Global Stabilization with Almost Disturbance Decoupling of a Class of Uncertain Nonlinear Systems

In this paper we study global stabilization of a class of nonlinear uncertain systems while decoupling the output from external disturbances to any specified degree of accuracy. The class of nonlinear systems considered could be viewed as a generalization of uniform rank multivariable linear systems which have the property that all their infinite zeros are of the same order. Although the plants considered are nonlinear, the compensator developed here is linear. Our compensator which achieves global exponential stability and almost disturbance decoupling of the output requires only output feedback rather than full state feedback. Model uncertainty is dealt with either by restricting the uncertain elements to particular subspaces satisfying the so called "matching conditions" or/and by treating a family of plants P for which a single controller simultaneously globally exponentially stabilizes all the plants in P while achieving almost disturbance decoupling of the output.