Abstract

The research on autonomous flying robots has intensified considerably due to recent growth of civilian and military interests in Unmanned Aerial Vehicles (UAV). Miniature UAVs with the ability to vertically take off and land such as quadrotor aerial vehicles exhibit further advantages and features in maneuverability that have recently gained interest among the research community. Reliability of control systems require robustness and fault tolerance in presence of anomalies and unexpected failures in actuators, sensors or subsystems. Autonomy of dynamical systems that are vulnerable to the above failures has been an important topic of research during the past several years. Particularly, in small aerial vehicles due to hardware redundancy limitations design of a reliable control system plays an important role in ensuring acceptable and efficient performance. In view of the above, an autonomous recovery from actuators faults in under-actuated quadrotor aerial vehicles constitutes the main focus of the research investigated in this dissertation. A self-recovery mechanism, which extends the capabilities of the quadrotor system to operate under the presence of actuator faults is developed. The solution proposed takes into account the management of the control authority in the system by taking advantage of the post-fault model of an actuator. The first step in accomplishing this task is achieved by developing a controller under healthy condition that guarantees the stability of the quadrotor system in response to the commanded trajectories. This controller is then extended to incorporate the effects of a certain type of actuators fault by estimating the post-fault model of the system and then by properly commanding the faulty actuators accordingly. The performance of the proposed fault recovery scheme in presence of noise in the input and output channels and under different fault severities is evaluated through numerical simulations. It is shown that a significant reduction in the average tracking steady state errors are obtained through the application of the proposed recovery mechanism. The proposed scheme is applicable to rotorcraft systems even in presence of multiple faults in actuators.