Variable structure and variable coefficient proportional-integral-derivative control to prevent actuator saturation of yaw movement for a coaxial eight-rotor unmanned aerial vehicle

This paper focuses on the development of a coaxial eight-rotor unmanned aerial vehicle (UAV) with higher drive capability, greater payload capacity, and damage tolerance than a quad-rotor UAV. The dynamical and kinematical model for the coaxial eight-rotor is designed. Considering the yaw movement of the eight-rotor is weaker than the pitch movement and the roll movement, a new variable structure and variable coefficient proportional-integral-derivative (VSVCPID) anti-windup method is proposed as the yaw controller to prevent actuator saturation. VSVCPID method is easily implemented in practical engineering and has a strong robustness with conditional anti-windup. Finally, numerical simulations and prototype experiments indoors and outdoors corroborate that VSVCPID applied to the coaxial eight-rotor has accurate yaw control performance and strong robustness against external disturbances.