A Design Method of Compensator to Minimize Model Error

Abstract

The robust control design method has been studied in recent decades. A control system works well under the modeling errors and disturbances if controller design is based on the robust control method. However, it is well known that in control systems, generally, there exists a trade-off between control performance and robustness. To overcome the trade-off problem, this paper proposes an internal model type compensator structure that minimizes the modeling gap between the nominal model and actual plant dynamics. By using the proposed compensator, the dynamics of the compensated system closes to that of the nominal model. Then, a design method of the compensator parameters is also proposed for minimizing a set of plant dynamics. The proposed design method is reduced to the standard µ design control problem. If we use the proposed compensator for control systems instead of the plant itself, the output performance might be better despite plant uncertainty. Given that the proposed compensator can be used for the control of not only linear but also nonlinear plants, we can easily achieve robust control of nonlinear systems. The effectiveness of the proposed method is shown by numerical examples.