Design and experimental study of a dynamical adaptive backstepping–sliding mode control scheme for position tracking and regulating of a low‐cost pneumatic cylinder

A dynamical adaptive backstepping–sliding mode control scheme is designed and implemented for the first time, to track and regulate the position of a low-cost pneumatically driven single-rod, double-acting cylinder. The mass flow rate of compressed air into and out of the cylinder is regulated by a 5/3-way proportional directional control valve. The derivation of the controller, utilizing a design procedure that guarantees stability of the control system, is presented first. Next, experimental evaluation of the controller is conducted with respect to performance and robustness to parametric uncertainties. Experiments employ a sinusoidal reference trajectory with tracking frequencies of 0.05, 0.1, and 0.2 Hz; a multiple-step polynomial reference trajectory having step sizes of 0.0125, 0.025, 0.05, and 0.1 m; and three external loads of 4.4, 9, and 16 kg operating in two modes (motion assisting and resisting). From over 70 experiments involving various operating conditions, average root mean square of tracking error of 1.73 mm and steady-state error of 0.71 mm are achieved for the position tracking and regulating, respectively. As compared with the classical sliding mode control scheme alone, the new controller outperforms by more than twofold. The adaptive LuGrebased friction observer applied in this control scheme significantly assists in compensating the adverse effect of friction with the average of 55% less tracking error. Copyright © 2015 John Wiley & Sons, Ltd.