# Power Modeling and Experiment Study of Large Flapping-Wing Flying Robot during Forward Flight
## 5 Conclusions  
Unlike previous studies, in this paper, the lift is not directly and simply equal to gravity when calculating the induced drag and induced drag coefficient. Because the lift generated by the wings should change during the flapping cycle, we believe that the induced drag associated with it should also vary. However, such a simulation necessitates a more precise lift calculation, because the induced drag coefficient and induced power can only be determined if the lift calculation is accurate.  
However, the limitation of this method is that it relies on the accuracy of the flapping kinematic and aerodynamic models, for example, in the experiments, when the flapping frequency is low and the actual rotational speed deviates from the kinematic model, the calculation results will have deviations. Moreover, the variation of flexible wing deformation with flapping frequency is not considered comprehensively enough in this work, which is a subject we will address, including establishing the complete deformation equationsof wing span and axial direction, and verifying them with the assistance of experimental equipment. However, the advantage of this method is to calculate the accurate power consumption of the FWAV during level flight, instead of simply estimating it by gravity. Extended efforts should concentrate on improving the accuracy of aerodynamic models and then using the power model to solve for the optimal flight speed of FWAVs and even to optimize the wing characteristics.  
In any case, the proposed model provides some guidance for the prototype's stability and flight strategy design. The prototype's center of gravity is normally situated closer to the rear end of the body to ensure flight stability, so that the prototype is always kept in a \"head-up\" posture with a large angle of attack. This design, however, is not conducive to expanding the endurance of FWAVs. As a result, during the cruising flight, the angle of attack should be reduced to improve endurance performance. Second, enhancing thrust and wind resistance performance is another technique to extend the range while maintaining enough lift for flight. According to the experimental data, the total power consumption of the FWAVs decreases slightly with increasing forward flight speed within the permitted wind speed. Third, the induced power and inertial power of FWAVs will be much greater if the wings keep flapping than if the wings remain stationary. Thus, the controller should be designed to manipulate the FWAVs to be able to fly similar to birds in nature, with a fully expanded wingspan and capable of performing flap-glide flight.  
Conceptualization, S.Z. and W.X.; methodology, S.Z. and W.X.; software, S.Z.; validation, S.Z., W.X.; formal analysis, S.Z.; investigation, S.Z.; resources, W.X.; data curation, S.Z. and W.X.; writing--original draft preparation, S.Z.; writing--review and editing, S.Z.; visualization, S.Z.; supervision, W.X.; project administration, W.X.; funding acquisition, W.X. All authors have read and agreed to the published version of the manuscript.  
This work is supported by the Shenzhen Excellent Scientific and Technological Innovation Talent Training Project under grant RCJC20200714114436040, and the Basic Research Program of Shenzhen under grant JSGG20200103103401723.  
Not applicable.  
The authors declare no conflict of interest.