STUDY ON THE TRANSIENT DYNAMIC CHARACTERISTICS OF THE PITCH-REGULATED DEVICE FOR COAXILCOPTER UNDER AERODYNAMIC LOADS

Coaxilcopter with variable rotor space can dynamically adjust the parameters such as the angle of attack of blades through the pitch-regulated device, so it can adjust and change flight attitude. However, both the rotor aerodynamics and the structure of the pitch-regulated device are complex, and some of the forces generated by the rotor will act on such device in the form of a hinge moment, which would affect the realiablity of the variable pitch-regulated device and the whole craft. Therefore, a coaxilcopter with a pitch-regulated device is designed, and the finite element numerical simulation method is promoted to calculate and analyze the transient aerodynamic loads of the rotor under different rotor spaces and unbalanced angle between blades. The hinge moment load results are further applied to the variable pitch-regulated device, and the dynamic characteristics of the variable pitch-regulated device under the action of hinge moment are further studied. The results show that when the unbalanced angle between the left and right blade would lead to the increase of the hinge moment of both blade, and with the increase of rotor speed, the hinge moment of both the left and right blades gradually increases; When the hinge moment is applied to the variable pitch-regulated device, the steering gear load of the lower rotor is 1.57 times that of the rotor steering gear when the propeller spacing is 0.1R (R is rotor radius); When the propeller spacing is 1.2R, the actuator load of the upper rotor is 6%~12% different from that of the single rotor mode, indicating that the influence of propeller spacing on the upper rotor is negligible at 1.2R, but the actuator load of the lower rotor is about 35% different from that of the single rotor mode, which has a significant influence. It also reveals that the aerodynamic interaction between rotors would affect the hinge moment, it provides a basis for the design of variable pitch-regulated device, and provides a reference for the variable pitch control strategy of aerodynamic performance, which has practical engineering significance.