The velocity control of an electro-hydraulic displacement-controlled system using adaptive fuzzy controller with self-tuning fuzzy sliding mode compensation

Hydraulic servo control systems have been used widely in industry. Within the realm of hydraulic control systems, conventional hydraulic valve-controlled systems have higher response and lower energy efficiency, where as hydraulic displacement-controlled servo systems have higher energy efficiency. This paper aims to investigate the velocity control performance of an electro-hydraulic displacement-controlled system (EHDCS), where the controlled hydraulic cylinder is altered by a variable displacement axial piston pump to achieve velocity control. For that, a novel adaptive fuzzy controller with self-tuning fuzzy sliding-mode compensation (AFC-STFSMC) is proposed for velocity control in EHDCS. The AFC-STFSMC approach combining adaptive fuzzy control and the self-tuning fuzzy sliding-mode control scheme, has the advantages of the capability of automatically adjusting the fuzzy rules and of reducing the fuzzy rules. The proposed AFC-STFSMC scheme can design the sliding-mode controller with no requirement on the system dynamic model, and it can be free of chattering, thereby providing stable tracking control performance and robustness against uncertainties. Moreover, the stability of the proposed scheme via the Lyapunov method is proven. Therefore, the velocity control of EHDCS controlled by AFC-STFSMC is implemented and verified experimentally in different velocity targets and loading conditions. The experimental results show that the proposed AFC-STFSMC method can achieve good velocity control performance and robustness in EHDCS with regard to parameter variations and external disturbance. © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society.