Disturbance observer-based nonlinear feedback control for position tracking of electro-hydraulic systems in a finite time

In this paper, a disturbance observer-based backstepping tracking control is designed for an electro-hydraulic actuator (EHA) system to estimate and track reference signals in a finite time. It is assumed that the system is uncertain with unknown upper bounds. Different from the existing ones, the proposed observer can deal with strong uncertainties in which the estimation error converges to an arbitrarily small neighborhood of zero in a finite time. Then, the disturbance observer-based backstepping tracking control is provided to compensate the uncertainties and estimation errors and to guarantee the finite-time tracking of the piston position toward the desired time-varying reference signal. The key idea is to employ a monotonically increasing function associated with the control objective to improve the control performance, where the finite-time boundedness criterion is guaranteed using Lyapunov stability analysis. Finally, the efficacy of the proposed robust scheme for the EHA system with unknown measurement noise is illustrated in numerical simulations as compared to a leading observer-based control strategy in the literature. It is shown that the proposed approach results in more accuracy and faster convergence than that in the literature, making it a qualified alternative approach with noteworthy potential.