Parametric design of robust fault isolation observers for linear non-square systems

In this article, two different approaches to design fault isolation observers (FIOs) for linear systems are developed. They extend the existing results to arbitrary fault detectability indices and allow to isolate simultaneously occurring actuator and sensor faults by employing only a single, specifically parameterized observer. While the presented parametric eigenstructure assignment approach gives a comprehensive interpretation of the degrees of freedom arising in non-square systems with additional sensors, the time-domain solution proves to be well suited for optimizing disturbance rejection. Furthermore, this paper presents an approach to optimize the robustness of FIOs with respect to disturbances in finite frequency ranges. This enables to reduce conservatism if knowledge of relevant disturbance frequencies is available.