Gliding Flight Research Articles

Drift Counteraction and Control of Downsized and Underactuated Systems: What MPC Has to Offer?

Motivated by practical applications, the paper highlights MPC formulations suitable for counteracting system drift and the effects of large measured disturbances/set-point changes, and for overcoming limitations of underactuation. For drift counteraction, where the objective is to maximize the time or yield until the system trajectory exits a prescribed set, defined by system safety constraints, operating limits and/or efficiency requirements, MPC, based on mixed integer or conventional linear programming, can lead to effective solutions for higher order systems than possible with dynamic programming and value iterations based methods. Such solutions can have broad applicability including for fuel optimal Geostationary Orbit (GEO) station keeping, spacecraft Low Earth Orbit (LEO) maintenance, underactuated spacecraft attitude control, hybrid electric propulsion energy management, glider flight management, and the development of driving policies for adaptive cruise control and autonomous driving. The paper also highlights the capability of MPC to achieve non-smooth local stabilization of underactuated systems that can be exploited for attitude control of underactuated spacecraft with reaction wheel failures. Related results for systems that cannot be globally stabilized by continuous feedback are also mentioned. Finally, opportunities to handle large load and set-point changes with reference governors are discussed.

The influence of fundamental frequency on perceived duration in spectrally comparable sounds.

The perceived duration of a sound is affected by its fundamental frequency and intensity: higher sounds are judged to be longer, as are sounds with greater intensity. Since increasing intensity lengthens the perceived duration of the auditory object, and increasing the fundamental frequency increases the sound’s perceived loudness (up to ca. 3 kHz), frequency modulation of duration could be potentially explained by a confounding effect where the primary cause of the modulation would be variations in intensity. Here, a series of experiments are described that were designed to disentangle the contributions of fundamental frequency, intensity, and duration to perceived loudness and duration. In two forced-choice tasks, participants judged duration and intensity differences between two sounds varying simultaneously in intensity, fundamental frequency, fundamental frequency gliding range, and duration. The results suggest that fundamental frequency and intensity each have an impact on duration judgments, while frequency gliding range did not influence the present results. We also demonstrate that the modulation of perceived duration by sound fundamental frequency cannot be fully explained by the confounding relationship between frequency and intensity.

PERANCANGAN AWAL SCALE MODEL GLIDER STTA-25-02_SAILPLANE

The knowledge and experience in aircraft design, especially for glider or sailplane are very important to have. Today, process of designing glider developed so rapidly, especially in America and Europe, one of the significant achievement is the performance aspect of glider. For example, the German-built Eta has a wingspan 30.78 m, aspect ratio 51 and wing loading 50.97 kg/m2, with glide angle of 0.8 degree and 3 km altitude, the glider able to fly 213 km in horizontal direction. Therefore, as the first step to understand the preliminary design of glider, it is important to start with designing a scale model glider STTA-25-02_Sailplane. The goals of this design are to get geometry and configuration of the glider, to obtained stability of glider and to gain performance data that meet with design requirements and objectives data (DR&O). The conclusions from the preliminary design of scale model glider STTA-25-02_Sailplane are the geometry and configuration are good, for example the achivement in performance, the minimum sink rate 0.52 m/s, the glide ratio more than 20 at a cruising speed over 13 m/s, stall speed 11.45 m/s at angle of attack 0 degree. In addition glider STTA-25-02_Sailplane has static and dynamic stability, the static stability condition is indicated by the value of trim angle is positive 1 degree, curve of Cma and Clfi has negative slope, Cnfi curve has positive slope. The dynamic stability condition is indicated by the eigen value for each mode o f movement are negative except on phugoid and spiral mode, eigen value for short period -5.7681 ± 7.0010, phugoid 0.0403 ± 1.1136, rool damping -32.6243, dutch roll -1.0468 ± 3.4891 and spiral 0.1467. Positive eigen value on phugoid and spiral mode can be solved by adding a control parameter of the controlsurfaces.

Improved Analytical Model for Propelled and Unpropelled Hypersonic Vehicles

Hypersonic gliders are a new family of aerospace vehicles. They operate at quasi-orbital velocities with centrifugal acceleration balancing part of gravity. Although their aerodynamic lift-to-drag ratio is modest, the effective gravity resulting from a combination of the effects of gravity and of centrifugal acceleration allows for increased ranges. This paper presents an extension of traditional flight mechanics formulas over flat Earth to an oblate rotating Earth by including a relative gravity factor applicable to propelled and unpropelled flight. An analytical model is developed that includes this factor with formulations of flight time, cruising altitude, and range. Formulas for calculating gliding flight and accelerated and ascending cruise are developed. The model shows good agreement with high-fidelity simulation results. The simulation developed includes flight/orbital mechanics with an aerothermodynamic model of the scramjet and its multiple shocks air intake.

Global dynamics of non-equilibrium gliding in animals

Gliding flight—moving horizontally downward through the air without power—has evolved in a broad diversity of taxa and serves numerous ecologically relevant functions such as predator escape, expanding foraging locations, and finding mates, and has been suggested as an evolutionary pathway to powered flight. Historically, gliding has been conceptualized using the idealized conditions of equilibrium, in which the net aerodynamic force on the glider balances its weight. While this assumption is appealing for its simplicity, recent studies of glide trajectories have shown that equilibrium gliding is not the norm for most species. Furthermore, equilibrium theory neglects the aerodynamic differences between species, as well as how a glider can modify its glide path using control. To investigate non-equilibrium glide behavior, we developed a reduced-order model of gliding that accounts for self-similarity in the equations of motion, such that the lift and drag characteristics alone determine the glide trajectory. From analysis of velocity polar diagrams of horizontal and vertical velocity from several gliding species, we find that pitch angle, the angle between the horizontal and chord line, is a control parameter that can be exploited to modulate glide angle and glide speed. Varying pitch results in changing locations of equilibrium glide configurations in the velocity polar diagram that govern passive glide dynamics. Such analyses provide a new mechanism of interspecies comparison and tools to understand experimentally-measured kinematics data and theory. In addition, this analysis suggests that the lift and drag characteristics of aerial and aquatic autonomous gliders can be engineered to passively alter glide trajectories with minimal control effort.

Shape optimization of blended-wing-body underwater glider by using gliding range as the optimization target

Blended-Wing-Body Underwater Glider (BWBUG), which has excellent hydrodynamic performance, is a new kind of underwater glider in recent years. In the shape optimization of BWBUG, the lift to drag ratio is often used as the optimization target. However this results in lose of internal space. In this paper, the energy reserve is defined as the direct proportional function of the internal space of BWBUG. A motion model, which relates gliding range to steady gliding motion parameters as well as energy consumption, is established by analyzing the steady-state gliding motion. The maximum gliding range is used as the optimization target instead of the lift to drag ratio to optimizing the shape of BWBUG. The result of optimization shows that the maximum gliding range of initial design is increased by 32.1% though an Efficient Global Optimization (EGO) process.

グライド推進時の車輪に加わる力に着目したグライド角の決定方法の検討

A glide angle is an important factor to obtain arbitrary driving force for gliding locomotion. Therefore, the optimum glide angle should be determined from the speed of robot and the force applied to the wheel. A method that can output arbitrary propulsive force will be described. In this paper, as analyzing the behavior of wheels during glide locomotion, we have measured the force worked to a wheel and the paths of the wheel. By deciding the optimal glide angle based on these information, we will determine appropriate glide angle that can generate an arbitrary driving force.

Assessing the impact of a targeted plyometric training on changes in selected kinematic parameters of the swimming start.

The aim of this study was to analyse changes taking place within selected kinematic parameters of the swimming start, after completing a six-week plyometric training, assuming that the take-off power training improves its effectiveness. The experiment included nine male swimmers. In the pre-test the swimmers performed three starts focusing on the best performance. Next, a plyometric training programme, adapted from sprint running, was introduced in order to increase a power of the lower extremities. The programme entailed 75 minute sessions conducted twice a week. Afterwards, a post-test was performed, analogous to the pre-test. Spatio-temporal structure data of the swimming start were gathered from video recordings of the swimmer above and under water. Impulses triggered by the plyometric training contributed to a shorter start time (the main measure of start effectiveness) and glide time as well as increasing average take-off, flight and glide velocities including take-off, entry and glide instantaneous velocities. The glide angle decreased. The changes in selected parameters of the swimming start and its confirmed diagnostic values, showed the areas to be susceptible to plyometric training and suggested that applied plyometric training programme aimed at increasing take-off power enhances the effectiveness of the swimming start.

EFFECT OF WATER CURRENT ON UNDERWATER GLIDER VELOCITY AND RANGE

An autonomous underwater glider speed and range is influenced by water currents. This is compounded by a weak actuation system for controlling its movement. In this work, the effects of water currents on the speed and range of an underwater glider at steady state glide conditions are investigated. Extensive numerical simulations have been performed to determine the speed and range of a glider with and without water current at different net buoyancies. The results show that the effect of water current on the glider speed and range depends on the current relative motion and direction. In the presence of water current, for a given glide angle, glide speed can be increased by increasing the net buoyancy of the glider.

Modeling Micro Air Vehicle Aerodynamics in Unsteady High Angle-of-Attack Flight

An approach to modeling longitudinal airplane aerodynamics during unsteady maneuvers was developed for a micro air vehicle at angles of attack well past stall under unsteady conditions, including dynamic stall as might be experienced in perching maneuvers. To gather unsteady micro air vehicle flight data, an offboard motion tracking system was used to capture free-flight trajectories of a micro air vehicle with a weight of 14.44 g (0.0594 oz) and a wingspan of 37.47 cm (14.75 in.), operating at a nominal Reynolds number of 25,000. The measured trajectories included nominal gliding flight as well as mild-to-aggressive stalls. For the most aggressive stall case, the maximum lift coefficient reached a value near 2.5. The new model derived from the test data relied on a so-called separation parameter that modeled the aerodynamic lag during rapid changes in the angle of attack, and it thereby captured the effects of dynamic stall seen in the lift, drag, and moment coefficient data. Results from the model were shown for flights that covered a range of conditions from quasi-steady low angle-of-attack flight to aggressive stalls with angles of attack approaching 90 deg.

Path Planning to Improve Reachability in a Forced Landing

This paper proposes a novel path planning method for improving the feasibility of a forced landing. When an aircraft completely loses its thrust, the only measure it can take is to make a forced landing at an adjacent airport as soon as possible. In such a situation, the flight path to the landing point must be safe and viable. This paper details a method which enables safer and easier landing by transferring the benefits of excess altitude to the final approach length. Moreover, by planning the descent angle of final approach to be in the middle of a non-spoiler and a full-spoiler glide angle, this method enables a change in descent angle to correct any tracking errors, without using thrust. To verify the effectiveness of the proposed method, six degrees-of-freedom nonlinear simulations were performed and the results are compared with comparable methods. From the simulation results, it was confirmed that the proposed method could plan a safe path in a sufficiently short time and the aircraft could reach the landing point safely.

A study of thermal comfort enhancement by the optimization of airflow induced by a ceiling fan

In this study, the air flow generated by a ceiling fan inside a room is investigated by Computational Fluid Dynamics (CFD) simulation. In the model, a thermal mannequin sits in front of a computer desk with a rotating ceiling fan above the thermal mannequin around which the flow and thermal field was analyzed. The objective of this study is to optimize a ceiling fan’s parameters which include the rotation speed, diameter, blade count, horizontal inclination angle, vertical inclination angle, camber angle, stagger angle, flow angles at inlet/ outlet, incidence angle, glide angle, etc. by conducting comprehensive CFD simulation. For a ceiling fan to generate a preferable flow and thermal field, the effect of convective heat transfer needs to be enhanced so that the air flow can effectively take the heat generated by a human body away. The CFD analyses provide a better understanding of the velocity and temperature distributions around a human body so that the effects of various fan parameters can be estimated. The results indicated that the airflow velocity on the rotation plane of a blade is the most important indicator. By changing the rotational speed in the simulation model, the resulting effects on thermal comfort characteristics can be investigated. It was found in this study that, the circulation of air is optimized by an optimal rotation speed at which the thermal characteristics are greatly enhanced while the comfort level perceived by a human body is kept to a reasonable extent. Since the cooling condition can be optimized without the need of turning on any air conditioner at a higher outside ambient temperature, the electric bill can be greatly reduced without affecting the degree of thermal comfort. The results of this study indicated that, a ceiling fan can keep the thermal comfort at a reasonable level and greatly save the power cost as compared to air conditioners.

Wake analysis of aerodynamic components for the glide envelope of a jackdaw (Corvus monedula).

Gliding flight is a relatively inexpensive mode of flight used by many larger bird species, where potential energy is used to cover the cost of aerodynamic drag. Birds have great flexibility in their flight configuration, allowing them to control their flight speed and glide angle. However, relatively little is known about how this flexibility affects aerodynamic drag. We measured the wake of a jackdaw (Corvus monedula) gliding in a wind tunnel, and computed the components of aerodynamic drag from the wake. We found that induced drag was mainly affected by wingspan, but also that the use of the tail has a negative influence on span efficiency. Contrary to previous work, we found no support for the separated primaries being used in controlling the induced drag. Profile drag was of similar magnitude to that reported in other studies, and our results suggest that profile drag is affected by variation in wing shape. For a folded tail, the body drag coefficient had a value of 0.2, rising to above 0.4 with the tail fully spread, which we conclude is due to tail profile drag.

Gliding performance of the red giant gliding squirrel Petaurista petaurista in the tropical rainforest of Indian eastern Himalaya

Gliding squirrels occur globally and many are of conservation concern due to habitat fragmentation and degradation. Information on their ability to cover the distance between two trees by gliding is lacking in many species which might be vital for habitat management and conservation. The aim of the study was to present the field observations on gliding behaviour of the red giant gliding squirrel Petaurista petaurista observed within tropical rain‐forest of Namdapha National Park, Arunachal Pradesh, Indian eastern Himalaya. The data were collected on 71 glides observed at nights. The mean height of launching and landing trees were 28.5 ± 1.0 m and 16.4 ± 0.9 m, respectively. Gliding variables calculated were vertical drop (mean = 13.4 ± 1.0 m), horizontal distance (mean = 36.3 ± 2.7 m), air speed (mean = 8.9 ± 0.2 m s‐1), ground speed (mean = 7.9 ± 0.2 m s‐1), glide ratio (mean = 3.1 ± 0.2), glide angle (mean = 19.0 ± 0.9°), GBH of launching tree (mean = 156.8 ± 8.5 cm) and GBH of landing tree (mean = 195.2 ± 9.5 cm). Gliding distance was categorized in four types. The highest glides in a 26–50 m glide‐class (44% (n = 31)) were the most frequently observed. Gliding squirrels preferred top canopy (56%, n = 40) for distant glides. Forest structure has an influence on the gliding habits of gliding squirrels and thus our data on gliding parameters should be used when planning forest management actions.

Aerodynamic Performance of DragonflyWing withWell-designed Corrugated Section in Gliding Flight

Aerodynamic Performance of DragonflyWing withWell-designed Corrugated Section in Gliding Flight

Particle-image velocimetry investigation of the fluid-structure interaction mechanisms of a natural owl wing

The increasing interest in the development of small flying air vehicles has given rise to a strong need to thoroughly understand low-speed aerodynamics. The barn owl is a well-known example of a biological system that possesses a high level of adaptation to its habitat and as such can inspire future small-scale air vehicle design. The combination of the owl-specific wing geometry and plumage adaptations with the flexibility of the wing structure yields a highly complex flow field, still enabling the owl to perform stable and at the same time silent low-speed gliding flight. To investigate the effects leading to such a characteristic flight, time-resolved stereoscopic particle-image velocimetry (TR-SPIV) measurements are performed on a prepared natural owl wing in a range of angles of attack and Reynolds numbers 40 000 based on the chord length at a position located at 30% of the halfspan from the owl’s body. The flow field does not show any flow separation on the suction side, whereas flow separation is found on the pressure side for all investigated cases. The flow field on the pressure side is characterized by large-scale vortices which interact with the flexible wing structure. The good agreement of the shedding frequency of the pressure side vortices with the frequency of the trailing-edge deflection indicates that the structural deformation is induced by the flow field on the pressure side. Additionally, the reduction of the time-averaged mean wing curvature at high Reynolds numbers indicates a passive lift-control mechanism that provides constant lift in the entire flight envelope of the owl.

Study on Wing Aspect Ratio on the Performance of a Gliding Robotic Fish

In this paper, the performance of a gliding robotic fish with different wing aspect ratio is investigated. The gliding robotic fish, developed by Michigan State University, has the energy efficient locomotion of an underwater glider and high maneuverability of a robotic fish. ANSYS Computational Fluid Dynamics turbulence model was used to determine lift and drag coefficients for various wing aspect ratios at different angle of attack. Subsequently, the corresponding glide angle and velocity were determined analytically based on its dynamic model. The simulation results compare well with published experimental data and shows that the drag and lift coefficients are inversely proportional to the wing aspect ratio. As such, a gliding robotic fish with a low wing aspect ratio is suitable for shallow waters only, due to the high lift forces generated for a given angle of attack, requiring greater energy to sustain the glide velocity and vice versa.

New model of flap-gliding flight

A new modelling approach is presented for describing flap-gliding flight in birds and the associated mechanical energy cost of travelling. The new approach is based on the difference in the drag characteristics between flapping and non-flapping due to the drag increase caused by flapping. Thus, the possibility of a gliding flight phase, as it exists in flap-gliding flight, yields a performance advantage resulting from the decrease in the drag when compared with continuous flapping flight. Introducing an appropriate non-dimensionalization for the mathematical relations describing flap-gliding flight, results and findings of generally valid nature are derived. It is shown that there is an energy saving of flap-gliding flight in the entire speed range compared to continuous flapping flight. The energy saving reaches the highest level in the lower speed region. The travelling speed of flap-gliding flight is composed of the weighted average of the differing speeds in the flapping and gliding phases. Furthermore, the maximum range performance achievable with flap-gliding flight and the associated optimal travelling speed are determined.

Cruising the rain forest floor: butterfly wing shape evolution and gliding in ground effect.

Flight is a key innovation in the evolutionary success of insects and essential to dispersal, territoriality, courtship and oviposition. Wing shape influences flight performance and selection likely acts to maximize performance for conducting essential behaviours that in turn results in the evolution of wing shape. As wing shape also contributes to fitness, optimal shapes for particular flight behaviours can be assessed with aerodynamic predictions and placed in an ecomorphological context. Butterflies in the tribe Haeterini (Nymphalidae) are conspicuous members of understorey faunas in lowland Neotropical forests. Field observations indicate that the five genera in this clade differ in flight height and behaviour: four use gliding flight at the forest floor level, and one utilizes flapping flight above the forest floor. Nonetheless, the association of ground level gliding flight behaviour and wing shape has never been investigated in this or any other butterfly group. We used landmark-based geometric morphometrics to test whether wing shapes in Haeterini and their close relatives reflected observed flight behaviours. Four genera of Haeterini and some distantly related Satyrinae showed significant correspondence between wing shape and theoretical expectations in performance trade-offs that we attribute to selection for gliding in ground effect. Forewing shape differed between sexes for all taxa, and male wing shapes were aerodynamically more efficient for gliding flight than corresponding females. This suggests selection acts differentially on male and female wing shapes, reinforcing the idea that sex-specific flight behaviours contribute to the evolution of sexual dimorphism. Our study indicates that wing shapes in Haeterini butterflies evolved in response to habitat-specific flight behaviours, namely gliding in ground effect along the forest floor, resulting in ecomorphological partitions of taxa in morphospace. The convergent flight behaviour and wing morphology between tribes of Satyrinae suggest that the flight environment may offset phylogenetic constraints. Overall, this study provides a basis for exploring similar patterns of wing shape evolution in other taxa that glide in ground effect.

The descent of ant: field-measured performance of gliding ants.

Gliding ants avoid predatory attacks and potentially mortal consequences of dislodgement from rainforest canopy substrates by directing their aerial descent towards nearby tree trunks. The ecologically relevant measure of performance for gliding ants is the ratio of net horizontal to vertical distance traveled over the course of a gliding trajectory, or glide index. To study variation in glide index, we measured three-dimensional trajectories of Cephalotes atratus ants gliding in natural rainforest habitats. We determined that righting phase duration, glide angle, and path directness all significantly influence variation in glide index. Unsuccessful landing attempts result in the ant bouncing off its target and being forced to make a second landing attempt. Our results indicate that ants are not passive gliders and that they exert active control over the aerodynamic forces they experience during their descent, despite their apparent lack of specialized control surfaces.