Robust fault tolerant control scheme for descriptor systems using fixed control allocation

This paper investigates the design problem of fixed control allocation (CA) scheme for the multi-input multi-output (MIMO) linear time invariant (LTI) uncertain descriptor system (DS) to achieve fault tolerant control (FTC) where the control strategy is designed based on integral sliding mode. The CA technique used here has the capability to redistribute the control actions to the remaining redundant actuators in the face of faults/ failures without reconfiguring the structure of the controller. The control allocation scheme uses the information of actuator effectiveness matrix to redistribute the control actions there-fore it doesn't require any information about the actuator faults/ failures. The proposed scheme has the capability to handle actuator faults as well as total failure of certain actuators, provided that there is enough redundancy in the system. Unlike traditional integral sliding mode control (ISMC), the discontinuous control part of ISMC is replaced by a multivariable super-twisting sliding mode control. Under this modification, the control signal become continuous while retaining the nominal system's performance in the face of actuator faults/ failures and external disturbances. The integral switching surface is designed in the context of descriptor system in such a way that this strategy will guarantee the robustness almost from the initial time of the system response. The rigorous stability analysis is performed to find the condition for stability to ensure robust closed loop stability of the uncertain descriptor systems in the presence of actuator faults and failures. Finally, in the simulation section, various situations related to fault/ failure cases are considered for a numerical example of descriptor system, to verify the effectiveness of the proposed design. (c) 2020 European Control Association. Published by Elsevier Ltd. All rights reserved.