Two-Degrees-of-Freedom Speed Control of Resonant Mechanical System Based on H.INF. Control Theory.

Abstract

In the industrial motor drive systems such as industrial plants and industrial robots, a torsional vibration is often generated because of the elastic elements in torque transmission. This vibration makes it difficult to achieve quick responses of speed and may result in damage to the plant. Such system is simply modelled as a two-mass mechanical system.In this paper, H∞ control theory is applied to design the speed controller for the two-mass system. This controller determines the closed-loop characteristics such as suppression of torsional vibration, rejection of torque disturbance and robust stability. Moreover, two types of two-degrees-of-freedom control system, which includes the H∞ controller, are proposed in order to improve the command response. One is based on the TDOF PI control, in which the PI controller included in the H∞ controller is rearranged to the TDOF system. Another is based on the model matching feedforward control, in which the pre-filter and the feedforward compensator are added to the H∞ controller. The proposed control system is applied to two types of resonant mechanical system with different inertia ratio. From several examinations, it is clarified that the proposed speed control system is useful for the resonant mechanical system.