JP3001343B2 - Motor speed control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor speed control system.

[0002]

2. Description of the Related Art Conventionally, there is a speed control system for a motor of this type shown in FIG. In such a conventional method, the output of the rotation detector G for detecting the speed of the electric motor M is used to obtain the rotation speed voltage VO by the F / V converter 2, and the speed setting pulse 5 is similarly output by the F / V converter 7. Obtain the speed setting voltage V1.

The difference (V1−VO) is set as a speed control amount by a differential amplifier circuit 3 including an operational amplifier that inputs the speed setting voltage V1 of the analog voltage and the rotation speed voltage VO, and this speed control amount is used as a power control circuit. 4 to control the speed of the electric motor.

However, in such a conventional motor speed control system, the signals of the rotational speed and the set rotational speed are both converted by using independent F / V converters 2 and 7, and the difference between the operational amplifiers Since the speed control amount is calculated by the analog operation using the dynamic amplification circuit 3, the following problem occurs.

That is, variations in the F / V conversion amount of the resistors, capacitors, transistors, etc. used in the F / V converters 2 and 7 due to temperature change and aging change, and the speed control amount (V1− VO) changes and the stability of speed control is low.

[0006]

[0007]

SUMMARY OF THE INVENTION The present invention provides a motor speed control system capable of solving the problems of the conventional system as described above.

Therefore, in the motor speed control method of the present invention, the output of the rotation detector for detecting the speed of the motor is converted into a rotation speed pulse having a certain pulse width by a reference clock, and the speed setting is similarly set to the same value. By converting to a speed setting pulse of the same pulse width by the reference clock, highly stable processing can be performed by using the reference clock, and at the same time, even if there is some fluctuation, both pulse widths are completely the same, and this conversion is performed. Set the rotation speed pulse and the speed setting pulse to F
The pulse is synthesized without performing the / V conversion and without using the operational amplifier, and the difference pulse is used as the speed control amount by this synthesis.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in further detail with reference to the illustrated embodiments.

FIG. 1 is a block diagram of a motor speed control system according to the present invention. FIG. 2 is a timing chart when (rotation speed <speed setting), and FIG.
(Speed setting).

In FIG. 1, M is a motor, G is a rotation detector, 4 is a power control circuit, 5 is a speed setting pulse, 8 is a constant pulse width generation circuit based on a reference clock, 9 is a reference clock, and 10 is a logic. A sum / product circuit, 11 is a waveform synthesis circuit, and 12 is an integrator.

First, the operation when the speed setting is higher than the rotation speed as shown in FIG. 2, that is, when the speed of the motor M is delayed from the set value will be described with reference to FIG. A constant pulse width generation circuit 8 generates a waveform b from a signal a from a rotation detector G that detects the speed of the motor M by using a reference clock. This waveform b outputs a pulse t having a constant width triggered by the rising edge and the falling edge of the signal a.

Similarly, the speed setting pulse c generates a waveform d by the constant pulse width generating circuit 8 based on the reference clock. Like the waveform b, the waveform d outputs a pulse t having a constant width triggered by the rising edge and the falling edge of the speed setting pulse c.

The operation amount of the rotation speed b and the speed setting d is obtained as the rotation speed difference e by the logical sum in the logical sum / product circuit 10, and the operation amount is obtained as the speed setting amount difference f by the logical product. Then, the waveform synthesizing circuit 11 synthesizes the rotational speed difference e and the speed set amount difference f to obtain a synthesized waveform g which is a speed control amount based on the potential V1. The waveform g represents the rotation speed difference e by the OV-V1 potential and the speed setting difference f by the V1-V2 potential with reference to the potential V1.

Therefore, a waveform g, which is a speed control amount, is obtained as a pulse of a difference between the rotational speed b and the speed setting d by the logical sum / product circuit 10 and the waveform synthesizing circuit 11,
The waveform g representing the speed control amount is converted by the integrator 12 into an analog speed control amount using V1 as a reference voltage.

[0016] The speed control amount, the V1 synthesized waveform g compared area of 0V-V1, V1-V2 to the reference, looking at the difference in potentially becomes a voltage of + [Delta] V to the reference voltage V1, the amplification Then, the motor M is accelerated by the next power control circuit 4 to control the speed of the motor to follow the speed setting.

On the other hand, when the rotation speed is equal to the speed setting (the speed of the motor is equal to the set speed), as can be seen from the timing chart of FIG. 3, the block diagram of FIG. 1 and the timing chart of FIG. By the same operation, a synthesized waveform g that is a speed control amount based on the voltage V1 is obtained. Therefore, the speed control amount obtained by integrating the synthesized waveform g is 0V-V1 based on V1 of the synthesized waveform g. , V1-V
2 and the difference is viewed in terms of potential, the reference voltage V
A voltage of ± 0 V with respect to 1 is amplified and amplified, and the next power control circuit 4 drives the motor M at a constant speed, and controls the speed of the motor to follow the speed setting. Actually, including the motor
Because the amplification of the whole system is finite, it is slightly slower than the speed setting.
Equilibrate at high rotation speed.

When the rotation speed is greater than the speed setting (the speed of the motor is faster than the speed setting), the speed control amount obtained by the F / V conversion is equal to the reference voltage, contrary to the composite waveform g of FIG. The voltage becomes −ΔV with respect to V1, is amplified, and the next electric power control circuit 4 decelerates the electric motor M to perform speed control of the electric motor to follow the speed setting.

[0019] In the above, the pulse t of constant width is set constant at a rotational speed range (high speed rotation speed from low speed), setting
The constant pulse width t is changed according to the number of rotations,
Control the duty of the pulse width t of d to be approximately 50%.
This further improves the speed stability at each rotation speed.

[0020]

According to the present invention, the process up to calculating the difference is different from the conventional analog system using two F / V conversion circuits of a rotation speed detection system and a speed setting system for calculating the difference between the rotation speed and the set rotation speed. Is a digital system using a reference clock, and the digital system uses the difference speed control amount as a pulse difference.Therefore, there is little change in speed control amount due to temperature change and aging. Can be stabilized.

[0021]

By changing the analog processing to digital processing, resistors and capacitors used in the F / V conversion circuit and the differential amplifier become unnecessary, and the number of parts is reduced to reduce the size and cost. Can be down.

As described above, by converting a part which has been conventionally subjected to analog processing to digital processing, not only hardware but also software can be realized. Therefore, the number of parts can be reduced to reduce the size and cost. I can do it.

Further, as described above, by changing a portion which has been conventionally subjected to analog processing to digital processing, the speed setting becomes a digital input, so that the upper controller can be digitized, and the control of the entire system can be performed. It will be easier.

[Brief description of the drawings]

FIG. 1 is a block diagram of a motor speed control system according to the present invention.

FIG. 2 is a timing chart when rotation speed <speed setting.

FIG. 3 is a timing chart when the rotation speed is set to a speed.

FIG. 4 is a block diagram of a conventional motor speed control system.

[Explanation of symbols]

 Reference Signs List 4 power control circuit 5 speed setting pulse 8 constant pulse width generation circuit 9 reference clock 10 logical sum / product circuit 11 waveform synthesis circuit 12 integrator

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H02P 5/00

Claims (2)

(57) [Claims] 1. A rotation detector for detecting a rotation speed of a motor with a frequency proportional to the speed, a speed setting device having a frequency proportional to the speed, and an amplifier for amplifying an output signal corresponding to a difference between the rotation speed and the set rotation speed. a circuit, in the speed control system of the electric motor and a power control circuit for controlling the power supply to the motor according to the output of the amplifier circuit, set to the rotational speed
One of the signals for each of the rotation speeds is
Negative logic duty signal with a certain pulse width
And the other uses a reference clock to set a certain pulse width
Digital signal of both signals as duty signal of positive theory
And the logical sum and logical product of these two digital quantities
And the logical sum and logical product of the two digital quantities are
1 of power supply voltage for analog operation with power supply operational amplifier
/ 2 as a reference potential to form a synthesized waveform
Then, the integrated waveform is integrated by an integrator.
To calculate the difference between the rotation speed and the set number of rotations.
A speed control method for an electric motor, which is used for speed control of a motor. 2. A rotation detector for detecting a rotation speed of a motor at a frequency proportional to the speed, a speed setting device having a frequency proportional to the speed, and an amplifier for amplifying an output signal corresponding to a difference between the rotation speed and the set rotation speed. a circuit, in the speed control system of the electric motor and a power control circuit for controlling the power supply to the motor according to the output of the amplifier circuit, set to the rotational speed
One of the signals for each of the rotation speeds is
Negative logic duty signal with a certain pulse width
And the other uses a reference clock to set a certain pulse width
Digital signal of both signals as duty signal of positive theory
And the logical sum and logical product of these two digital quantities
And the logical sum and logical product of the two digital quantities
Power supply voltage of 0 when analog operation is performed by power supply
Composite waveform by combining volts as reference potential
And the integrated waveform is integrated by an integrator.
To calculate the difference between the rotation speed and the set number of rotations.
A speed control method for an electric motor, which is used for speed control of a motive .