Sliding-mode control based on internal model principle

This paper proposes a sliding-mode control (SMC) scheme based on the internal model principle (IMP) for robust reference tracking and disturbance rejection. The conventional linear IMF-based controller is known for its capability of perfect tracking and disturbance rejection with an internal model of exogenous signals, while the traditional SMC controller is robust to system perturbations and exogenous signals with unknown dynamics. The proposed SMC design combines the best features of these two fundamentally different but effective methods. Furthermore, with the help of the SMC, an initial state of the internal model is determined independently of system perturbations in order that transient performance is greatly improved compared with that of the linear IMF-based controller. In addition, by properly assigning the initial state of the internal model, a sliding-control law is derived to ensure the existence of a sliding mode during an entire response. This global sliding motion yields excellent robustness of the entire system from the very beginning of a system response. Experimental results show the feasibility of the proposed scheme.