Abstract
To date,no experimental study has been done on eliminating the energy consumption of the flapping wing rotor(FWR;caused by inertial force)based on an energy capture mechanism(such as a spring).Also,the effect of the variation amplitude of the twist angles on the FWR remains unknown.In this study,a 19.2-g FWR model is designed and manufactured.Three different kinds of springs are then selected and assembled onto the FWR to reduce the energy consumption caused by the inertial forces.Afterward,a motion capture system and a lift measurement system are built to test the aerodynamic and kinematic performance of the FWR.Then,the influence of the variation range of the twist angles and the dimensions of the spring on the motion parameters and lift efficiency of the FWR is analyzed.If the rigid twist angle variation range is set to 10°-70°instead of 10°-50°,the FWR can generate 3 to 10 g of greater average lifts under the same input voltage.In most cases,the introduction of the spring also improves the average lifting rate by 1-4 g.The lift enhancement effect induced by the spring is more pronounced when the main frequency with the maximum amplitude is close to or coincides with the resonant frequency of the FWR structure.If the main frequency is greater than the resonance frequency of the FWR structure,the lift enhancement effect is hardly observed.In conclusion,according to experimental analyses,both the selection of 10°-70°preset twist angles and the application of springs can improve the lift efficiency of FWR and overcome the weight of the FWR system(37.8 g)assembled with a flight control system.Free-flight test results show that the FWR system(including the 19.2-g FWR model and an 18.6-g flight control system)has sufficient lifting margin to successfully perform a take-off mission and achieve a stable hovering action.
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