Responses and suppression of Joined-Wing UAV in wind field based on distributed model and active disturbance rejection control

Abstract For a Joined-Wing configuration UAV, the front and rear wing are joined at the wingtip, but they are far away at the roots, and their areas are comparable. These special geometric features make its behaviors quite different in wind field. So it's important to comprehend these behaviors accurately and to improve the safety of flight of Joined-Wing configurations. In this paper, firstly, a high-fidelity nonlinear distributed flight dynamics model coupling with distributed wind field are derived based on a distributed aerodynamics model. Base on this, the influence of gust on flight dynamics mode characteristics are analyzed. The mechanism that gust will significantly weaken the longitudinal stability of a UAV are derived. After that, the dynamic responses of a Joined-Wing UAV flying through a 3D wind field are studied by adopting centralized and distributed dynamics model respectively. Finally, a pitch controller is designed by Active Disturbance Rejection Control (ADRC) method for the Joined-Wing UAV in the 3D wind field environment, and the advantage of ADRC for the safety of flight is demonstrated by simulations. The results show that, with the help of the high-fidelity distributed model, a distinct traveling wave form excitation phenomenon is revealed while a Joined-Wing UAV flying through a 3D wind field. It's also can be found that, for the high-fidelity distributed model, the effect time of wind is longer, the disturbance of flight parameters is about twice more than the centralized model. More seriously, the initial response of pitch angle is reversed compared with that of the centralized model. With the traveling wave form excitation while flying through a 3D wind field, a traditional PID controller wouldn't ensure the safety of flight since the max pitch angle would reach to about 16 degrees. In comparison, the maximum pitch angle disturbance is suppressed to less than 3 degrees at the same conditions while applying the ADRC controller.