# Power Modeling and Experiment Study of Large Flapping-Wing Flying Robot during Forward Flight
###### Abstract  
A power estimation approach for calculating the power of a flapping-wing air vehicle (FWAV) in forward flight is proposed in this paper. One of the challenges and essential points of FWAVs is endurance. In order to optimize FWAVs, it is necessary to analyze power required for flight in addition to kinematic and aerodynamic analyses of the prototype. Previously, calculating the power of birds was limited to calculating their average power, which assumed the lift was usually the same as the gravitational force. However, the lift varies with the flapping angle during flight. As a result, the power required for forward flight of FWAVs is determined in this work by using a kinematic model of the drive element and wing flapping, along with the aerodynamic model, which varies with the flapping angle during the flapping cycle. Experiments were performed with two prototypes with wingspans of 1.6 and 1.8 m, utilizing a wind tunnel platform. The correlations between power and angle of attack, flapping frequency, and incoming flow velocity were discovered, and recommendations for FWAVs and flying mode design were provided. However, several challenges are highlighted in the application of the model to practical design efforts. flapping-wing air vehicles; biomimetic robot; power estimation; forward flight +
Footnote †: journal: _Sci_  
efficiency. University of Maryland developed the RoboRaven [7] using two independent servo motors to drive both wings, enabling independent control of individual wings and thus obtaining complex flight patterns and greater maneuverability with a wingspan of 1.168 m, a mass of 0.29 kg, and a flight time of 4 min 45 s. The team of [PERSON] from Northwestern Polytechnic University constructed a bionic pigeon [8,9] with a wingspan of more than 60 cm, a takeoff weight of 220 g, and a flight period of 20 min. The HIT-Hawk and HIT-Phoenix [10], with wingspan of 2 and 2.3 m, were constructed by [PERSON]'s team from Harbin Institute of Technology, Shenzhen, utilizing the eagle and phoenix as imitation items, respectively. In order to estimate the power of birds or FWMAVs, scholars have also conducted relevant studies on the power estimation during flight. Researchers have conducted studies related to the calculation of power consumption in the flight of birds as well as large flapping-wing flying robots. Previously, calculating the power of birds was limited to calculating their average power, which assumed the lift was usually the same as the gravitational force [11,12]. However, the lift varies with the flapping angle during flight. [PERSON] et al. [13] discussed a flapping aerodynamic model to study lift, drag, and power of birds, and summarized the biological scaling laws, including wingspan, cruise speed, flapping frequency, and power. [PERSON] et al. [11,12,14] introduced a new way to quantitatively characterize flapping drag, which demonstrates that wing tilt produces an increase in induced drag by changing the direction and magnitude of lift throughout the flapping cycle. They also described flap-gliding flight in birds and the associated mechanical energy cost of traveling. In addition, the power required for flapping fly and fixed-wing flying was also measured and compared. [PERSON] et al. [15] studied the U-shaped curve of mechanical power for birds as a function of forward speed, then present mechanical power curves for cockatiels (_Nymphicus holandicus_) and ringed turtle-doves (_Streptopedia risoria_). [PERSON] et al. [16] derived the effect of reciprocating wing motion on the aerodynamic power model coefficients of a forward-flight fixed wing in terms of thrust demand, flapping frequency, and stroke plane angle, and obtained the optimal flapping amplitude, demonstrating the relationship between airfoil power and airfoil kinematics. [PERSON] et al. [17] experimentally investigated the effects of individual parameters of span chord ratio, wing offset, and flapping frequency on the thrust and power consumption of an FWMAV. [PERSON] et al.