Robust nonlinear control: beyond backstepping and nonlinear forwarding

This paper considers the problem of robust global stabilization of a large class of nonlinear systems. We introduce a recursive design approach based on a powerful technique of Wei (1990) for quadratic stabilization of linear systems. This approach allows us to globally stabilize an uncertain nonlinear system which is augmented from a robustly globally stabilizable system via either down-augmentation or up-augmentation. These augmentations are similar to the so-called backstepping and integrator forwarding. However, the advantage of the proposed augmentation approach is that robust stabilizability is achieved for nonlinear systems involving large uncertain parameters