JPH0365089A - Dc motor runaway detection method - Google Patents

Abstract

PURPOSE:To see that a motor is not damaged when a transistor has broken down in short conditions by detecting the speed of a motor based on the photosignal from a rotary encoder so as to detect it as runaway condition when the speed difference between instruction speed and detection speed has become over some value. CONSTITUTION:Upon runaway of a motor, the period of the photosignal from a rotary encorder is shortened. Thereupon, the value that a counter 4 counts within a certain time becomes large. This value is corresponding to the motor speed, and if this value and the value of instruction speed data are input into a speed arithmetic circuit 5, speed difference data can be obtained. The larger the value of the counter 4 (than the instruction speed data), the larger the speed difference data. At this time, if the speed difference exceeds over a set value, and arithmetic circuit 7 detects the runaway of the motor, and outputs an alarm signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a DC servo motor control method, and particularly to a runaway detection method for the DC servo motor.

[Conventional technology]

Conventionally, the speed control method for this type of DC servo motor is based on a photo signal from a rotary encoder, detects the speed difference from a pre-instructed speed, converts this speed difference into a pulse width, and converts it into a motor acceleration signal. Generates motor deceleration signal. The motor driver circuit controls the motor speed based on these two signals.

[Problem to be solved by the invention]

An example of this motor driver circuit is shown in FIG. In the circuit shown in FIG. 3, when transistor 1 is short-circuited and broken, motor 3 will always be accelerated regardless of the motor acceleration signal.

Therefore, when the transistor 1 is short-circuited and broken, the motor 3 runs out of control, resulting in damage to the motor 3.

[Means to solve the problem]

The present invention detects the speed of a DC servo motor based on a photo signal from a rotary encoder, and when the speed difference between the indicated speed and the detected speed exceeds a certain value,
To provide a DC servo control circuit having a runaway detection circuit capable of detecting a runaway state.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

Referring to FIG. 1, an embodiment of the invention includes a counter 4;
It includes a speed difference calculation circuit 5, a pulse width conversion circuit 6, and a calculation circuit 7.

When the motor runs out of control, the period of the photo signal from the rotary encoder becomes shorter. Then, the value counted by the counter 4 within a certain period of time increases. This value corresponds to the motor speed, and when this value and the value of the command speed data are input to the speed difference calculation circuit 5, speed difference data is obtained.

Now, the larger the value of the counter 4 is than the command speed data, the larger the speed difference data becomes. At this time, when the set value, that is, the speed difference exceeds the set value, the arithmetic circuit 7 detects runaway of the motor and outputs an alarm signal. This time chart is shown in FIG. When the alarm signal is output, the power supply can be stopped to prevent damage to the motor.

〔Effect of the invention〕

As explained above, the present invention is configured to detect the speed difference between the motor speed and the commanded speed to detect whether or not the motor is in a runaway state, thereby making it possible to prevent the motor from being damaged in the event of runaway. There is an effect.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, and Fig. 2 is a circuit diagram showing an embodiment of the present invention.
The time chart of the circuit diagram shown in the figure, and FIG. 3 is a circuit diagram of a conventional example. 1. Transistor; 2. transistor, 3. DC motor, 4. Counter, 5. Speed difference calculation circuit, 6. Pulse width conversion circuit, 7. Arithmetic circuit.

Claims (1)

[Claims] In the speed control method of a DC servo motor, the detected speed data from the speed detector is compared with the commanded speed data, and the speed difference between the motor speed and the commanded speed is checked to detect whether the motor is running out of control. A DC motor runaway detection method that has the feature of being able to.