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1
Ashford, David. "High speed commercial flight." Space Policy 6, no. 1 (February 1990): 75. http://dx.doi.org/10.1016/0265-9646(90)90010-u.
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Schiffner, Ingo, and Mandyam V. Srinivasan. "Budgerigar flight in a varying environment: flight at distinct speeds?" Biology Letters 12, no. 6 (June 2016): 20160221. http://dx.doi.org/10.1098/rsbl.2016.0221.
Повний текст джерелаАнотація:
How do flying birds respond to changing environments? The behaviour of budgerigars, Melopsittacus undulatus , was filmed as they flew through a tapered tunnel. Unlike flying insects—which vary their speed progressively and continuously by holding constant the optic flow induced by the walls—the birds showed a tendency to fly at only two distinct, fixed speeds. They switched between a high speed in the wider section of the tunnel, and a low speed in the narrower section. The transition between the two speeds was abrupt, and anticipatory. The high speed was close to the energy-efficient, outdoor cruising speed for these birds, while the low speed was approximately half this value. This is the first observation of the existence of two distinct, preferred flight speeds in birds. A dual-speed flight strategy may be beneficial for birds that fly in varying environments, with the high speed set at an energy-efficient value for flight through open spaces, and the low speed suited to safe manoeuvring in a cluttered environment. The constancy of flight speed within each regime enables the distances of obstacles and landmarks to be directly calibrated in terms of optic flow, thus facilitating simple and efficient guidance of flight through changing environments.
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McDuie, Fiona, Michael L. Casazza, David Keiter, Cory T. Overton, Mark P. Herzog, Cliff L. Feldheim, and Joshua T. Ackerman. "Moving at the speed of flight: dabbling duck-movement rates and the relationship with electronic tracking interval." Wildlife Research 46, no. 6 (2019): 533. http://dx.doi.org/10.1071/wr19028.
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Abstract Context Effective wildlife management requires information on habitat and resource needs, which can be estimated with movement information and modelling energetics. One necessary component of avian models is flight speeds at multiple temporal scales. Technology has limited the ability to accurately assess flight speeds, leading to estimates of questionable accuracy, many of which have not been updated in almost a century. Aims We aimed to update flight speeds of ducks, and differentiate between migratory and non-migratory flight speeds, a detail that was unclear in previous estimates. We also analysed the difference in speeds of migratory and non-migratory flights, and quantified how data collected at different temporal intervals affected estimates of flight speed. Methods We tracked six California dabbling duck species with high spatio-temporal resolution GPS–GSM transmitters, calculated speeds of different flight types, and modelled how estimates varied by flight and data interval (30min to 6h). Key results Median migratory speeds were faster (but non-significant) for the larger mallard (Anas platyrhynchos; 82.5kmh–1), northern pintail (Anas acuta; 79.0kmh–1) and gadwall (Mareca strepera; 70.6kmh–1), than the smaller-bodied northern shoveler (Spatula clypeata; 65.7kmh–1), cinnamon teal (Spatula cyanoptera; 63.5kmh–1) and American wigeon (Mareca Americana; 52kmh–1). Migratory flights were faster than non-migratory flights for all species and speeds were consistently slower with an increasing data interval. Implications The need to balance time and energy requirements may drive different speeds for migratory and non-migratory flights. Lower speeds at longer intervals are likely to be due to a greater proportion of ‘loafing’ time included in flighted segments, demonstrating that data acquired at different intervals provide a means to evaluate and estimate behaviours that influence speed estimation. Shorter-interval data should be the most accurate, but longer-interval data may be easier to collect over lengthier timeframes, so it may be expedient to trade-off a degree of accuracy in broad-scale studies for the larger dataset. Our updated flight speeds for dabbling duck species can be used to parameterise and validate energetics models, guide management decisions regarding optimal habitat distribution, and, ultimately, improve conservation management of wetlands for waterfowl.
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Barrett-Gonzalez, Ronald, and Nathan Wolf. "High Speed Microactuators for Low Aspect Ratio High Speed Micro Aircraft Surfaces." Actuators 10, no. 10 (October 13, 2021): 265. http://dx.doi.org/10.3390/act10100265.
Повний текст джерелаАнотація:
This paper covers a class of actuators for modern high speed, high performance subscale aircraft. The paper starts with an explanation of the challenges faced by micro aircraft, including low power, extremely tight volume constraints, and high actuator bandwidth requirements. A survey of suitable actuators and actuator materials demonstrates that several classes of piezoceramic actuators are ideally matched to the operational environment. While conventional, linear actuation of piezoelectric actuators can achieve some results, dramatic improvements via reverse-biased spring mechanisms can boost performance and actuator envelopes by nearly an order of magnitude. Among the highest performance, low weight configurations are post-buckled precompressed (PBP) actuator arrangements. Analytical models display large deflections at bandwidths compatible with micro aircraft flight control speed requirements. Bench testing of an example PBP micro actuator powered low aspect ratio flight control surface displays +/−11° deflections through 40 Hz, with no occupation of volume within the aircraft fuselage and good correlation between theory and experiment. A wind tunnel model of an example high speed micro aircraft was fabricated along with low aspect ratio PBP flight control surfaces, demonstrating stable deflection characteristics with increasing speed and actuator bandwidths so high that all major aeromechanical modes could be easily controlled. A new way to control such a PBP stabilator with a Limit Dynamic Driver is found to greatly expand the dynamic range of the stabilator, boosting the dynamic response of the stabilator by more than a factor of four with position feedback system engaged.
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Melo, Gabriel Adriano, Marcos Maximo, and Paulo Andre Castro. "High Speed Marker Tracking for Flight Tests." IEEE Latin America Transactions 20, no. 10 (October 2022): 2237–43. http://dx.doi.org/10.1109/tla.2022.9885171.
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Loquercio, Antonio, Alessandro Saviolo, and Davide Scaramuzza. "AutoTune: Controller Tuning for High-Speed Flight." IEEE Robotics and Automation Letters 7, no. 2 (April 2022): 4432–39. http://dx.doi.org/10.1109/lra.2022.3146897.
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Clay, Christopher L. "High Speed Flight Vehicle Structures: An Overview." Journal of Aircraft 41, no. 5 (September 2004): 978–85. http://dx.doi.org/10.2514/1.3880.
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Tucker, Alistair. "High speed commercial flight — The coming era." Tourism Management 9, no. 2 (June 1988): 176–77. http://dx.doi.org/10.1016/0261-5177(88)90032-5.
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Chen, Shuxing. "High Speed Flight and Partial Differential Equations." Chinese Annals of Mathematics, Series B 43, no. 5 (September 2022): 855–68. http://dx.doi.org/10.1007/s11401-022-0363-0.
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Cheney, Jorn A., Jonathan P. J. Stevenson, Nicholas E. Durston, Masateru Maeda, Jialei Song, David A. Megson-Smith, Shane P. Windsor, James R. Usherwood, and Richard J. Bomphrey. "Raptor wing morphing with flight speed." Journal of The Royal Society Interface 18, no. 180 (July 2021): 20210349. http://dx.doi.org/10.1098/rsif.2021.0349.
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In gliding flight, birds morph their wings and tails to control their flight trajectory and speed. Using high-resolution videogrammetry, we reconstructed accurate and detailed three-dimensional geometries of gliding flights for three raptors (barn owl, Tyto alba ; tawny owl, Strix aluco , and goshawk, Accipiter gentilis ). Wing shapes were highly repeatable and shoulder actuation was a key component of reconfiguring the overall planform and controlling angle of attack. The three birds shared common spanwise patterns of wing twist, an inverse relationship between twist and peak camber, and held their wings depressed below their shoulder in an anhedral configuration. With increased speed, all three birds tended to reduce camber throughout the wing, and their wings bent in a saddle-shape pattern. A number of morphing features suggest that the coordinated movements of the wing and tail support efficient flight, and that the tail may act to modulate wing camber through indirect aeroelastic control.
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Wu, Ying, Yun Xie, Sen Li, and Depei Wang. "Stable High-Speed Quadrotor Flight using Differential Trajectory." Mathematical Problems in Engineering 2021 (January 8, 2021): 1–11. http://dx.doi.org/10.1155/2021/9825790.
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This paper addresses the trajectory tracking control issue of a quadrotor with environmental disturbances, which particularly focuses on attitude correction during flight and response speed improvement. In this paper, the proposed control method uses the differential equation to transform the desired trajectory for improving the robustness of a quadrotor during high-speed flight. Meanwhile, a nonlinear controller based on the rotation matrix is designed to avoid singularities of Euler angles. The controller can also stabilize the position error to zero without reducing the control thrust when the attitude error is large. Finally, we conduct simulations on a tethered quadrotor to achieve high-speed flight in limited space. The simulation results show that the control method can stabilize a quadrotor at high-speed trajectory flight and keep a quadrotor stable when it is disturbed by aerodynamic drag and mass change.
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Wu, Ying, Yun Xie, Sen Li, and Depei Wang. "Stable High-Speed Quadrotor Flight using Differential Trajectory." Mathematical Problems in Engineering 2021 (January 8, 2021): 1–11. http://dx.doi.org/10.1155/2021/9825790.
Повний текст джерелаАнотація:
This paper addresses the trajectory tracking control issue of a quadrotor with environmental disturbances, which particularly focuses on attitude correction during flight and response speed improvement. In this paper, the proposed control method uses the differential equation to transform the desired trajectory for improving the robustness of a quadrotor during high-speed flight. Meanwhile, a nonlinear controller based on the rotation matrix is designed to avoid singularities of Euler angles. The controller can also stabilize the position error to zero without reducing the control thrust when the attitude error is large. Finally, we conduct simulations on a tethered quadrotor to achieve high-speed flight in limited space. The simulation results show that the control method can stabilize a quadrotor at high-speed trajectory flight and keep a quadrotor stable when it is disturbed by aerodynamic drag and mass change.
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Barrett-Gonzalez, Ronald. "High Performance Convertible Coleopter Drones." Drones 6, no. 11 (November 8, 2022): 346. http://dx.doi.org/10.3390/drones6110346.
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This paper opens with an historical overview of efforts to develop micro-, mini-, and organic aerial vehicles (MAVs and OAVs) in the 1990’s. Although conceived during WWII, coleopters would not see serial production for 60 years. The paper continues with programmatic aspects of hovering coleopter development of the 1990’s and describes the technical motivations behind in-flight conversion from hover-mode to missile-mode flight and the record-setting XQ-138 family of convertible coleopters. As the first commercially successful family of such aircraft, the XQ-138 was taken from initial concept through configuration design, detailed design, patenting, prototyping, proof-of-concept, production, flight testing, qualification, and eventually high rate production, all with private funding. The paper lists basic engineering drivers, covers fundamental sizing methods, presents weight fraction data, and describes flight test procedures, locations, conditions, and results. High-speed flight test data show the stock aircraft achieving speeds in excess of 164 mph (263 kph) with endurances in excess of an hour at that speed with a special dash-optimized version reaching 288 mph (463 kph) for a few minutes. Videos from flight testing and live-fire exercises are shown at Redstone Arsenal, Eglin Air Force Base, and Fort Benning test ranges under extreme conditions. The paper concludes with an assessment of civil and military variants for a variety of military missions and commercial uses.
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MAY, MICHAEL L. "Dragonfly Flight: Power Requirements at High Speed and Acceleration." Journal of Experimental Biology 158, no. 1 (July 1, 1991): 325–42. http://dx.doi.org/10.1242/jeb.158.1.325.
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Most studies of insect flight deal primarily with hovering or with forward flight at constant, moderate speed. This paper reports investigations of flight characteristics that are especially relevant to the performance of dragonflies at high and/or changing velocity. Dragonflies were filmed in free flight in the field to determine velocity and acceleration. The power required for repeated acceleration is shown to be large, in some circumstances, relative to the estimated maximum available power and probable top power requirements for steady flight. Distributions of velocity and acceleration, and concomitant power requirements, differ markedly among species, however. In addition, parasite drag was measured in winds of 2–7ms−1 and drag coefficients determined to be about 0.40 at Reynolds number greater than 104. This result implies substantially lower power requirements at high speeds, compared to previous estimates. Other aspects of power output, including the probable magnitude of inertial power, are considered in relation to published data.
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Sachs, Gottfried, and Benedikt Grüter. "Trajectory Optimization and Analytic Solutions for High-Speed Dynamic Soaring." Aerospace 7, no. 4 (April 17, 2020): 47. http://dx.doi.org/10.3390/aerospace7040047.
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Dynamic soaring is a non-powered flight mode that enables extremely high speeds by extracting energy from thin shear wind layers. Trajectory optimization is applied to construct solutions of the maximum speed achievable with dynamic soaring and to determine characteristic properties of that flight mode, using appropriate models of the vehicle dynamics and the shear wind layer. Furthermore, an energy-based flight mechanics model of high-speed dynamic soaring is developed, with reference made to trajectory optimization. With this model, analytic solutions for high-speed dynamic soaring are derived. The key factors for the maximum speed performance are identified and their effects are determined. Furthermore, analytic solutions for other, non-performance quantities of significance for high-speed dynamic soaring are derived. The analytic solutions virtually agree with the results achieved with the trajectory optimization using the vehicle dynamics model. This is considered a validation of the energy-based model yielding analytic solutions. The analytical solutions are also valid for the high subsonic Mach number region involving significant compressibility effects. This is of importance for future developments in high-speed dynamic soaring, as modern gliders are now capable of reaching that Mach number region.
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Wang, Bo, Xin Yuan, Qi-jun Zhao, and Zheng Zhu. "Geometry Design of Coaxial Rigid Rotor in High-Speed Forward Flight." International Journal of Aerospace Engineering 2020 (December 4, 2020): 1–18. http://dx.doi.org/10.1155/2020/6650375.
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The aerodynamic performance analysis and blade planform design of a coaxial rigid rotor in forward flight were carried out utilizing CFD solver CLORNS. Firstly, the forward flow field characteristics of the coaxial rotor were analyzed. Shock-induced separation occurs at the advancing side blade tip and severe reverse flow occurs at the retreating side blade root. Then, the influence of geometrical parameters of the coaxial rigid rotor on forward performance was investigated. Results show that swept-back tip could reduce the advancing side compressibility drag and elliptic shape of blade planform could optimize the airload distribution at high advance ratio flights. A kind of blade planform combining swept-back tapered tip and nonlinear chord distribution was optimized to improve the rotor efficiency for a given high-speed level flight based on geometric parameter studies. The optimized coaxial rotor increases lift-to-drag ratio by 30% under the design conditions.
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Li, Shun, Gong Duo Zhang, Shi Hui Bi, Xiao Tang Li, and Guo Wei Xie. "Experimental Investigation on Influence of Important Parameters in Centrifugal Granulation for MBFS." Advanced Materials Research 968 (June 2014): 202–5. http://dx.doi.org/10.4028/www.scientific.net/amr.968.202.
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The difficulties of molten metallurgical slag heat recovery caused by low thermal conductivity and high enthalpy are analyzed.Centrifugal granulation is an environment-friendly process in treating the slag. The existing researches on centrifugal granulation are concentrated in the shape, size and mass distribution of slag particles. The relations between flight distance of slag, divorced speed of slag and outside speed of cup and rotary speed and rotary cup diameter were studied. The experimental results indicate that flight distance is farther from the cup and the speeds increase with increasing rotary speed. While rotary speed reaches 1000 rpm, divorced speed and flight distance of slag are almost invariant. When rotary cup diameter increases, the flight distance and the speeds increase simultaneously. Flight is reasonably simplified as:uniform motion in horizontal direction and motion of free falling body in the vertical direction,The experimental results have certain guiding significance to design of heat recovery equipment.
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Knight, Doyle, and Nadia Kianvashrad. "Review of Energy Deposition for High-Speed Flow Control." Energies 15, no. 24 (December 19, 2022): 9645. http://dx.doi.org/10.3390/en15249645.
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Energy deposition for flow and flight control has received significant interest in the past several decades due to its potential application to high-speed flow and flight control. This paper reviews recent progress and recommends future research.
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Zhu, Hao Jie, and Mao Sun. "Kinematics Measurement and Power Requirements of Fruitflies at Various Flight Speeds." Energies 13, no. 16 (August 18, 2020): 4271. http://dx.doi.org/10.3390/en13164271.
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Energy expenditure is a critical characteristic in evaluating the flight performance of flying insects. To investigate how the energy cost of small-sized insects varies with flight speed, we measured the detailed wing and body kinematics in the full speed range of fruitflies and computed the aerodynamic forces and power requirements of the flies. As flight speed increases, the body angle decreases and the stroke plane angle increases; the wingbeat frequency only changes slightly; the geometrical angle of attack in the middle upstroke increases; the stroke amplitude first decreases and then increases. The mechanical power of the fruitflies at all flight speeds is dominated by aerodynamic power (inertial power is very small), and the magnitude of aerodynamic power in upstroke increases significantly at high flight speeds due to the increase of the drag and the flapping velocity of the wing. The specific power (power required for flight divided by insect weigh) changes little when the advance ratio is below about 0.45 and afterwards increases sharply. That is, the specific power varies with flight speed according to a J-shaped curve, unlike those of aircrafts, birds and large-sized insects which vary with flight speed according to a U-shaped curve.
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Rosenow, Judith, Ehsan Asadi, Daniel Lubig, Michael Schultz, and Hartmut Fricke. "Long Range Air Traffic Flow Management with Flight-Specific Flight Performance." Future Transportation 2, no. 2 (March 29, 2022): 310–27. http://dx.doi.org/10.3390/futuretransp2020017.
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The increasing need for dynamic in-flight adjustments of a trajectory allows the airport, air traffic control and the airline a high degree of flexibility in terms of in-flight execution. This concept enables numerous optimisation options to jointly meet the requirements of sustainable air transport to increase economic and ecological efficiency, as well as safety. One promising measure is to control the aircraft arrival rate to prevent over-demand in the approach sector around the airport. In so-called Long-Range Air Traffic Management, the arrival time of long-haul flights, in particular, is already controlled many hours before arrival. However, the control options and their effects on arrival time and fuel burn are heavily dependent on flight performance and the (hardly predictable) influence of the weather. In this study, we optimize the arrival time of 26 long-haul flights in the Asia-Pacific region with arrival at Changi Airport within a peak hour considering the arrival rate of medium-haul and short-haul flights. This control is done by speed adjustments and by choosing alternative routes. For the first time, we model each long-haul flight and its control options individually in real weather conditions. We found that speed adjustments should start three to four hours before arriving at the approach sector to maximize the fuel-saving potential of small deviations from the optimal cruising speed, considering the predictability of the arrival time under real weather conditions. Allowing the aircraft to additionally choose an alternative lateral route, different from the filed flight plan, both maximizes the potential for harmonization of the number of aircraft in the approach sector and minimizes the total fuel burn. Unlike speed adjustments, alternative routes changes are effective even during the last hour of the cruise phase.
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Alekseev, A. A., M. V. Grishin, and E. V. Stepashkina. "ANALOG INSTRUMENT READING USING THE EXAMPLE OF HIGH-ALTITUDE AND HIGH-SPEED FLIGHT INSTRUMENTS." Izvestiya of Samara Scientific Center of the Russian Academy of Sciences 24, no. 1 (2022): 55–58. http://dx.doi.org/10.37313/1990-5378-2022-24-1-55-58.
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The article considers the issue of analog instrument reading using the example of high-altitude and high-speed flight instruments. The article provides a detailed description of the software that can read analog gauge data through the example of flight instruments during their verification. The article describes the main functions of computer vision library, image processing, and general-purpose numerical algorithms with open source (OpenCV), used for instrument readings. The software is developed in the high-level universal programming language Python 3.7.7. The results of the program are presented, showing this method performance of checking high altitude flight instruments.
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Tobalske, B., and K. Dial. "Flight kinematics of black-billed magpies and pigeons over a wide range of speeds." Journal of Experimental Biology 199, no. 2 (February 1, 1996): 263–80. http://dx.doi.org/10.1242/jeb.199.2.263.
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To investigate how birds that differ in morphology change their wing and body movements while flying at a range of speeds, we analyzed high-speed (60 Hz) video tapes of black-billed magpies (Pica pica) flying at speeds of 4-14 m s-1 and pigeons (Columba livia) flying at 6-20 m s-1 in a wind-tunnel. Pigeons had higher wing loading and higher-aspect-ratio wings compared with magpies. Both species alternated phases of steady-speed flight with phases of acceleration and deceleration, particularly at intermediate flight speeds. The birds modulated their wingbeat kinematics among these phases and frequently exhibited non-flapping phases while decelerating. Such modulation in kinematics during forward flight is typical of magpies but not of pigeons in the wild. The behavior of the pigeons may have been a response to the reduced power costs for flight in the closed wind-tunnel relative to those for free flight at similar speeds. During steady-speed flight, wingbeat frequency did not change appreciably with increasing flight speed. Body angle relative to the horizontal, the stroke-plane angles of the wingtip and wrist relative to the horizontal and the angle describing tail spread at mid-downstroke all decreased with increasing flight speed, thereby illustrating a shift in the dominant function of wing flapping from weight support at slow speeds to positive thrust at fast speeds. Using wingbeat kinematics to infer lift production, it appeared that magpies used a vortex-ring gait during steady-speed flight at all speeds whereas pigeons used a vortex-ring gait at 6 and 8 m s-1, a transitional vortex-ring gait at 10 m s-1, and a continuous-vortex gait at faster speeds. Both species used a vortex-ring gait for acceleration and a continuous-vortex gait or a non-flapping phase for deceleration during flight at intermediate wind-tunnel speeds. Pigeons progressively flexed their wings during glides as flight speed increased but never performed bounds. Wingspan during glides in magpies did not vary with flight speed, but the percentage of bounds among non-flapping intervals increased with speed from 10 to 14 m s-1. The use of non-flapping wing postures seemed to be related to the gaits used during flapping and to the aspect ratio of the wings. We develop an 'adverse-scaling' hypothesis in which it is proposed that the ability to reduce metabolic and mechanical power output using flap-bounding flight at fast flight speeds is scaled negatively with body mass. This represents an alternative to the 'fixed-gear' hypothesis previously suggested by other authors to explain the use of intermittent flight in birds. Future comparative studies in the field would be worthwhile, especially if instantaneous flight speeds and within-wingbeat kinematics were documented; new studies in the laboratory should involve simultaneous recording of wing kinematics and aerodynamic forces on the wing.
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Schmirler, Michal. "Flight Speed Evaluation Using a Special Multi-Element High-Speed Temperature Probe." Aerospace 9, no. 4 (March 31, 2022): 185. http://dx.doi.org/10.3390/aerospace9040185.
Повний текст джерелаАнотація:
In the context of aircraft aerodynamics, the compressibility of air flowing around the aircraft must always be considered. This fact brings with it one inconvenience: to evaluate the velocity of the flowing air (airspeed), it is necessary to know its temperature as well. Unfortunately, direct measurement of the temperature of air flowing at high speed (usually at Ma > 0.3) is practically impossible without knowledge of its velocity. Thus, there are two unknown quantities in the problem that depend on each other. The solution is achieved by a method that uses temperature probes composed of multiple sensors with different properties (different recovery factors). The comparison of rendered temperatures subsequently allows the elimination of the necessary knowledge of static temperature and the evaluation of velocity. In this paper, one of such probes is described together with its thermodynamic properties and possible applications.
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Yuan, Y., D. Thomson, and R. Chen. "Variable rotor speed strategy for coaxial compound helicopters with lift–offset rotors." Aeronautical Journal 124, no. 1271 (September 27, 2019): 96–120. http://dx.doi.org/10.1017/aer.2019.113.
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ABSTRACTThe coaxial compound helicopter with lift-offset rotors has been proposed as a concept for future high-performance rotorcraft. This helicopter usually utilizes a variable-speed rotor system to improve the high-speed performance and the cruise efficiency. A flight dynamics model of this helicopter associated with rotor speed governor/engine model is used in this article to investigate the effect of the rotor speed change and to study the variable rotor speed strategy. Firstly, the power-required results at various rotor rotational speeds are calculated. This comparison indicates that choice of rotor speed can reduce the power consumption, and the rotor speed has to be reduced in high-speed flight due to the compressibility effects at the blade tip region. Furthermore, the rotor speed strategy in trim is obtained by optimizing the power required. It is demonstrated that the variable rotor speed successfully improves the performance across the flight range, but especially in the mid-speed range, where the rotor speed strategy can reduce the overall power consumption by around 15%. To investigate the impact of the rotor speed strategy on the flight dynamics properties, the trim characteristics, the bandwidth and phase delay, and eigenvalues are investigated. It is shown that the reduction of the rotor speed alters the flight dynamics characteristics as it affects the stability, damping, and control power provided by the coaxial rotor. However, the handling qualities requirements are still satisfied with different rotor speed strategies. Finally, a rotor speed strategy associated with the collective pitch is designed for maneuvering flight considering the normal load factor. Inverse simulation is used to investigate this strategy on maneuverability in the Push-up & Pull-over Mission-Task-Element (MTE). It is shown that the helicopter can achieve Level 1 ratings with this rotor speed strategy. In addition, the rotor speed strategy could further reduce the power consumption and pilot workload during the maneuver.
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Öhrle, Constantin, Felix Frey, Jakob Thiemeier, Manuel Keßler, Ewald Krämer, Martin Embacher, Paul Cranga, and Paul Eglin. "Compound Helicopter X3 in High-Speed Flight: Correlation of Simulation and Flight Test." Journal of the American Helicopter Society 66, no. 1 (January 1, 2021): 1–14. http://dx.doi.org/10.4050/jahs.66.012011.
Повний текст джерелаАнотація:
This work presents the correlation of simulation results and flight-test data for a high-speed (V = 220 kt), high advance ratio (μ > 0.5) flight of the compound helicopter X3. The simulation tool chain consists of state-of-the-art coupling between the computational fluid dynamics (CFD) code FLOWer and the comprehensive analysis tool HOST. By applying a freeflight trim procedure, the experimental flight state is accurately represented in the simulation. The deviations of most trim controls is below 1°, and the maximum deviation is less than 1.4°. The analysis of the high-fidelity CFD results illustrates key features of the flow physics at this high advance ratio, such as wake interactions, reverse flow, and advancing side loading. The correlation of rotor dynamics data between simulation and flight test is favorable. Good accordance is demonstrated for flap bending moments, torsion moments, and pitch link loads. In contrast, the correlation is weaker for the chord bending moments for which it is shown that the interblade damper and drive train model mostly determine the structural loads.
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Strandberg, Roine, Thomas Alerstam, and Mikael Hake. "Wind-dependent foraging flight in the Osprey Pandion haliaetus." Ornis Svecica 16, no. 3 (July 1, 2006): 150–63. http://dx.doi.org/10.34080/os.v16.22711.
Повний текст джерелаАнотація:
We studied the foraging technique of Ospreys Pandion haliaetus during different wind speed conditions at Lake Hammarsjön, Sweden in autumn 2003. Different fishing techniques were used with a shift in relation to wind speed: (1) without hovering, (2) hovering with pure flapping flight, (3) hovering with flapping flight and gliding into the wind, and (4) hovering with pure gliding. The results supported our predictions that hovering is constrained at low wind speeds and gliding restricted to wind speeds exceeding 7 m/s. Mixing flapping and gliding flight when hovering may be done as a trade-off between increased fishing efficiency associated with flapping flight and energy-saving combined with gain in total hovering time associated with gliding intervals. The relationship between hovering time and wind speed differed significantly between males and females. At wind speeds up to about 3.0 m/s, the hovering time increased more steeply with increasing wind speed for males than for females. In contrast, hovering time was shorter for males than for females at high wind speeds. The juveniles showed a lower mean, smaller scatter, and less increase in hovering time along the wind speed gradient.
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Nachtigall, Werner. "Equipment, Recording and Evaluation Methods for Insect Flight Analysis by Camcorders with High-speed Shutter II." Entomologia Generalis 20, no. 4 (May 6, 1996): 225–39. http://dx.doi.org/10.1127/entom.gen/20/1996/225.
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Anderson, John D. "History of High-Speed Flight and Its Technical Development." AIAA Journal 39, no. 5 (May 2001): 761–71. http://dx.doi.org/10.2514/2.1385.
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Peltzer, I., W. Nitsche, and J. Suttan. "Low- and High-Speed Flight Experiments on Transition Detection." Journal of Aircraft 45, no. 6 (November 2008): 1937–44. http://dx.doi.org/10.2514/1.35184.
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Anderson, John D. "History of high-speed flight and its technical development." AIAA Journal 39 (January 2001): 761–71. http://dx.doi.org/10.2514/3.14800.
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Niemiec, Robert, George Jacobellis, and Farhan Gandhi. "Reversible airfoils for stopped rotors in high speed flight." Smart Materials and Structures 23, no. 11 (October 1, 2014): 115013. http://dx.doi.org/10.1088/0964-1726/23/11/115013.
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Jones, J. G., and D. E. Fry. "Ride-bumpiness in high-speed flight at low altitude." Aeronautical Journal 93, no. 926 (July 1989): 219–28. http://dx.doi.org/10.1017/s0001924000017073.
Повний текст джерелаАнотація:
SummaryAircraft longitudinal ride-bumpiness during flight at high speed and low altitude is described in terms of the response to discrete gust patterns. Results are expressed statistically in a form that incorporates data from recent turbulence measurements. Effects of basic airframe parameters and of active controls are illustrated and data from a computer-simulation study are used to confirm the validity of the prediction method.
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Willmott, A. P., and C. P. Ellington. "The mechanics of flight in the hawkmoth Manduca sexta. I. Kinematics of hovering and forward flight." Journal of Experimental Biology 200, no. 21 (November 1, 1997): 2705–22. http://dx.doi.org/10.1242/jeb.200.21.2705.
Повний текст джерелаАнотація:
High-speed videography was used to record sequences of individual hawkmoths in free flight over a range of speeds from hovering to 5 ms-1. At each speed, three successive wingbeats were subjected to a detailed analysis of the body and wingtip kinematics and of the associated time course of wing rotation. Results are presented for one male and two female moths. The clearest kinematic trends accompanying increases in forward speed were an increase in stroke plane angle and a decrease in body angle. The latter may have resulted from a slight dorsal shift in the area swept by the wings as the supination position became less ventral with increasing speed. These trends were most pronounced between hovering and 3 ms-1, and the changes were gradual; there was no distinct gait change of the kind observed in some vertebrate fliers. The wing rotated as two functional sections: the hindwing and the portion of the forewing with which it is in contact, and the distal half of the forewing. The latter displayed greater fluctuation in the angle of rotation, especially at the lower speeds. As forward speed increased, the discrepancy between the rotation angles of the two halfstrokes, and of the two wing sections, became smaller. The downstroke wing torsion was set early in the halfstroke and then held constant during the translational phase.
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Bullen, R. D., and N. L. McKenzie. "Scaling bat wingbeat frequency and amplitude." Journal of Experimental Biology 205, no. 17 (September 1, 2002): 2615–26. http://dx.doi.org/10.1242/jeb.205.17.2615.
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SUMMARYWingbeat frequency (fw) and amplitude(θw) were measured for 23 species of Australian bat,representing two sub-orders and six families. Maximum values were between 4 and 13 Hz for fw, and between 90 and 150° forθ w, depending on the species. Wingbeat frequency for each species was found to vary only slightly with flight speed over the lower half of the speed range. At high speeds, frequency is almost independent of velocity. Wingbeat frequency (Hz) depends on bat mass (m, kg) and flight speed (V, ms-1) according to the equation: fw=5.54-3.068log10m-2.857log10V. This simple relationship applies to both sub-orders and to all six families of bats studied. For 21 of the 23 species, the empirical values were within 1 Hz of the model values. One species, a small molossid, also had a second mode of flight in which fw was up to 3 Hz lower for all flight speeds.The following relationship predicts wingbeat amplitude to within±15° from flight speed and wing area (SREF,m2) at all flight speeds:θ w=56.92+5.18V+16.06log10SREF. This equation is based on data up to and including speeds that require maximum wingbeat amplitude to be sustained. For most species, the maximum wingbeat amplitude was 140°.
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DUDLEY, ROBERT. "Biomechanics of Flight in Neotropical Butterflies: Morphometrics and Kinematics." Journal of Experimental Biology 150, no. 1 (May 1, 1990): 37–53. http://dx.doi.org/10.1242/jeb.150.1.37.
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Wing and body kinematics of free cruising flight are described for 37 species of Panamanian butterflies ranging over two orders of magnitude in body mass. Butterflies exhibit considerable diversity in body and wing shape, but morphological design is, in general, isometric. Wing loading and mean body diameter show positive allometry. The cruising flight of butterflies is characterized by low wingbeat frequencies (here averaging 11 Hz), stroke amplitudes averaging 103°, and forward speeds in excess of 1m s−1. Body angles during flight are close to horizontal, and stroke plane angles are correspondingly high. Advance ratios are typically greater than 0.9, indicating that the forward and flapping velocity vectors are of comparable magnitude. Flight speed scales with morphological parameters in general accordance with predictions based on isometric design. Interspecifically, no consistent correlation exists between wing kinematics and absolute flight speed. However, maximum positional angle and stroke amplitude tend to increase while body angle decreases with increased relative flight speed.
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Zhang, Jialong, Jianguo Yan, Pu Zhang, Xiaoqiao Qi, and Maolong Lü. "Study on the High-Speed and Close of the UVA Cooperative Formation Controller Design." Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University 36, no. 2 (April 2018): 345–52. http://dx.doi.org/10.1051/jnwpu/20183620345.
Повний текст джерелаАнотація:
Aiming at the high-speed flight of the UAVs cooperative formation, when a single UAV has occurred, need to exit the formation flight and be close or super close to form of the formation quickly. A fast close cooperative formation controller design method is proposed to make up for low the fighting robustness, and be shortcomings of timeliness poorly and analyze the dynamic characteristic of UAV formation flight. Taking the external factors known into consideration, setting up for the longitude maneuver of nonlinear thrust vector and unsteady aerodynamic model, according to the formation velocity, flat tail rudder angle and thrust vector and pitch angle velocity for corresponding input commend signals for the controller to research the dynamic characteristic of UAV formation flight. Meanwhile, the formation flight distance error is the convergence to a fixed value, and the stability of the cooperative formation flight is good. The simulation of results show that the controller can effectively improve the speed of the close or super close to formation, and maintain the stability of the formation flight, which provides a method of the close or super close formation flight controller design.
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ZHAO, Yameng, and Jian JIANG. "Algorithm Design of Mirror Tracking System." Journal of Physics: Conference Series 2290, no. 1 (June 1, 2022): 012101. http://dx.doi.org/10.1088/1742-6596/2290/1/012101.
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Abstract In the current national defense background, the requirements for the performance of weapons are increasing day by day, the speed of the flying target and the flight state provide important parameters for the improvement of the characteristics of weapons, ballistics and ammunition. In the shooting range test, the high-speed flying target is tracked and photographed to obtain important indicators such as the flight status of the flying target in high-speed flight. This paper studies a ballistic tracking camera system based on a rotating mirror. It is composed of a system, which can track the flight trajectory of the flying target in the air in real time, and obtain important information of the flying target in flight through high-speed camera shooting. Design the mirror tracking system to capture the flight status of the flying target, analyze the flight trajectory parameters of the target through MATLAB, and optimize the accuracy and response speed of the motor control algorithm. The motor turns the mirror to reflect the flying target to the high-speed camera. The feasibility of the system is ver ifi ed. Th e tot al sc ann ing range of the system for tracking flying targets is 90°, and the scanning accuracy is ±0.5°.
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Farisenkov, Sergey E., Nadejda A. Lapina, Pyotr N. Petrov, and Alexey A. Polilov. "Extraordinary flight performance of the smallest beetles." Proceedings of the National Academy of Sciences 117, no. 40 (September 21, 2020): 24643–45. http://dx.doi.org/10.1073/pnas.2012404117.
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Size is a key to locomotion. In insects, miniaturization leads to fundamental changes in wing structure and kinematics, making the study of flight in the smallest species important for basic biology and physics, and, potentially, for applied disciplines. However, the flight efficiency of miniature insects has never been studied, and their speed and maneuverability have remained unknown. We report a comparative study of speeds and accelerations in the smallest free-living insects, featherwing beetles (Coleoptera: Ptiliidae), and in larger representatives of related groups of Staphylinoidea. Our results show that the average and maximum flight speeds of larger ptiliids are extraordinarily high and comparable to those of staphylinids that have bodies 3 times as long. This is one of the few known exceptions to the “Great Flight Diagram,” according to which the flight speed of smaller organisms is generally lower than that of larger ones. The horizontal acceleration values recorded in Ptiliidae are almost twice as high as even in Silphidae, which are more than an order of magnitude larger. High absolute and record-breaking relative flight characteristics suggest that the unique morphology and kinematics of the ptiliid wings are effective adaptations to flight at low Reynolds numbers. These results are important for understanding the evolution of body size and flight in insects and pose a challenge to designers of miniature biomorphic aircraft.
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Tobalske, B. W., W. L. Peacock, and K. P. Dial. "Kinematics of flap-bounding flight in the zebra finch over a wide range of speeds." Journal of Experimental Biology 202, no. 13 (July 1, 1999): 1725–39. http://dx.doi.org/10.1242/jeb.202.13.1725.
Повний текст джерелаАнотація:
It has been proposed elsewhere that flap-bounding, an intermittent flight style consisting of flapping phases interspersed with flexed-wing bounds, should offer no savings in average mechanical power relative to continuous flapping unless a bird flies 1.2 times faster than its maximum range speed (Vmr). Why do some species use intermittent bounds at speeds slower than 1.2Vmr? The ‘fixed-gear hypothesis’ suggests that flap-bounding is used to vary mean power output in small birds that are otherwise constrained by muscle physiology and wing anatomy to use a fixed muscle shortening velocity and pattern of wing motion at all flight speeds; the ‘body-lift hypothesis’ suggests that some weight support during bounds could make flap-bounding flight aerodynamically advantageous in comparison with continuous flapping over most forward flight speeds. To test these predictions, we studied high-speed film recordings (300 Hz) of wing and body motion in zebra finches (Taenopygia guttata, mean mass 13.2 g, N=4) taken as the birds flew in a variable-speed wind tunnel (0–14 m s-1). The zebra finches used flap-bounding flight at all speeds, so their flight style was unique compared with that of birds that facultatively shift from continuous flapping or flap-gliding at slow speeds to flap-bounding at fast speeds. There was a significant effect of flight speed on all measured aspects of wing motion except percentage of the wingbeat spent in downstroke. Changes in angular velocity of the wing indicated that contractile velocity in the pectoralis muscle changed with flight speed, which is not consistent with the fixed-gear hypothesis. Although variation in stroke-plane angle relative to the body, pronation angle of the wing and wing span at mid-upstroke showed that the zebra finch changed within-wingbeat geometries according to speed, a vortex-ring gait with a feathered upstroke appeared to be the only gait used during flapping. In contrast, two small species that use continuous flapping during slow flight (0–4 m s-1) either change wingbeat gait according to flight speed or exhibit more variation in stroke-plane and pronation angles relative to the body. Differences in kinematics among species appear to be related to wing design (aspect ratio, skeletal proportions) rather than to pectoralis muscle fiber composition, indicating that the fixed-gear hypothesis should perhaps be modified to exclude muscle physiology and to emphasize constraints due to wing anatomy. Body lift was produced during bounds at speeds from 4 to 14 m s-1. Maximum body lift was 0.0206 N (15.9 % of body weight) at 10 m s-1; body lift:drag ratio declined with increasing air speed. The aerodynamic function of bounds differed with increasing speed from an emphasis on lift production (4–10 m s-1) to an emphasis on drag reduction with a slight loss in lift (12 and 14 m s-1). From a mathematical model of aerodynamic costs, it appeared that flap-bounding offered the zebra finch an aerodynamic advantage relative to continuous flapping at moderate and fast flight speeds (6–14 m s-1), with body lift augmenting any savings offered solely by flap-bounding at speeds faster than 7.1 m s-1. The percentage of time spent flapping during an intermittent flight cycle decreased with increasing speed, so the mechanical cost of transport was likely to be lowest at faster flight speeds (10–14 m s-1).
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Park, Kirsty J., Mikael Rosén, and Anders Hedenström. "Flight kinematics of the barn swallow (Hirundo rustica) over a wide range of speeds in a wind tunnel." Journal of Experimental Biology 204, no. 15 (August 1, 2001): 2741–50. http://dx.doi.org/10.1242/jeb.204.15.2741.
Повний текст джерелаАнотація:
SUMMARYTwo barn swallows (Hirundo rustica) flying in the Lund wind tunnel were filmed using synchronised high-speed cameras to obtain posterior, ventral and lateral views of the birds in horizontal flapping flight. We investigated wingbeat kinematics, body tilt angle, tail spread and angle of attack at speeds of 4–14ms−1. Wingbeat frequency showed a clear U-shaped relationship with air speed with minima at 8.9ms−1(bird 1) and 8.7ms−1 (bird 2). A method previously used by other authors of estimating the body drag coefficient (CD,par) by obtaining agreement between the calculated minimum power (Vmin) and the observed minimum wingbeat frequency does not appear to be valid in this species, possibly due to upstroke pauses that occur at intermediate and high speeds, causing the apparent wingbeat frequency to be lower. These upstroke pauses represent flap-gliding, which is possibly a way of adjusting the force generated to the requirements at medium and high speeds, similar to the flap-bound mode of flight in other species. Body tilt angle, tail spread and angle of attack all increase with decreasing speed, thereby providing an additional lift surface and suggesting an important aerodynamic function for the tail at low speeds in forward flight. Results from this study indicate the high plasticity in the wingbeat kinematics and use of the tail that birds have available to them in order to adjust the lift and power output required for flight.
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Letzgus, Johannes, Manuel Keßler, and Ewald Krämer. "Simulation of Dynamic Stall on an Elastic Rotor in High-Speed Turn Flight." Journal of the American Helicopter Society 65, no. 2 (April 1, 2020): 1–12. http://dx.doi.org/10.4050/jahs.65.022002.
Повний текст джерелаАнотація:
A highly loaded, high-speed turn flight of Airbus Helicopters' Bluecopter demonstrator helicopter is simulated to investigate dynamic stall using a loose computational fluid dynamics/structural dynamics (CFD/CSD) coupling of the flow solver FLOWer and the rotorcraft comprehensive code CAMRAD II. The rotor aerodynamics is computed using a high-fidelity delayed detached-eddy simulation (DDES). A three-degree-of-freedom trim of an isolated rotor is performed, yielding main-rotor control angles that agree well with the flight-test measurements. The flow field in this flight condition is found to be highly unsteady and complex, featuring massively separated flow, blade–vortex interaction, multiple dynamic-stall events, and shock-induced separation. The computed pitch-link loads are compared to flight-test measurements. This shows that all CFD/CSD cases underpredict the amplitudes of the flight test and yield phase shifts. However, overall trends agree reasonably. Also, varying the computational setup reveals that the shear stress transport–DDES turbulence model performs better than Spalart–Allmaras–DDES, that the consideration of the rotor hub and fuselage improves the agreement with flight-test data, and that the elastic twist plays only a minor role in the dynamic-stall events.
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OZAWA, Shuhei, Masateru MAEDA, Toshiyuki NAKATA, and Hao LIU. "8G45 High-speed video camera-based imaging of flapping flight kinematics and flight dynamics." Proceedings of the Bioengineering Conference Annual Meeting of BED/JSME 2012.24 (2012): _8G45–1_—_8G45–2_. http://dx.doi.org/10.1299/jsmebio.2012.24._8g45-1_.
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Li, S., C. De Wagter, CC de Visser, QP Chu, and GCHE de Croon. "In-flight model parameter and state estimation using gradient descent for high-speed flight." International Journal of Micro Air Vehicles 11 (January 2019): 175682931983368. http://dx.doi.org/10.1177/1756829319833685.
Повний текст джерелаАнотація:
High-speed flight in GPS-denied environments is currently an important frontier in the research on autonomous flight of micro air vehicles. Autonomous drone races stimulate the advances in this area by representing a very challenging case with tight turns, texture-less floors, and dynamic spectators around the track. These properties hamper the use of standard visual odometry approaches and imply that the micro air vehicles will have to bridge considerable time intervals without position feedback. To this end, we propose an approach to trajectory estimation for drone racing that is computationally efficient and yet able to accurately estimate a micro air vehicle’s state (including biases) and parameters based on sparse, noisy observations of racing gates. The key concept of the approach is to optimize unknown and difficult-to-observe state variables so that the observations of the racing gates best fit with the known control inputs, estimated attitudes, and the quadrotor dynamics and aerodynamics during a time window. It is shown that a gradient-descent implementation of the proposed approach converges ∼4 times quicker to (approximately) correct bias values than a state-of-the-art 15-state extended Kalman filter. Moreover, it reaches a higher accuracy, as the predicted end-point of an open-loop turn is on average only ∼20 cm away from the actual end-point, while the extended Kalman filter and the gradient descent method with kinematic model only reach an accuracy of ∼50 cm. Although the approach is applied here to drone racing, it generalizes to other settings in which a micro air vehicle may only have sparse access to velocity and/or position measurements.
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YANAGIHARA, Masaaki, Hirokazu SUZUKI, Taro TSUKAMOTO, and Tetsujiro NINOMIYA. "3406 Mathematical Model and Flight Test Results of High Speed Flight Demonstration Phase II." Proceedings of the JSME annual meeting 2005.5 (2005): 413–14. http://dx.doi.org/10.1299/jsmemecjo.2005.5.0_413.
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Yoda, Ken, Tadashi Tajima, Sachiho Sasaki, Katsufumi Sato, and Yasuaki Niizuma. "Influence of Local Wind Conditions on the Flight Speed of the Great CormorantPhalacrocorax carbo." International Journal of Zoology 2012 (2012): 1–7. http://dx.doi.org/10.1155/2012/187102.
Повний текст джерелаАнотація:
In seabirds, the relationship between flight speed and wind direction/speed is thought to be particularly important for studying energy-saving strategy and foraging habitat selection. In this study, we examined whether the ground and calculated air speeds of four great cormorants (Phalacrocorax carbo) were affected by wind conditions using high-resolution GPS data loggers. The birds increased their ground flight speed in tailwinds, decreased it in headwinds, and changed their air speed in relation to wind components. However, they did not change their foraging sites according to the wind conditions. They were likely to respond to moderate wind conditions by adjusting their air speed without changing their foraging sites.
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Mazzawy, Robert S. "Next Generation of Transport Engines." Mechanical Engineering 132, no. 12 (December 1, 2010): 54. http://dx.doi.org/10.1115/1.2010-dec-6.
Повний текст джерелаАнотація:
This article discusses the features of very high bypass ratio turbofans and open rotor engines. Each of these engine options has its pros and cons to consider. The very large bypass ratio turbofan engine maintains that the proven capability of containment of blade failures is inherently quieter due to ability to incorporate acoustic treatment in the fan duct and is not subject to high fan tip losses associated with direct exposure to higher cruise level flight speeds. The duct does not come for free, however, and installed weight becomes a primary concern as the increased bypass ratio drives up the engine diameter. Additionally, the fan is subject to higher local airfoil incidence when the fan nozzle un-chokes at low flight speed. The open rotor engine can achieve potentially greater improvements in propulsive efficiency than a turbofan but lacks the containment and noise reduction benefits of a duct. The rotor is also exposed to flight speed, driving up tip losses at today's accepted cruise flight speeds.
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Lu, Ke, Chunsheng Liu, Chunhua Li, and Renliang Chen. "Flight Dynamics Modeling and Dynamic Stability Analysis of Tilt-Rotor Aircraft." International Journal of Aerospace Engineering 2019 (August 14, 2019): 1–15. http://dx.doi.org/10.1155/2019/5737212.
Повний текст джерелаАнотація:
The tilt-rotor aircraft has often been proposed as a means to increase the maximum speed of the conventional helicopter. The tilt-rotor aircraft consists of three primary flight modes that are the helicopter flight mode in low forward speed flight, airplane flight mode in high forward speed flight, and conversion flight mode. The aim of this paper is to develop a nonlinear flight dynamics mathematical modeling method of tilt-rotor aircraft and investigate the dynamic stability characteristics of tilt-rotor aircraft. First, a nonlinear tilt-rotor aircraft flight dynamics model is developed. The trim and linearized results are present to verify the model. Then, using a numerical differentiation technique, the dynamic stability of the tilt-rotor aircraft is assessed. The results show that the flight speed and nacelle angle would affect the magnitude and the trend of the aerodynamic derivatives. The damping of the pitch short period mode and the Dutch roll mode is insensitive to flight speed while they could be affected by nacelle angle. In all flight modes, as flight speed increases, the natural modes become more stable.
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Aldridge, H. D. "Turning flight of bats." Journal of Experimental Biology 128, no. 1 (March 1, 1987): 419–25. http://dx.doi.org/10.1242/jeb.128.1.419.
Повний текст джерелаАнотація:
The turning flight of six microchiropteran bat species is described. The bats' abilities to turn tightly were determined by their abilities to fly slowly and to generate high lateral accelerations. Rhinolophus ferrumequinum developed high lateral accelerations by flapping its banked wings while flying at very low speed. Plecotus auritus turned at relatively low speed and at low lateral acceleration. The other species were all moving fast as they turned and generated lateral accelerations either by developing high bank angles or by flapping their wings with low bank angles. There was a significant correlation between wing loading and turning curvature, indicating that low wing loadings improve manoeuvrability.
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Willmott, A. P., and C. P. Ellington. "The mechanics of flight in the hawkmoth Manduca sexta. II. Aerodynamic consequences of kinematic and morphological variation." Journal of Experimental Biology 200, no. 21 (November 1, 1997): 2723–45. http://dx.doi.org/10.1242/jeb.200.21.2723.
Повний текст джерелаАнотація:
Mean lift coefficients have been calculated for hawkmoth flight at a range of speeds in order to investigate the aerodynamic significance of the kinematic variation which accompanies changes in forward velocity. The coefficients exceed the maximum steady-state value of 0.71 at all except the very fastest speeds, peaking at 2.0 or greater between 1 and 2 ms-1. Unsteady high-lift mechanisms are therefore most important during hovering and slow forward flight. In combination with the wingtip paths relative to the surrounding air, the calculated mean lift coefficients illustrate how the relative contributions of the two halfstrokes to the force balance change with increasing forward speed. Angle of incidence data for fast forward flight suggest that the sense of the circulation is not reversed between the down- and upstrokes, indicating a flight mode qualitatively different from that proposed for lower-speed flight in the hawkmoth and other insects. The mid-downstroke angle of incidence is constant at 30-40 degrees across the speed range. The relationship between power requirements and flight speed is explored; above 5 ms-1, further increases in forward velocity are likely to be constrained by available mechanical power, although problems with thrust generation and flight stability may also be involved. Hawkmoth wing and body morphology, and the differences between males and females, are evaluated in aerodynamic terms. Steady-state force measurements show that the hawkmoth body is amongst the most streamlined for any insect.
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Witcher, Kenneth, Ian McAndrew, and Elena Vishnevskaya. "Aerodynamic Analysis of Low Speed Wing Design using Taguchi L9 Orthogonal Array." MATEC Web of Conferences 151 (2018): 04005. http://dx.doi.org/10.1051/matecconf/201815104005.
Повний текст джерелаАнотація:
The study of aerodynamics has been preoccupied with understanding flight at increasing speeds and ultimately supersonic. Today, this pursuit has advanced the science for both Hypersonic and Transonic flight to near Mach 1 supporting economical commercial flight operations. This research presents the data from a Taguchi array on low speed with twin wing designs to establish the design parameters for their use in low speed and high altitude. Also presented is how aerodynamic advantages can be achieved through understanding the interactions of parameters and their use. This is compared to operational effectiveness when applied to remotely piloted aircraft that are not constrained by direct requirements. The research concludes with suggestions for improved designs and further work that may enable higher altitudes with low speeds.