Static Anti-windup Compensation Control of Yaw Movement for a Coaxial Eight-Rotor UAV

A coaxial eight-rotor unmanned aerial vehicle (UAV) with higher drive capability, greater payload capacity and damage tolerance than a quad-rotor UAV is developed. Firstly, the UAV dynamic model is set up. The actuator saturation tends to occur in the yaw movement of the coaxial eight-rotor UAV, for the reason that the yaw movement is much weaker than the pitch movement and roll movement in the coaxial eight-rotor UAV. For this problem, a static anti-windup compensator based on linear active disturbance rejection controller (LADRC) is proposed from the view point of practical engineering. LADRC is easy to be adjusted in engineering and able to estimate and compensate external disturbances in real time. The static anti-windup compensator can prevent actuator saturation in the yaw movement without increasing the system order. Then, the stability of the yaw control system with static anti-windup compensator based on LADRC is proved based on Lyapunov stability theory. Finally, the validity and robustness of the algorithm are verified via numerical simulations and coaxial eight-rotor prototype experiments. Experimental results indicate that the yaw control system with static anti-windup compensator based on LADRC spends 4 s to exit saturation for the longest time with yaw angle error limited to ± 0.085 rad indoors in the case of constant disturbances, and it spends 9 s to exit saturation for the longest time with yaw angle error limited to ± 0.127 rad outdoors in the case of varied disturbances. The static anti-windup compensator based on LADRC can effectively prevent actuator saturation with accurate yaw control and strong robustness for the coaxial eight-rotor UAV in the presence of external disturbances.