Robust sliding-mode tip position control for flexible arms

In this paper, we consider the robust tip position control problem for flexible arms by using the sliding-mode method. The higher order modes of the flexible arm are treated as disturbances, and are compensated by introducing a disturbance observer. The remaining disturbance and the model uncertainties are considered as the system uncertainty. The robustness of the sliding-mode control is effectively employed to cope with the system uncertainty, where the upper and lower bounds of the uncertainty are adaptively updated. The stability of the closed-loop system is analyzed by using the fact that a part of the control input is the approximate estimate of the uncertainty. Experimental results show that the robustness and superiority of the proposed method, where only the strain moment at the root and motor angular position of the arm are measured.