Robust Model Reference Adaptive Controller For Trajectory Tracking Of Fixed-Wing UAV
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Date
2023-09
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Addis Ababa University
Abstract
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.
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Keywords
Surveillance, Model Reference Adaptive Controller, Robust Model Reference Adaptive Controller, Fixed Wing UAV