A derivative-free output feedback adaptive control architecture for minimum phase dynamical systems with unmatched uncertainties

In this paper, we extend the model reference adaptive control architecture for minimum phase dynamical systems developed in [1] by constructing derivative-free adaptive update laws predicated on current information of the system states and system errors as well as delayed information of the update gains. The advantage of the proposed derivative-free adaptive control law architecture over adaptive update laws predicated on differentiation requiring an intermediate discretization step for implementation is that the former architecture can account for abrupt changes in system dynamics due to system faults or major variation in system parameters. In addition, the derivative-free architecture subverts high-gain feedback which can excite unmodeled system dynamics. Two illustrative numerical examples are given to demonstrate the efficacy of the proposed approach.