A Switching Controller Design Framework for Active Incipient Fault Diagnosis

Active fault diagnosis provides an efficient means for incipient fault detection by injecting auxiliary signal or modifying controller, which, however, usually infringes on system performance. In this paper, an amicable active fault diagnosis method based on controller modification is developed for incipient fault diagnosis of closed-loop control systems. As any stabilizing controller can be equivalently realized in the observer based form, a switching controller based on a bank of observers is firstly constructed. Then, by making a good tradeoff between the sensitivity of a specific actuator fault and the robustness of other faults and disturbances with the help of an iterative algorithm, the observers in the controller are obtained with high sensitivity to fault, wherein the difference of the outputs are also utilized to enhance incipient fault diagnosis ability. Further, a switching mechanism of the controller is developed, based on which actively switching the observers in the controller can not only detect and isolate the incipient fault timely but also guarantee the system stability. An heating, ventilation and air conditioning (HVAC) system example is finally adopted to demonstrate the effectiveness and superiority of the proposed method.