Enhanced Variable-Gain Sliding Mode Control for Robot Manipulators

Robotic manipulators must operate in complex scenarios, which make the overall operational space quite large, and the system dynamics within that space subject to significant variations and uncertainties. Sliding mode control (SMC) strategies have been successfully applied in this context, yet, if a worst-case approach is taken in the face of large operational variations, the resulting performance may happen to be suboptimal. Moreover, attention must be paid, in an industrial setting, to vibrations that may be induced on the robot joints by the presence of chattering induced by the SMC algorithm. This work tests, in a challenging application context, a recently-proposed r-order SMC strategy that encompasses both continuous and discrete adaptation strategies to adjust its parameters, giving rise to an overall switched approach. In particular, two realistic case studies of robot motion control are discussed, proving its effectiveness in enhancing both performance and robustness in complex operational scenarios.