Robust fault detection and isolation technique for single-input/single-output closed-loop control systems that exhibit actuator and sensor faults

An integrated quantitative feedback design and frequency-based fault detection and isolation (FDI) approach is presented for single-input/single-output systems. A novel design methodology, based on shaping the system frequency response, is proposed to generate an appropriate residual signal that is sensitive to actuator and sensor faults in the presence of model uncertainty and exogenous unknown (unmeasured) disturbances. The key features of this technique are: (1) the uncertain phase information is fully addressed by the design equations, resulting in a minimally conservative over-design and (2) a graphical environment is provided for the design of fault detection (FD) filter, which is intuitively appealing from an engineering perspective. The FD filter can easily be obtained by manually shaping the frequency response into the complex plane. The question of interaction between actuator and sensor fault residuals is also considered. It is discussed how the actuator and sensor faults are distinguished from each other by appropriately defining FDI threshold values. The efficiency of the proposed method is demonstrated on a single machine infinite bus power system wherein a stabilised coordinate power system incorporating a robust FDI capability is achieved.