| Unmanned co-axial helicopter has been widely used to all kinds of fields like armed attack and geological survey. Therefore, the working environment of UAV(unmanned aircraft vehicle) becomes more complex. So higher performance and system stability have a more important meaning for UAV, especially for co-axial helicopter. Combined with the national "863" project- " Development of Heavy Loads Intelligent Geophysical-dedicated Unmanned Helicopter "(2013AA063903), the vibration analysis of rotor drive system is studied in the paper based on mathematical modeling and numerical simulation. The major research work is as follows:Firstly, torsional stiffness and moment of inertia of drive system components are equivalent simplified and the vibration mathematical model is established. Then the equivalent vibration dynamics model is established.Secondly, vibration differential equation of blade flapping, blade twist and blade lagging are derived, while more accurate mode shapes and frequencies are obtained base on Rayleigh-Ritz method and MATLAB. And the influence of rotor speed, blade stiffness, and steering system linear stiffness are analyzed.Thirdly, rigid-flexible coupled simulation model of rotor drive system is established by ANSYS and ADAMS. Then the free and forced vibration characteristics are studied. The fisrt five orders of torsional modal and the fisrt six orders of bending modal are extracted and analyzed. All essential excitations are calculated and corresponding forced vibration response is simulated separately. Vibation response under different working conditions are compared and points of maximum response are obtained.Finally, a sensitivity analysis of key parameters like stiffness of the support bearings and hub moment of inertia to quality, natural frequency and vibration response are calculated. Structural dynamic modification aimed at dangerous parts is conducted and optimized sheme is obtained. |
