Development of a hardware-in-the-loop demonstrator for the validation of fault-tolerant control methods for a hybrid UAV

Many aircraft are inherently over-actuated with regard to their input variables. This can be particularly advantageous in the context of unmanned aerial vehicles (UAV), where actuator functions can fail in critical situations. In such cases, the redundant actuators can be used to further fulfil the control strategies used and thus increase the operational safety. Within such an active fault-tolerant control system, a fault detection and isolation (FDI) module is required. To evaluate such safety–critical systems, hardware-in-the-loop simulations (HIL) are a necessary step prior to real flight tests. These simulations can verify the correct implementation of the flight controller on the target hardware as well as the real-time capability of the algorithms used. Particularly in the context of active fault-tolerant control, investigations concerning the robustness of the used FDI module with regard to real, noisy sensor signals, which can be generated by a HIL demonstrator, are of utter importance. This paper presents the development of a HIL demonstrator for the validation of fault-tolerant control methods for a hybrid UAV. This includes a detailed description of the demonstrator’s design, control and interfacing between the integrated subsystems. As an application example, a hybrid UAV model will be shortly presented, which, in addition to the primary aerodynamic control surfaces, can also use four lift rotors to control the aircraft during cruise and is therefore inherently over-actuated. Finally, a closed-loop real-time simulation of the UAV model on the HIL demonstrator is presented on the basis of the exemplary simulation of an actuator failure and subsequent reconfiguration by the fault-tolerant flight control law.