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MARGUERETTAZ, PAOLO. "Development of an integrated/multidisciplinay methodology for the analysis of rotorcraft flight mechanics with external loads." Doctoral thesis, Politecnico di Torino, 2014. http://hdl.handle.net/11583/2540692.
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Helicopter is an invaluable tool in many civil applications and a fundamental asset in military operations. Two of its most appreciated capabilities, are the ability to transport external loads suspended from a cable and the possibility to carry stores rigidly mounted to the fuselage or to stub wings.
Unfortunately, a suspended load adds its aerodynamics, rigid body and elastic suspen- sion dynamics to the helicopter bare airframe dynamics and less than satisfactory handling can ensue. Moreover, rigidly mounted stores must be dropped before a forced landing in order to get rid of dangerous items (e.g. fuel or explosives) and decrease weight as much as possible. In this conditions a safe store separation is not guaranteed and the store may collide with the helicopter. It is, then, clear that carrying external stores can pose safety issues.
The first objective of this dissertation is the evaluation of helicopter handling qualities in presence of an external suspended load. A simple helicopter model is coupled with two different load models (pendulum and 6-DoFs). The system is, then, linearised, the modal and the frequency domain responses are evaluated and the handling qualities are assessed according to the current regulations. This approach requires very little knowledge of the actual helicopter an can be useful as a tool for preliminary handling qualities assessment during the design phase. The coherence of external load modal dynamics and the helicopter response to control input obtained with the present approach is compared with available reference data. Finally, the impact of the slung load parameters on helicopter handling qualities is assessed.
The second objective of this dissertation is the study of a comprehensive approach to the problem of external load jettison from a helicopter and the development of an associated software tool.
First a specialised tool for the simulation of the release of an external store is devel- oped. An important aspect of the simulation is the collision detection. The minimum distance between the helicopter and the store is evaluated at each simulation step. Multiple simulations are performed in order to determine the safe drop envelope.
The following section describes a methodology to reconstruct the trajectory and the attitude of the jettisoned load from video frames. A manual procedure is developed to identify the same markers in two video frames taken at the same time by video cameras mounted on the helicopter. A simple camera calibration technique, capable of computing camera orientation and aperture angle, is also discussed.
Finally the possibility to identify the aerodynamics properties of the released body from flight test data is investigated. The objective is to build, from the reconstructed trajectory, an aerodynamic model functional to the refining of the store drop simulation. The problem is a minimization one. An Evolutionary Algorithm is used with good results on different test cases, also including measurement noise.
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Willmott, Alexander Peter. "The mechanics of hawkmoth flight." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390186.
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Merlet, Pierre Miguel. "Flight Mechanics of an Airship." Thesis, KTH, Flygdynamik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-290178.
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Airships were very popular 90 years ago with, for example, german Zeppelins. Now theyare back for several reasons, like their low energy consumption.But there are also still many problems to deal with like their sensitivity to wind gusts.In addition, the airships need more studies to improve their flight mechanics and sensitivityto the wind.This degree project, done with the French Aerospace Lab ONERA in Lille, studies a specificairship which is 5mlong and 1.7mwide. First, the airship is studied without wind to determineaerodynamic coefficients and added masses. Then, the model is confronted to experiments withwind gusts.Luftskepp var mycket populär för 90 år sedan, till exempel med tyska Zeppelinare. Nu ärde tillbaka av flera skäl, som deras låga energiförbrukning.Men det finns fortfarande många problem att hantera som deras känslighet för vindbyar.Dessutom behöver luftskeppen fler studier för att förbättra sina flygegenskaper och vindkänslighet.Detta examsarbete, utfört vid den franska institutionenONERAi Lille, studerar ett specifiktluftskepp som är 5 m långt och 1.7 m brett. Först, studeras luftskeppet utan vind för attbestämma aerodynamiska data och tröghetsegenskaper. Sedan genomförs experiment därmodellen utsätts för vindbyar.
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Dudley, Theodore Robert. "Mechanics of forward flight in insects." Thesis, University of Cambridge, 1987. https://www.repository.cam.ac.uk/handle/1810/250902.
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Zhou, Hui M. S. Massachusetts Institute of Technology. "Micromechanical actuators for insect flight mechanics." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/44319.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2008.Includes bibliographical references (p. 95-97).
This project aims to develop MEMS actuators to aid in the study of insect flight mechanics. Specifically, we are developing actuators that can stimulate the antennae of the crepuscular hawk moth Manduca Sexta. The possible mechanosensory function of antennae as airflow sensors has been suggested, and recent discoveries of our collaborators reveal that mechanosensory input from the antennae of flying moths serves a similar role to that of the hind wings of two-winged insects, detecting Coriolis forces and thereby mediating flight stability during maneuvers. Early evidence suggests that mechanical stimulus of the antennae may enable flight control. In addition, the crepuscular hawk moth Manduca Sexta has a wide wingspan (~110 mm) and is capable of carrying at least one quarter of its own weight. Thus, studying the flight of Manduca Sexta by attachment of microsystems seems plausible. The goal of our project is to design and fabricate micromechanical actuators, which will be mounted onto the moth antennae. Our collaborators will study the flight control mechanism by mechanical stimulation. Our first step was to fabricate "dummy" silicon rings for our biologist collaborators for implant experiment. A series of mounting kits were developed, and due to the nature of the moth antennae, ring-beam-ring construction was finally designed and fabricated, like a "shackle", to meet the mounting requirements. Next, we integrated actuators onto the mounting kit. Piezoelectric film/sheet, piezoelectricbender and piezoelectric-stack were considered as the actuators. Live testing was also taken while the moth was resting or flapping its wings. The moth apparently responds to the mechanical stimulus under both circumstances, by swinging its wings and abdomen. Actuation amplifier was also modeled and tested, which might be used for future mechanical stimulators.
by Hui Zhou.
S.M.
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Falquier, Rene. "Longitudinal Flight Mechanics of Paraglider Systems." Thesis, KTH, Flygdynamik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-261698.
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This project outlines a cost-effective numerical simulation method for the analysis of the longitudinal mechanics of paraglider systems. It is built on static stability methods for the analyses of low subsonic aircraft, non-linear lifting line methods for aerodynamic parameterization, and frequency domain analysis methods derived from system theory. Paragliders possess a glide polar in the range of ≈ 25-60 km.h−1 and display underdamped dynamic responses dominated by a long-period mode. The simulation results for performance and dynamic response are qualitatively valid relative to experimental data and in the same order of magnitude.Projektet handlar om utveckling och utvärdering av en kostnadseffektiv simuleringsmodell för longitudinella frihetsgrader av skärmflyg. Modellen är byggd med fundamentala metoder för stabilitetsanalys av låghastighetsflygplan, ickelinjära liftingline metoden för aerodynamikanalys samt frekvensanalys från systemteori. Ett skärmflygs glidepolar är definierad på hastighetsintervallet ≈ 25-60 km.h−1 och visar ett underdämpat dynamiskt svar med lång period. Simuleringsresultaten för prestanda och dynamisk stabilitet ¨ar kvalitativt giltiga i förhållande till experimentella data och visar samma magnitud.
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Helgesson, Fredrik. "Analysis of a flight mechanics simulator." Thesis, KTH, Flygdynamik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-265616.
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Aircraft design is an act of art requiring dedication and careful work to ensure good results. An essential tool in that work is a flight mechanics simulator. Such simulators are often built up of modules/models that are executed in a sequential order in each time iteration. This project aims to analyze potential improvements to the model execution order based on the dependency structure of one such simulator. The analysis method Design Structure Matrix (DSM), was used to define/map the dependencies and then Binary Linear Programming (BLP) was utilized to find five new potentially improved model orders to minimize the number of feedbacks from one iteration to the next one. Those five proposed execution orders were next compared and evaluated. The result is a model order that reduce the number of models receiving feedbacks from the previous iteration from 13 to 6, with insignificant changes in the precision of the simulator.Vid flygplanskonstruktion krävs hårt och noggrant arbete för att säkerställa gott resultat. Ett oumbärligt verktyg är då en flygmekanisk simulator. Den typen av simulatorer är ofta uppbyggda av moduler/modeller som exekveras i en bestämd sekventiellt ordning i varje tidsteg. Syftet med detta projekt är att undersöka möjliga förbättringar av exekverings ordningen av de olika modellerna i en existerande simulator, baserat på beroendestrukturen. Analysmetoden Design Structure Matrix (DSM) användes för att bestämma beroendestrukturen och sedan utnyttjades Binär Linjär Programmering (BLP) för att hitta fem förbättrade modellordningar med avseende på att minimera antalet modeller som erhåller indata från föregående tidsiteration. De fem förbättringsförslagen jämfördes och utvärderades. Resultatet är en modellordning som kan minska antalet återkopplande modeller från 13 till 6, med insignifikanta skillnader i precisionen av simulatorn.
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Karail, Kursat. "Image Based Flight Data Reconstruction Using Aeroballistic Range Yaw Cards." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/2/12605768/index.pdf.
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The only aeroballistic laboratory of Turkey is the Flight Mechanics Laboratory, FML of TÜBITAK - SAGE. In FML, flight profiles of projectiles are reconstructed using their tear marks on paper sheets, called yaw cards. Tear marks are created on yaw cards as projectiles pass through them. These yaw cards are tightly stretched to metal frames which are positioned normal to the direction of projectile flight path. The use of yaw cards for flight profile reconstruction is a low cost and reliable solution. However, the yaw card method requires a heavy workload for the analysis of tear marks. Yaw cards collected from the frames are fed through an optical scanner and converted to digital images. These digital images are then processed by operators to calculate the projectile&rsquo
s flight position and angles. To automate this manual process, an algorithm is developed by using histogram based segmentation techniques, custom search algorithms, and Radon transform. This algorithm identifies and locates the projectile marks and finds angle of attack, angle of side slip and roll angle at each frame station by conducting the necessary transformations. Using this automated algorithm, a considerable amount of improvement is accomplished in terms of both decreasing the analysis time and increasing the accuracy of flight profile reconstruction.
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Goupil, Marc Y. "Dynamic Pressure Sensing for the Flight Test Data System." DigitalCommons@CalPoly, 2019. https://digitalcommons.calpoly.edu/theses/2115.
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This thesis describes the design, assembly, and test of the FTDS-K, a new device in the Boundary Layer Data System (BLDS) family of flight data acquisition systems. The FTDS-K provides high-frequency, high-gain data acquisition capability for up to two pressure sensors and an additional three low-frequency pressure sensors. Development of the FTDS-K was separated into a core module, specialized analog subsystem, and practical testing of the FTDS-K in a flow measurement mission. The core module combines an nRF52840-based microcontroller module, switching regulator, microSD card, real-time clock, temperature sensor, and trio of pressure sensors to provide the same capabilities as previous-generation BLDS-P devices. An expansion header is included in the core module to allow additional functionality to be added via daughter boards. An analog signal chain comprised of two-stage amplification and fourth-order active antialiasing filters was implemented as a daughter board to provide an AC-coupled end-to-end gain of 7,500 and a DC-coupled end-to-end gain of 50. This arrangement was tested in a wind tunnel to demonstrate that sensors with a full-scale range of 103 kPa can be used to reliably discriminate between laminar and turbulent flows based on pressure fluctuation differences on the order of tens of Pa. A combination of wind-off correction and band-filtering was used to reduce the effect of inherent and induced electrical noise, while two-sensor correlation was tested and shown to be effective at removing certain types of noise. Total power consumption for the FTDS-K in a representative mission is 208 mW, which translates to an operational endurance of 9 hours with 2 AAA LiFeS2 cells at -40°C.
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Larsson, Roger. "System Identification of Flight Mechanical Characteristics." Licentiate thesis, Linköpings universitet, Reglerteknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-92823.
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With the demand for more advanced fighter aircraft, relying on relaxed stability or even unstable flight mechanical characteristics to gain flight performance, more focus has been put on model-based system engineering to help with the design work. The flight control system design is one important part that relies on this modeling. Therefore it has become more important to develop flight mechanical models that are highly accurate in the whole flight envelop. For today’s newly developed fighters, the basic aircraft characteristics change between linear and nonlinear as well as stable and unstable as an effect of the desired capability of advanced maneuvering at subsonic, transonic and supersonic speeds. This thesis combines the subject of system identification, which is the art of building mathematical models of dynamical systems based on measurements, with aeronautics in order to find methods to identify flight mechanical characteristics from flight tests. Here, a challenging aeronautical identification problem combining instability and nonlinearity is treated. Two aspects are considered. The first is identification during a flight test with the intent to ensure that enough information is available in the resulting test data. Here, a frequency domain method is used. This idea has been taken from an existing method to which some improvements have been made. One of these improvements is to use an Instrumental Variable approach to take care of disturbances coming from atmospheric turbulence. The method treats linear systems that can be both stable and unstable. The improved method shows promising results, but needs further work to become robust against outliers and missing data. The other aspect is post-flight identification. Here, five different direct identification methods, which treat unstable and nonlinear systems, have been compared. Three of the methods are variations of the prediction-error method. The fourth is a parameter and state estimation method and the fifth method is a state estimation method based on an augmented system approach. The simplest of the prediction-error methods, based on a parametrized observer approach, is least sensitive to noise and initial offsets of the model parameters for the studied cases. This approach is attractive since it does not have any parameters that the user has to tune in order to get the best performance. All methods in this thesis have been validated on simulated data where the system is known, and have also been tested on real flight test data.
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Brown, Ainsmar Xavier. "Inflatable wing UAV experimental and analytical flight mechanics." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/39492.
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The field of man portable UASs (Unmanned Aerial Systems) is currently a key area in improving the fielded warrior's capabilities. Pressurized aerostructures that can perform with similar results of solid structures can potentially change how this objective may be accomplished now and in the future. Construction with high density polymers and other composites is currently part of active inflatable vehicle research. Many shape forming techniques have also been adapted from the airship and balloon manufacturing industry. Additional research includes modeling techniques so that these vehicles may be included in simulation packages.
A flight dynamics simulation with reduced-order aeroelastic effects derived with Lagrangian and Eulerian dynamics approaches were developed and optimized to predict the behavior of inflatable flexible structures in small UASs. The models are used to investigate the effects of significant structural deflections (warping) on aerodynamic surfaces. The model also includes compensation for large buoyancy ratios. Existing literature documents the similarity in structural dynamics of rigid beams and inflatable beams before wrinkling. Therefore, wing bending and torsional modes are approximated with the geometrically exact ntrinsic beam equations using NATASHA (Nonlinear Aeroelastic Trim And Stability for HALE Aircraft) code. An approach was also suggested for inclusion of unique phenomena such as wrinkling during flight. A simplified experimental setup will be designed to examine the most significant results observed from the simulation model. These methods may be suitable for specifying limits on flight maneuvers for inflatable UASs.
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Taylor, Graham K. "Animal flight dynamics : mechanics of stability and control." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270179.
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Rust, Martin. "The mechanics of continuous flight augers in clay." Thesis, University of Southampton, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398723.
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Taha, Haithem Ezzat Mohammed. "Mechanics of Flapping Flight: Analytical Formulations of Unsteady Aerodynamics, Kinematic Optimization, Flight Dynamics and Control." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/24428.
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A flapping-wing micro-air-vehicle (FWMAV) represents a complex multi-disciplinary system whose analysis invokes the frontiers of the aerospace engineering disciplines. From the aerodynamic point of view, a nonlinear, unsteady flow is created by the flapping motion. In addition, non-conventional contributors, such as the leading edge vortex, to the aerodynamic loads become dominant in flight. On the other hand, the flight dynamics of a FWMAV constitutes a nonlinear, non-autonomous dynamical system. Furthermore, the stringent weight and size constraints that are always imposed on FWMAVs invoke design with minimal actuation. In addition to the numerous motivating applications, all these features of FWMAVs make it an interesting research point for engineers.
In this Dissertation, some challenging points related to FWMAVs are considered. First, an analytical unsteady aerodynamic model that accounts for the leading edge vortex contribution by a feasible computational burden is developed to enable sensitivity and optimization analyses, flight dynamics analysis, and control synthesis. Second, wing kinematics optimization is considered for both aerodynamic performance and maneuverability. For each case, an infinite-dimensional optimization problem is formulated using the calculus of variations to relax any unnecessary constraints induced by approximating the problem as a finite-dimensional one. As such, theoretical upper bounds for the aerodynamic performance and maneuverability are obtained. Third, a design methodology for the actuation mechanism is developed. The proposed actuation mechanism is able to provide the required kinematics for both of hovering and forward flight using only one actuator. This is achieved by exploiting the nonlinearities of the wing dynamics to induce the saturation phenomenon to transfer energy from one mode to another. Fourth, the nonlinear, time-periodic flight dynamics of FWMAVs is analyzed using direct and higher-order averaging. The region of applicability of direct averaging is determined and the effects of the aerodynamic-induced parametric excitation are assessed. Finally, tools combining geometric control theory and averaging are used to derive analytic expressions for the textit{Symmetric Products}, which are vector fields that directly affect the acceleration of the averaged dynamics. A design optimization problem is then formulated to bring the maneuverability index/criterion early in the design process to maximize the FWMAV maneuverability near hover.Ph. D.
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Lee, Hongchul. "Advanced aircraft service life monitoring method via flight-by-flight load spectra." Diss., Online access via UMI:, 2009.
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Thesis (Ph. D.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Science, Department of Mechanical Engineering, 2009.Includes bibliographical references.
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Fletcher, Timothy M. "The effect of aerodynamic interactions on helicopter flight mechanics." Thesis, Imperial College London, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486588.
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During the last 40 years many helicopters have suffered adverse effects on their performance and handling qualities as a result of various forms of aerodynamic interaction. These problems have tended to become apparent only after a substantial amount of development work has been performed and flight testing has commenced, leading to expensive re-designs. Aerodynamic interaction between the main rotor and stabiliser leads to pitch-up in low speed forward . flight, whilst interaction between the main rotor and tail rotor in a conventional helicopter is known to strongly influence the performance of the tail rotor. Consequently, poor handling qualities in response to loss of tail rotor effectiveness and dynamic characteristics such as tail shake can emerge. The capability of an advanced numerical model for the simulation of rotorcraft flows, the Vorticity Transport Model, has been demonstrated by investigating the circumstances in which these interactions occur, and used to expose some of the underlying fluid dynamic mechanisms. This dissertation shows that the origin of pitch-up lies in the impingement of the main rotor wake on the stabiliser of a helicopter, and that the characteristic pitch and roll moments on the vehicle are dependent on the helicopter geometry and the angle of sideslip. The characteristic effects of main rotor - tail rotor interaction are also a function of helicopter geometry, but are highly dependent on the flight trajectory and are sensitive to the sense of rotation of the tail rotor. In forward flight with a high angle of sideslip, the predominant effect is to change the steady thrust developed by the tail rotor. This is caused by a modification of the velocity field at the tail���· rotor which benefits tail rotors with a top-aft sense of rotation. In aft quartering flight, the predominant effect is of substantial unsteadiness in tail rotor performance, which is greater for a top-forward tail rotor, and is related to the dynamics of the helicopter wake.
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Halter, Ronald Vaughn. "A universal time of flight equation for space mechanics." Thesis, Virginia Tech, 1988. http://hdl.handle.net/10919/43406.
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A universal time of flight equation for any orbit is developed as a
function of the initial and final radius, the change in true anomaly
and the initial flight path angle. Lambert's theorem, a new corollary
to this theorem, a trigonometric variable substitution and a continuing
fraction expression are used in this development. The resulting
equation is not explicitly dependent upon eccentricity and is
determinate for -2n < (change in true anomaly) < 2n. A method to
make the continuing fraction converge rapidly is evaluated using a top
down algorithm. Finally, the accuracy of the universal time of flight
equation is examined for a representative set of orbits including near
parabolic and near rectilinear orbits.
Master of Science
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Gao, Yang. "Advances in low-thrust trajectory optimization and flight mechanics /." free to MU campus, to others for purchase, 2003. http://wwwlib.umi.com/cr/mo/fullcit?p3115547.
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Bayati, Arastoo, and Peter Reinders. "Conceptual Design of a Small Size Unmanned Air Vehicle : Part B: Flight Performance and Flight Mechanics." Thesis, KTH, Skolan för teknikvetenskap (SCI), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-297889.
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This report summarizes the task of conceptually designing an UAV suited for agricultural observation of Swedish farmland. The design of the UAV was divided into two parts. This report focuses on the flight mechanics, performance analysis, and cost analysis of the UAV, whereas the other part centers around the aerodynamic performance. Therefore, some elements, such as the wing selection, will not be subject to discussion in this report. A set of different requirements were posed, such as having a flight time longer than two hours, being able to between 5-10 m/s, able to perform vertical take-off and landing, fly at a maximum of 100 meters, and weighing less than 5 kg. By using different sources of literature, reasonable assumptions, and Matlab analytics, a UAV was designed that met all constraints demanded. The cost analysis yielded a result that was reasonable, which overall makes this conceptual UAV a realistic product that could be manufactured using the project design.
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Evans, Alexander Nicholas. "Coupling the mechanics and energetics of bird and insect flight." Thesis, University of Leeds, 2018. http://etheses.whiterose.ac.uk/21441/.
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Humanity has long been fascinated by the mysteries of bird and insect flight, but only recently have we developed the technologies required to understand the complex mechanisms at work. These mechanisms range from molecular interactions to the interactions between whole organisms, encompassing a great number of mechanical and energetic processes. Research into animal flight has made great progress over the past half-century thanks to developments in technology and methodology, allowing for greater insights into the metabolic, mechanical and aerodynamic processes central to animal flight. Currently, there is a good understanding of several of these components but the topic of animal flight has been explored with a rather piecemeal approach and a more integrative understanding of the mechanics and energetics of animal flight is required. The research presented in this thesis aims to bridge our understanding of the often separately analysed mechanical and energetic aspects of animal flight and address key gaps in the existing knowledge. Many volant bird species exhibit asymmetrical wingbeat cycles such that the flight muscles spend relatively more time shortening than lengthening. Through the simultaneous determination of mechanical work generation and energy consumption in the mouse soleus during in vitro contraction cycles with asymmetrical length trajectories, we reveal that mechanical power production can be increased by increasing the proportion of the cycle spent shortening without sacrificing net muscle efficiency. These experiments also served to validate a methodology for estimating the net muscle efficiency of the avian pectoralis muscle. The following experiments determined the mechanical power generation, muscular costs of contraction and muscle efficiency of the budgerigar pectoralis during a range of simulated flight speeds. The efficiency of avian flight muscle was previously unknown and unsubstantiated values had been used in common predictive models of flight energetics. It was found that avian flight muscle efficiency is approximately 21% during the downstroke and remains constant with flight speed, with muscular energy consumption and power generation sharing characteristics with whole-animal metabolic and mechanical power-speed relationships. The consequences of these findings for the estimation of energetic flight costs are discussed. While respirometry serves as the gold standard for measuring metabolic expenditure during activity, accelerometry affords the potential for estimating the energetic costs of flight in birds in the field. However, there has been no calibration of the relationship between body acceleration and energy expenditure. By measuring energy consumption via respirometry and dynamic body acceleration in masked lovebirds during wind tunnel flights at a range of speeds, we determine the metabolic requirements of flight for a new avian species and validate the use of accelerometry for estimating energy expenditure and flight kinematics. Finally, we examined the previously unexplored relationship between myoplasmic calcium ion concentration, contraction frequency, mechanical power and myofibrillar efficiency in asynchronous insect flight muscles. There is increasing evidence to suggest that calcium plays an important role in the modulation of mechanical power during flight in insects with asynchronous flight muscles. By simultaneously measuring mechanical power generation and ATPase activity of flight muscles from giant waterbugs (Lethocerus), we reveal a positively shifting relationship between increasing calcium concentrations and optimal frequency for generating power, but with no evidence of a shift in optimal frequency for muscle efficiency. This research demonstrates scientific impact by improving our understanding of the factors that affect muscle efficiency, refining the models used to predict wild animal metabolism during flight, developing and validating existing experimental techniques for determining the costs of flight, and improving our understanding of how both mechanical and physiological factors can affect the mechanical and energetic performance of bird and insect flight muscles.
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Crozon, Clément. "Coupling flight mechanics and CFD : numerical simulation of shipborne rotors." Thesis, University of Liverpool, 2015. http://livrepository.liverpool.ac.uk/2030079/.
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This thesis demonstrates the use of Computational Fluid Dynamics (CFD) for the simulation of manoeuvring helicopters. Results are presented for the problem of shipborne operations, for which a literature survey showed that little work has been carried out. The CFD solver HMB2 was first validated using available experimental data for isolated ship wakes and helicopter loads at low advance ratios. A rotorcraft flight mechanics model was then developed and integrated into HMB2. The model includes a trimming method and a linearisation routine based on finite differences. The linear model of the aircraft can be used to estimate the controls applied by the pilot during a prescribed manoeuvre via the use of the SYCOS inverse-simulation method or via an LQR auto-pilot. The methods developed in the framework of this thesis include a general multi-body grid motion and an alternative formulation for earth-fixed frame of reference in the CFD. A study of the ship/rotor wake interaction was carried out using the actuator disc method that approximated the effect of the rotor, in a steady fashion and without resolving the flow around the blades. Various positions and thrust of the rotor were tested and the flowfield obtained via coupled simulations were compared with those obtained by super-imposing isolated rotor and ship flowfields. The results show that the superposition principle is not valid and leads to flowfields that have little to do with the real flow that is dominated by the interaction of helicopter and ship airwakes. The case of a rotor hovering in close proximity to a frigate deck was reproduced with fullyresolved blades, and the results shows a significant reduction of thrust due to the flow topology behind the hangar. The Helicopter Flight Mechanics (HFM) method was tested by simulating the aircraft response to a collective pilot input, using simplified models and coupled with CFD. Then, the coupled HFM/HMB2 method was used, in conjunction with the LQR auto-pilot, to simulate the phase of landing of a Sea King helicopter. Simulations were carried-out in free-air and above the frigate deck and the specified trajectories were followed adequately. Results for the ship landing show that the wake of the ship alters the obtained landing trajectory and that the current method captures some of the effects of the wake interaction.
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Saldivar, Orlando. "Levy flight as a robotic search pattern." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/75715.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 23-24).
Levy flights have been recently found to approximate the trajectories of animal foragers in their search for resources and food. Levy flights have proved to be effective in searching tasks because of their characteristic combination of long trajectories followed by bursts of short trajectories. In addition, some developments in robotics are currently geared toward robot miniaturization and mimicry of living creatures. For example, robots based on the features of hummingbirds and bees have already been developed though they are not yet autonomous. Incorporating Levy flight searching strategies into these miniaturized robots could yield more efficient and effective searching machines.
by Orlando Saldivar.
S.B.
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Tipping-Woods, William P. "Wing trailing vortex paths in formation flight." Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/13228.
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Includes bibliographical references.Formation flight has been shown to reduce the induced drag for a formation of aircraft. The mechanism by which this is achieved is caused by the wake velocity field of the aircraft. This field is dominated by wing-tip trailing vortices. The paths of these vortices become too complex for rigid wake models downstream of the second aircraft in the formation. To tackle this problem, a combined vortex lattice and vortex filament numerical model was developed. For each simulation the vortex lattice model determined the lift distribution which was applied to the vortex filament model. The vortex filament model used the Burnaham-Hallock vortex profile with a core size of 5% of the wing span to eliminate numerical instabilities. Individual components of the model were verified successfully against literature and the overall approach was validated against wind tunnel data. The wind tunnel data was extracted from apparatus designed and build as part of this study. The apparatus consisted of two NACA 0012 rectangular planform wings mounted in various formation positions and a tuft grid placed downstream of the wings to visualise the vortex paths. Test were performed with both wings at 8◦ angle of attack. Span-wise wing-tip overlap distances were set at 38%, 10%, 0% and -10% of the span, where 0% implies wing-tip alignment and a positive value indicates a wing-tip overlap. Vertical separations were set at -3%, 0% and 3% of the span for each span-wise wing-tip overlap condition apart from 38% which was only tested at 0 vertical separation. The formation outboard vortex paths were predicted well within the 3% span accuracy of the tuft grid. The predictions of the paths of the formation inboard vortices, however were less accurate. The errors were attributed to a combination of bias errors in the experimental apparatus as well as the pseudo-viscous effects of the Burnham-Hallock vortex profile.
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Zhang, Shiping. "FEM analysis of in-flight ice break-up." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=114560.
Full textAbstract:
Using a fracture mechanics framework, we present a finite element method to simulate the break-up of 2D ice accreted on the wings of aircraft and the shedding of 3D ice accreted on blades of helicopter. The fully automated ice break-up module is integrated in FENSAP-ICE [1-2], which is an in-flight ice accretion simulation code that solves flow, droplet impingement and ice accretion, in sequence. The 2D and 3D crack propagation packages are developed and validated by comparing with published results for a single edge cracked plate test case and a single edge-notched specimen with three points bending load, respectively. Numerous complicated ice-shapes are analyzed and comparisons are performed with a contemporary fracture mechanics code. Under typical icing and flow conditions, linear elasticity is found to be adequate for ice break-up analysis. For ice accreted on wings, an important finding of this study is that the breaking of ice has a strong dependence on its shape, i.e. under similar aerodynamic loading, some ice shapes fail while others do not. For ice accreted on helicopters, the finding is that the rotational speed of the blade and interface strength between ice and blade material are the major factors governing the ice break-up. The main objective of this work is to analyze complex multi-physics phenomenon and provide a simplified ice break-up model for the industrial users and aerodynamic designers. The potential use of this tool, however, is not limited to aerodynamics; it can be applied in areas of environmental science, material science, glaciology, earthquake and rupture analysis.Dans le cadre de la mécanique des fractures, nous présentons une méthode d'éléments finis qui simule le bris de la glace accumulée sur les ailes d'avions, en deux dimensions, ainsi que le délestage du givre accumulé sur les pales de l'hélicoptère, en trois dimensions. Le module de bris de glace, entièrement automatisé, est intégré en FENSAP-ICE [1-2], un logiciel de simulation qui résout séquenciellement le flux, l'impact des gouttelettes et le cumul de glace. Les modules bidimensionnels et tridimensionnels de propagation de fissures sont développés et validés par comparaison avec des résultats expérimentaux sur une plaque fissurée d'un seul côté, ainsi que pour un spécimen entaillé d'un seul côté avec une charge de flexion en trois points. Plusieurs formes de glace sont analysées et des comparaisons faites avec un autre code traitant la mécanique des fractures. Dans des conditions typiques de givrage et d'écoulement, l'élasticité linéaire s'est avérée adéquate pour une analyse du bris de glace. Pour la glace accumulée sur les ailes, une conclusion importante de cette étude est que le bris de glace dépend fortement de sa forme, c'est-à-dire que pour des charges aérodynamiques similaires, certaines formes de glace briseront, tandis que d'autres ne le feront pas. En ce qui concerne la glace accumulée sur les hélicoptères, il a été conclu que les facteurs les plus importants pour le bris de glace sont la vitesse rotationnelle de la pale et la force d'adhésion entre la glace et la pale. L'objectif principal de cet ouvrage est d'analyser des phénomènes multi-physiques complexes et de fournir un modèle simplifié du bris de la glace pour les utilisateurs industriels et les concepteurs en aéronautique. L'utilisation de cet outil n'est toutefois pas limitée à l'aérodynamique, puisqu'il peut être employé dans des domaines tels que les sciences environnementales, les sciences des matériaux, la glaciologie et l'analyse des tremblements de terre et de rupture.
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Bizinos, Nicholas. "Passenger comfort during formation flight within atmospheric turbulence." Master's thesis, University of Cape Town, 2012. http://hdl.handle.net/11427/12050.
Full textAbstract:
Includes abstract.Includes bibliographical references.
Formation flight is currently being investigated as a means to reduce drag and improve fuel efficiency in commercial aviation. In light of this, the potential for passenger discomfort due to the formation flying through free air turbulence was considered in this study. In an attempt to approximately ascertain the increase in discomfort, a simple formation flight aerodynamic model for two aircraft in formation was developed. The wing trailing vortices were assumed to shift in an ideal fashion within atmospheric turbulence resulting in aerodynamic disturbance loads acting on the trailing aircraft. As the sensitivity of the human body to vibrations is frequency dependent, spectral representation of atmospheric turbulence was incorporated. Monte Carlo simulations were done for various levels of turbulence intensity.
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Cheng, Bo. "Passive rotational damping in flapping flight." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 89 p, 2009. http://proquest.umi.com/pqdweb?did=1889090361&sid=9&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Martin, Justin N. "Nonlinear tracking of natural mechanical systems for HWIL simulation." Auburn, Ala., 2007. http://repo.lib.auburn.edu/07M%20Theses/MARTIN_JUSTIN_8.pdf.
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George, Ryan Brandon. "Design and Analysis of a Flapping Wing Mechanism for Optimization." BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/2737.
Full textAbstract:
Furthering our understanding of the physics of flapping flight has the potential to benefit the field of micro air vehicles. Advancements in micro air vehicles can benefit applications such as surveillance, reconnaissance, and search and rescue. In this research, flapping kinematics of a ladybug was explored using a direct linear transformation. A flapping mechanism design is presented that was capable of executing ladybug or other species-specific kinematics. The mechanism was based on a differential gear design, had two wings, and could flap in harsh environments. This mechanism served as a test bed for force analysis and optimization studies. The first study was based on a Box-Behnken screening design to explore wing kinematic parameter design space and manually search in the direction of flapping kinematics that optimized the objective of maximum combined lift and thrust. The second study used a Box-Behnken screening design to build a response surface. Using gradient-based techniques, this surface was optimized for maximum combined lift and thrust. Box-Behnken design coupled with response surface methodology was an efficient method for exploring the mechanism force response. Both methods for optimization were capable of successfully improving lift and thrust force outputs. The incorporation of the results of these studies will aid in the design of more efficient micro air vehicles and with the ultimate goal of leading to a better understanding of flapping wing aerodynamics and the development of aerodynamic models.
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Maccarana, Yamuna. "Health Monitoring of Electro-Mechanical Actuators for primary flight surfaces." Doctoral thesis, Università degli studi di Bergamo, 2019. http://hdl.handle.net/10446/128462.
Full textAbstract:
This thesis has been developed under the funded project named REPRISE (Reliable Electromechanical actuator for PRImary SurfacE with health monitoring), which aims to design a novel Electro-Mechanical Actuator (EMA) to be used on primary flight surfaces of small aircrafts. The main feature of the enhanced system is a novel embedded Health Monitoring (HM) component, which aims at assessing the grade of deterioration of the specimen without resorting to additional sensing within the EMA, but by monitoring the indirect effects that the operating degradation of the mechanical transmission elements has on measurements not directly related to their status.
The entire work has been validated experimentally by the employment of a dedicated test bench to perform endurance tests, gradually leading the mechanical components to final failure. The deterioration has been evaluated also by visual inspection and screw thread profile measurements. The effectiveness of the CD algorithm has been proven despite there was no evidence of loss of ability in pursuing the EMA main function of position tracking.
This work delivers an important contribution to the More Electric Aircraft mission and lies the foundation for the development of an HM module able to estimate the Remaining Useful Life (RUL) of the specimen and thus allowing maintenance actions when the an upcoming failure is advised, in a Predictive Maintenance strategy.
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Zambotti, Andrea. "Ground Testing and In-Flight Performance of a Space Mechanism." Doctoral thesis, Università degli studi di Trento, 2019. http://hdl.handle.net/11572/242871.
Full textAbstract:
LISA Pathfinder is a mission designed for testing the key technologies of the future LISA mission, whose goal is the detection of gravitational waves through the measurement of the relative motion of dedicated proof masses.
In LISA Pathfinder, a critical task is the release of two Test Masses (TMs); each TM has to be injected into free fall by a dedicated Grabbing Positioning and Release Mechanism (GPRM). Despite the symmetrical design of the GPRM, during the release, as an effect of asymmetric impulses exchanged by the TM and the release tips of the GPRM, the TM can acquire a residual momentum. The release is successful if the residual momentum of the TM can be compensated by the force authority of the capacity control, which allows to centre the TM in its housing; as a consequence, a residual momentum of the TM higher than a maximum requirement can be critical for the mission.
In the nominal release configuration, which assumes a monodimensional dynamics of the mechanism along the axis of the release tips, the residual momentum can be produced by the asymmetry of pushing forces (due to relative time delays between the two tips) or by two unbalanced adhesive pulls on the two sides. In particular, the low repeatability of the adhesive pulls suggests their characterization through a dedicated on-ground experimental campaign.
The characterization of the adhesive pulls exchanged by the TM and the GPRM has been the focus of the on-ground experimental campaigns performed by the University of Trento since the early 2000s. The Transferred Momentum Measurement Facility (TMMF) has been developed: a mock-up of the TM release, which allows a high measurability of the adhesive pulls and guarantees the representativeness of the experiment, has been tested in order to estimate the properties of the adhesive force at the contact between the two bodies. The estimated parameters, applied to a model of the in-flight release, allowed to predict that the effect of the asymmetric adhesive pulls applied by the GPRM to the TM should not be critical for the residual momentum.
In this thesis we report the completion of the research on the effect of adhesion in the TM release of LISA Pathfinder, by means of additional on-ground experimental campaigns, and by comparing the predictions with the actual behaviour of the GPRM in the releases performed during the early stages of the LISA Pathfinder mission (2016).
Prior to the launch of the mission, the on-ground TMMF facility has been modified in 2015 in order to host a copy of the GPRM, thus increasing the representativeness of the experiment w.r.t. the nominal release. The on-ground test campaign, consisting in several release tests, allowed to obtain a new (conservative) estimation of the effect of adhesion in the TM release of LISA Pathfinder.
The estimation of the adhesive effect, which yielded first a conservative prediction, has been then improved by investigating in detail the release dynamics of the TMMF. Thanks to a vibration mode-based model of the TMMF, the effect of the adhesive pull on the measured dynamics has been estimated with its uncertainty, thus yielding a more precise prediction for the in-flight case.
The launch of the LISA Pathfinder mission occurred on December 3, 2015, and prior to the beginning of the scientific operations the two TMs have been injected into free fall. Due to the criticalities observed in the releases, an additional in-flight release test campaign has been planned during the end-of-life activities (June 2017), by alternating several times grab and release of each TM. The in-flight release campaign yielded a statistical distribution of the residual momentum of the TM at the release, which we analysed in detail in order to characterize the actual in-flight GPRM performance. In particular, we focused on the deviation of the predictions (based on the assumption of nominal release) w.r.t. the in-flight observations, by looking for the motivations of the residual momentum measured in the in-flight case.
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Zambotti, Andrea. "Ground Testing and In-Flight Performance of a Space Mechanism." Doctoral thesis, Università degli studi di Trento, 2019. http://hdl.handle.net/11572/242871.
Full textAbstract:
LISA Pathfinder is a mission designed for testing the key technologies of the future LISA mission, whose goal is the detection of gravitational waves through the measurement of the relative motion of dedicated proof masses.
In LISA Pathfinder, a critical task is the release of two Test Masses (TMs); each TM has to be injected into free fall by a dedicated Grabbing Positioning and Release Mechanism (GPRM). Despite the symmetrical design of the GPRM, during the release, as an effect of asymmetric impulses exchanged by the TM and the release tips of the GPRM, the TM can acquire a residual momentum. The release is successful if the residual momentum of the TM can be compensated by the force authority of the capacity control, which allows to centre the TM in its housing; as a consequence, a residual momentum of the TM higher than a maximum requirement can be critical for the mission.
In the nominal release configuration, which assumes a monodimensional dynamics of the mechanism along the axis of the release tips, the residual momentum can be produced by the asymmetry of pushing forces (due to relative time delays between the two tips) or by two unbalanced adhesive pulls on the two sides. In particular, the low repeatability of the adhesive pulls suggests their characterization through a dedicated on-ground experimental campaign.
The characterization of the adhesive pulls exchanged by the TM and the GPRM has been the focus of the on-ground experimental campaigns performed by the University of Trento since the early 2000s. The Transferred Momentum Measurement Facility (TMMF) has been developed: a mock-up of the TM release, which allows a high measurability of the adhesive pulls and guarantees the representativeness of the experiment, has been tested in order to estimate the properties of the adhesive force at the contact between the two bodies. The estimated parameters, applied to a model of the in-flight release, allowed to predict that the effect of the asymmetric adhesive pulls applied by the GPRM to the TM should not be critical for the residual momentum.
In this thesis we report the completion of the research on the effect of adhesion in the TM release of LISA Pathfinder, by means of additional on-ground experimental campaigns, and by comparing the predictions with the actual behaviour of the GPRM in the releases performed during the early stages of the LISA Pathfinder mission (2016).
Prior to the launch of the mission, the on-ground TMMF facility has been modified in 2015 in order to host a copy of the GPRM, thus increasing the representativeness of the experiment w.r.t. the nominal release. The on-ground test campaign, consisting in several release tests, allowed to obtain a new (conservative) estimation of the effect of adhesion in the TM release of LISA Pathfinder.
The estimation of the adhesive effect, which yielded first a conservative prediction, has been then improved by investigating in detail the release dynamics of the TMMF. Thanks to a vibration mode-based model of the TMMF, the effect of the adhesive pull on the measured dynamics has been estimated with its uncertainty, thus yielding a more precise prediction for the in-flight case.
The launch of the LISA Pathfinder mission occurred on December 3, 2015, and prior to the beginning of the scientific operations the two TMs have been injected into free fall. Due to the criticalities observed in the releases, an additional in-flight release test campaign has been planned during the end-of-life activities (June 2017), by alternating several times grab and release of each TM. The in-flight release campaign yielded a statistical distribution of the residual momentum of the TM at the release, which we analysed in detail in order to characterize the actual in-flight GPRM performance. In particular, we focused on the deviation of the predictions (based on the assumption of nominal release) w.r.t. the in-flight observations, by looking for the motivations of the residual momentum measured in the in-flight case.
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Doepke, Edward Brady. "DESIGN AND FLIGHT TESTING OF A WARPING WING FOR AUTONOMOUS FLIGHT CONTROL." UKnowledge, 2012. http://uknowledge.uky.edu/me_etds/20.
Full textAbstract:
Inflatable-wing Unmanned Aerial Vehicles (UAVs) have the ability to be packed in a fraction of their deployed volume. This makes them ideal for many deployable UAV designs, but inflatable wings can be flexible and don’t have conventional control surfaces. This thesis will investigate the use of wing warping as a means of autonomous control for inflatable wings. Due to complexities associated with manufacturing inflatable structures a new method of rapid prototyping deformable wings is used in place of inflatables to decrease cost and design-cycle time. A UAV testbed was developed and integrated with the warping wings and flown in a series of flight tests. The warping wing flew both under manual control and autopilot stabilization.
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Ferguson, Kevin M. "Towards a better understanding of the flight mechanics of compound helicopter configurations." Thesis, University of Glasgow, 2015. http://theses.gla.ac.uk/6859/.
Full textAbstract:
The compound helicopter is a high speed design concept that is once again being explored due to the emerging requirements for rotorcraft to obtain speeds that significantly surpass the conventional helicopter. The speed of the conventional helicopter is limited by retreating blade stall, however the introduction of compounding delays the onset of this aerodynamic limitation until greater flight speeds. There are two common types of compounding known as lift and thrust compounding. Lift compounding, provided by the addition of a wing offloads the main rotor of its lifting responsibilities in high speed flight. Thrust compounding, provided by the addition of a propulsive source such as a propeller, provides additional axial force divorcing the main rotor of its propulsive duties at high speeds. The addition of compounding to the helicopter design can therefore increase the maximum speed of the aircraft. This increase in speed, provided that efficient hover capability is maintained, would make the compound helicopter suitable for various roles and missions in both military and civil markets. The compound helicopter is not a novel idea with many compound helicopter configurations flight tested in the 1960's. Due to these test programmes, as well as other studies, there is some material relating to the compound helicopter in the literature. However, the majority of the compound helicopter work describes flight tests of experimental aircraft or focuses on the design of the aircraft configuration. There are no systematic studies of the flight dynamics of compound helicopters which have been published. This Thesis targets this gap in the literature. Consequently, the aim of this Thesis is to investigate the effects of compounding on the conventional helicopter and how this addition to the helicopter design influences the flight mechanics of this aircraft class. With the renewed interest in the compound helicopter design this work is both original and timely. To investigate the flight dynamics of this aircraft class, two mathematical models of compound helicopter configurations are developed and compared with a conventional helicopter. The first compound helicopter configuration features a coaxial rotor with a pusher propeller providing additional axial thrust, and is referred to as the coaxial compound helicopter. The second configuration, known as the hybrid compound helicopter, features two wings each with a tip mounted propeller providing thrust compounding. The conventional helicopter features a standard helicopter design with a main rotor providing the propulsive and lifting forces, whereas a tail rotor, mounted at the rear of the aircraft, provides the yaw control. Other authors have focused on design considerations and have quantified all of the benefits of compounding but to date, a comprehensive study of the effect of compounding on the flight dynamics of a helicopter has not been published. The strategy of the work is to take the three aircraft configurations, the two compound helicopter configurations and the conventional helicopter, and determine their flight mechanics characteristics. Subsequently, the compound helicopter results can be compared with the baseline configuration, thereby isolating the effects of compounding. The flight mechanics characteristics that are determined in this Thesis include: trim, performance, stability and manoeuvrability attributes of the three helicopter configurations. These attributes are assessed by calculating the control angles which result in a steady flight condition and by the use of numerical linearisation and inverse simulation algorithms. All of these flight mechanics characteristics were assessed with the results, in some aspects, reinforcing the potential of the compound helicopter as well as highlighting some possible difficulties that will have to be addressed in the design of a compound helicopter.
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Onn, Oscar. "Application of a flight chip in an underwater quadcopter." Thesis, KTH, Skolan för teknikvetenskap (SCI), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-297467.
Full textAbstract:
This paper aims to describe the entire processof developing and testing an underwater quadcopter using aflight chip (FC) as the steering computer. The problem withthe FC is that the physics differs between using an air droneand an underwater drone. Most importantly, buoyancy is notnegligible underwater, while it is negligible in the air. Ultimately,it proved to be possible to design and build a usable underwaterquadcopter using an FC. The main design requirements foundto be important to make this possible is to decrease buoyancyas much as possible while still creating a watertight enclosure.
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Deshpande, Aditya. "Robot Swarm Based On Ant Foraging Hypothesis With Adaptive Levy Flights." University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1504780906566663.
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Beaugendre, Héloïse. "A PDE-based 3D approach to in-flight ice accretion." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=19535.
Full textAbstract:
Each year, sudden aircraft performance degradation due to ice accretion causes several incidents and accidents. Icing is a serious and not yet totally mastered meteorological hazard due to supercooled water droplets (liquid water droplets at a temperature below the dew point) that impact on aerodynamic surfaces. Icing results in performance degradations including substantial reduction of engine performance and stability, reduction in maximum lift and stall angle and an increase of drag. A realistic ice accretion simulation is achieved if the three contributing factors: the aerodynamic flow field, the water droplet trajectories, and the thermodynamic ice accretion process, are accurately modeled. A new approach to in-flight icing analysis is formulated and validated into this work. The methodology presented in this thesis is intended to be based on modern CFD algorithms to develop a useable new ice accretion tool for aircraft and engines, including: the solution of the 3D compressible turbulent Navier-Stokes equations; the computation of the collection efficiency by an Eulerian method; and a new module for the three-dimensional ice accretion process. To successfully complete the work, an appropriate turbulence model has been added to the existing flow solver. Therefore a part of this work has been the implementation and validation of the Spalart-Allmaras model. This turbulence model appeared to be robust and easy to use even in situation of complex 3D flow patterns encountered in icing. The new ice accretion model is expressed with mass and heat transfer balance at the aerodynamic surface using partial differential equations and four compatibility relations to close the system. An appropriate numerical scheme based on finite volume method is derived to solve the resulting system. 2D and 3D validations of the complete in-flight system (dry air flow field/droplets/ice accretion) conclude this work.
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Mazhar, Hashim. "Dynamics, control and flight testing of an unmanned, finless airship." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=117157.
Full textAbstract:
This thesis discusses a number of developments in the dynamics and control of a novel, autonomous, highly-maneuverable, finless, almost-lighter-than-air vehicle (ALTAV). The airship is inherently unstable due to absence of fins and is highly prone to winds. Four vectored thrusters are used to ensure closed-loop stability. This thesis deals with improvements made to an existing dynamics model, including the incorporation of the rotational damping moments of the airship, the drag resulting from the protuberances on the airship hull, the reaction torques and the gyroscopic moments on the airship due to the thrusters. Open-loop and closed-loop tests were designed and carried out to validate thephysical parameters that were empirically estimated, and, in general, good agreement was obtained. Furthermore, a complete controller suite that includes a low-level controller and a high-level guidance controller was designed and implemented for autonomous operation of the vehicle. Experimental testing was carried out to validate the performance of the controller suite in the presence of winds. The controller suite was shown to perform reliably even under the influence of winds of comparable magnitude to the airship's speed.Cette thèse examine le dynamique et contrôle d'un dirigeable autonome, extrêmement manoevrable, dépourvu d'ailerons et presque plus léger que l'air (ALTAV). Ce dirigeable est intrinsèquement instable dû à l'absence de surfaces stabilisatrices et aussi très succeptible au vent. Quatre propulseurs vectorisés sont utilisés pour assurer la stabilité en boucle fermée. Cette thèse concerne les améliorations au modèle dynamique existant, incluant l'incorporation des moments d'amortissements rotationnels du dirigeable, la traînée résultant des protubérances du dirigeable, les torques de réactions et moments gyroscopiques sur le dirigeable dû aux propulseurs. Des essais à boucle ouverte et boucle fermée ont été conçus et effectuées pour valider les paramètres physiques estimé empiriquement, et, en général, un bon accord a été obtenu. En outre, une suite de contrôle incluant un contrôleur à bas niveau et un contrôleur d'orientation de haut niveau a été conçu et mis en oeuvre pour l'opération autonome du véhicule. Les essais expérimentaux ont été effectués pour valider la performance de la suite de contrôle en présence de vents variables. Cet ensemble de contrôle a été c'est démontré fiable même sous l'influence de vents de vitesses comparable à la vitesse du dirigeable.
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Hilton, Emily M. (Emily Margaret). "Characterization and analysis of the flight dynamics of fruit flies." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/40431.
Full textAbstract:
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.Includes bibliographical references (p. 39).
For centuries, the human race has been perplexed by the various complex physical manifestations in nature. Much of what we have seen in nature we have tried to recreate, from the migration tendencies and routes of sea creatures to the flight of birds and insects. The flight of the fly, in particular, is of interest because of their natural stabilization techniques. The works of two scientists, Steven Vogel and Michael Dickinson, were researched in order to find out how the flight dynamics of the fly worked. It was found that the fast horizontal wing beating of the fly as well as the body angle of the fly helped to generate lift and thrust within the fly. Equilibrium was achieved due to the haltere of the fly, a small stubby organ behind the forewing which detected Coriolis forces at the base of the wing and created counter-rotations. Both scientists used work done by earlier scientist J.W. Pringle, who modeled the haltere as a mass-dashpot-spring system using dynamics in order to analyze the oscillatory motion and how it affects flight. The research done by all three scientists can serve to one day be able to produce micro aerial vehicles, using the flight dynamics of the fly as the basis of the flight of these vehicles.
by Emily M. Hilton.
S.B.
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Senneberg, Sofia. "Methods for validating a flight mechanical simulation model for dynamic maneuvering." Thesis, KTH, Flygdynamik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-299412.
Full textAbstract:
Flight mechanical simulators play an important role in the design steps during development of a new aircraft. To be able to simulate and evaluate flight mechanical characteristics during development it is important to minimize development time and cost while keeping flight safety high during early flights. The aim of the project presented in this thesis is to develop a method for validating a flight mechanical simulator against flight test data from dynamic maneuvering. An important part in this thesis is about how deviations in the result data can be found and analyzed, for example deviations between aircraft individuals or store configurations. The work presented here results in a good model for comparison of a big amount of data where it is easy to backtrace where the deviation occurs.Flygmekaniska simulatorer är av stor betydelse under utvecklingen av ett nytt stridsflygplan. Möjligheten att simulera och utvärdera under tidens gång har stor betydelse både ur tid- och kostnadsbesparings perspektiv men även ur flygsäkerhetsperspektiv när det är dags för första flygning. Syftet med det här projektet är att utveckla en metod för jämförelse mellan simulering och flygprov för att validera hur bra den flygmekaniska simulatorn kan förutspå flygplansbeteende. En viktig del i projektet syftar till hur skillnader i resultaten kan hittas och analyseras, till exempel skillnader mellan olika flygplansindivider eller lastkonfigurationer. Arbetet presenterat här har resulterat i en modell som är bra för jämförelse av en stor mängd data där det är enkelt att spåra var skillnaderna har uppstått.
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Vignotto, Davide. "Analysis of the in-Flight Performance of a Critical Space Mechanism." Doctoral thesis, Università degli studi di Trento, 2021. http://hdl.handle.net/11572/323575.
Full textAbstract:
Gravitational waves detection is a challenging scientific objective, faced by scientist in the last 100 years, when Einstein theorized their existence. Despite multiple attempts, it was only in 2016 that the first observation of a gravitational wave was officially announced. The observation, worth a Nobel Prize, was made possible thanks to a worldwide collaboration of three large ground-based detectors. When detecting gravitational waves from ground, the noisy environment limits the frequency bandwidth of the measurement. Thus, the type of cosmic events that are observable is also limited. For this reason, scientists are developing the first gravitational waves detector based in space, which is a much quieter environment, especially in the sub-Hertz bandwidth. The space-based detector is named laser interferometer space antenna (LISA) and its launch is planned for 2034. Due to the extreme complexity of the mission, involving several new technologies, a demonstrator of LISA was launched and operated between 2015 and 2017. The demonstrator mission, called LISA Pathfinder (LPF), had the objective to show the feasibility of the gravitational waves observation directly from space, by characterizing the noise affecting the relative acceleration of two free falling bodies in the milli-Hertz bandwidth. The mission was a success, proving the expected noise level is well below the minimum requirement.
The free-falling bodies of LPF, called test masses (TMs), were hosted inside dedicated electrode housings (EH), located approximately 30 cm apart inside the spacecraft. When free falling, each TM stays approximately in the center of the EH, thus having milli-meter wide gaps within the housing walls. Due to the presence of such large gaps, the TMs were mechanically constrained by dedicated mechanisms (named CVM and GPRM) in order to avoid damaging the payload during the launch phase and were released into free fall once the spacecraft was in orbit. Prior to the start of the science phase, the injection procedure of the TMs into free-fall was started. Such a procedure brought each TM from being mechanically constrained to a state where it was electro-statically controlled in the center of the EH. Surprisingly, the mechanical separation of the release mechanism from the TM caused unexpected residual velocities, which were not controllable by the electrostatic control force responsible for capturing the TM once released. Therefore, both the TMs collided with either the surrounding housing walls or the release mechanism end effectors. It was possible to start the science phase by manually controlling the release mechanism adopting non-nominal injection strategies, which should not be applicable in LISA, due to the larger time lag. So, since any release mechanism malfunctioning may preclude the initialization of LISA science phase, the GPRM was extensively tested at the end of LPF, by means of a dedicated campaign of releases, involving several modifications to the nominal injection procedure. The data of the extended campaign are analyzed in this work and the main conclusion is that no optimal automated release strategy is found for the GPRM flight model as-built configuration that works reliably for both the TMs producing a nominal injection procedure. The analysis of the in-flight data is difficult since the gravitational referencesensor of LPF is not designed for such type of analysis. In particular, the low sampling frequency (i.e., 10 Hz) constitutes a limiting factor when detecting instantaneous events such as collisions of the TM. Despite the difficulties of extracting useful information on the TM residual velocity from the in-flight data, it is found that the main cause of the uncontrollable state of the released TM is the collision of the TM with the plunger, i.e., one of the end-effectors of the GPRM. It is shown that the impact is caused by the oscillation of the plunger or by the elastic relaxation of the initial preload force that holds the TM. At the end of the analysis, some improvements to the design of the release mechanism are brie y discussed, aimed at maximizing the probability of performing a successful injection procedure for the six TMs that will be used as sensing bodies in the LISA experiment.
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Iliffe, Cathryn Ann. "The kinetics and mechanics of myosin and subfragment-1 from insect flight muscle." Thesis, University of York, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251800.
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Vetrisano, Massimo. "Uncertainty quantification and state estimation for complex nonlinear problems in space flight mechanics." Thesis, University of Strathclyde, 2017. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=28435.
Full textAbstract:
The complex dynamics which describe the motion of a spacecraft far from a massive planetary body or in a highly perturbed environment close to minor celestial objects raises two fundamental but related problems. The first is represented by the difficulty to accurately predict the evolution of its orbit even over short period when its initial conditions are known with a small degree of confidence. The second is given by the need for precise real time estimation of the trajectory when the spacecraft orbits near the asteroid’s surface to avoid impacting on it. The main example of the first problem is the perturbed four body problem for the Earth-Sun-Moon system. Earth-Sun Lagrangian Point Orbits (LPOs) are often selected for astrophysics and solar terrestrial missions while low cost missions aim at exploiting the so called Weak Stability Boundaries (WSB) to move at low propellant expense within the Earth sphere of influence. As current and future missions are planned to be placed on LPOs, it is a critical aspect to clear these regions at the end of operations to avoid damages to other spacecraft. For the second problem, we have a great number of asteroids and comets orbiting the inner solar system; they represent the so-called minor celestial objects which are very interesting for science since they preserve the remnants of the early formation of the planets and could shed light on the origins of life. At the same time they are very appealing for future commercial applications for the high content of precious ore. Among these celestial objects, the family of Near Earth Objects (NEOs) follows trajectories which lie close to, and sometimes cross, the Earth’s orbit. The impact hazard with the Earth has started to become considered as serious threat. Over the last three decades a number of missions have flown to and explored asteroids and comets, relying heavily on ground support with limited autonomy. In order to perform either asteroid’s exploration or collision hazard protection, autonomous navigation is needed, also to deal with the uncertain environment. Then the manipulation of asteroids’ orbit and attitude for deflection purposes is therefore required and an interesting problem to be studied. The aim of the research presented in this dissertation is to identify and develop methodologies for uncertainty propagation for spacecraft orbit and the application to orbit determination for complex nonlinear space mechanics problems, with particular care paid to the case of close proximity operations which are required when performing missions to minor celestial objects. The results are not limited only to this kind of problem but can be applied also to different scenarios. A first set of results focuses on the prediction of the trajectory evolution under initial condition uncertainties. The accuracy of the propagation of uncertainties is intimately related to the process of trajectory estimation, which relies on the use of the covariance matrix. The covariance matrix gives an idea of the dispersion of the spacecraft in terms of position and velocity. Different techniques to propagate the covariance matrix are used to predict the evolution of the trajectory when the initial conditions are known only to a certain degree of accuracy. They are compared under a highly nonlinear scenario where a spacecraft is injected into a disposal orbit towards an impacting trajectory with the Moon from a Lagrangian Point Orbit. A second set of results focuses on the identification of the estimation techniques applied to a single spacecraft. The estimation process performs well depending on the capability to propagate the covariance matrix and to incorporate the new information. A number of filtering techniques based on the Kalman and H∞ filters, employing different methods to handle the propagation of the covariance matrix, are presented and tested in typical nonlinear environments, i.e. a WSB transferan asteroid proximity, to draw precious information on their performance. The analyses demonstrate that only a hybrid Kalman- H∞ filter can enable the spacecraft to estimate its trajectory with a good balance between accuracy and computational costs. Then this method is applied to the navigation of spacecraft formation about a NEO showing that the navigation performance is significantly improved by sharing relative information among the spacecraft and the overall system is shown to be fault-tolerant. Finally the orbit’s and attitude manipulation of a small asteroid using a laser ablation system is analysed. An on-board state estimation and control algorithm is presented that simultaneously provides an optimal proximity control and control of the rotational motion of the asteroid. During the deflection, the proximity motion of the spacecraft is coupled with the orbital and rotational motion of the asteroid. The combination of the deflection acceleration, solar radiation pressure, and gravity field and plume impingement will force the spacecraft to drift away from the asteroid. In turn, a variation of the motion of the spacecraft produces a change in the modulus and direction of the deflection action which modifies the rotational and orbital motion of the asteroid.
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TORASSO, ALBERTO. "Low-order models and numerical techniques for the analysis of rotorcraft flight mechanics." Doctoral thesis, Politecnico di Torino, 2012. http://hdl.handle.net/11583/2497848.
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The dissertation describes (i) a mathematically rigorous approach for the derivation and validation of low–order helicopter mathematical models from first principles and (ii) the development or improvement of a set of numerical techniques that provide computationally efficient and reliable tools for the analysis of rotorcraft flight mechanics, and in particular evaluation of maximum performance and assessment of handling qualities. Simplified models are expected to provide results at a fraction of the computational cost required for performing the same analysis on the basis of higher order models, but, at the same time, the reliability of these results needs to be carefully assessed, which is one of the objectives of the present work. The techniques developed are tested on various single main rotor rotorcraft configurations, with a focus on articulated, teetering, and two–bladed–gimballed rotors.
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Noonan, Andrea L. "Flight plan generation for unmanned aerial vehicles." Thesis, Manhattan, Kan. : Kansas State University, 2007. http://hdl.handle.net/2097/385.
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Thamann, Michael. "AERODYNAMICS AND CONTROL OF A DEPLOYABLE WING UAV FOR AUTONOMOUS FLIGHT." UKnowledge, 2012. http://uknowledge.uky.edu/me_etds/18.
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UAV development and usage has increased dramatically in the last 15 years. In this time frame the potential has been realized for deployable UAVs to the extent that a new class of UAV was defined for these systems. Inflatable wing UAVs provide a unique solution for deployable UAVs because they are highly packable (some collapsing to 5-10% of their deployed volume) and have the potential for the incorporation of wing shaping. In this thesis, aerodynamic coefficients and aileron effectiveness were derived from the equations of motion of aircraft as necessary parameters for autonomous flight. A wind tunnel experiment was performed to determine the aerodynamic performance of a bumpy inflatable wing airfoil for comparison with the baseline smooth airfoil from which it was derived. Results showed that the bumpy airfoil has improved aerodynamics over the smooth airfoil at low-Re. The results were also used to create aerodynamic performance curves to supplement results of aerodynamic modeling with a smooth airfoil. A modeling process was then developed to calculate the aileron effectiveness of a wing shaping demonstrator aircraft. Successful autonomous flight tests were then performed with the demonstrator aircraft including in-flight aileron doublets to validate the predicted aileron effectiveness, which matched within 8%.
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Guo, Theresa (Theresa W. ). "Design and prototype of a hovering ornithopter based on dragonfly flight." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/40419.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.Includes bibliographical references (leaf 31).
Hovering is normally achieved using a horizontal wing path to create lift; bees, wasps and helicopters use this technique. Dragonflies hover using a unique method, by flapping along an inclined stroke plane. This seems to create a higher efficiency than is possible for normal hovering. The aim of this project is to build a mechanical model to mimic the aerodynamic properties and hovering motion of dragonflies. Through the design and evaluation of this model, we can evaluate the mechanical feasibility of reproducing the wing path using single motor control and establish whether the difference in stroke plane is advantageous for the dragonfly. By adjusting the initial angle of attack of the ornithopter's wings, we can artificially recreate varying stroke planes. A comparison of the resultant lift generated from different stroke planes showed that greater lift forces were generated with non-zero stroke planes as demonstrated in normal hovering.
by Theresa Guo.
S.B.
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Singh, Mukul Kumar. "Evaluating levy flight parameters for random searches in a 2D space." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/83632.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pag 23).
It is experimentally known that the flight lengths of random searches by foragers such as honey bees statistically belong to a power law distribution. Optimality of such random searches has been a topic of extensive research because knowing their optimal parameters may help applied sciences. Viswanathan et al. have shown the inverse-square power law to be the optimal law for such random searches. This thesis explores the capability of the model presented in such that it can be applied to Unmanned Autonomous Vehicles (UAVs). The thesis also identifies the minimum flight length, lmin, as an important factor that needs to be controlled based on the UAV's sensor range. We present a theoretical lmin as an explicit function of the sensor range, rv, and an estimated target density, p.
by Mukul Kumar Singh.
S.B.
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Biden, Kirsty Joy. "The effect of wing flexibility on ride comfort in formation flight." Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/24318.
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The paper addresses the issue of passenger ride comfort during formation flight. The study focuses on the vibration attenuation that occurs due to the aeroelastic effect, more particularly, on the influences these effects have on the magnitude of the fuselage accelerations. No distinction is made between the fuselage and passenger accelerations in the present work. The objective of the present study was to develop a representative aircraft model incorporating an aerodynamic model, based on the classical Vortex Lattice Method (VLM) and structural and inertial models defined by stiffness and mass matrices. The VLM code was validated for both large aspect ratio wings with low frequencies in unsteady aerodynamic conditions, as well as swept wings in steady flow, using the Warren 12 wing planform as reference. The structural model was developed using both a discretization method, as well as a continuous integration method. The results of these two approaches were carefully compared with one another as discrepancies were encountered during the analysis. The BAH jet transport wing was utilised in this study as it is widely recognised as a standard calibration case. This model was successfully implemented within a MATLAB/Simulink simulation environment. This paper presents the theoretical development of both the structural and aerodynamic models, along with the results of various test simulations. The restrained fuselage model was validated by performing a modal analysis and comparing the results with the Nastran Aeroelastic User's Guide results for a BAH wing. When the fuselage was permitted to translate vertically, a Fast Fourier Transform (FFT) was used to highlight the dominant frequencies of the system's motion and the damping ratio determined by a least squares method used to best fit the peaks of the displacement. A simple flutter analysis was performed and the results compared with those documented in the Nastran Aeroelastic User's Guide. The trailing wake vortices shed by the lead aircraft in formation flight were considered to have a solid core using the Burnham-Hallock Model. The optimal positioning of the trailing aircraft in a two-aircraft formation was discussed and all subsequent simulations run with the trailing vortex core initially located at the wing tip and 0.1 of a wingspan above the wing. The Von Karman turbulence model was used to simulate random atmospheric turbulence and the trailing vortex pair was assumed to shift in an ideal fashion within the atmospheric turbulence, resulting in fluctuating aerodynamic disturbance loads acting on the trailing aircraft. The results indicated that while the effect of turbulence on the aircraft itself was noteworthy, the motion of the trailing vortex pair in the spanwise-direction due to the turbulence, dominated the trailing aircraft's response. This was because the turbulence in the y-direction effectively altered the spanwise separation of the aircraft, varying the downwash distribution over the wing. The motion of the turbulence in the z-direction merely affected the intensity of the aerodynamic loads caused by the trailing vortices. From these results, it was concluded that an aircraft flying in formation will experience greater accelerations in turbulent conditions than a solo aircraft, due to the movement of the trailing vortices. A comparison of the motion of the airplane in response to atmospheric turbulence was compared to that documented by Fung, who made use of the Dryden turbulence model. For reasons discussed the results did not correlate exactly; however, the trends of the two sets agreed well. The individual contributions to vibrations due to shifting trailing vortices and turbulence in solo flight were analysed separately and then combined. The findings indicated that a significant difference exists between the fuselage accelerations of an aircraft with a flexible wing as opposed to a rigid wing. The results showed that the variance of the accelerations for the flexible aircraft were approximately 25% of those for the rigid aircraft. It was also found that by flying in formation the variance of the fuselage accelerations increase by approximately 18% from those of a solo aircraft flying in turbulent conditions. The predicted acceleration responses of the trailing aircraft were used as an indication of the passenger comfort levels. Thus it was concluded that while flight in formation does adversely affect the passenger ride comfort, the vibration attenuation that occurs due to the flexibility of the aircrafts wing is so significant as to minimise the discomfort levels.
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Larsson, Felix, and Christian Johansson. "Digital hydraulic actuator for flight control." Thesis, Linköpings universitet, Fluida och mekatroniska system, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-165262.
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In aviation industry, one of the most important aspects is weight savings. This since with a lowered weight, the performance of the aircraft can be increased together with increased fuel savings and thus lowered running costs. One way of saving weight is to reduce energy consumption, since with lowered energy consumption, lowered mass of fuel is required etc. Most aircraft are today maneuvered with hydraulic systems due to its robustness and power density. It is the primary source of power for primary and secondary flight controls. The control of a conventional system which is using proportional valves is done by altering flow by restricting it to the extent where the desired output is achieved, which implies heat losses since the full performance of its supply is wasted through the valve. In previous research, more energy efficient hydraulic systems called digital hydraulics has been investigated. In difference with conventional hydraulics, digital hydraulics uses low cost, high frequency on/off valves, which either are fully opened, or fully closed, instead of proportional valves to achieve the desired output. With this comes the benefit of no energy losses due to leakage and restriction control. The downsides with digital hydraulics is the controlabillity. One way of controlling it is by using several pressure sources which outputs different pressure levels. By using the on/off valves in different combinations, different outputs can be achieved in a discrete manner. In this thesis, the aim was to remove the impact of the discrete force steps which are present in digital hydraulics by creating concepts with hybrid solutions containing both digital hydraulics and restrictive control. Three concepts were developed and investigated using simulation. The energy consumption and performance was analysed and compared with a reference model, the concepts redundancy compared to conventional systems was discussed and finally the concepts were tested with an aircraft simulation model. The concepts were found to reduce the energy consumption with different magnitude depending on the load cycle. The performance was found to be almost as good as the reference model. The redundancy compared with conventional systems should be possible to maintain with slight modifications, but further investigation is needed. It was found that one of the most important aspects regarding energy consumption is which combination of supply pressures is used to supply the system since it influences leakage and flow due to compression.
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Wilcox, Michael Schnebly. "Trajectory Generation and Optimization for Experimental Investigation of Flapping Flight." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/3953.
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Though still in relative infancy, the field of flapping flight has potential to have a far-reaching impact on human life. Nature presents a myriad of examples of successful uses of this locomotion. Human efforts in flapping flight have seen substantial improvement in recent times. Wing kinematics are a key aspect of this study. This study summarizes previous wing trajectory generators and presents a new trajectory generation method built upon previous methods. This includes a novel means of commanding unequal half-stroke durations subject to robotic trajectory continuity requirements. Additionally, previous optimization methods are improved upon. Experimental optimization is performed using the new trajectory generation method and a more traditional means. Methods for quantifying and compensating for sensor time-dependence are also discussed. Results show that the Polar Fourier Series trajectory generator advanced rapidly through the optimization process, especially during the initial phase of experimentation. The Modified Berman and Wang trajectory generator moved through the design space more slowly due to the increased number of kinematic parameters. When optimizing lift only, the trajectory generators produced similar results and kinematic forms. The findings suggest that the objective statement should be modified to reward efficiency while maintaining a certain amount of lift. It is expected that the difference between the capabilities of the two trajectory generators will become more apparent under such conditions.