Robustness analysis of commonly used adaptive control structures

Three commonly used adaptive control structures, the model reference control structure, the pole placement control structure, and the linear quadratic control structure, are considered. The robustness properties of these control structures with respect to a large class of dynamical plant perturbations is analyzed. The analysis gives an upper bound on the size of the uncertainty that can be tolerated by a particular control structure and provides a benchmark against which to compare the robustness margins of adaptive schemes obtained from these control structures