Global Position Tracking of Robot Manipulators via SM-NPID-like Controllers with Two Nonlinear Integral Actions

Abstract

This paper deals with the tracking control of robot manipulators with uncertain payload. Proposed is a set of novel SM-NPID-like tracking controllers consisting of a linear combination of the linear sliding mode control, proportional control mode, derivative control mode, nonlinear control mode shaped by a nonlinear function of position errors, and two nonlinear integral control modes driven by a nonlinear function of position errors and its derivative, respectively. 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 proposed controllers have the faster convergence, better flexibility and stronger robustness with respect to initial errors and uncertain payload; 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.