Can scalable design of wings for flapping wing micro air vehicle be inspired by natural flyers?

Lift production is constantly a great challenge for flapping wing micro air vehicles (MAVs). Designing a workable wing, therefore, plays an essential role. Dimensional analysis is an effective and valuable tool in studying the biomechanics of flyers. In this paper, geometric similarity study is firstly presented. Then, the pw−AR ratio is defined and employed in wing performance estimation before the lumped parameter is induced and utilized in wing design. Comprehensive scaling laws on relation of wing performances for natural flyers are next investigated and developed via statistical analysis before being utilized to examine the wing design. Through geometric similarity study and statistical analysis, the results show that the aspect ratio and lumped parameter are independent on mass, and the lumped parameter is inversely proportional to the aspect ratio. The lumped parameters and aspect ratio of flapping wing MAVs correspond to the range of wing performances of natural flyers. Also, the wing performances of existing flapping wing MAVs are examined and follow the scaling laws. Last, the manufactured wings of the flapping wing MAVs are summarized. Our results will, therefore, provide a simple but powerful guideline for biologists and engineers who study the morphology of natural flyers and design flapping wing MAVs

A CFD-informed quasi-steady model of flapping-wing aerodynamics

Aerodynamic performance and agility during flapping flight are determined by the combination of wing shape and kinematics. The degree of morphological and kinematic optimization is unknown and depends upon a large parameter space. Aimed at providing an accurate and computationally inexpensive modelling tool for flapping-wing aerodynamics, we propose a novel CFD (computational fluid dynamics)-informed quasi-steady model (CIQSM), which assumes that the aerodynamic forces on a flapping wing can be decomposed into quasi-steady forces and parameterized based on CFD results. Using least-squares fitting, we determine a set of proportional coefficients for the quasi-steady model relating wing kinematics to instantaneous aerodynamic force and torque; we calculate power as the product of quasi-steady torques and angular velocity. With the quasi-steady model fully and independently parameterized on the basis of high-fidelity CFD modelling, it is capable of predicting flapping-wing aerodynamic forces and power more accurately than the conventional blade element model (BEM) does. The improvement can be attributed to, for instance, taking into account the effects of the induced downwash and the wing tip vortex on the force generation and power consumption. Our model is validated by comparing the aerodynamics of a CFD model and the present quasi-steady model using the example case of a hovering hawkmoth. This demonstrates that the CIQSM outperforms the conventional BEM while remaining computationally cheap, and hence can be an effective tool for revealing the mechanisms of optimization and control of kinematics and morphology in flapping-wing flight for both bio-flyers and unmanned aerial systems

Simulation of Flapping-wing Unmanned Aerial Vehicle using X-plane and Matlab/Simulink

This paper presents the simulation of flapping-wing unmanned aerial vehicle model using X-plane and Matlab/ Simulink. The flapping-wing ornithopter model (i.e. an aircraft that flies by flapping its wings) has been developed in plane maker software and executed in the X-plane environment. The key idea of flapping-wing mechanism in X-plane software is by varying its dihedral angle sinusoidally. This sinusoidally varying dihedral angle of wing creates upward and downward stroke moments inturn this creates a lift and a forward thrust for flying the flapping-wing model. Here pitch, roll, yaw and throttle (flapping rate) is fed as reference input through the user datagram protocol (UDP) port. The difference between the reference inputs, the simulated outputs are again fed back to simulator through UDP port and the gains are observed for the responses of flapping-wing unmanned aerial vehicle in Matlab/Simulink environment. Here various gains are used to monitor the optimized flying of flapping-wing model.Defence Science Journal, Vol. 64, No. 4, July 2014, pp.327-331, DOI:http://dx.doi.org/10.14429/dsj.64.493

The GRIFFIN perception dataset: Bridging the gap between flapping-wing flight and robotic perception

The development of automatic perception systems and techniques for bio-inspired flapping-wing robots is severely hampered by the high technical complexity of these platforms and the installation of onboard sensors and electronics. Besides, flapping-wing robot perception suffers from high vibration levels and abrupt movements during flight, which cause motion blur and strong changes in lighting conditions. This letter presents a perception dataset for bird-scale flapping-wing robots as a tool to help alleviate the aforementioned problems. The presented data include measurements from onboard sensors widely used in aerial robotics and suitable to deal with the perception challenges of flapping-wing robots, such as an event camera, a conventional camera, and two Inertial Measurement Units (IMUs), as well as ground truth measurements from a laser tracker or a motion capture system. A total of 21 datasets of different types of flights were collected in three different scenarios (one indoor and two outdoor). To the best of the authors' knowledge this is the first dataset for flapping-wing robot perceptionConsejo Europeo de Investigación 788247ARM-EXTEND DPI2017-8979-

Validating an Open-Source UVLM Solver for Analyzing Flapping Wing Flight

Scientists have long used the unsteady vortex lattice method (UVLM) to simulate flapping wing flight. However, until recently, there has not been an available open-source UVLM solver designed explicitly for this field. Ptera Software is the only open-source UVLM solver that can simulate flapping wing aerodynamics without the modifications required by other open-source solvers. This report documents the next step in the software’s development: validation of its results. Comparing Ptera Software’s output to high-fidelity experimental data of the pressures on a flapping wing robot shows that the simulated results predict the trends and magnitudes of the net lift over time with good accuracy. The present results demonstrate that Ptera Software correctly implements the UVLM and can simulate flapping wing flight with reasonable accuracy under this method’s assumptions

Unsteady aerodynamic model of flexible flapping wing

Bio-inspired flapping wing has potential application to micro air vehicles (MAV). Due to the nature of lightweight and flexibility of micro flapping wing structures, elastic deformation as a result of aeroelastic coupling is inevitable in flapping motion. This effect can be significant and beneficial to the aerodynamic performance as revealed in the present investigation for a flexible flapping wing of variable camber versus a rigid one. Firstly a two dimensional (2D) unsteady aerodynamic model (UAM) based on potential flow theory has been extended from previous study. Both leading and trailing edge discrete vortices are included in the model with unsteady Kutta condition satisfied to fully characterize the unsteady flow around a flapping wing. A wall function is created to modify the induced velocity of the vortices in the UAM to solve the vortices penetration problem. The modified UAM is then validated by comparing with CFD results of a typical insect-like flapping motion from previous research. Secondly the UAM is further extended for a flexible flapping wing of camber variation. Comparing with a rigid wing in a prescribed plunging and pitching motion, the results show lift increase with positive camber in upstroke by mitigating negative lift. The results also agree well with CFD simulation. Thirdly the 2D UAM is extended to calculate the aerodynamic forces of a 3D wing with camber variation, and validated by CFD results. Finally the model is applied to aerodynamic analysis of a 3D flexible flapping wing with aeroelastic coupling effect. Significant increase of lift coefficient can be achieved for a flexible flapping wing of positive camber and twist in upstroke produced by the structure elastic deformation

Bioinspired low-noise wing design for a two-winged flapping-wing micro air vehicle

This work investigates the acoustic and thrust performances of different wing designs for a two-winged flapping-wing micro air vehicle (FW-MAV). The reference wings, made of a Mylar film membrane supported by carbon-fiber rods, produce a perceived overall noise of about 68.8 dBA when operating at the flapping frequency of 10 Hz typically required for flying such a flapping wing vehicle. This noise is much higher than the value of the environmental background. Wings of various materials and structural configurations are designed and tested in order to reduce the flapping-wing noise. Sound and force measurements are used to assess their acoustic and lift capabilities. It is found that a wing made with a highly elastic dielectric elastomer membrane can reduce the overall perceived noise of the flapping wing by 12 dBA while slightly increasing the thrust. The mechanisms leading to this noise reduction and their potential applications in quiet FW-MAVs are discussed

Efficacy of Flapping-wing Flight Via Dual Piezoelectric Actuation

A novel piezoelectric-actuated wing system featuring dual actuators for increased wing control is presented and evaluated for its forward-flight characteristics via theoretical modeling and physical wind tunnel testing. Flapping wing aerial systems serve as a middle ground between the traditional fixed-wing and rotary systems. Flapping wing aerial systems exhibit high maneuverability and stability at low speeds (like rotary systems) while maintaining increased efficiency (like fixed-wing systems). Flapping wings also eliminate the necessity of dangerous fast-moving propellers and open the door to actuation mechanisms other than traditional motors. This research explores one of these alternatives: the piezoelectric bending actuator. Piezoelectric materials produce a mechanical strain when an electric charge is applied. With an applied sinusoidal voltage, cantilevered bending piezoelectric actuators create oscillatory motion at the free end that can be translated into wing movement much more directly than a rotational motor. This direct actuation eliminates the need for gears and provides a mechanism for reducing the system\u27s weight. Furthermore, the simplified mechanism can improve robustness by removing contact surfaces that can become clogged or worn (e.g., using gears). While piezoelectric flapping-wing flight has many potential benefits, the combination has only been explored in insect-inspired hovering flight. This work explores the feasibility of larger, forward-flight systems to identify a framework for piezoelectrically-driven flapping-wing vehicles with wing-bending control. Theoretical and experimental analysis methods are presented to study piezoelectric flapping wing motion characteristics for lift and drag effects in flapping-wing aerial systems

A Comparison between Frame-based and Event-based Cameras for Flapping-Wing Robot Perception

Perception systems for ornithopters face severe challenges. The harsh vibrations and abrupt movements caused during flapping are prone to produce motion blur and strong lighting condition changes. Their strict restrictions in weight, size, and energy consumption also limit the type and number of sensors to mount onboard. Lightweight traditional cameras have become a standard off-the-shelf solution in many flapping-wing designs. However, bioinspired event cameras are a promising solution for ornithopter perception due to their microsecond temporal resolution, high dynamic range, and low power consumption. This paper presents an experimental comparison between frame-based and an event-based camera. Both technologies are analyzed considering the particular flapping-wing robot specifications and also experimentally analyzing the performance of well-known vision algorithms with data recorded onboard a flapping-wing robot. Our results suggest event cameras as the most suitable sensors for ornithopters. Nevertheless, they also evidence the open challenges for event-based vision on board flapping-wing robots

Experimental method for perching flapping-wing aerial robots

In this work, we present an experimental setup and guide to enable the perching of large flapping-wing robots. The combination of forward flight, limited payload, and flight oscillations imposes challenging conditions for localized perching. The described method details the different operations that are concurrently performed within the 4 second perching flight. We validate this experiment with a 700 g ornithopter and demonstrate the first autonomous perching flight of a flapping-wing robot on a branch. This work paves the way towards the application of flapping-wing robots for long-range missions, bird observation, manipulation, and outdoor flight.Comment: IROS 2022 Workshop: Agile Robotics: Perception, Learning, Planning, and Control, 202