Fault-Tolerant Control of a Hexacopter UAV based on Self-Scheduled Control Allocation

In this paper, a control allocation (CA) algorithm for the fault-tolerant control (FTC) system of a multirotor unmanned aerial vehicle (UAV) is presented. The proposed CA design is based on gain-scheduling control in the framework of structured H
_∞
synthesis. Given the appropriate fault detection and diagnosis (FDD) system, allocation laws are parameterized as polynomial functions of actuators effectiveness levels. The polynomial coefficients are then tuned with MATLAB-based function systune to meet the robustness and fault tolerance requirements. Unlike conventional CA schemes in the literature, the proposed method has the advantage of not solving any online optimization problem. Moreover, actuator constraints after a failure are also taken into account during the tuning process using a multi-model approach. In comparison with other FTC systems based on reconfigurable controller, this smooth self-scheduled CA has a very simple structure and allows one to avoid undesirable transient phenomena during the controller reconfiguration process. High fidelity simulations and experimental results performed on a hexacopter show the effectiveness and robustness of the proposed FTC in accommodating different levels of actuator degradation.