Regressor-free second order sliding mode control for exponential tracking of constrained robot manipulators

Constrained motion has been the subject of intensive study in the robotics community in the last decade, because it is a fundamental problem for a variety of robotic tasks, such as walking, dynamic simulation, hand manipulation, to mention a few. In the paper, a locally stable control for simultaneous exponential convergence of force and position trajectories is proposed. Within the framework of our second order sliding mode technique proposed for free motion robots, compensation for constrained robot dynamics arises by a careful exploitation of its properties, under a convenient choice of the error coordinate system. The new model-free continuous second order sliding mode feedback loop induces locally very fast exponential tracking for any initial conditions. Simulations data on the full model of a six degrees of freedom industrial robot CRS A-465 are presented and discussed.