JPS6380789A - Controller for dc servo motor - Google Patents

Abstract

PURPOSE:To prevent a motor from running away due to the malfunction, such as a command current by limiting a current flowing to the motor when the motor is continuously rotated at a low speed. CONSTITUTION:A speed command signal 8 from a motor controller 1 and a speed feedback signal 9 from a moving unit are applied to a servo amplifier 2, which amplifies its deviation to obtain a command current 10 for a motor 6. The current 10 is input to a motor driver 3. At this time, a motor power source controller 4 decides a power source voltage supplied to the motor 6 by a control signal 7 from the controller 1. Here, when the motor 6 is desired to be rotated at a high speed, the power source voltage supplied to the motor is raised so that a current limit is not effective, while when the motor 6 is desired to be rotated at a low speed, the power source voltage supplied to the motor is reduced to limit the current.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a control device for a DC servo motor, and particularly to a DC servo motor suitable for controlling the rotational speed of the motor to a low speed state by limiting the current. The present invention relates to a control device.

[Conventional technology]

As described in Japanese Patent Application Laid-open No. 59-136086, the conventional device is operated by a limit signal depending on the operation of an external actuator between an amplifier that amplifies the speed deviation and a motor drive circuit that drives the motor. A variable limiter is provided to control the rotational speed of the motor by limiting the current command value obtained by the amplifier with the variable limiter.

[Problem that the invention seeks to solve]

In the above conventional technology, the motor rotation speed is controlled by limiting the current command value to the motor using the variable limiter controlled by the jI7U in response to the limit signal corresponding to the operation of the external actuator. If the limit signal is generated in response to the operation of the actuating section, as the rotational speed of the motor increases, the limit signal is not fixed and fluctuates in the direction of increasing, so that the current limiting effect is lost. Also,
Since only the current command value is limited, if an abnormality occurs in the limit signal or variable limiter during current limitation and the current command value momentarily increases, there is no current check mechanism and the supply to the motor will be interrupted. Because of the high voltage, there was a risk that the motor would suddenly start rotating at high speed.An object of the present invention is to prevent the motor from suddenly starting to rotate at a high speed due to an abnormality in the current command value when the motor is operated continuously at low speed by current limitation. An object of the present invention is to provide a control device for a DC servo motor that can safely control the motor without causing it to run out of control.

[Means for solving problems]

The above purpose is to use a motor control device consisting of a servo amplifier that amplifies the deviation between the speed command value and the speed feedback value and uses it as a current command value, and a motor drive circuit that controls the operation of the motor based on the current command value. This is achieved by providing a current detection circuit that detects the current and a motor power supply control circuit that controls the power supply voltage supplied to the motor.
[Operation] The motor power supply control circuit operates to control the voltage supplied to the motor and apply the power supply voltage to the motor drive circuit. By lowering the power supply voltage supplied to the motor, the current flowing through the motor is controlled and the rotation speed of the motor is suppressed.In addition, the current detection circuit detects the current flowing through the motor drive circuit and the motor, and detects abnormalities in the circuit. Detects overcurrent to prevent motor runaway.

〔Example〕

An embodiment of the present invention will be explained below with reference to FIG. In FIG. 1, a control device for a DC servo motor includes a motor control section 1, a servo amplifier 2, a motor drive circuit 3, a power supply control circuit 4, and a current detection circuit 5. A speed command signal 8 from the motor control section 1 and a speed feedback signal 9' from the movable section are applied to the servo amplifier 2, and the deviation is amplified to obtain a command current 10 to the motor 6. By inputting this command current 10 to the motor drive circuit 3, the operation of the motor 6 is controlled. At this time, motor power control circuit 4
The power supply voltage supplied to the motor 6 is determined in advance by the control signal 7 from the motor control unit 1, and the motor drive circuit 3
The power supply voltage is applied to the Further, the control signal 7 can be freely generated in the motor control section 1 in its magnitude. Here, the relationship between the rotational speed of the motor 6 and the motor power supply control circuit 4 will be briefly explained. If you want the motor 6 to rotate at high speed, it is necessary to make the power supply voltage supplied to the motor as high as possible so that the current limit does not work.
If you want to rotate the motor at a low speed, it is necessary to lower the power supply voltage supplied to the motor so that the current is limited. This motor power supply control circuit 4 can be configured, for example, by a power supply circuit using phase control of a thyristor, and is controlled to an arbitrary power supply voltage by a control signal 7 from the motor control section 1, that is, a phase pulse signal. Therefore, by lowering the power supply voltage supplied to the motor 6, the current flowing to the motor is limited, thereby suppressing the rotational speed of the motor and preventing runaway of the motor.

〔Effect of the invention〕

According to the present invention, when the motor is rotated continuously at a low speed, the rotational speed of the motor is suppressed by limiting the current flowing through the motor, so that the motor can be safely operated without causing the motor to run out of control due to an abnormality such as a command current. The driving can be controlled. Therefore, it is effective in cases where humans are involved, such as in robot teaching work.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a motor control device that implements low-speed operation control of a motor according to the present invention. 1...Motor control unit, 2...Servo amplifier, 3...
・Motor drive circuit, 4... Motor power supply control circuit, 5.
...Current detection circuit, 6...Motor, 7...Control signal, 8...Speed command signal, 9...Speed feedback signal, 10
... Command current, 11 ... Current flowing through the motor, 12
...Current detection value, 13...Motor supply power supply voltage.

Claims (1)

[Claims] 1. A motor control device consisting of a servo amplifier and a motor drive circuit includes a motor power supply control circuit that controls the power supply voltage applied to the motor, and a current detection circuit that detects the current flowing through the motor. A DC servo motor control device that limits the motor current, suppresses the rotational speed of the motor, and prevents the motor from running out of control by lowering the power supply voltage.