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Objective
Design a robust nonlinear path following control law for a fixed-wing UAV to track a reference path under the wind disturbance
Disturbance Observer
System model for the wind estimator
$$ \begin{bmatrix} \dot{x} \\ \dot{y} \end{bmatrix} = \begin{bmatrix} V_a \cos \psi + W_N \\ V_a \sin \psi + W_E \end{bmatrix}$$
Update law of the disturbance observer
$$ \dot{\hat{\bf{w}}} = -T_w \hat{\bf{w}} + T_w ( \dot{\bf{x}} – \bf{u}) $$
where, \( \hat{\bf{w}} = \begin{bmatrix} \hat W_n & \hat W_e \end{bmatrix}^T \) is the wind velocity estimate in the north and east direction, \( T_w \) is the diagonal observer gain matrix, and \( \bf{u} = \begin{bmatrix} V_a \cos \psi & V_a \sin \psi \end{bmatrix}^T \)
System Model
![](https://control.kau.ac.kr/wp-content/uploads/2023/04/error_kinematics.jpg)
The error kinematics model becomes,
$$ \begin{align} \dot{e}_t &= V_g \cos (\chi – \chi_r ) – ( 1 – \kappa (s) e_n ) \dot{s} \\ \dot{e}_n &= V_g \sin (\chi – \chi_r ) – \kappa (s) e_t \dot{s} \end{align} $$
Path Following Control Law
Command Filtered Backstepping
![](https://control.kau.ac.kr/wp-content/uploads/2023/04/Commnadbackstepping.jpg)
Hardware-in-the-loop Tests
Bspline Path Following
![](https://control.kau.ac.kr/wp-content/uploads/2023/04/FlightExperiment_RobustBspline.jpg)
![](https://control.kau.ac.kr/wp-content/uploads/2023/04/FlightExperiment_RobustBspline_Errorstates.jpg)
Flight Tests
Circular trajectory following
![](https://control.kau.ac.kr/wp-content/uploads/2023/04/FlightExperiment_RobustCircular.jpg)
![](https://control.kau.ac.kr/wp-content/uploads/2023/04/FlightExperiment_RobustCircularWind.jpg)
Conclusion
The experimental results show that the improved tracking performance as well as the enhanced robustness, proving the applicability of the proposed algorithm in the various mission of the fixed-wing UAV in wind disturbance environment.
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Researcher
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김수현(Kim Su Hyeon)
한국항공대학교 스마트항공모빌리티학과 무인시스템제어연구실(KAU USCL)
박사과정
10540 경기도 고양시 덕양구 항공대학로 76 전자관 322호
angelfive92@gmail.com
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