Research On Dynamics Of Soft-inplane Tiltrotor Model

Combining the operating features of vertical take-off and landing capability of a helicopter withthe high-speed and long-range of a conventional fixed-wing aircraft, tiltrotors aircraft has its ownoperating features. These unique characters are determined by its configuration features. Due to these,the tiltrotor is subject to aeroelastic dynamical problems of the two aircrafts, and in addition, it mayencounter more complex aeroelastic instability problems like Inertia force and unsteady aerodynamiccondition during transition flight. To address these problems, full-span soft-inplane tiltrotor model isestablished with consideration of fuselage. Aeroelastical analysis is made in helicopter, airplane andconversion flight condition.Based on Hamilton Principle, taking structure offsets, rigid-flexible, aeroelastic coupling, theimpact of nonlinear and higher order terms into consideration, the components of system aredescribed in kinematics by the method of multibody dynamics. The elastic and dampling componentsare modeled by assigning mechanical properties (stiffness and damping) of landing gear, tilt-hinge,and lag damper independently, or by putting it into viscoelastic damper and being solved withaeroelastic dynamics equations. Dynamic-inflow is employed. Airfoil unsteady aerodynamic model isused to simulate complex aerodynamic environment of tiltrotor aircraft. Leishman and ONERAunsteady aerodynamic models are employed. Metal beam and tailored composite box-beam are usedto model wing beam. Then the right and left rotor/pylon/wing aeroelastic coupled equations combinedwith fuselage equations can be used to constitute full-span soft-inplane tiltrotor aeroelastic dynamicsequations. The method of generalized-combined with Newton iteration is used to improve theefficiency of solving aeroelastic dynamics equations for transient response.In order to ensure the correctness of submodules of full-span soft-inplane tiltrotor model, eachtheory modeling is supposed to be verified. Theory analysis results of advanced geometry blade arecompared with experimental results in different root restraints. Furthermore, integral modes ofgimbaled rotor with advanced geometry blades are analyzed theoretically and measured. For differentcomposite plys, coupling properties of tailored composite box-beam are discussed by comparison withtheoretical analysis and experiments. Viscoelastic dampers are measured in multiple-excitation cases.Stiffness characteristic and ability of energy dissipation of dampers are studied in anelasticdisplacement field theory. Leishman and ONERA unsteady aerodynamic models are employed in foilsection aerodynamic analysis. Aerodynamic coefficients of calculation are compared with foreign research literatures in various changing laws of angles of attack. In conclusion, the above processreaches the goal of validating the every submodules.Aerolatic stability of full-span soft-inplane tiltrotor model also needs analyzing in various flightconditions like helicopter, airplane and conversion. In airplane mode, parameters influence on whirlflutter of full-span soft-inplane tiltrotor are discussed, and compared with analysis results ofsemi-span gimbaled tiltrotor. In helicopter mode, parameters influence on ground resonanceaeroelastic stability of full-span soft-inplane tiltrotor model are studied. Aeroelastic stability offull-span soft-inplane tiltrotor is researched in different nacelle tilting angles and forward speeds.Transient response analysis of full-span soft-inplane tiltrotor model is made. Ground resonanceand rotor starting process on ground are researched by transient response of full-span soft-inplanetiltrotor model in helicopter mode. Transient response of whirl flutter and gust disturbance arediscussed in airplane mode. Transient response of full-span soft-inplane tiltrotor model is analyzed invarious structure parameters, nacelle tilting angles, changing laws of rotor speed, flight conditions.Aeroelastic stability and transient response analysis is made by established full-spansoft-inplane tiltrotor aeroelastic dynamical model in helicopter, airplane and conversion flightcondition. Some valuable conclusions of full-span soft-inplane tiltrotor are summarized by analyzingparameters influence on aeroelastic stability and transient response in three common operating modes.Essential laws have guiding significance in engineering practice of dynamic design.