State and Disturbance Observer-Based Controller Design for Fully Actuated Systems

In this paper, an observer that combines the design ideas of disturbance observer and state observer is proposed for fully actuated systems with external disturbances. The integral term is also added to the observer to improve steady-state accuracy and design degrees of freedom. With the use of the linear parameter varying method, the Lipschitz nonlinearity is converted to the varying linearity, and the observer gains are then determined via solving a set of linear matrix inequalities. Furthermore, due to the full-actuation property, a control scheme for state stabilization using estimated states and disturbances is given. All the states are ultimately uniformly bounded if the linear part of the closed-loop system is stable. An example of an electromechanical system is presented to demonstrate the practicality of the proposed method.