Simplifying robust energy shaping controllers for mechanical systems via coordinate changes
Abstract
The problem of robustness improvement, vis 'a vis external disturbances, of energy shaping controllers for mechanical systems was addressed by the authors in a previous paper. It was shown that-if the inertia matrix is constant-- constant disturbances (both, matched and unmatched) can be rejected simply adding a suitable integral action. For systems with nonconstant inertia matrix and non-constant disturbances the controller, that adds nonlinear damping and gyroscopic forces terms, is quite complicated. The purpose of this paper is to show that, including a partial change of coordinates, the controller can be significantly simplified, achieving the same robustness property of input--to-state stability with respect to matched and unmatched disturbances of the previous controller.