Integrated control and fault diagnosis design: a polynomial approach

A design method is presented which integrates control action and fault detection and isolation. Control systems operating under potentially faulty conditions are considered, and it is demonstrated how to design a single unit which handle both the required control action, as well as identifying faults occurring in actuators and sensors. This unit is able to: 1) follow references and reject disturbances robustly; 2) control the system such that undetected failures do not have disastrous effects; 3) reduce the number of false alarms; and 4) identify which faults have occurred. The method uses a type of separation principle which makes the design process very transparent, and a polynomial H_∞ formulation which makes weight selection straightforward. As a consequence of the separation between control and diagnosis, we prove that the controller needs not be detuned in order to get good diagnosis results, in contrast to common beliefs