Trajectory tracking control of powered parafoils using anti-windup active disturbance rejection control under wind disturbances and actuator saturation

This paper investigates the trajectory tracking control of a powered parafoil in the presence of wind disturbances and actuator saturation. An anti-windup active disturbance rejection control method is developed on the basis of an eight-degree-of-freedom nonlinear model. For controller design and implementation, the system is organized into horizontal and vertical channels. The residual coupling, model uncertainty, and wind effects are not ignored; instead, they are incorporated into lumped disturbances and estimated online by an extended state observer. The key idea of the proposed method is to explicitly feed the mismatch between the commanded input and the saturated actuator output back into the observer update, so that actuator saturation is handled within the observer and controller loop rather than treated as a simple external limitation. A boundedness analysis is further provided to show that the closed-loop tracking errors are uniformly ultimately bounded under bounded disturbance derivatives and admissible gain selection. The proposed method is evaluated through same-platform simulations involving dynamic wind, horizontal saturation, thrust saturation, step disturbances, parameter variations, Monte Carlo tests, and sensitivity analysis. The results show that the proposed method is particularly effective in saturation-dominant cases and during disturbance transitions. Outdoor flight experiments further confirm its practical feasibility. Using the currently available flight data, the proposed anti-windup active disturbance rejection control reduces the maximum horizontal tracking error from 37.11 m to 8.11 m and decreases the altitude overshoot from 13.3% to about 8.0% compared with the deployed linear active disturbance rejection control baseline. These results demonstrate the practical value of saturation-aware observer correction for trajectory tracking of powered parafoils.