Adaptive fuzzy controller with self-tuning fuzzy sliding-mode compensation for position control of an electro-hydraulic displacement-controlled system

The electro-hydraulic displacement-controlled system (EHDCS) performs specific non-linear and time-varying characteristics such that an exact model-based controller is complicated to be realized and the servo control is difficult to be implemented. In this study, the design method and experimental implementation of an adaptive fuzzy controller with self-tuning fuzzy slidingmode compensation (AFC-STFSMC) are proposed which has on-line tuning ability for dealing with the system time-varying and non-linear uncertain behaviours for adjusting the control rule parameters. This control strategy employs the adaptive fuzzy approximation technique to design the equivalent controller of the conventional sliding-mode control (SMC). Furthermore, the fuzzy sliding-mode control scheme with self-tuning ability is introduced to compensate the approximation error of the equivalent controller for improving the control performance. The proposed AFC-STFSMC scheme can design the sliding-mode controller with no requirement of the system dynamic model, be free from chattering, be stable tracking control performance, and be robust to uncertainties. Moreover, the stability proof of the proposed scheme using Lyapunov method is presented. The experimental results of the position control and the path control in EHDCS with different strokes and external disturbance forces show that the proposed AFC-STFSMC approach can achieve excellent control performance and robustness with regard to parameter variations and external disturbance.