Interval observer‐based fault tolerant control strategy with fault estimation and compensation

Abstract

AbstractIn this paper, a new strategy of fault tolerant control (FTC) is proposed for linear system with unknown inputs and actuator faults. First, a reduced‐order observer which can estimate asymptotically the system states is designed. Secondly, an interval observer which is robust to the unknown inputs but sensitive to the actuator faults in a sense of interval estimations of the states is developed for the output variables. So the interval observer is then used as actuator detector. Third, another interval observer which is different from the first one in that it is robust to not only the unknown inputs but also the actuator faults is constructed. Moreover, based on the interval observer, an asymptotical unknown input reconstruction method is proposed. Third, an observer‐based state feedback controller with a fault compensation controller is designed based on H∞ index performance. In our control strategy, the fault detector and robust H∞ state feedback controller are always in active, while the fault estimator and the fault compensation controller is activated only when the fault detector issues an alarm. Finally, a simulation example is given to illustrate the effectiveness of this new control strategy.