Derivative-Free Output Feedback Adaptive Control

This paper presents an output feedback adaptive control architecture for continuoustime uncertain dynamical systems based on state observer and derivative-free delayed weight update law. The assumption of constant unknown ideal weights is generalized to the existence of time-varying weights without assuming the existence of their derivatives in a time interval. As a result, this approach is particularly well suited for adaptation in the presence of sudden change in uncertain system dynamics, such as might be due to reconfiguration, deployment of a payload, docking, structural damage, or there is a difficult to model disturbance. Using a Lyapunov-Krasovskii functional, it is proven that the error dynamics are uniformly ultimately bounded, without the need for modification terms in the adaptive law. The complexity of the proposed approach is less than many other output feedback adaptive control architectures available in the literature and it can be used to augment an existing state observer based linear controller.