Robust Adaptive Control Based on Reduced-Order Unknown Input Observer for Fully Actuated Systems With Uncertainties

In this paper, a robust adaptive control scheme based on the unknown input observer is proposed for fully actuated systems with uncertainties. First, a nonlinear reduced-order unknown input observer with an integral term is introduced to decouple the uncertainties in the system and suppresses the output noises via the action of integral term. Then the linear matrix inequality for solving the observer gains is given by using the linear parameter varying method to treat the nonlinearity. Second, a robust adaptive controller based on the proposed observer, with the adaptive law to estimate the bound of uncertainties, is designed to make the states uniformly ultimately bounded. Due to the design of robust part, the ultimate bounds of states of the closed-loop system can be adjusted via the designed parameters. A simulation of the electromechanical system is given to demonstrate the effectiveness of the proposed method.