A Hybrid Dynamic Model Of An Insect-Like MAV With Soft Wings

International audienceThis paper presents a hybrid dynamic model of a 3-D aerial insect-like robot. The soft-bodied insect wings modeling is based on a continuous version of the Newton-Euler dynamics where the leading edge is treated as a continuous Cosserat beam. These wings are connected to an insect's rigid thorax using a discrete recursive algorithm based on the Newton-Euler equations. Here we detail the inverse dynamic model algorithm. This version of the dynamic model solves the following two problems involved in any locomotion task: 1◦) it enables the net motion of a reference body to be computed from the known data of internal motions (strain fields); 2◦) it gives the internal torques required to impose these internal (strain fields) motions. The essential fluid effects have been taken into account using a simplified analytical hovering flight aerodynamic model. To facilitate the analysis of numerical results, a visualization tool is developed

A hybrid dynamic model for bio-inspired soft robots - Application to a flapping-wing micro air vehicle.

International audienceThe paper deals with the dynamic modeling of bio-inspired robots with soft appendages such as flying insect-like or swimming fish-like robots. In order to model such soft systems, we propose to use the Mobile Multibody System framework introduced in [1][2][3]. In such a framework, the robot is considered as a tree-like structure of rigid bodies where the evolution of the position of the joints is governed by stress-strain laws or control torques. Based on the Newton-Euler formulation of these systems, we propose a new algorithm able to compute at each step of a time loop both the net and passive joint accelerations along with the control torques supplied by the motors. To illustrate, based on previous work [4], the proposed algorithm is applied to the simulation of the hovering flight of a soft flapping-wing insect-like robot (see the attached video)

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

Investigation of Aerodynamics of Flapping Wings for Miro Air Vehicle Applications

A coupled CFD-CSD solver was used to simulate the aerodynamics of a flexible flapping wing. The CFD solver is a compressible RANS (Reynolds Averaged Navier Stokes) solver. Multibody dynamics solver `MBDyn', was used as the structural solver to take into account non linear shell straining, making it possible to analyze low aspect ratio wings with large deformations. Validation of the two codes was carried out independently. The solvers were then coupled using python and validated against prior experiments and analysis on spanwise and chordwise flexible wings. As realistic MAV wings are extremely flexible and lightweight, under the effect of high inertial and aerodynamic forces, they undergo large non linear deformations over a flap cycle. However, there is a dearth of experimental data on well characterized flapping wings (with known structural and mass properties) at MAV-scale Reynolds numbers. Systematic experiments were carried out on rigid and flexible flapping wings in an open jet wind tunnel and forces were measured using a test bed. Pure flapping of rigid wings did not generate sufficient propulsive force and may not be a viable configuration. Passive pitching of rigid wing generated both, target vertical and propulsive forces. Dynamic wing twist was then incorporated using flexible wings. A flexible wing was fabricated using a combination of unidirectional carbon fiber strips (chordwise ribs), carbon rod (leading edge spar) and mylar film (membrane). Structural model of the wing (combination of beam and shell elements) was developed and then coupled to the CFD model. CFD-CSD analysis of flexible wing was carried out and good correlation was obtained for all the configurations. This comprehensive experimental data set can also be used to validate other aeroelastic analyses of the future. Further, the analysis was used to gain more insights into flow physics. It was observed that as a result of flexibility, by taking advantage of unsteady flow features, a lighter, simpler mechanism could be used to produce larger forces than a rigid wing. The validated, comprehensive analysis developed in this work may serve as a design tool for deciding configurations and wing kinematics of next generation MAVs

The Characterization of Material Properties and Structural Dynamics of the Manduca Sexta Forewing for Application to Flapping Wing Micro Air Vehicle Design

The Manduca Sexta species of moth serves as a source of biological inspiration for the future of micro air vehicle flapping flight. The ability of this species to hover in flapping flight has warranted investigation into the critical material, structural, and geometric properties of the forewing of this biological specimen. A rigorous morphological study of the Manduca Sexta forewing was conducted to characterize the physical and material properties of the biological forewing for the purpose of developing an advanced parametric three dimensional model finite element analysis (FEA) model. This FEA model was tuned to match the experimentally determined structural dynamics of the biological specimen and serves as the basis for an engineered wing design. Manufacturing methods are developed and implemented to fabricate the baseline engineered wing design. Biological wings and engineered wings are experimentally tested to determine the aerodynamic lift production of each of wings under the same boundary conditions. Through this research, a structural dynamics based engineering methodology has been used to design, develop, and identify biomimetic engineered wings that experimentally produce aerodynamic forces equivalent to their biological analog

Micro-Scale Flapping Wings for the Advancement of Flying MEMS

This research effort presents conceptual micro scale air vehicles whose total dimensions are less than one millimeter. The initial effort was to advance the understanding of micro aerial vehicles at sub-millimeter dimensions by fabricating and testing micro scale flapping wings. Fabrication was accomplished using a surface micromachining process called PolyMUMPs™. Both rigid mechanical structures and biomimetic devices were designed and fabricated as part of this effort. The rigid mechanical structures focused on out of plane deflections with solid connections and assembling a multiple hinge wing structure through the aid of residual stress. These devices were actuated by double hot arm thermal actuators. The biomimetic structures derived from three different insect wings to include; the dragonfly, house fly, and butterfly were selected based off of an attribute that each insect possesses in nature. The dragonfly was chosen for its high maneuverability and hovering capabilities. The house fly wing was chosen because of its durability and the butterfly wing was chosen because of its flexibility. The fabricated wings utilize a thermal bimorph structure consisting of polysilicon and gold which allows device actuation through joule heating. The released micro wings had an initial upward deflection due to residual stress between the gold and polysilicon material layers. Joule heating, from an applied bias, forces the wing to deflect downward due to the coefficient of thermal expansion mismatch between the material layers. Each fabricated bio-wing structure was tested for deflection range as well as operating frequency. From the experimental testing of the micro scale flapping bio-wings, aerodynamic values were calculated to include; aspect ratio, reduced frequency in a hover, Reynolds number of a hovering device, drag force, and gravitational force. The research verified insect based wings on the micro scale are capable of producing the desired flapping motion

Design, Manufacture, and Structural Dynamic Analysis of a Biomimetic Insect-Sized Wing for Micro Air Vehicles

The exceptional flying characteristics of airborne insects motivates the design of biomimetic wing structures that can exhibit a similar structural dynamic behavior. For this purpose, this investigation describes a method for both manufacturing a biomimetic insect-sized wing using the photolithography technique and analyzing its structural dynamic response. The geometry of a crane fly forewing (family Tipulidae) is acquired using a micro-computed tomography scanner. A computer-aided design model is generated from the measurements of the reconstructed scanned model of the insect wing to design the photomasks of the membrane and the venation network required for the photolithography procedure. A composite material wing is manufactured by patterning the venation network using photoresist SU-8 on a Kapton film for the assembling of the wing. A single material artificial wing is fabricated using the photoresist SU-8 for both the membrane and the network of veins. Experiments are conducted using a modal shaker and a digital image correlation (DIC) system to determine the natural frequencies and the mode shapes of the artificial wing from the fast Fourier transform of the displacement response of the wing. The experimental results are compared with those from a finite element (FE) model of the wing. A numerical simulation of the fluid-structure interaction is conducted by coupling the FE model of the artificial wing with a computational fluid dynamics model of the surrounding airflow. From these simulations, the deformation response and the coefficients of drag and lift of the artificial wing are predicted for different freestream velocities and angles of attack. Wind-tunnel experiments are conducted using the DIC system to determine the structural deformation response of the artificial wing under different freestream velocities and angles of attack. The vibration modes are dominated by a bending and torsional deformation response. The deformation along the span of the wing increases nonlinearly from the root of the wing to the tip of the wing with Reynolds number. The aerodynamic performance, defined as the ratio of the coefficient of lift to the coefficient of drag, of the artificial wing increases with Reynolds number and angle of attack up to the critical angle of attack

Design, Manufacture, and Structural Dynamic Analysis of a Biomimetic Insect-Sized Wing for Micro Air Vehicles

The exceptional flying characteristics of airborne insects motivates the design of biomimetic wing structures that can exhibit a similar structural dynamic behavior. For this purpose, this investigation describes a method for both manufacturing a biomimetic insect-sized wing using the photolithography technique and analyzing its structural dynamic response. The geometry of a crane fly forewing (family Tipulidae) is acquired using a micro-computed tomography scanner. A computer-aided design model is generated from the measurements of the reconstructed scanned model of the insect wing to design the photomasks of the membrane and the venation network required for the photolithography procedure. A composite material wing is manufactured by patterning the venation network using photoresist SU-8 on a Kapton film for the assembling of the wing. A single material artificial wing is fabricated using the photoresist SU-8 for both the membrane and the network of veins. Experiments are conducted using a modal shaker and a digital image correlation (DIC) system to determine the natural frequencies and the mode shapes of the artificial wing from the fast Fourier transform of the displacement response of the wing. The experimental results are compared with those from a finite element (FE) model of the wing. A numerical simulation of the fluid-structure interaction is conducted by coupling the FE model of the artificial wing with a computational fluid dynamics model of the surrounding airflow. From these simulations, the deformation response and the coefficients of drag and lift of the artificial wing are predicted for different freestream velocities and angles of attack. Wind-tunnel experiments are conducted using the DIC system to determine the structural deformation response of the artificial wing under different freestream velocities and angles of attack. The vibration modes are dominated by a bending and torsional deformation response. The deformation along the span of the wing increases nonlinearly from the root of the wing to the tip of the wing with Reynolds number. The aerodynamic performance, defined as the ratio of the coefficient of lift to the coefficient of drag, of the artificial wing increases with Reynolds number and angle of attack up to the critical angle of attack