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UBC Theses and Dissertations

Globally robust tracking control of a quadrotor aerial vehicle for multi-behavior applicants Emran, Bara Jamal


This research contributes to the development of a practical controller for a quadrotor unmanned aerial vehicle (UAV) by addressing three main challenges: underactuation, model uncertainty, and actuator failure. Depending on flight conditions and the interaction with the environment, quadrotors require to operate in different flight regimes including hovering, aggressive maneuver, near-ground maneuver, and fault-tolerant flight. By realizing sensor readings and system requirements, the control system seamlessly switches between different designed schemes in real time to engage the most suitable one in the feedback loop. To enable the full capacity of the quadrotor and perform agile maneuvers, a global attitude tracking control system is proposed. The controller is developed directly on the special Euclidean group with a region of attraction covering the entire configuration space, i.e., globally valid. The control law is based on the dynamic surface control (DSC) method to avoid “explosion of terms”, i.e., a common problem of previously reported solutions. Asymptotical convergence of tracking error is guaranteed in presence of system uncertainties and extreme disturbances without a priori knowledge of their bounds. A position control system is proposed that outclasses the performance of existing solutions under extreme disturbances. It consists of a second order sliding mode control (SMC) system to guarantee stability of the position dynamics by generating a proper command for the attitude controller, and a switching mechanism based on multiple Lyapunov functions (MLFs) to improve tracking performance despite extreme disturbances. A fault-tolerant tracking controller featuring fault detection and robust control capable of coping with the total failure of one or two adjacent rotors is proposed. A wind-speed sensor is used to detect actuator failure regardless of its cause. A significant novelty of this work is that a single generic control feedback strategy is adopted for both the normal flight operation and when a fault occurs. Hence, unlike previous solutions, there is no risk of instability while switching between control laws. Finally, the proposed attitude and position control methods have been verified on a testbed developed in this research, and the efficacy of the controller in coping with fault scenarios was proven in simulation.

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