Human Memory/Learning Inspired Control Method for Flapping-Wing Micro Air Vehicles

The problem of flapping motion control of Micro Air Vehicles (MAVs) with flapping wings was studied in this paper.Based upon the knowledge of skeletal and muscular components of hummingbird, a dynamic model for flapping wing wasdeveloped.A control scheme inspired by human memory and learning concept was constructed for wing motion control ofMAVs.The salient feature of the proposed control lies in its capabilities to improve the control performance by learning fromexperience and observation on its current and past behaviors, without the need for system dynamic information.Furthermore,the overall control scheme has a fairly simple structure and demands little online computations, making it attractive for real-timeimplementation on MAVs.Both theoretical analysis and computer simulation confirms its effectiveness.

An Improved Evolvable Oscillator and Basis Function Set for Control of an Insect-Scale Flapping-Wing Micro Air Vehicle

This paper introduces an improved evolvable and adaptive hardware oscillator design capable of supporting adaptation intended to restore control precision in damaged or imperfectly manufactured insect-scale flapping-wing micro air vehicles. It will also present preliminary experimental results demonstrating that previously used basis function sets may have been too large and that significantly improved learning times may be achieved by judiciously culling the oscillator search space. The paper will conclude with a discussion of the application of this adaptive, evolvable oscillator to full vehicle control as well as the consideration of longer term goals and requirements.

Modeling and Trajectory Tracking Control for Flapping-Wing Micro Aerial Vehicles

This paper studies the trajectory tracking problem of flapping-wing micro aerial vehicles(FWMAVs)in the longitudinal plane.First of all,the kinematics and dynamics of the FWMAV are established,wherein the aerodynamic force and torque generated by flapping wings and the tail wing are explicitly formulated with respect to the flapping frequency of the wings and the degree of tail wing inclination.To achieve autonomous tracking,an adaptive control scheme is proposed under the hierarchical framework.Specifically,a bounded position controller with hyperbolic tangent functions is designed to produce the desired aerodynamic force,and a pitch command is extracted from the designed position controller.Next,an adaptive attitude controller is designed to track the extracted pitch command,where a radial basis function neural network is introduced to approximate the unknown aerodynamic perturbation torque.Finally,the flapping frequency of the wings and the degree of tail wing inclination are calculated from the designed position and attitude controllers,respectively.In terms of Lyapunov's direct method,it is shown that the tracking errors are bounded and ultimately converge to a small neighborhood around the origin.Simulations are carried out to verify the effectiveness of the proposed control scheme.

Micro air vehicle-motivated computational biomechanics in bio-flights:aerodynamics,flight dynamics and maneuvering stability

Aiming at developing an effective tool to unveil key mechanisms in bio-flight as well as to provide guidelines for bio-inspired micro air vehicles（MAVs） design,we propose a comprehensive computational framework,which integrates aerodynamics,flight dynamics,vehicle stability and maneuverability.This framework consists of（1） a Navier-Stokes unsteady aerodynamic model;（2） a linear finite element model for structural dynamics;（3） a fluidstructure interaction（FSI） model for coupled flexible wing aerodynamics aeroelasticity;（4） a free-flying rigid body dynamic（RBD） model utilizing the Newtonian-Euler equations of 6DoF motion;and（5） flight simulator accounting for realistic wing-body morphology,flapping-wing and body kinematics,and a coupling model accounting for the nonlinear 6DoF flight dynamics and stability of insect flapping flight.Results are presented based on hovering aerodynamics with rigid and flexible wings of hawkmoth and fruitfly.The present approach can support systematic analyses of bio- and bio-inspired flight.

Model Identification of a Micro Air Vehicle

This paper is focused on the model identification of a Micro Air Vehicle （MAV） in straight steady flight condition. The identification is based on input-output data collected from flight tests using both frequency and time dorrtain techniques. The vehicle is an in-house 40 cm wingspan airplane. Because of the complex coupled, multivariable and nonlinear dynamics of the aircraft, linear SISO structures for both the lateral and longitudinal models around a reference state were derived. The aim of the identification is to provide models that can be used in future development of control techniques for the MAV.

Piezoelectric energy harvesting from morphing wing motions for micro air vehicles

Wing flapping and morphing can be very beneficial to managing the weight of micro air vehicles through coupling the aerodynamic forces with stability and control. In this letter, harvesting energy from the wing morphing is studied to power cameras, sensors, or communication devices of micro air vehicles and to aid in the management of their power. The aerodynamic loads on flapping wings are simulated using a three-dimensional unsteady vortex lattice method. Active wing shape morphing is considered to enhance the performance of the flapping motion. A gradient-based optimization algorithm is used to pinpoint the optimal kinematics maximizing the propellent efficiency. To benefit from the wing deformation, we place piezoelectric layers near the wing roots. Gauss law is used to estimate the electrical harvested power. We demonstrate that enough power can be generated to operate a camera. Numerical analysis shows the feasibility of exploiting wing morphing to harvest energy and improving the design and performance of micro air vehicles.

Development of the NWPU20 Micro Air Vehicle

This paper reports the design, construction, and operation of NWPU20 Micro Air Vehicle (MAV), which is the smallest that has, up to now, been developed in PR China. The miniaturization level in PR China makes smaller MAV, in our opinion, not possible to implement. The NWPU20 is a 20-centimeter span, battery powered, fixed-wing aircraft with an off-the-shelf color video camera that can transmit live video back to the ground station. The on-board electronic subsystems are smallest and lightest among the commercial products, including an 8-gram wireless video camera, an 8-gram receiver, a 5-gram electronic speed controller (ESC), two 4.5-gram fully proportional radio frequency control servos, and the total mass of NWPU20 is less than 80 grams. An experimental model was fabricated and tested in the Low Turbulent Flow Wind Tunnel (LTFWT) at Northwestern Polytechnical University (NWPU) to research low Reynolds number flow characteristics of the NWPU20. The result of the wind tunnel test shows that stall angle of attack of NWPU20 can reach 30°, which is higher than that of the general aircrafts, and the maximum lift-to-drag ratio of NWPU20 can nearly reach 6 at the angle of attack of 10°, which can satisfy design requirements of the NWPU20. A small-sized propulsion/torque testing system was developed to measure and analyze the propulsion and torque performances of the motor-propeller combination used in the NWPU20. A center of gravity (c.g.) testing apparatus was developed and used to adjust the c.g. of the NWPU20 so that it has good longitudinal static stability and control. The NWPU20 prototype has undergone successfully flight tests many times; it flies at 32 kilometers per hour, with an endurance of 15 minutes, and a maximum communications range of 300 meters. With the color video camera, NWPU20 successfully transmits real-time video back to the ground station. The success of NWPU20 proves preliminarily that 20-centimeter span micro air vehicle is feasible and usable.

Kinematic and Aerodynamic Modelling of Bi- and Quad-Wing Flapping Wing Micro-Air-Vehicle

A generic approach to model the kinematics and aerodynamics of flapping wing ornithopter has been followed, to model and analyze a flapping bi- and quad-wing ornithopter and to mimic flapping wing biosystems to produce lift and thrust for hovering and forward flight. Considerations are given to the motion of a rigid and thin bi-wing and quad-wing ornithopter in flapping and pitching motion with phase lag. Basic Unsteady Aerodynamic Approach incorporating salient features of viscous effect and leading-edge suction are utilized. Parametric study is carried out to reveal the aerodynamic characteristics of flapping bi- and quad-wing ornithopter flight characteristics and for comparative analysis with various selected simple models in the literature, in an effort to develop a flapping bi- and quad-wing ornithopter models. In spite of their simplicity, results obtained for both models are able to reveal the mechanism of lift and thrust, and compare well with other work.

Low-Power Operational Amplifier for Real-Time Signal Processing System of Micro Air Vehicle

A low-power complementary metal oxide semiconductor（CMOS） operational amplifier （op-amp） for real-time signal processing of micro air vehicle （MAV） is designed in this paper.Traditional folded cascode architecture with positive channel metal oxide semiconductor（PMOS） differential input transistors and sub-threshold technology are applied under the low supply voltage.Simulation results show that this amplifier has significantly low power,while maintaining almost the same gain,bandwidth and other key performances.The power required is only 0.12 mW,which is applicable to low-power and low-voltage real-time signal acquisition and processing system.

Obstacle Avoidance of Flapping⁃Wing Air Vehicles Based on Optical Flow and Fuzzy Control

The flapping-wing air vehicle(FWAV)is a kind of bio-inspired robot whose wings can flap up and down like bird and insect wings.A vision-based obstacle avoidance method for FWAVs is proposed in this paper.First,the Farneback algorithm is used to calculate the optical flow field of the first-view video frames taken by the on-board image transmission camera.Based on the optical flow information,a fuzzy obstacle avoidance controller is then designed to generate the FWAV steering commands.Experimental results show that the proposed obstacle avoidance method can accurately identify obstacles and achieve obstacle avoidance for FWAVs.

Development of Air Vehicle with Active Flapping and Twisting of Wing

This paper addresses mechanisms for active flapping and twisting of robotic wings and assesses flying effectiveness as a function of twist angle. Unlike the flapping motion of bird wings, insects generally make a twisting motion at the root of their wings while flapping, which makes it possible for them to hover in midair. This work includes the development of a Voice Coil Motor （VCM） because a flapping-wing air vehicle should be assembled with a compact actuator to decrease size and weight. A linkage mechanism is proposed to transform the linear motion of the VCM into the flapping and twisting motions of wings. The assembled flapping-wing air vehicle, whose weight is 2.86 g, produces an average positive vertical force proportional to the twist angle. The force saturates because the twist angle is mechanically limited. This work demonstrates the possibility of developing a flapping-wing air vehicle that can hover in midair using a mechanism that actively twists the roots of wings during flapping.

IMPROVED UVLM FOR FLAPPING-WING AERODYNAMICS COMPUTATION

To calculate the aerodynamics of flapping-wing micro air vehicle（MAV） with the high efficiency and the engineering-oriented accuracy,an improved unsteady vortex lattice method （UVLM） for MAV is proposed. The method considers the influence of instantaneous wing deforming in flapping,as well as the induced drag,additionally models the stretching and the dissipation of vortex rings,and can present the aerodynamics status on the wing surface. An implementation of the method is developed. Moreover,the results and the efficiency of the proposed method are verified by CFD methods. Considering the less time cost of UVLM,for application of UVLM in the MAV optimization,the influence of wake vortex ignoring time saving and precision is studied. Results show that saving in CPU time with wake vortex ignoring the appropriate distance is considerable while the precision is not significantly reduced. It indicates the potential value of UVLM in the optimization of MAV design.

Generation of Control Moments in an Insect-like Tailless Flapping-wing Micro Air Vehicle by Changing the Stroke-plane Angle

We propose a control moment generator to control the attitude of an insect-like tailless Flapping-wing Micro Air Vehicle （FW-MAV）, where the flapping wings simultaneously produce the flight force and control moments. The generator tilts the stroke plane of each wing independently to direct the resultant aerodynamic force in the desired direction to ultimately generate pitch and yaw moments. A roll moment is produced by an additional mechanism that shifts the trailing edge, which changes the wing rotation angles of the two flapping wings and produces an asymmetric thrust. Images of the flapping wings are captured with a high-speed camera and clearly show that the FW-MAV can independently change the stroke planes of its two wings. The measured force and moment data prove that the control moment generator produces reasonable pitch and yaw moments by tilting the stroke plane and realizes a roll moment by shifting the position of the trailing edge at the wing root.

Passive attitude stabilization of ionic-wind-powered micro air vehicles

The ionic-wind-powered Micro Air Vehicles(MAVs)can achieve a higher thrust-toweight ratio than other MAVs.However,this kind of MAV has not yet achieved controlled flight because of the unstable thrust produced by the ionic wind and the dynamic instability related to the small size.In this paper,a passive attitude stabilization method of the ionic-wind-powered MAV using air dampers is introduced.The key factors that influence the performance of the air dampers,including the layout,position,and area of the air dampers,are theoretically studied.The appropriate optimal position of the air dampers is also obtained by Monte Carlo stochastic simulations.Then the proposed passive attitude stabilization method is applied to the ionic-wind-powered MAVs of different wingspan(2 cm and 6.3 cm).Finally,the experimental results show that using the proposed method,attitude stabilization is achieved for the first time for the ionic-wind-powered MAV.Moreover,the altitude control of an ionic-wind-powered MAV with a wingspan of 6.3 cm is also demonstrated.

Topology optimization in lightweight design of a 3D-printed flapping-wing micro aerial vehicle

Topology optimization is an effective method to obtain a lightweight structure that meets the requirements of structural strength.Whether the optimization results meet the actual needs mainly depends on the accuracy of the material properties and the boundary conditions,especially for a tiny Flapping-wing Micro Aerial Vehicle(FMAV)transmission system manufactured by 3D printing.In this paper,experimental and numerical computation efforts were undertaken to gain a reliable topology optimization method for the bottom of the transmission system.First,the constitutive behavior of the ultraviolet(UV)curable resin used in fabrication was evaluated.Second,a numerical computation model describing further verified via experiments.Topology optimization modeling considering nonlinear factors,e.g.contact,friction and collision,was presented,and the optimization results were verified by both dynamic simulation and experiments.Finally,detailed discussions on different load cases and constraints were presented to clarify their effect on the optimization.Our methods and results presented in this paper may shed light on the lightweight design of a FMAV.

仿绿头鸭扑翼飞行器的低速飞行气动特性仿真研究

针对仿绿头鸭扑翼飞行器,在刚性扑动基础上引入了展向弯折和弦向扭转两种运动方式,提出了4种不同扑动路径的描述方程,并对其低速飞行气动特性进行了研究。首先,根据绿头鸭翼翅外形选择NACA 6411翼型并对其弯度和长度进行修正,通过放样创建扑翼几何构型。之后,基于动网格技术构建扑翼流场网格模型,包含刚性扑动、机翼弯折和机翼扭转等3种不同扑动形态。最后,使用Fluent进行瞬态仿真,基于压力耦合求解器和k-ω湍流模型得到不同扑动形态下飞行速度为2 m/s时的气动特性。结果表明,在低速飞行时,非对称扑动效应、展向弯折效应和弦向扭转效应均可起到增加升力、降低阻力的效果。所提出的3个扑动模型相对传统的对称刚性扑动模型分别能提高3.89%、14.78%、24.44%的升力,其中弯扭组合形式的扑动提供的推力能够抵消前飞时的空气阻力。

道路交通排放对周边环境影响的分析——以兰州市安宁区学府路为例

探究城市道路中机动车污染物的排放对周边环境的影响,对环境治理起着至关重要的作用。通常通过分析污染物的影响因素,来建立排放模型。根据研究尺度的不同,将应用较广泛的模型进行划分,并对模型原理、应用及存在不足等方面进行归纳和总结。为了探究学府路道路污染状况,选取COPERT模型进行污染物排放量的测算,并使用ANSYS软件模拟了道路交通排放对学府路周边环境的影响,得出了污染物地图。结果表明:学府路工作日内4项主要大气污染物NO_(2)、CO、PM_(2.5)、PM_(10)排放量分别为67.7、269.1、15.1和22.8 t。数量占10.0%的轻型货车排放贡献较大,分别占机动车NO_(2)和PM排放总量的50.5%和69.1%。通过模拟值与实测值的对比发现,COPERT模型对于中观尺度的研究具有较好的支撑。

Flight mechanism and design of biomimetic micro air vehicles

This paper summaries the investigations on natural flyers and development of bio-mimetic micro air vehicles(MAVs)at NUAA,China,where the authors have led a group to conduct research for a decade. The investigations include the studies of low Reynolds number aerodynamics,unsteady computational fluid dynamics and flight control for the fixed-wing MAVs,the bird-like MAVs,the dragonfly-like MAVs and the bee-like MAVs.

An experimental study of elastic properties of dragonfly-like flapping wings for use in biomimetic micro air vehicles(BMAVs)

This article studies the elastic properties of several biomimetic micro air vehicle（BMAV）wings that are based on a dragonfly wing.BMAVs are a new class of unmanned micro-sized air vehicles that mimic the flapping wing motion of flying biological organisms（e.g.,insects,birds,and bats）.Three structurally identical wings were fabricated using different materials：acrylonitrile butadiene styrene（ABS）,polylactic acid（PLA）,and acrylic.Simplified wing frame structures were fabricated from these materials and then a nanocomposite film was adhered to them which mimics the membrane of an actual dragonfly.These wings were then attached to an electromagnetic actuator and passively flapped at frequencies of 10-250 Hz.A three-dimensional high frame rate imaging system was used to capture the flapping motions of these wings at a resolution of 320 pixels x 240 pixels and 35000 frames per second.The maximum bending angle,maximum wing tip deflection,maximum wing tip twist angle,and wing tip twist speed of each wing were measured and compared to each other and the actual dragonfly wing.The results show that the ABS wing has considerable flexibility in the chordwise direction,whereas the PLA and acrylic wings show better conformity to an actual dragonfly wing in the spanwise direction.Past studies have shown that the aerodynamic performance of a BMAV flapping wing is enhanced if its chordwise flexibility is increased and its spanwise flexibility is reduced.Therefore,the ABS wing（fabricated using a 3D printer） shows the most promising results for future applications.

Structural Characteristics of Allomyrina Dichotoma Beetle＇s Hind Wings for Flapping Wing Micro Air Vehicle

In this study, we present a complete structural analysis ofAllomyrina dichotoma beetle＇s hind wings by investigating their static and dynamic characteristics. The wing was subjected to the static loading to determine its overall flexural stiffness. Dy- namic characteristics such as natural frequency, mode shape, and damping ratio of vibration modes in the operating frequency range were determined using a Bruel ＆ Kjaer fast Fourier transform analyzer along with a laser sensor. The static and dynamic characteristics of natural Allomyrina dichotoma beetle＇s hind wings were compared to those of a fabricated artificial wing. The results indicate that natural frequencies of the natural wing were significantly correlated to the wing surface area density that was defined as the wing mass divided by the hind wing surface area. Moreover, the bending behaviors of the natural wing and artificial wing were similar to that of a cantilever beam. Furthermore, the flexural stiffness of the artificial wing was a little higher than that of the natural one whereas the natural frequency of the natural wing was close to that of the artificial wing. These results provide important information for the biomimetic design of insect-scale artificial wings, with which highly ma- neuverable and efficient micro air vehicles can be designed.