Dual extended state observer–based prescribed performance control of output-constrained hydraulic-driven barrel pitching servo system

This research focuses on the position-tracking control of the output-constrained hydraulic-driven barrel pitching servo system with partial unknown states, strong nonlinearities, and huge model uncertainties. Based on the established nonlinear dynamic model of the hydraulic-driven barrel pitching servo system, a dual extended state observer–based prescribed performance dynamic surface control approach is proposed. The dual extended state observer is developed to simultaneously estimate the angular velocity, mismatched lumped uncertainty in the velocity dynamic channel, and matched lumped uncertainty in the pressure dynamic channel. A novel barrier Lyapunov function–inspired error transformation function contributes to the integration of the prescribed performance control into the backstepping controller and circumvents the complex logarithmic calculation caused by the traditional error transformation function. The prescribed performance control scheme restrains the tracking error within the constraint boundaries in the entire moving process. Dual uncertainty compensation is added to the prescribed performance control scheme to further improve the control performance of the hydraulic-driven barrel pitching servo system. The dynamic surface control technique is applied in the last step of the controller design to prevent the ‘differential explosion’ in the traditional backstepping controller. The theoretical stability and convergence of the proposed controller are proved in the sense of Lyapunov, and the practical effectiveness of the dual extended state observer–based prescribed performance dynamic surface control is verified via extensive comparative experiments.