Adaptive fuzzy Internal Model Control design with bias term compensator

Internal Model Control (IMC) is a powerful method for control system design. However, the classic EMC scheme will not be sufficient in the case of modelling mismatches that might generally occur in the design of nonlinear control systems. Fuzzy modelling is a powerful tool in representing nonlinear systems. Thus, a new fuzzy model based EMC structure is proposed to provide an effective and robust control performance. In this structure, a fuzzy proportional controller is introduced into the feedback loop of the IMC structure to stabilize system and obtain an offset free response while the inverse fuzzy model controller is used for set point tracking. The timing formula of the fuzzy proportional controller in the feedback loop is obtained by instantaneous linearization of the fuzzy model at a certain operating point via simple calculations. In order to increase the robustness and disturbance rejection performance of the modified IMC scheme, an adaptation mechanism is introduced on the fuzzy model. A simulation study has been performed on the nonlinear mass-spring-damper system to show the effectiveness of the proposed scheme.