A globally stable SM-PD-INP-D tracking control of robot manipulators

This paper deals with the tracking control of robot manipulators. Synthesizing the strong robustness of the sliding mode control and the good flexibility of PD-I
^NP-D
control, Proposed is a simple class of robot tracking controller consisting of a linear sliding mode term plus a linear PD feedback plus an integral action driven by an NP-D controller. By using Lyapunov's direct method and LaSalle's invariance principle, the simple explicit conditions on the controller gains to ensure global asymptotic stability are provided. The theoretical analysis and simulation results show that: i) the SM-PD-I
^NP-D
controller has the faster convergence, better flexibility and stronger robustness with respect to initial errors; ii) the proposed control laws can not only achieve the asymptotically stable trajectory tracking control but also the tracking errors quickly tend to almost zero without oscillation as time increases; iii) after the sign function is replaced by saturation function in the SM-PD-I
^NP-D
control law, the high-frequency oscillation of the control input vanishes.