Effect Of Elastic Restriction Stiffness Of Blade Root On The Characteristics Of Helicopter Flight Dynamics

The rotor and ducted fan unmanned helicopter is a new configuration air vehicle, which lift system is coaxially consisted of the upper seesaw rotor and the lower ducted fan. Because the control efficacy of the seesaw rotor was deficient, its control efficacy was improved by adding an elastic support to the root of the rotor blade. The effects of the elastic restriction stiffness of the blade root on flight dynamics and flying qualities of helicopter were analyzed and researched. Meantime, the major parameter of the elastic support of blade root was also designed.First, rotor dynamics model was built basing on simplifying the elastic support as a hinge spring. Meanwhile, the aerodynamic models of the rotor, the ducted fan and fuselage were set up and the flight dynamic model of the whole helicopter wascompleted. As the rotor and ducted fan unmanned helicopter assembled and unassembled with elastic support examples, the trim characteristics, stability and control response of both were computed. And on this basis, the effects of elastic restriction stiffness of blade root on trim characteristics, stability and control response of helicopter were compared and analyzed.Secondly, the stability, maneuverability and inter-axis coupling were pruned applicably based on the U.S army’s aviation design standard ADS-33E-PRF and the flight control characteristics of unmanned helicopter. As the sample helicopter assembled and unassembled with elastic support examples, the parameters of flying qualities of both were computed. And on this basis, the effects of elastic restriction stiffness of blade root on flying qualities of helicopter were compared and analyzed.Finally on the basis of previous work, as the sample helicopter assembled with elastic support an example,the trim characteristics and the parameters of flying qualities of different elastic restriction stiffness were computed. Then the equivalent stiffness of the elastic support which could make the flying qualities of the sample helicopter best was found based on the evaluation method of flying qualities and all aspects of compromise. The elastic support chose rubber, and the finite element analysis software ANSYS was used to compute and analyze for it. And on this basis, the shore scleroscope hardness of rubber corresponding to the best equivalent stiffness was found.