Robot control via robust estimated state feedback

The problem of controlling a robot manipulator without needing the precise knowledge of the robot model physical parameters and by using only angular position feedback is considered. Sliding observers are used to estimate the link velocities. This observer and a nonlinear control law are modified, according to the Leitmann procedure, in order to face uncertainties on the robot model parameters and to yield locally exponentially closed-loop systems. The use of discontinuous functions seems to be necessary to reach exponential stability for this particular problem formulation. The same type of results would be difficult, if not impossible, to obtain using only nonlinear smooth functions because the switching terms generate a special kind of dynamics into the sliding patch, which is created only by the sign functions