Flapping-Wing Air Vehicles(FWAVs)have been developed to pursue the efficient,agile,and quiet flight of flying animals.However,unlike lightweight FWAVs capable of vertical takeoff,relatively heavy FWAVs face challenges...Flapping-Wing Air Vehicles(FWAVs)have been developed to pursue the efficient,agile,and quiet flight of flying animals.However,unlike lightweight FWAVs capable of vertical takeoff,relatively heavy FWAVs face challenges in self-takeoff,which refers to taking off without both external device and energy input.In this study,a cliff-drop method is implemented for an independent takeoff of a heavy FWAV,relying solely on gravity.In the takeoff process using the cliff-drop method,the FWAV moves on the ground to a cliff edge using a wheel-driving motor and then descends from the cliff to achieve the necessary speed for flight.To demonstrate the cliff-drop method,the KAIST Robotic Hawk(KRoHawk)with a mass of 740 g and a wingspan of 120 cm is developed.The takeoff tests demonstrate that the KRoHawk,significantly heavier than the vertical-takeoff capable FWAVs,can successfully take off using the gravity-assisted takeoff method.The scalability of cliff-drop method is analyzed through simulations.When drop constraints are absent,the wheel-driving motor mass fraction for cliff-drop method remains negligible even as the vehicle's weight increases.When drop constraints are set to 4 m,FWAVs heavier than KRoHawk,weighing up to 4.4 kg,can perform the cliff-drop takeoffs with a wheel-driving motor mass fraction of less than 8%.展开更多
This paper is based on a previously developed bio-inspired Flapping Wing Aerial Vehicle(FWAV),RoboFalcon,which can fly with a morphing-coupled flapping pattern.In this paper,a simple flapping stroke control system bas...This paper is based on a previously developed bio-inspired Flapping Wing Aerial Vehicle(FWAV),RoboFalcon,which can fly with a morphing-coupled flapping pattern.In this paper,a simple flapping stroke control system based on Hall effect sensors is designed and applied,which is capable of assigning different up-and down-stroke speeds for the RoboFalcon platform to achieve an adjustable downstroke ratio.The aerodynamic and power characteristics of the morphing-coupled flapping pattern and the conventional flapping pattern with varying downstroke ratios are measured through a wind tunnel experiment,and the corresponding aerodynamic models are developed and analyzed by the nonlinear least squares method.The relatively low power consumption of the slow-downstroke mode of this vehicle is verified through outdoor flight tests.The results of wind tunnel experiments and flight tests indicate that increased downstroke duration can improve aerodynamic and power performance for the RoboFalcon platform.展开更多
Birds and bats retract and stretch their wings dynamically during each flap in level flights, implying intriguing mechanisms for the aerodynamic performance improvement of flapping wings. A numerical investigation int...Birds and bats retract and stretch their wings dynamically during each flap in level flights, implying intriguing mechanisms for the aerodynamic performance improvement of flapping wings. A numerical investigation into the aerodynamic effects of such bio-inspired concept in forward flights has been performed based on a three-dimensional wing in plunging motion and a twosection wing in flapping motion. The currently considered Reynolds number and Strouhal number are Re=1.5×10^(5) and St=0.3, respectively. During the research, the mean angle of attack is varied in relatively wide ranges to achieve lift-thrust interconversion for the wings. The conclusive results show that dynamical spanwise retraction and stretch has induced three absolutely desirable scenarios for the oscillating wings in forward flights, namely producing more lift and consuming less power for a given thrust generation, producing more thrust and consuming less power for a given lift generation, and producing more lift and more thrust while consuming less power. Furthermore,the morphing wings have alleviated periodical aerodynamic load fluctuations compared with the non-morphing baseline. The mechanism of the aerodynamic effects of the bionic morphing mode is analyzed with the aid of field visualization. The current article is the first to reveal the absolute advantages of the bionic spanwise morphing. Hopefully, it may help comprehend the behaviors of natural fliers and provide inspirations for performance enhancement of micro artificial flappingwing vehicles.展开更多
基金supported by Unmanned Vehicles Core Technology Research and Development Program through the National Research Foundation of Korea(NRF)Unmanned Vehicle Advanced Research Center(UVARC)funded by the Ministry of Science and ICT,the Republic of Korea(2020M3C1C1A01083415).
文摘Flapping-Wing Air Vehicles(FWAVs)have been developed to pursue the efficient,agile,and quiet flight of flying animals.However,unlike lightweight FWAVs capable of vertical takeoff,relatively heavy FWAVs face challenges in self-takeoff,which refers to taking off without both external device and energy input.In this study,a cliff-drop method is implemented for an independent takeoff of a heavy FWAV,relying solely on gravity.In the takeoff process using the cliff-drop method,the FWAV moves on the ground to a cliff edge using a wheel-driving motor and then descends from the cliff to achieve the necessary speed for flight.To demonstrate the cliff-drop method,the KAIST Robotic Hawk(KRoHawk)with a mass of 740 g and a wingspan of 120 cm is developed.The takeoff tests demonstrate that the KRoHawk,significantly heavier than the vertical-takeoff capable FWAVs,can successfully take off using the gravity-assisted takeoff method.The scalability of cliff-drop method is analyzed through simulations.When drop constraints are absent,the wheel-driving motor mass fraction for cliff-drop method remains negligible even as the vehicle's weight increases.When drop constraints are set to 4 m,FWAVs heavier than KRoHawk,weighing up to 4.4 kg,can perform the cliff-drop takeoffs with a wheel-driving motor mass fraction of less than 8%.
基金supported by National Natural Science Foundation of China under Grants No.52175277 and 12272318,and ND Basic Research Funds under Grants G2022WDwas supported in part by the Basic Research Program of Shenzhen under GrantJCYJ20190806142816524.
文摘This paper is based on a previously developed bio-inspired Flapping Wing Aerial Vehicle(FWAV),RoboFalcon,which can fly with a morphing-coupled flapping pattern.In this paper,a simple flapping stroke control system based on Hall effect sensors is designed and applied,which is capable of assigning different up-and down-stroke speeds for the RoboFalcon platform to achieve an adjustable downstroke ratio.The aerodynamic and power characteristics of the morphing-coupled flapping pattern and the conventional flapping pattern with varying downstroke ratios are measured through a wind tunnel experiment,and the corresponding aerodynamic models are developed and analyzed by the nonlinear least squares method.The relatively low power consumption of the slow-downstroke mode of this vehicle is verified through outdoor flight tests.The results of wind tunnel experiments and flight tests indicate that increased downstroke duration can improve aerodynamic and power performance for the RoboFalcon platform.
基金mainly supported by the National Natural Science Foundation of China (No. 52175277, 52275293)Resources provided by the Basic Research Program of Shenzhen, China (No. JCYJ 20190806142816524)the Guangdong Basic and Applied Basic Research Foundation, China (No. 2023A1515010774)。
文摘Birds and bats retract and stretch their wings dynamically during each flap in level flights, implying intriguing mechanisms for the aerodynamic performance improvement of flapping wings. A numerical investigation into the aerodynamic effects of such bio-inspired concept in forward flights has been performed based on a three-dimensional wing in plunging motion and a twosection wing in flapping motion. The currently considered Reynolds number and Strouhal number are Re=1.5×10^(5) and St=0.3, respectively. During the research, the mean angle of attack is varied in relatively wide ranges to achieve lift-thrust interconversion for the wings. The conclusive results show that dynamical spanwise retraction and stretch has induced three absolutely desirable scenarios for the oscillating wings in forward flights, namely producing more lift and consuming less power for a given thrust generation, producing more thrust and consuming less power for a given lift generation, and producing more lift and more thrust while consuming less power. Furthermore,the morphing wings have alleviated periodical aerodynamic load fluctuations compared with the non-morphing baseline. The mechanism of the aerodynamic effects of the bionic morphing mode is analyzed with the aid of field visualization. The current article is the first to reveal the absolute advantages of the bionic spanwise morphing. Hopefully, it may help comprehend the behaviors of natural fliers and provide inspirations for performance enhancement of micro artificial flappingwing vehicles.
