Improved sliding-mode control for servo-solenoid valve with novel switching surface under acceleration and jerk constraints

The nonlinear sliding-mode (SLM) controller based on the maximum jerk and time-optimal step response has been developed for the control of servo-solenoid valves, which exhibits its performance advantages when compared to traditional PID controller. However, the experiments shows the responses of the SLM control under only jerk constraint will largely vary with different damping and loads, leading to the large overshoot and breakdown under some working conditions (e.g., large viscous damping coefficient). Thus, an improved SLM controller is developed in this paper to deal with the existing drawbacks, where a novel nonlinear SLM surface is proposed by taking into account both spool's acceleration and jerk limitation. Firstly, the nominal model of servo-solenoid valve is built by linearizing the dynamics on the null position, and the system identification is carried out to achieve the model parameters and their variation ranges. Subsequently, the valve constraints under the power limitation are analyzed through the frequency response of the identified model, which comes out the maximum available velocity, acceleration and jerk. Finally, the improved SLM control algorithm is proposed, where the novel SLM surface considers the maximum plus jerk, the maximum minus jerk and the maximum acceleration. Experimental studies are conducted and the results show that the improved SLM controller under both acceleration and jerk constraints can achieve the continuous and stable sliding mode state, realize the time-optimal step response of the valve, and exhibit strong disturbance rejection abilities.