Robust Design of Observer-Based Fault Estimation and Fault-Tolerant Control for Linear Systems

This paper discusses the design of observer-based fault estimation (FE) and fault-tolerant control (FTC) for a linear time-invariant (LTI) system subject to uncertainties, external disturbances, actuator faults, and sensor faults. Initially, an unknown input observer for an augmented system is designed to simultaneously estimate system states, actuator faults, and sensor faults. This augmented system was created by introducing an augmented state vector composed of system states and various faults. Subsequently, the fault-tolerant controller is designed to stabilize the system outputs. To reduce the effect of disturbances on the fault estimation, and make the controller robust, the UIO and the FTC gain matrices are obtained by minimizing a multi-objective function formed from a set of performance indices defined in the frequency domain. The effectiveness of the proposed method is demonstrated through its application to a DC motor system.