Output feedback variable structure-like control of nonlinear mechanical systems

In this paper, we develop a new output feedback, variable structure-like (discontinuous) tracking controller for a class of uncertain, nonlinear, multi-input multi-output, mechanical systems whose dynamics are first-order differentiable. A novel filter design and Lyapunov-type stability analysis are used to prove semi-global asymptotic tracking. As a by-product of the proposed framework, we also present the design of a new variable structure-like velocity observer that ensures global asymptotic velocity observation.