Simultaneous control of motion and maximized stiffness for an electro-pneumatic clutch actuator based on pressure observers

To improve gear-shifting quality of the clutch in automated manual transmission systems, motion trajectory tracking control of an electro-pneumatic clutch actuator is first considered in this article. Each chamber of the clutch actuating pneumatic cylinder is controlled independently by a pair of two-way on/off solenoid valves using pulse width modulation. Thus, motion and stiffness control of the actuating pneumatic cylinder can be realized simultaneously. With stiffness-maximizing control, the actuator has the best disturbance rejection from force to motion, which facilitates the realization of high-accuracy servo motion control. Nevertheless, model-based nonlinear control technologies are sure to require full-state information of the system. For cost considerations, nonlinear pressure observers which are independent of the load and stable in the sense of Lyapunov theory were applied to acquire the pressure states of the chambers in place of pressure sensors in this article. Moreover, a dedicated sliding mode controller with nonlinear pressure observers was put forward. Extensive experiments show that the proposed technical methods can fulfill the high-accuracy motion servo control of an electro-pneumatic clutch actuator.