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The ship deck landing problem of a multi-rotor UAV is solved in this thesis. This problem is divided into tracking and landing sub-problems. In the tracking sub-problem, the multi-rotor UAV needs to follow the ship's trajectory throughout its recovery process. In the landing sub-problem, the multi-rotor UAV is to be landed in a way that is minimally affected by the ship's heave motion and other disturbances. In the tracking sub-problem, a full state backstepping control is formulated using a novel re-formulated dynamics which eliminates the use of inverse kinematics. In addition, this control formulation is based on a contraction theory-based backstepping control framework that produces a closed-form control law for implementation on large cascaded-feedback systems. In addition, a quaternion-based tracking controller is also formulated using this backstepping control framework and a re-formulated quaternion-based dynamics. In the landing sub-problem, the invariant ellipsoid method is used to derive an optimality condition for an estimate of the output response bound with respect to known bounds on disturbances and noises. This methodology is applied as a gain tuning algorithm for a PID control system derived from the multi-rotor UAV heave dynamics in the landing sub-problem. The flexibility and usefulness of the optimal control framework is also demonstrated on a full state feedback and output feedback controller for the same landing sub-problem. The framework developed in this thesis is able to take into account multiple disturbances, system uncertainties and noises. In both sub-problems, extensive simulations are performed to verify the proposed controllers. The proposed tracking controller is shown to improve its robustness performance against inverse kinematics-based backstepping controller. On the other hand, the optimal performance of the landing controllers are verified with realistic simulation of effects such as ship heave, wind disturbances and measurement noises using static state feedback, PID and output feedback controllers. The different control structures demonstrate the generality of the proposed framework in achieving similar performance. Finally, this thesis is concluded with discussions on the significance and implications of the research results as well as limitations and possible future research directions. DOCTOR OF PHILOSOPHY (MAE) |
