Fault Detection and Tolerant Control for Aero2 2DOF Two-rotor Helicopter

Stability and satisfactory performance are key control requirements for any Unmanned Aerial Vehicle (UAV) application. Although conventional control systems for UAVs are designed to ensure flight stability and safe operation while achieving a desired task, a UAV may develop different types of flight faults that could lead to degradation in performance or, worse, instability. Unsatisfactory performance or instability of a UAV poses threats to lives, properties, and the flying environment. Therefore, it is crucial to design a system that can detect the occurrence of faults, identify the location at which the fault occurs, determine the severity of the fault, and subsequently use this information to accommodate the fault so that the vehicle can continue to operate satisfactorily. Even though performance analysis of faults is crucial in selecting the best strategies for fault detection and tolerance, little has been done in this regard, especially with real systems. Therefore, this paper analyzes the performance of a 2-degree-of-freedom (2DOF) bi-rotor helicopter's control system in the presence of various actuator faults. Results from different faulty conditions indicate that faults degrade the performance of a conventional control system on UAVs and introduce vibrations into the system. These findings are more apparent when a fault leads to asymmetry or imbalance of the system. However, further experiments have shown that proper fault diagnosis and accommodation methods could help maintain satisfactory performance of the system in the presence of faults.