Stability Analysis Of The Coupled Spheriflex Rotor/Fuselage With Magneto-rheological Damper

The spheriflex flexible hub was a new type of elastic bearing rotor hub.Compared with the traditional metal articulated hub,the number of parts was reduced by 60%,the weight was reduced by 25%,the reliability was higher,and the service life was longer.When the parameters of the spheriflex rotor helicopter were not properly configured,the motion of each degree of freedom was excited by coupling action,so that the vibration amplitude would diverge,which would cause the ground resonance.To improve the stability of the coupled rotor/fuselage system,one common method was to install dampers at the roots of blades.The demand for the damping of the damper was different in the different working conditions of the helicopter,because the helicopter needed a larger damping of the damper only in the takeoff,landing and large weight maneuver,and it did not require too much damping in normal flight.Too large damping would lead to a larger hub load.However,most of the current damper was passive damper,which was difficult to meet the adjustable damping demand,and the damping force provided by the magnetor-heological damper has the advantages of continuously controllable and adjustable.In order to study the dynamic instability of a spheriflex rotor helicopter,a magneto-rheological damper was applied to the helicopter damper.Firstly,a magneto-rheological damper for helicopter dampers was designed.According to the damping and vibration conditions of the original model,the maximum damping force of the magneto-rheological damper was estimated,The magneto-rheological damper was designed in terms of parameter estimation,structure design and magnetic field simulation.Secondly,based on Hamilton principle,a dynamic model of a coupled spheriflex rotor/fuselage with magneto-rheological damper was established.Considering the influence of spheriflex rotor,aerodynamic forces,magneto-rheological damper and landing gear,a system dynamic equation which can be used for eigenvalue analysis and transient response analysis was derived.Then,the stability of the blade and the airframe degree of freedom was obtained by using the linearized eigenvalue analysis method.The influence of magnetorheological damper,spheriflex hinge offset rotor height and moment of inertia of the body on the ground resonance of a flexible rotor helicopter was analyzed.It was concluded that the magneto-rheological damper and the moment of inertia of the body have great influence on the ground resonance of the spheriflex rotor helicopter,but the influence of ball hinge offset and rotor height was relatively small.In the last,the transient response analysis method was applied to simulate the ground start process of the spheriflex rotor helicopter.The influence of different current and different driving parameters on the ground driving was analyzed.It was concluded that the the magneto-rheological damper could control the dynamic instability of rotor / fuselage coupling system,driving mode with a more continuous and slow driving function and a low collective pitch to start and then lift the collective pitch was more suitable.