Browsing by Author "Tofik Kemal"

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    Robust Model Reference Adaptive Controller For Trajectory Tracking Of Fixed-Wing UAV
    (Addis Ababa University, 2023-09) Tofik Kemal; Lebsewerk Negash (PhD)
    In recent years, the application of UAVs has increased. Fixed-wing Unmanned Aerial Vehicle (UAV) is an airborne vehicle that is largely used for surveillance, reconnaissance, monitoring, and data collection or to patrol an area that is not safe for a human being. This thesis addresses Robust Model Reference Adaptive Control for trajectory tracking of fixedwing UAV. The fixed-wing UAV is under actuated system and due to this reason controlling all six degrees of freedom directly is impossible. To overcome this problem, the proposed control algorithm has two loops inner(attitude) and outer(position)loop. The outer loop provides the pitch and yaw angle reference trajectories for the inner loop. The inner loop controls attitude(roll, pitch, and yaw angle). First, fixed-wing UAV dynamic models are driven using the Newton-Euler approach, and the dynamic models are decoupled to reduce complexity. The decoupled dynamics have six second-order Single Input Multiple Output (SIMO) systems. Second, a conventional Model Reference Adaptive Control (MRAC) is designed. However, this controller causes instability in the presence of unmatched uncertainty. Third, Robust Model Reference Adaptive Control (RMRAC) is developed to prevent parameter drift in off-nominal scenarios. This thesis addresses different robust modification techniques like σ-modification, e-modification, and optimal modification techniques. These control algorithms are tested on different trajectories and a comparative analysis is made. Lyapunov direct method is used as a mathematical tool for design and stability analysis. The performance of the proposed control strategy is verified by developing simulation results in MATLAB/SIMULINK software. Finally, the developed Robust Model Reference Adaptive Controller is tested for parametric uncertainty and external disturbance. The simulation result shows that the proposed controller is able to track the desired trajectory in the presence of external disturbance(wind gust environment) and parametric variation.