Two‐degrees‐of‐freedom speed control of resonant mechanical system based on H∞ control theory

Abstract

AbstractIn industrial motor drive systems such as those used in industrial plants and robots, a torsional vibration is often generated as a result of the elastic elements present in the torque transmission systems. This vibration makes it difficult to achieve quick speed responses and may result in plant damage. Such systems are simply modeled as two‐mass mechanical systems.The H∞ control theory is applied herein to design a speed controller for the two‐mass system. This controller determines closed‐loop characteristics, including suppression of torsional vibration, rejection of torque disturbance and robust stability. Moreover, two types of two‐degrees‐of‐freedom control systems, which includes the H∞ controller, are proposed to improve command response. One is based on the TDOF PI control, in which the PI controller included in the H∞ controller is rearranged for the TDOF system. Another is based on the model matching feedforward control, in which the prefilter and the feedforward compensator are added to the H∞ controller. The proposed control system is applied to two types of resonant mechanical systems having different inertia ratio. Several examinations demonstrate that the proposed speed control system is useful for a resonant mechanical system.