METHOD OF SUPPRESSING TORSIONAL VIBRATION IN A MOTMETHOD OF SUPPRESSING TORSIONAL VIBRATION IN A MOTOR SPEED CONTROL SYSTEM AND APPARATUS THEREFOR OR SPEED CONTROL SYSTEM AND APPARATUS THEREFOR

摘要

Herein disclosed are a method and an apparatus for suppressing a torsional vibration in an electric motor speed control system including a mechanism for transmitting a drive torque from an electric motor to a load through a drive shaft having a torsional spring system. Generally speaking, the signal Or a speed detector (3) of an electric motor is a pulsating signal of high frequency. Even if this speed detecting signal is differentiated, it is impossible to obtain a signal proportional to the changing rate of the motor speed. By computing an average value of the signals of the motor speed detector (3) for every predetermined period, however, the pulsating value of the speed signal can be reduced to compute the changing rate of the motor speed from that signal. In the present invention, an acceleration torque command of the electric motor is given in terms of the output signal of a speed controller (11) to cancel the load torque of the electric motor from disturbing the acceleration torque of the motor, with the torque command compensating signal outputted from a motor acceleration torque controller (25) having a proportional gain and an integrator. As a result, the disturbing torque of the electric motor, which is generated by the load and the torsion of the drive shaft during an acceleration and at an abrupt load fluctuating time, is canceled so that the torsional vibration is suppressed to stabilize the variable speed characteristics.