Aerodynamic Load Identification Of Helicopter Rotor Blade Based On Hybrid Force-Modal Analysis

The helicopter rotor work in the cyclical alternating airflow environment.Its slender,low rigidity blades will produce sustained elastic vibration under the action of the periodic aerodynamic load,and the vibration will feedback to the aerodynamic load,thus forming a very complex aeroelastic coupling response.Accurate calculation of aerodynamic loads on rotor blades has been one of the most complex problems in helicopter aerodynamics and dynamics.Based on the Hybrid Force-Modal Analysis method,the coupled flap-lag-torsion rotor blade aerodynamic load identification is studied in this thesis.Firstly,according to the force analysis method and Myklestad method,the inverse transfer matrix of rotor blade aerodynamic load identification is established.The blade displacement condition and the structural load are used to calculate the displacement response of each section by continuous matrix multiplication.Secondly,based on the Hamilton principle,the 2-node 12-DOF finite element model is adopted to derive the motion equations and the natural characteristics of the rotating blade.The generalized coordinates are also calculated from the modal displacement and displacement response.Then the coupled flap-lag-torsion rotor blade aerodynamic load identification equations are established.The blade aerodynamic load identification programs are developed by using Matlab software.And the measured structural loads of SA349/2 helicopter are used to identify the blade flapwise aerodynamic loads.The identified aerodynamic loads are compared with the measured airloads,the result of the comparison shows that the method and the program have a certain accuracy.At last,the model rotor blade load test is carried out on the rotor/body coupled dynamic stability test rig,and the flapwise aerodynamic load of the model blades in the hovering condition is identified and analyzed.