JPH04282458A - Electric motor rotation speed detector - Google Patents

Abstract

PURPOSE:To control a position and a speed over a wide range regardless of a rotational speed and to ensure high accuracy by also setting the output form of a rotational speed detector to sine wave output in addition to rectangular wave output. CONSTITUTION:The sine wave raw signal from the rotational speed detector connected to the rotary shaft of an electromotor is converted to DC voltage Vx by a frequency/voltage converter to be compared with a certain reference value V1. When this voltage Vx is voltage V1 or more, the raw signal becomes rectangular wave output through a waveform shaping device and the edges of the rising and falling thereof are set to a control cycle to perform speed control. When the voltage Vx is below voltage V1, the raw signal becomes sine wave output as it is. Since the cycle of the sine wave output becomes long when the rotational speed of the electromotor becomes low, when the division number of waveforms is set so as to increase, a stable control cycle is obtained regardless of a rotational speed.

Description

[Detailed description of the invention]

0001

[Industrial application field] In the OA or FA field,
The number of products that use electric motors to control speed and position is increasing.

The present invention is a rotational speed detection method that is effective for speed control systems and position control systems of these electric motors.

0003

[Prior art] In the conventional technology, patent application No. 56-6686
No. 7, Japanese Patent Application No. 56-190877, the output is an incremental two-phase rectangular wave, and the control method is to detect the rising or falling portion of the output waveform.

In the conventional method, the cycle of the encoder output waveform becomes short when the motor rotates at high speed, making it possible to perform highly accurate control; however, conversely, the cycle of the encoder output waveform becomes long when the motor rotates at low speed, making it difficult to Or the accuracy of speed control was low.

[0005]

SUMMARY OF THE INVENTION In the present invention, in a rotational speed detector, that is, an encoder connected to an electric motor,
By combining both the sine wave output and the rectangular wave output, the purpose is to improve the accuracy of position control or speed control during low rotation of the electric motor.

[0006]

[Means for Solving the Problems] In the present invention, the output form of the rotational speed detector and encoder of the electric motor is capable of outputting a sine wave in addition to the conventional rectangular wave output. Using the output, we converted the frequency to DC voltage to increase resolution and achieve higher accuracy during low-speed rotation.

Note that during high-speed rotation, high-precision control is performed using the rising and falling edges of the rectangular wave output, as in the conventional system.

[0008]

[Operation] The frequency of the original signal (sine wave) output from the rotational speed detector is converted into a voltage, and when the voltage exceeds a certain value V1, it is output as a rectangular wave, and when it is below V1, it is output as a sine wave. Furthermore, in the case of V1 or lower, the sine wave output was divided according to the voltage value to achieve high resolution.

[0009]

EXAMPLES The present invention will be specifically described in detail.

FIG. 1 shows a block diagram of the present invention. From the same figure,
A rotational speed detector connected to the rotating shaft of the electric motor outputs an original signal of a sine wave.

Next, the original signal is converted into a DC voltage by a frequency-voltage converter and compared with a certain reference value V1.

[0012] When the DC voltage converted here is V1 or more, the original signal becomes a rectangular wave output waveform via the output waveform shaping circuit of the next stage.

In the case of a rectangular wave output, the rising and falling edges of the rectangular wave are captured and used as a control period to control the speed of the motor.

On the other hand, when the converted DC voltage is less than V1, the original signal is output as is, that is, the output waveform is a sine wave.

In the case of a sine wave output, the number of divisions is determined by the converted DC voltage value as shown in FIGS. 2 and 3,
For example, the number of divisions is 12 in the case of FIG. 2, and 8 in the case of FIG. 3. The sine wave output waveform is divided, the control period is adjusted, and the speed of the motor is controlled.

According to the present invention, the higher the rotational speed of the electric motor, the higher the DC voltage value converted by the frequency-voltage converter. Or speed control is performed.

On the other hand, the lower the rotational speed of the electric motor, the lower the frequency of the original signal output from the rotational speed detector, and the converted DC voltage value also falls below the reference value V1.
, resulting in a sine wave output.

The period of the sine wave output waveform becomes longer as the rotational speed of the electric motor decreases, so if the number of divisions is set to be large, a stable control period can be obtained regardless of the rotational speed of the electric motor. .

[0019]

According to the present invention, a stable control period can be obtained regardless of the rotational speed of the electric motor, so that it can be applied to position or speed control over a wide range, and high accuracy is guaranteed.

[Brief explanation of the drawing]

FIG. 1 is a specific configuration diagram of the present invention.

FIG. 2 is a diagram showing an example of a method for dividing a sine wave output waveform.

FIG. 3 is a diagram showing an example of a method of dividing a sine wave output waveform.

Claims (4)

[Claims] 1. An optical encoder comprising a rotating disk, an optical detector, and an output waveform shaping circuit board, in which a sine wave and a rectangular wave can be output by adjusting the amplification factor of an amplifier in the output waveform shaping circuit. Features: Electric motor rotation speed detector. 2. A magnetic encoder comprising a magnetic drum, a magnetic detector, and an output waveform shaping circuit board, comprising:
By adjusting the amplification factor of the amplifier in the output waveform shaping circuit,
Motor rotation speed detector that can output sine waves and square waves. 3. An electric motor comprising the rotational speed detector according to claim 1 or claim 2. 4. A speed or position control system for an electric motor, characterized in that the electric motor according to claim 3 is one component.