A globally exponentially stable tracking controller for mechanical systems using position feedback

International audienceA solution to the problem of global exponential tracking of mechanical systems without velocity measurements is given in the technical note. The proposed controller is obtained combining a redesign of the recently reported exponentially stable immersion and invariance velocity observer and a new state-feedback passivity-based controller, which assigns to the closed-loop a port-Hamiltonian structure with a desired energy function. The result is applicable to a large class of mechanical systems including those with unbounded inertia matrix and possible presence of friction forces. Unlike previous results that rely on the presence-exact knowledge and pervasiveness-of these forces, our design treats them as disturbances, which are suitably compensated