High Performance Servo-System by Rotational Machines. Digital Speed Control of 2-mass Systems with a Tortional Torque Observer.

Abstract

Recently, many researches for vibration suppression control of 2-mass systems have been reported because the effects of non-stiff coupling cannot be ignored when a faster speed response is required for motor driving systems. An observer based approach is one of the representative methods to suppress the vibration which assumes that the disturbance torque changes very slowly, or even is constant during the sampling period, and uses a disturbance observer to estimate the tortional torque. And the systems are almost analyzed as continuous time ones. But in case that the system is composed of small equipment, the resonance frequency becomes high enough to be close to the sampling frequency of the speed detector, so we have to use high gains for the observer with the result that the noise and parameter error have strong effects on the calculation of the observer.In this paper, treating the system as a discrete time one, we propose a novel vibration suppression control method. Assuming that the torsional torque is composed of a periodic component and dc component, we use PI type controller for the speed control system and feed the estimation torque forward to the current reference to suppress the vibration. Experimental results show the validity of the proposal method.