Motor control device and motor control method

Abstract

A motor control device has a motor current detector for detecting current in windings to control the operation of a motor with a stator having three-phase windings. The motor control device includes a digital controller for outputting a PWM switching signal, a power converter for applying drive voltage to the windings using the PWM switching signal, a motor current detector for converting current flowing in the windings to analog voltage, a ΔΣ AD converter for converting the analog voltage to a 1-bit digital signal, an AD conversion decimating filter for generating a detected motor current value from the 1-bit digital signal, a clock generator for generating a clock for the ΔΣ AD converter and the AD conversion decimating filter, and a stop signal generator for generating a clock stop signal for stopping the clock of the clock generator for a predetermined period. The stop signal generator generates the clock stop signal with a predetermined pulse width based on a timing of the PWM switching signal, and the clock generator stops the clock for a period of the predetermined pulse width, using the clock stop signal.

Description

TECHNICAL FIELD[0001]The present invention relates to motor control devices and motor control methods for freely controlling motor rotation by applying drive voltage generated by the PWM control to a winding of a motor to control current, and more particularly to motor control devices equipped with a function to detect a value of current generated by applying the drive voltage to the winding and motor control methods of these devices.BACKGROUND ART[0002]A position, speed, and torque of a servo motor used in FA (Factory Automation) are controlled to follow a drive command (position command) from a host device (host controller), and digital control is broadly adopted, using a microprocessor as its control operation device. In a general PWM (Pulse Width Modulation) control system for controlling motor torque, there is a method of detecting and using a value of current flowing to a winding of the motor (hereafter referred to as “motor current”). In digital control of this method, a moto...

AI Technical Summary

Benefits of technology

The motor control device and method described in this patent can reduce the accuracy of detection due to leak current caused by PWM switching. This helps to reduce the unwanted torque generated in the motor and minimize vibration.

Problems solved by technology

However, in the configuration of driving the motor using the PWM control, this ΔΣ AD converter is likely affected by leak current due to the PWM control.

Therefore, a leak current occurs at a moment of switching.

However, the leak current also flows via shunt resistance, and voltage at both ends of the shunt resistance changes by this leak current.

In the digital control, the unwanted current component is processed as disturbance, and voltage that cancels the disturbance is applied to the motor, causing undesired torque in the motor.

In particular, at the time of servo lock and low-speed rotation in which the current flowing in the motor is small and switching timings of phases tend to overlap, an influence of the leak current becomes relatively large.

Accordingly, a minute vibration of the motor output shaft occurs due to undesired torque even in the servo-lock state in which the motor output shaft should be still under normal conditions.

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