Browsing by Author "Pan, Yingjun"

Now showing 1 - 5 of 5
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    Aerodynamic performance of a flyable flapping wing rotor with dragonfly-like flexible wings
    (Elsevier, 2024-03-29) Pan, Yingjun; Guo, Shijun; Whidborne, James F.; Huang, Xun
    Drawing inspiration from insect flapping wings, a Flapping Wing Rotor (FWR) has been developed for Micro Aerial Vehicle (MAV) applications. The FWR features unique active flapping and passive rotary kinematics of motion to achieve a high lift coefficient and flight efficiency. This study thoroughly investigates the aerodynamic performance and design of a bio-inspired flexible wing for FWR-MAVs, emphasizing its novel backward-curved wingtip and variable spanwise stiffness resembling a dragonfly's wing. The research departs from previous aerodynamic studies of FWR, which focused predominantly on rectangular and rigid wings, and delves into wing flexibility. Employing Computational Fluid Dynamics (CFD), Computational Structural Dynamics (CSD), and experimental measurements, the study demonstrates the aerodynamic benefits of the dragonfly-inspired FWR wingtip shape and its reinforced structure. Fluid-Structure Interaction (FSI) analysis is used to examine the effects of elastic deformation encompassing twist and bending on aerodynamic forces. The results underscore the importance of bending deformation in enhancing lift and power efficiency and propose a method for analysing variable stiffness along the wingspan using a vortex delay mechanism that is induced by delayed flapping motion. By comparing modelled and measured stiffness, the study validates the flexibility of the FWR wing, revealing optimal aerodynamic efficiency is achieved through moderate flexibility and spanwise stiffness variation. The curving leading-edge beam forming the sweep-back wingtip offers a practical approach to obtaining variable stiffness and aerodynamic benefits for FWR-MAVs. Using the same pair of dragonfly-like flexible wings, FWR-MAVs have effectively exhibited VTOL and hovering flight capabilities, spanning from a 25-g single-motor drive model to a 51-g dual-motor drive model. This research provides valuable insights into flexible wing design for FWR-MAVs, leveraging biomimicry to improve flight efficiency.
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    Aerodynamic performance of a flyable flapping wing rotor with passive pitching angle variation
    (IEEE, 2021-09-22) Chen, Si; Wang, Le; He, Yuanyuan; Tong, Mingbo; Pan, Yingjun; Ji, Bing; Guo, Shijun
    The present work was based on an experimental study on the aerodynamic performance of a flapping wing rotor (FWR) and enhancement by passive pitching angle variation (PPAV) associated with powered flapping motion. The PPAV (in this study 10o~50o) was realized by a specially designed sleeve-pin unit as part of a U-shape flapping mechanism. Through experiment and analysis, it was found that the average lift produced by an FWR of PPAV was >100% higher than the baseline model, the same FWR of a constant pitching angle 30o under the same input power. It was also noted that the lift-voltage relationship for the FWR of PPAV was almost linear and the aerodynamic efficiency was also over 100% higher than the baseline FWR when the input voltage was under 6V. The aerodynamic lift or efficiency of the FWR of PPAV can be also increased significantly by reducing the weight of the wings. An FWR model was fabricated and achieved vertical take-off and free flight powered by 9V input voltage. The mechanism of PPAV function provides a feasible solution for aerodynamic improvement of a bio-inspired FWR and potential application to micro-air-vehicles (MAVs).
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    Analysis and experiment of a VTOL flapping wing rotor micro aircraft
    (Cranfield University, 2023-06) Pan, Yingjun; Guo, Shijun J.; Whidborne, James F.
    This thesis presents an in-depth study of the aerodynamic and structural analysis of a novel bio-inspired flapping wing rotor (FWR) micro aerial vehicle (MAV) capable of vertical take-off and landing. The FWR is characterized by a combination of active flapping motion with passive rotation of the wings in an asymmetric installation to produce a significantly higher lift coefficient than traditional flapping wings. This research is aimed at further enhancing the FWR MAV’s efficiency and aerodynamic performance with flight capability and stability. This is approached by improving the FWR kinematics of motion and mechanism through analytical, numerical simulation, and experimental methods. In the first step, an efficient wing rotation method that allowed a small angle of attack in the downstroke and a larger one in the upstroke was considered. A novel Passive Pitching Angle Variation (PPAV) device, replacing traditional active rotation, was developed and integrated into the flapping mechanism. Using a high-speed camera and a load cell device for experiments, the PPAV-integrated FWR demonstrated a significant increase in aerodynamic efficiency compared to its constant pitch angle counterpart. In the second step, the study focused on enhancing FWR-MAV power efficiency by integrating springs into the mechanism, thereby reducing input power due to the counterbalance between elastic and inertia forces. Numerical analysis and experimentation with an FWR test model were conducted to simulate and measure the resultant kinematics of motion and forces. Specific emphasis was placed on the influence of spring stiffness on the FWR’s aerodynamic and power efficiency. This led to the development of a PPAV-integrated FWR model capable of remote-controlled vertical take-off and hovering. In the third step, the study explored wing flexibility’s impact on FWR’s unsteady aerodynamics using Fluid-Structure Interaction (FSI) analysis and experiments. A novel dragonfly-like wing with a curved sweep-back wingtip demonstrated aerodynamic benefits. The study elucidates the mechanism of wing bending deformation linked to vortex variation, implying that optimal spanwise variable stiffness can enhance lift and power efficiency. Employing flexible wings, the FWR model’s lift significantly increased from 25 g to 51 g, highlighting enhanced efficiency and payload capacity. The study finally explored the FWR-MAV's flight performance and efficiency, including VTOL and forward flight. It proposed a transformable MAV concept from VTOL FWR mode to a bird-like flapping-wing mode in forward flight. A test model was built to validate the transformation concept. Using MSC.ADAMS/Simulink co- simulations and a quasi-steady aerodynamic method, the flights of the FWR model in both flight modes were simulated and stability was demonstrated.
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    Analysis and testing of a flyable micro flapping-wing rotor with a highly efficient elastic mechanism
    (MDPI, 2024-12-03) Pan, Yingjun; Su, Huijuan; Guo, Shijun; Chen, Si; Huang, Xun
    A Flapping-Wing Rotor (FWR) is a novel bio-inspired micro aerial vehicle configuration, featuring unique wing motions which combine active flapping and passive rotation for high lift production. Power efficiency in flight has recently emerged as a critical factor in FWR development. The current study investigates an elastic flapping mechanism to improve FWRs’ power efficiency by incorporating springs into the system. The elastic force counteracts the system inertia to accelerate or decelerate the wing motion, reducing the power demand and increasing efficiency. A dynamic model was developed to simulate the unique kinematics of the FWR’s wing motions and its elastic mechanism, considering the coupling of aerodynamic and inertial forces generated by the wings, along with the elastic and driven forces from the mechanism. The effects of the spring stiffness on the aerodynamic performance and power efficiency were investigated. The model was then verified through experimental testing. When a spring stiffness close to the mechanical system resonance was applied, the power efficiency of the test model increased by 16% compared to the baseline model without springs, generating an equivalent average lift. With an optimal elastic flapping mechanism for greater lift and lower power consumption, the FWR was fully constructed with onboard power and a control receiver weighing 27.79 g, successfully achieving vertical take-off flight. The current model produces ten times greater lift and has nearly double the wing area of the first 2.6 g flyable FWR prototype.
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    Research progress on bio-inspired flapping-wing rotor micro aerial vehicle development
    (Springer, 2024-07-12) Pan, Yingjun; Guo, Shijun; Huang, Xun
    Flapping-wing rotor (FWR) is an innovative bio-inspired micro aerial vehicle capable of vertical take-off and landing. This unique design combines active flapping motion and passive wing rotation around a vertical central shaft to enhance aerodynamic performance. The research on FWR, though relatively new, has contributed to 6% of core journal publications in the micro aerial vehicle field over the past two decades. This paper presents the first comprehensive review of FWR, analysing the current state of the art, key advances, challenges, and future research directions. The review highlights FWR’s distinctive kinematics and aerodynamic superiority compared to traditional flapping wings, fixed wings, and rotary wings, discussing recent breakthroughs in efficient, passive wing pitching and asymmetric stroke amplitude for lift enhancement. Recent experiments and remote-controlled take-off and hovering tests of single and dual-motor FWR models have showcased their effectiveness. The review compares FWR flight performance with well-developed insect-like flapping-wing micro aerial vehicles as the technology readiness level progresses from laboratory to outdoor flight testing, advancing from the initial flight of a 2.6 g prototype to the current free flight of a 60-gram model. The review also presents ongoing research in bionic flexible wing structures, flight stability and control, and transitioning between hovering and cruise flight modes for an FWR, setting the stage for potential applications.