A mixed fuzzy controller for MIMO systems

The multi-input/multi-output (MIMO) systems usually possess characteristics of nonlinear dynamics coupling. Therefore, the difficulty of MIMO systems control is how to overcome the coupling effects among each degree of freedo m. The model-based decoupling approach is not practical for real-time contr ol due to computation burden and dynamic uncertainty of MIMO systems. Hence , a mixed fuzzy controller (MFC) is proposed here to solve this problem and to improve control performance. Firstly, a traditional fuzzy controller (T FC) is designed based on single-input/single-output (SISO) systems point of view for controlling each degree of freedom of a MIMO system. Secondly, ac cording to the characteristics of the system's dynamics coupling, an approp riate coupling fuzzy controller is incorporated into a TFC to compensate fo r coupling effects among each degree of freedom. This control strategy can not only simplify the implementation problem of fuzzy control, but can also improve control performance. In order to evaluate the stability and robust ness of this mixed fuzzy controller, the state-space approach of fuzzy cont rol systems stability analysis is employed for further expansion. In additi on, a dynamic absorber with two-level mass-spring damper structure was desi gned and constructed to verify the stability and robustness of an MFC by nu merical simulation, and to investigate the control performance by comparing the experimental results of the MFC with that of a TFC for this MIMO syste m. (C) 2001 Elsevier Science B.V. All rights reserved.