, Figure 3: A block diagram showing the configuration of the speed control device of the present invention, and Figure 4. : Operation explanatory diagram of the device in Figure 3 Symbol, 1...Electric motor, 2...Frequency generator, 3
... Waveform shaping circuit, 4 ... Third monostable multivibrator, 5 ... Reference oscillator, 6 ... Phase comparator, 7 ... Adder, 8 ... Smoothing amplification circuit, 9 ...
Speed control circuit, 10...Power supply, 11...First monostable multivibrator, 12...Second monostable multivibrator, 13...Order circuit.

Claims (1)

[Scope of utility model registration request] a frequency generator that is coupled to an electric motor and generates a voltage that has periodicity at a frequency corresponding to the rotational speed of the electric motor and has periodicity approximately every half period; a waveform shaping circuit that shapes the output of the frequency generator; A first monostable multivibrator that operates on the rising edge of the output of the waveform shaping circuit, a second monostable multivibrator that also operates on the falling edge of the output, and the outputs of the first and second monostable multivibrators. an OR circuit, a third monostable multivibrator operated by the output of the OR circuit, a reference oscillator that generates a pulse voltage of a predetermined frequency, an output of the reference oscillator, and an output of the OR circuit. and an adder that adds the output of the phase comparator and the output of the third monostable multivibrator, and a signal obtained by smoothing and amplifying the output of the adder. A speed control device for an electric motor, characterized in that the speed control circuit is controlled by a speed control circuit.