Control strategy design for the transitional mode of tiltrotor UAV

Focusing on the transitional mode of tiltrotor UAV, which is nonlinear, strongly coupled and uncertain due to its complexity in layout, structure and aerodynamic peculiarity, a control strategy is designed and proposed. First, considering of the aerodynamics of rotor and its tilt machinery, the mathematic model of this kind of UAV is presented. Then, the reasonable anticipant global trajectory is framed based on the force and moment balance relationship of transitional mode. The control loop structure based upon time-scale separation is developed. And then, the dynamic model inversion technique based on reference model tracking is applied to linearize the object and eliminate the coupled factors, and the unknown disturbances are estimated and compensated by extended-state-observer (ESO). Finally, the mapping between the virtual effectors and the actual effectors is realized by dynamic control allocation. The simulation results show that the anticipant movement and mode conversion of tiltrotor UAV can be realized properly, and the method has strong robustness.