A virtual actuator and sensor approach for fault tolerant control of LPV systems

• The virtual actuator/sensor technique is extended to LPV systems.
• Virtual actuators and virtual sensors are merged to cope with faults affecting actuators and sensors at the same time.
• The principle of separation allows to design separately the controller, the observer and the virtual sensor and actuator.
• Fault estimation and fault compensation are combined in order to achieve FTC within an LPV framework.

In this paper, a fault tolerant control (FTC) strategy using virtual actuators and sensors for linear parameter varying (LPV) systems is proposed. The main idea of this FTC method, initially developed for LTI systems, is to reconfigure the control loop such that the nominal controller could still be used without need of retuning it. The plant with the faulty actuator/sensor is modified adding the virtual actuator/sensor block that masks the actuator/sensor fault. The suggested technique is an active FTC strategy that reconfigures the virtual actuator/sensor on-line taking into account faults and operating point changes. The stability of the reconfigured control loop is guaranteed if the faulty plant is stabilizable/detectable. The LPV virtual actuator/sensor is designed using polytopic LPV techniques and linear matrix inequalities (LMIs). A two-tank system simulator is used to assess the performance of the proposed method. In particular, it is shown that the application of the proposed technique results in an improvement, in terms of performance, with respect to the LTI counterpart.