Globally stable pressure-observer-based servo control of an electro-pneumatic clutch actuator

To achieve rapid disengagement and smooth engagement of clutch in automated manual transmission systems, servo control of an electro-pneumatic clutch actuator controlled by solenoid on–off valves is considered. Nevertheless, realization of high-accuracy servo control usually depends on model-based non-linear control technologies requiring full-state knowledge of the system. Pressure sensors are not used in automated manual transmission systems owing to cost considerations. Thus, the pressure states in the chambers are unknown. To address this issue, non-linear pressure observers taking the place of pressure sensors were proposed in this paper. It is stable in the sense of the Lyapunov theory and independent of the load. Furthermore, the pressure observer’s polytropic exponent was analysed and then determined experimentally. Finally, a compound sliding-mode controller with pressure observers was presented. Extensive experiments demonstrated the feasibility and the effectiveness of the proposed pressure-observer-based controller.