A Predictive Command Governor for Nonlinear Systems under Constraints

Abstract

A command governor (CG) is described for solving set-point track­ing problems for nonlinear systems when pointwise-in-time input and/or state related inequality constraints have to be fulfilled. A CG is a nonlinear device which is added to a primal compensated system. The CG action, based on the current state, set-point and prescribed constraints, is finalized to select, at any time, a command sequence under which the constraints are possibly fulfilled with acceptable tracking performance. It is shown how to use off-line an iterative algorithm so as to restrict to a fixed finite integer the infinite num­ber of time-instants over which the prescribed constraints must be checked in order to test admissibility of command sequences. An analysis based on a Lya­punov function argument shows that, if the reference becomes constant, the CG output converges to the closest admissible approximation to the set-point. An example is presented to illustrate the method.