JPS622879A - Controller of dc servo motor - Google Patents

Abstract

PURPOSE:To obtain a smooth rotation by altering the width and the voltage of a pulse supplied to a DC servo motor in response to the amplitude of an error signal. CONSTITUTION:An error signal applied to an error signal input unit 5 is input through a motor drive voltage controller 3, a comparator 6 and an inverter 7 to a comparator 8. The controller 3 outputs a voltage in response to the prescribed maximum voltage when the amplitude of the error signal is the prescribed value or higher, and a voltage in response to the amplitude of the error signal when the error signal is the prescribed value or lower. A motor drive power pulsating unit 4 converts a DC power controlled at the voltage by the controller 3 to a pulse regulated to the prescribed pulse width in response to a control pulse from the comparator 6 or 8, and supplies the pulsated DC power to a DC servo motor 1.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a control device for a DC servo motor that drives a material testing machine or the like.

(b) Conventional technology Pulse wide control is a control method for DC servo motors. This is a method in which pulses with a constant period are applied to the motor, and the power supplied to the motor is controlled by changing the pulse width.

In a closed loop control system that controls a DC servo motor using this pulse width control, when the error signal becomes smaller, the pulse width becomes smaller and the power supplied to the motor decreases, as shown in FIG. 2(a). On the other hand, when the error signal becomes thick (as shown in FIG. 2 (bl), the pulse width becomes large and the power supplied to the motor increases.

In this way, the pulse width is reduced as the error signal becomes smaller, but when the error signal is extremely small, the power supplied to the motor increases even with the minimum pulse width.

Therefore, when the error signal is small, as shown in Figure 3, after outputting 2 or 3 pulses, there is a certain pause period, and then 2 or 3 pulses are output again, which is repeated. In this case,
The motor will rotate unevenly. In particular, if this uneven rotation occurs in the DC servo motor that drives the material testing machine, it will cause problems such as inability to perform tests with high accuracy.

(c) Purpose of the Invention The present invention has been made in view of the above circumstances, and its purpose is to provide a control device for a DC servo motor that enables smooth control.

(D) Structure of the Invention The present invention provides a DC servo motor control device comprising a control system that controls the power supplied to the DC servo motor by changing the width of constant periodic pulses supplied to the DC servo motor. The present invention is characterized by comprising a pulse voltage adjusting means for changing the voltage of the pulse according to an error signal, and a pulse width adjusting means for changing the width of the pulse according to the error signal.

(e) Examples An embodiment of the present invention will be described below.

FIG. 1 shows a control device for a DC servo motor that constitutes a closed loop control system. The DC servo motor 1 drives a material testing machine (not shown). The DC servo motor 1 is supplied with the output of the DC power supply 2 having its voltage controlled by a motor drive voltage control section 3, and further converted into pulses having a constant period by a motor drive voltage pulsing section 4. A displacement detector (not shown) of a material testing machine, and a calculation device (not shown) that calculates the deviation between a displacement signal from this displacement detector and a displacement set value from a displacement setter (not shown) and provides an error signal to the error signal input section 5. , comparators 6 and 8, and motor drive power pulsating section 4 constitute a closed loop control system.

The error signal applied to the error signal input section 5 is input to the comparator 8 via the motor drive voltage control section 3, the comparator 6, and the inverter 7. The triangular wave generator 9 outputs a negative voltage triangular wave, and this triangular wave is input to the comparators 6 and 8. The output signals of the comparators 6 and 8 are sent to the motor drive power pulse generator 4.
is input to.

The motor drive voltage control unit 3 outputs a predetermined maximum voltage when the magnitude of the error signal is greater than or equal to a predetermined value, and outputs a predetermined maximum voltage stepwise or proportionally depending on the magnitude of the error signal when the error signal is less than or equal to the predetermined value. Outputs a reduced voltage. The comparator 6 compares the triangular wave from the triangular wave generator 9 with the error signal, and outputs a normal rotation control pulse according to the magnitude of the error signal when the error signal is negative. The comparator 8 compares the triangular wave from the triangular wave generator 9 and the inverted signal of the error signal from the inverter 7, and outputs a reversal control pulse according to the magnitude of this error signal when the error signal is positive. . The motor drive power pulsing unit 4 converts the DC power whose voltage has been controlled by the motor drive voltage control unit 3 into a forward control pulse from the comparator 6 or a comparator 8.
The reverse control pulse is converted into a pulse adjusted to the required pulse width according to the reverse control pulse from The DC power pulsed by the motor drive power pulse generator 4 is supplied to the DC servo motor 1.

In this way, the DC power whose voltage is controlled according to the magnitude of the error signal is pulsed to have a pulse width according to the error signal and is supplied to the DC servo motor.

Therefore, when the error signal is extremely small, the pulse width is minimized and the pulse voltage is reduced.

As a result, pulses can be continuously supplied to the DC servo motor, resulting in smooth rotation of the DC servo motor.

(f) As described in detail, in the present invention, the width of the pulse supplied to the DC servo motor and the voltage are changed according to the magnitude of the error signal, so even when the error signal is small, Smooth rotation can be obtained by continuously supplying pulses to the DC servo motor, and therefore, for example, tests can be performed with high accuracy in a material testing machine driven by this DC servo motor.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram showing the configuration of an embodiment of the present invention, and FIGS. 2 and 3 are diagrams showing pulse waveforms in conventional pulse wide control. 1... DC servo morph 3... Motor drive voltage control section

Claims (1)

[Claims] In a DC servo motor control device that constitutes a control system that controls power supplied to the DC servo motor by changing the width of constant-cycle pulses supplied to the DC servo motor, the voltage of the pulses is adjusted in response to an error signal. 1. A control device for a DC servo motor, comprising: pulse voltage adjusting means for changing the width of the pulse; and pulse width adjusting means for changing the width of the pulse according to an error signal.