Robust adaptive dynamic surface control of electro-hydraulic proportional system

A robust adaptive dynamic surface control method was presented for a single-rod electro-hydraulic actuator with unknown dead-zone. By introducing a novel description of general nonlinear dead-zone, the proposed scheme was extended to overcome the effect of dead-zone. The uncertain dead-zone model was transformed into a linear system with a time-varying gain and an uncertainty term. The time-varying gain of dead-zone model was treated by using a robust control method, and the unknown bound of dead-zone model uncertainty was estimated online. Furthermore, the backstepping design was simplified by utilizing dynamic surface control, and by combining a simple robust method, the electro-hydraulic proportional system's controller and adaptation laws for uncertain parameters were presented. The proposed control scheme is simple and insensitive to parameter and model uncertainties. Experimental results show that the nonlinear control algorithm has a good performance for the tracking task in the presence of unknown dead-zone of proportional directional valve.