A Design method for Two-Degree-of-Freedom Controller using the Dynamical Model of the Feedback Controller

Abstract

Two-degree-of-freedom (TDOF) system has a characteristic that the feedback property such as disturbance attenuation and the reference response property can be designed separately. But in general the order of TDOF controllers tend to be higher compared with that of one-degree-of-freedom (ODOF) controllers. For this reason, a new design method of the TDOF system using the dynamical model of the feedback controller was proposed by Y. Chida. In this method, the reference response achieved by the feedback controller can be improved by the TDOF controller whose order is same as that of the feedback controller. The TDOF controller is designed as such that minimizes a square integral performance index. But the choice of the weighting parameter of the performance index is difficult and some try-and-error is needed to get a good performance.
In this paper, we propose an alternative design method for the TDOF controller proposed by Y. Chida. We introduce a model transfer function and the controller is designed so that the output of the two-degree-of-freedom system follows the output of the model transfer function. Designers need only to choose the model transfer function which has desired time response.
Further, we apply this method to the 2-mass control system to improve the reference response. Simulation results are presented to demonstrate the control effects.