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

A solution to the problem of global exponential tracking of mechanical systems without velocity measurements is given in the paper. The proposed controller is obtained combining a recently reported exponentially stable immersion and invariance observer and a suitably designed 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 and, in particular, no assumptions are made on the presence-and exact knowledge-of friction forces.