The research of heterogeneous networked control systems based on modify Smith predictor and fuzzy adaptive control

Abstract

Fuzzy control is simple in design, and has strong robustness. It can obtain ideal control effect in the case of not firmly knowing the system model, and can be applied to many nonlinear systems. In order to effectively restrain the impact of network delays for networked control systems (NCS), a novel approach is proposed that modified Smith predictor combined with fuzzy adaptive PID control for the heterogeneous networked control systems (HNCS). The HNCS adopt the cascade control system structure, use P control in the inner loop and fuzzy adaptive control in the outer loop. The data communications of loops adopt heterogeneous wired networks. Based on modified Smith predictor, achieve complete compensations for delays of networks and controlled plants. Because modified Smith predictor does not include network delay models, it is no need for measuring, identifying or estimating network delays on line. Therefore it is applicable to occasions that network delays are larger than one, even tens of sampling periods. Based on CSMA/AMP (CAN bus) in the inner loop and CSMA/CD (Ethernet) in the outer loop, and there are data packets loss, the results of simulation show validity of the control scheme, and can improve dynamic performance, enhance robustness, self-adaptability and anti-jamming abilities.