Global Robust Servomechanism Problem of Lower-Triangular Systems in the General Case1

We will show that, for the class of nonlinear lower-triangular systems, the robust servomechanism problem can be cast into a robust regulation problem for the same class of systems augmented by dynamic uncertainties. Thus, using our recent result on adaptive regulation of lower-triangular systems with both static and dynamic uncertainties, we will solve the robust servomechanism problem of the lower-triangular systems for the general case where both the uncertain parameter and the exogenous signal can be arbitrarily large.