Switching Motion Control of Aircraft Skin Inspection Robot Using Back-stepping Scheme and Nussbaum Disturbance Observer

In this paper, a backstepping control using switching strategy is proposed for the motion control of the aircraft skin inspection robot with double frame in the presence of external disturbances. The inspection robot equipped with a CCD camera and an ultrasonic sensor can alternately adsorb and move on the aircraft surface. The influence of the external disturbances is obvious in the switching motion. The disturbances are efficiently estimated using a Nussbaum disturbance observer (NDO), and the disturbance observer errors are uniformly ultimately bounded. Then, the backstepping control method is used to design the motion controller. The stability of the closed-loop robot system is proved by Lyapunov analysis through the average dwell time method. The tracking errors and the disturbance observer errors are semi-globally uniformly bounded using the proposed control scheme with NDO,and NDO is compared with Super-twisting disturbance observer. Finally, simulation results illustrate that the proposed control scheme with NDO can achieve satisfactory tracking performance under the external disturbance.