Multi-input second-order sliding-mode hybrid control of constrained manipulators

This paper deals with the hybrid position/force control of constrained manipulators subjected to uncertainties. A solution is proposed that is based on sliding-mode control theory, which proved to be highly effective in counteracting uncertainties for some classes of nonlinear systems. Specific problems involved in this technique are chattering elimination and the algebraic coupling between constraint forces and possibly discontinuous control signals. Both the problems are addressed in this paper by exploiting the robustness properties of a second-order sliding-mode control algorithm. This algorithm, recently proposed by the authors for solving the single-input hybrid control problem, is generalized in this paper to deal with the class of multi-input differential algebraic systems describing the behaviour of constrained mechanical systems.