Proportional integral adaptive observer for parameter and disturbance estimations

This paper proposes an adaptive observer structure which can be employed in simultaneous estimation of system parameters and disturbances. The starting point is the proportional integral (PI) observer which has been shown to be effective not only in loop transfer recovery (LTR) but also in estimating and accommodating disturbances. We show that PI structure can further be generalized to PI adaptive observer (PIAO) to expand the applicability of integral action to systems with unknown parameters. A systematic design procedure is developed for estimating the states, the parameters, and the unknown inputs of a dynamic system in open-loop and closed-loop settings. Simulation results support the theoretical developments.