A robust feedback linearization control for constrained mechanical systems

A robust control approach is developed for the tracking problem of uncertain constrained mechanical systems. The dynamic model is modified to contain two sets of state variables, where one describes the constrained motion and the other describes the unconstrained motion. The controller consists of two control elements. The first is based on the input-output decoupling approach in nonlinear control theory; it is used to achieve exponential global tracking of both position and constraint forces on the constrained manifold of the nominal system. The second is a robust loop that ensures asymptotic stability of the uncertain system under parameters as well as environmental uncertainties. This control element consists of a class of continuous state feedback control. The only required information about the uncertainties is their Euclidean norm bound function. System stability is investigated using Lyapunov stability theory and it is shown that global stability holds for both system state vectors.