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Dissertations / Theses on the topic 'Vehicle center of Gravity'
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1
Price, Darryl Brian. "Estimation of Uncertain Vehicle Center of Gravity using Polynomial Chaos Expansions." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/33625.
Full textAbstract:
The main goal of this study is the use of polynomial chaos expansion (PCE) to analyze
the uncertainty in calculating the lateral and longitudinal center of gravity for a vehicle
from static load cell measurements. A secondary goal is to use experimental testing as a
source of uncertainty and as a method to confirm the results from the PCE simulation.
While PCE has often been used as an alternative to Monte Carlo, PCE models have
rarely been based on experimental data. The 8-post test rig at the Virginia Institute for
Performance Engineering and Research facility at Virginia International Raceway is the
experimental test bed used to implement the PCE model. Experimental tests are
conducted to define the true distribution for the load measurement systemsâ uncertainty.
A method that does not require a new uncertainty distribution experiment for multiple
tests with different goals is presented. Moved mass tests confirm the uncertainty analysis
using portable scales that provide accurate results.
The polynomial chaos model used to find the uncertainty in the center of gravity
calculation is derived. Karhunen-Loeve expansions, similar to Fourier series, are used to
define the uncertainties to allow for the polynomial chaos expansion. PCE models are
typically computed via the collocation method or the Galerkin method. The Galerkin
method is chosen as the PCE method in order to formulate a more accurate analytical
result. The derivation systematically increases from one uncertain load cell to all four
uncertain load cells noting the differences and increased complexity as the uncertainty
dimensions increase. For each derivation the PCE model is shown and the solution to the
simulation is given. Results are presented comparing the polynomial chaos simulation to
the Monte Carlo simulation and to the accurate scales. It is shown that the PCE
simulations closely match the Monte Carlo simulations.Master of Science
2
Barazanji, Deleer. "Model Based Estimation of Height of Center of Gravity in Heavy Vehicles." Thesis, KTH, Matematik (Inst.), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-92571.
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Abstract The center of gravity height in a vehicle a ects its dynamic driving properties but there is no accurate way of measuring the height of center of gravity today. One example of vehicle stabilizing systems is vehicle rollover warning and assist system which has to rely on a relatively accurate height of center of gravity estimate in order to be implemented in vehicles e_ciently and would otherwise be considered useless. In this thesis a literature study on the height of center of gravity in heavy vehicles in general and semitrailers in particular is conducted at Scania CV and emphasis is towards a model relying as little as possible on data from outside the tractor. A partly new model for detecting the vehicle's axle loads at di_erent acceleration values is developed and compared to other models, pros and cons are examined, furthermore an estimation tool is developed for the new model in a realistically applicable manner with regards to normal driving situations and solution limitations.The estimation tool is tested on Scania semitrailers with di_erent suspension con_gurations and the result shows that the height of center of gravity can be estimated as close as 4.1 (cm) from the real value for 4x2 Gen 2 Scania tractor and 3.3 (cm) for 4x2 Gen 3 Scania tractor.
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Rücker, Jan. "Měření hmotnostních parametrů vozidel." Master's thesis, Vysoké učení technické v Brně. Ústav soudního inženýrství, 2012. http://www.nusl.cz/ntk/nusl-232657.
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This thesis is the first part deals with methods of determining weight parameters of vehicles. By measuring the position of center of gravity and inertia measurements. In the second part focuses on the measurement of gravity position in a selected group of vehicles Škoda and their comparison between vehicles and comparison with simulation programs PCcrach and Virtual crach.
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Dušek, Otakar. "Vliv hmotnostních parametrů vozidel na jízdní dynamiku." Master's thesis, Vysoké učení technické v Brně. Ústav soudního inženýrství, 2016. http://www.nusl.cz/ntk/nusl-241368.
Full textAbstract:
This diploma thesis deals with assessment of weight parameters impact on driving dynamics. History and basic categories of personal vehicles are described in the introductory part. Weight parameters and driving dynamics of personal vehicles are described in the next part. Methodology and results of realized driving tests (braking test, circular test and avoidance maneuver) are presented in the experimental part of this work. Simulation of realized driving tests that was made by simulation software Virtual Crash is devised in the penultimate chapter. Evaluation of results that were found out from realized and simulated driving tests is made in the last chapter. Achieved results are briefly summarized in conclusion.
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Kutluay, Emir. "Identification Of Inertia Tensor Of Vehicles." Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/3/12608796/index.pdf.
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The aim of this thesis is to develop a methodology for obtaining mass properties of a vehicle using specific test rig. Investigated mass properties are the mass, location of center of gravity and the inertia tensor. Accurate measurement of mass properties of vehicles is crucial for vehicle dynamics research. The test rig consists of a frame on which the vehicle is fixed and which is suspended from the ceiling of the laboratory using steel cables. Mass and location of center of gravity are measured using the data from the test rig in equilibrium position and basic static equations. Inertia tensor is measured using the data from
dynamical response of the system. For this purpose an identification routine which employs prediction error method is developed using the built&ndashin functions from the System Identification Toolbox of MATLAB®
. The experiment was also simulated using Simmechanics Toolbox of MATLAB®
. Identification code is verified using the results of the experiment simulations for various cases.
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Kunovský, Martin. "Vliv polohy těžiště vozidla na jeho postřetový pohyb." Master's thesis, Vysoké učení technické v Brně. Ústav soudního inženýrství, 2012. http://www.nusl.cz/ntk/nusl-232690.
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This diploma thesis analyses the influence of the change to the vehicle’s center of gravity on its after-impact movement. The theoretical part of the thesis describes the basic methods which are used in investigation of the transverse, lengthwise and height position of center of gravity or the influence of center of gravity’s vehicle position to its stability and handling. Next part of the thesis deals with basic division of the road accidents and briefly describes the methods used in its analysis. Problematic maneuvers and everyday road traffic situations are stated in this thesis. Chosen situations were simulated in Virtual CRASH and PC crash programmes. Influence of the transverse, lengthwise and height position of center of gravity was investigated in these programmes with regards to the after-impact behaviour of vehicle. The obtained results were evaluated in the final chapter.
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Basson, Willem Albertus. "Fault tolerant adaptive control of an unmanned aerial vehicle." Thesis, Stellenbosch : Stellenbosch University, 2011. http://hdl.handle.net/10019.1/17898.
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Thesis (MScEng)--Stellenbosch University, 2011.ENGLISH ABSTRACT: This thesis presents the development of an adaptive longitudinal control system for an unmanned aerial vehicle (UAV). The project forms part of a research effort at Stellenbosch University into different fault-tolerant control techniques for UAVs. In order to demonstrate the usefulness of fault-tolerant adaptive control, the control system was designed to handle damage-induced longitudinal shifts in the centre of gravity (CG) of the aircraft, which are known to have a dramatic effect on the stability of a fixed-wing aircraft. Using a simplified force and moment model, equations were derived which model the effect of longitudinal CG shifts on the behaviour of the aircraft. A linear analysis of the longitudinal dynamics using these equations showed that the short period mode can become unstable for backward CG shifts. An adaptive pitch rate controller with the model reference adaptive control structure was designed to re-stabilise the short period mode when the CG shifts backwards. The adaptive law was designed using Lyapunov stability theory. Airspeed, climb rate and altitude controllers were designed around the pitch rate controller to allow full autonomous control of the longitudinal dynamics of the UAV. These outer loops were designed with constant parameters, since they would be unaffected by CG shifts if the adaptive pitch rate controller performed as desired. Pure software simulations as well as hardware-in-the-loop simulations showed that the adaptive control system is able to handle instantaneous shifts in the centre of gravity which would destabilise a fixed-gain control system. These simulation results were validated in flight tests, where the aircraft was destabilised using positive feedback and re-stabilised by the adaptive control system. Thus the simulation and flight test results showed that an adaptive control can re-stabilise an unstable aircraft without explicit knowledge of the change in the aircraft dynamics, and therefore could be effective as part of an integrated fault-tolerant control system.
AFRIKAANSE OPSOMMING: Hierdie tesis bied die ontwikkeling aan van ’n aanpassende longitudinale beheerstelsel vir ’n onbemande vliegtuig. Die projek is deel van navorsing by die Universiteit van Stellenbosch oor verskillende fout-tolerante beheertegnieke vir onbemande vliegtuie. Om die doeltreffendheid van aanpassende beheer te demonstreer, is die beheerstelsel ontwerp om situasies te kan hanteer waar die vliegtuig só beskadig word dat sy massamiddelpunt agtertoe skuif, wat ’n groot invloed op die stabiliteit van ’n vastevlerk-vliegtuig kan hê. ’n Vereenvoudigde model van die kragte en momente wat op die vliegtuig inwerk is gebruik om vergelykings af te lei wat beskryf hoe die gedrag van die vliegtuig verander as die massamiddelpunt agtertoe verskuif. Hierdie vergelykings is gebruik in ’n lineêre analise van die longitudinale dinamika van die vliegtuig, wat getoon het dat die kortperiode-modus onstabiel kan raak as die massamiddelpunt agtertoe verskuif. ’n Aanpassende heitempobeheerder met die modelverwysings-aanpassende beheerstruktuur is ontwerp om die kortperiode-modus weer te stabiliseer wanneer die massamiddelpunt agtertoe verskuif. Die aanpassingswet is ontwerp deur die gebruik van Lyapunov se stabiliteitsteorie. Lugspoed-, klimtempo- en hoogtebeheerders is rondom die aanpassende heitempobeheerder ontwerp sodat die longitudinale dinamika van die vliegtuig heeltemal outonoom beheer kan word. Hierdie buitelusse is ontwerp met vaste parameters, aangesien hulle nie geraak sal word deur verskuiwings in die massamiddelpunt as die aanpassende heitempobeheerder na wense werk nie. Suiwer sagteware-simulasies, sowel as hardeware-in-die-lus-simulasies, het getoon dat die aanpassende beheerstelsel oombliklike verskuiwings in die massamiddelpunt goed kan hanteer, waar sulke verskuiwings ’n beheerstelsel met vaste parameters onstabiel sou maak. Hierdie simulasie-resultate is bevestig deur vlugtoetse te doen, waar die vliegtuig onstabiel gemaak is deur positiewe terugvoer, en weer deur die aanpassende beheerstelsel stabiel gemaak is. Die simulasie- en vlugtoetsresultate wys dus dat aanpassende beheer ’n onstabiele vliegtuig weer kan stabiliseer sonder eksplisiete kennis van die veranderinge in die dinamika van die vliegtuig. Aanpassende beheer kan dus doeltreffend wees as deel van ’n geïntegreerde fout-tolerante beheerstelsel.
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Fedra, Tomáš. "Měření výškové polohy těžiště vozidla." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-228902.
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This diploma thesis deals with measurement of vehicle centre of gravity height position. All methods for measurement of CG height position are described in the first part. The second part deals with designing of device for measurement of CG height. This measurement device is analysed by Finite Element Method. The vehicle is tilt by hydraulic system. The third part shows the best tilt angle for minimal error of CG height. At the end, there is described a measuring procedure for designed device.
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Canale, Antonio Carlos. "Estudo de desempenho de autoveículos rodoviários considerando o passeio do centro de gravidade e restrições impostas pelo binômio pneumático x pavimento." Universidade de São Paulo, 1991. http://www.teses.usp.br/teses/disponiveis/18/18135/tde-29082016-150156/.
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Este trabalho aplica um procedimento para análise do desempenho de um autoveículo rodoviário (Kadett GS 2.0 da General Motors do Brasil), em aceleração e desaceleração (freagem), considerando o \"passeio do centro de gravidade\" e as \"restrições impostas pelo binômio pneumático x pavimento\". A dinâmica do processo de frenagem do veículo/exemplo é estudada, obtendo-se a desaceleração e o espaço percorrido, como função do \"passeio do centro de gravidade\" e duas \"restrições impostas pelo pneumático x pavimento\". Comparações teórico-experimentais são realizadas. Para o controle do processo de frenagem do veículo/exemplo, obtém-se uma \"função-transferência\" que muda continuamente o balanceamento das forças de frenagem nos eixos, utilizando-se, para isto, de sinais oriundos de um acelerômetro e de um sensor de peso instalados no veículo. Esta função otimiza o processo de frenagem para qualquer carregamento permissível do veículo e em qualquer nível de desaceleração (qualquer tipo de piso). Deste veículo obtêm-se os diagramas de rendimento, aceleração líquida para cada marcha engrenada, e, posteriormente, o \"tempo de aceleração\" e \"retomada de velocidade\", como função do \"passeio do centro de gravidade\" e das \"restrições impostas pelo pneumático x pavimento\". Comparações teórico-experimentais são também realizadas. Em todos os casos, foram obtidos bons resultados na comparação teórico-experimental, validando o modelo matemático elaborado e o procedimento de análise.This work applies a procedure for the analysis of the performance of a road vehicle, (General Motors do Brasil, Kadett GS 2.0), in acceleration and deceleration (braking), which takes into consideration the centre of gravity envelope and the restrictions imposed by the tyre/surface relationship. A study is made of the dynamic braking process of the vehicle/example, and the deceleration and distance covered are obtained as a functions of the c.g. position and the tyre/surface relationship. Comparisons are made between theory and experiment. A transfer function is obtained for the control of the braking process of the vehicle/example, that continually changes the balance of the braking forces on the axles, thorugh the use of signals transmitted from an accelerometer (g - meter) and a sensor giving the installed weight of the vehicle. This function optimizes the braking process for any permissible vehicle load and deceleration level, for any type of surface. The performance diagrams, the acceleration in each gear, and, following these the acceleration time and time-to-return-to-normal-speed are obtained as functions of the position of the c.g. and the restrictions imposed by the tyre/surface relationship. Comparisons of theory with practice are also made. In all cases, comparisons between theory and practice give good results, validating the mathematical model and the analysis procedure.
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Kubica, Petr. "Zařízení pro měření výškové polohy těžiště vozidla." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-232123.
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This diploma thesis deals the with measurment of the centre of gravity height position of a road vehicle and its issues. The introduction of this thesis focuses on the determining of the position of the center of gravity and the moment of inertia of a road vehicle. The next part is about creationing of a construction plan and its verification. The thesis contains a sensitivity analysis of this device including its results. The end of the thesis informs about the executed measurment in a laboratory and about recommendations for next measurments.
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Andersson, Jonas. "Center of gravity analysis : an actual or perceived problem?" Thesis, Försvarshögskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:fhs:diva-1197.
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Centers of Gravity (CoGs) analyses deliver vital input to the operational design. However, there are a great number of theories regarding the phenomenon which can create a certain degree of confusion. The diversity in theories may lead to misdirected mental energy where the focus is to discuss theories instead of using the theories at hand efficiently. The question is if the diversity in theory is an actual problem or if it just perceived as such? This research identifies the similarities and differences in the theories of Milan Vego and Joseph Strange & Richard Iron regarding CoGs, their sub elements and methods for analysis. The impact of the differences on the practical result is then surveyed by implementing the theories on adelimitated phase of the Falklands War, in order to conclude if the differences have a decisive impact on the product of the CoG analysis. The result of this thesis indicates that the diversity in theory is a perceived problem. The identified divergence does not reflect crucially on the CoG analysis and the variation of the input provided to the operational design is minor. The CoGs and the critical vulnerabilities identified are the same or at least similar, no matter which of the two theories was used in this research.Avdelning: ALB – Slutet Mag. 3 C-upps. Hylla: Upps. ChP 07-09
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Hack, Daniel E. "A cortical measure of the perceptual center of gravity." The Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=osu1406890046.
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Tell, Fredrik. "CCUAV : Cloud Center for Unmanned Aerial Vehicle." Thesis, Högskolan i Halmstad, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-36304.
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Projektets syfte är att bryta kopplingen mellan en specifik användare och drönare. Målet med projektet är att flera användare ska kunna hantera flera drönare från en central. En länk mellan en internetbaserad plattform vid namn Thingworx och en drönare med en inbyggd styrenhet, som kallas Pixhawk, sammankopplas med mikrodatorn Raspberry Pi 3. Sjöräddningssällskapet i Sverige önskar ett interface där flera av deras drönare med den inbyggda styrenheten kan hanteras och se dess position och videoström. PDSVisions mål är att skapa en demonstrator i en nyutvecklad plattform som förenklar uppkoppling med enheter med hjälp av ett begrepp som kallas IoT (Internet of Things). Resultat har resulterat i en prototyp av Sjöräddningssällskapets drönare ämnad att kontrolleras via den internetbaserade plattformen Thingworx. Drönaren startar, lyfter från marken och flyger en planerad rutt utan pilot. Slutsatsen visade att projektet kunde genomföras samt att det är möjligt att kommunicera med drönare via Thingworx
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Kelly, Rodney D. "Center of gravity in the asymmetric environment : applicable or not? /." Thesis, Monterey, CA : Naval Postgraduate School, 2006. http://handle.dtic.mil/100.2/ADA457503.
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Thesis (M.A. in National Security Affairs) -- Naval Postgraduate School, June 2006.Thesis advisor : Richard Grahlman. "June 2006." Includes bibliographical references (p. 61-63). Full text available on Public Stinet.
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Clark, Torin Kristofer. "Human perception and control of vehicle roll tilt in hyper-gravity." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/85692.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 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 (pages 96-105).
Pilots and astronauts experience a range of altered gravity environments in which they must maintain accurate perception and control of vehicle orientation for tasks such as landing and docking. To study sensorimotor function in altered gravity, a hyper-gravity test-bed was produced using a centrifuge. Previous experiments have quantified static tilt perception in hyper-gravity; however, studies of dynamic tilt, such as those experienced by astronauts and pilots, have been entirely qualitative. Current dynamic models of orientation perception cannot reproduce the characteristic perceptions observed in hyper-gravity. The aims of this thesis are to: 1) quantify static and dynamic roll tilt perception in hyper-gravity, 2) study pilot manual control of vehicle roll tilt in hyper-gravity, and 3) modify a dynamic model to predict hyper-gravity orientation perception. A long-radius centrifuge was utilized to create hyper-gravity environments of 1.5 and 2 Earth G's. In one experiment, over a range of roll tilt angles and frequencies, human subjects' (N=8) perceptions of orientation, in the dark, were assayed with a somatosensory task. Static roll tilts were overestimated in hyper-gravity with more overestimation at higher gravity levels and larger roll angles. Dynamic rotations were also overestimated in hyper-gravity, but generally less so than for static tilts. The amount of overestimation during dynamic rotations was dependent upon the angular velocity of the rotation with less overestimation at higher angular velocities. In a second experiment, human subjects (N=12) were tasked with nulling a pseudo-random vehicle roll disturbance using a rotational hand controller. Initial nulling performance was significantly worse in hyper-gravity as compared to the 1 G performance baseline. However, hyper-gravity performance improved with practice, reaching near the 1 G baseline over the time course of several minutes. Finally, pre-exposure to one hyper-gravity level reduced the measured initial performance decrement in a subsequent, different hyper-gravity environment. A modification to a previous dynamic spatial orientation perception model was proposed to allow for the prediction of roll tilt overestimation observed in hyper-gravity. It was hypothesized that the central nervous system treats otolith signals in the utricular plane differently from those out of plane. This was implemented in the model by setting a difference between the linear acceleration feedback gains in and out of the utricular plane. The modified model was simulated and found to accurately predict the static overestimation observed over a wide range of angles and hyper-gravity levels. Furthermore, it simulated the characteristic dependence of dynamic overestimation upon angular velocity with less overestimation at higher angular velocities. The modified model now allows for simulation across a range of altered gravity environments to predict human orientation perception. We conclude that hyper-gravity results in misperception of static and dynamic roll tilt and decrements in pilot manual control performance. Perception and manual control errors due to altered gravity, such as those observed here in hyper-gravity, may impact the safety of future crewed space exploration missions, in terms of accidents or aborts.
by Torin Kristofer Clark.
Ph. D.
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Takada, Hiroki, Yoshiyuki Kitaoka, Satoshi Iwase, Yuuki Shimizu, Tomoyuki Watanabe, Meiho Nakayama, Masaru Miyao, and Koshin Mihashi. "Characteristic Changes of Sway of Center of Gravity with Advancing Afe." Research Institute of Environmental Medicine, Nagoya University, 2003. http://hdl.handle.net/2237/7608.
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Cadwell, John Andres Jr. "Control of Longitudinal Pitch Rate as Aircraft Center of Gravity Changes." DigitalCommons@CalPoly, 2010. https://digitalcommons.calpoly.edu/theses/426.
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In order for an aircraft to remain in stable flight, the center of gravity (CG) of an aircraft must be located in front of the center of lift (CL). As the center of gravity moves rearward, pitch stability decreases and the sensitivity to control input increases. This increase in sensitivity is known as pitch gain variance. Minimizing the pitch gain variance results in an aircraft with consistent handling characteristics across a broad range of center of gravity locations.
This thesis focuses on the development and testing of an open loop computer simulation model and a closed loop control system to minimize pitch axis gain variation as center of gravity changes. DATCOM and MatLab are used to generate the open loop aircraft flight model; then a closed loop PD (proportional-derivate) controller is designed based on Ziegler-Nichols closed loop tuning methods. Computer simulation results show that the open loop control system exhibited unacceptable pitch gain variance, and that the closed loop control system not only minimizes gain variance, but also stabilizes the aircraft in all test cases. The controller is also implemented in a Scorpio Miss 2 radio controlled aircraft using an onboard microprocessor. Flight testing shows that performance is satisfactory.
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Ciobanu, Alexandra. "Lotus Firefly : The art of defeating gravity." Thesis, Umeå universitet, Institutionen Designhögskolan, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-72809.
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How many times have you been dreaming as a child that you run and after a few steps your body detaches off the ground and floats into the air? Most of the leisure activities we cultivate today have deep roots into humankind`s history and are still confined to land. The history of hovering has been inspired by the great comic books sci-fi stories and was illustrated through Star Wars flying vehicles, which have been later translated into jetpacks and hovering bikes. What if you would be stuck somewhere in the middle way between dream and reality? What if this vehicle would be at first available to you in a virtual platform, so that you could train to fly it, and when you would master the art or flying it, you could try the real experience?
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Harris, William Ray. "Anomaly detection methods for unmanned underwater vehicle performance data." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98718.
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Thesis: S.M., Massachusetts Institute of Technology, Sloan School of Management, Operations Research Center, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 101-102).
This thesis considers the problem of detecting anomalies in performance data for unmanned underwater vehicles(UUVs). UUVs collect a tremendous amount of data, which operators are required to analyze between missions to determine if vehicle systems are functioning properly. Operators are typically under heavy time constraints when performing this data analysis. The goal of this research is to provide operators with a post-mission data analysis tool that automatically identifies anomalous features of performance data. Such anomalies are of interest because they are often the result of an abnormal condition that may prevent the vehicle from performing its programmed mission. In this thesis, we consider existing one-class classification anomaly detection techniques since labeled training data from the anomalous class is not readily available. Specifically, we focus on two anomaly detection techniques: (1) Kernel Density Estimation (KDE) Anomaly Detection and (2) Local Outlier Factor. Results are presented for selected UUV systems and data features, and initial findings provide insight into the effectiveness of these algorithms. Lastly, we explore ways to extend our KDE anomaly detection algorithm for various tasks, such as finding anomalies in discrete data and identifying anomalous trends in time-series data.
by William Ray Harris.
S.M.
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Li, Xiaopeng. "Moving base INS/GPS vector gravimetry on a land vehicle." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1195677222.
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Kimball, J. Allen. "America's two-front war : the American media assault on our center of gravity /." Norfolk, Va. : Joint Forces Staff College, Joint Advanced Warfighting School, 2006. http://handle.dtic.mil/100.2/ADA451319.
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Thesis (M.S. in Joint Campaign Planning and Strategy)--Joint Forces Staff College, Joint Advanced Warfighting School, 2006."14 April 2006." Vita. "National Defense Univ Norfolk VA"--DTIC cover. Includes bibliographical references (p. 71-77). Also available via the Internet.
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Saeedkondori, Matin. "Estimation of the center of gravity of the human body using image processing." Thesis, California State University, Long Beach, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=1606699.
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Center of Gravity (COG) is an important parameter in many applications including aeronautics, astronomy, and kinesiology. This project focuses on the kinesiology application of the center of gravity, which helps people to understand their body’s stability and movement. The COG changes continually and does not have a fixed point inside the body. For example, in some exercises COG could be in the outer perimeter of the body.
In this project, we present an innovative approach to estimate the COG when the body is posed in an anatomical position. This approach uses image processing via MATLAB programing software. After preprocessing and processing of 2D images of the human body, we estimate the whole body’s COG in the three data sets. This project further considers alternate estimation in COG using reaction board technique, which allows us to estimate the accuracy of our method. In this project, the accuracy of the image processing COG estimation is 93% in compare to the reaction board. Finally, Body Mass Index (BMI) of the three data sets using the subject’s weight and height was calculated.
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Ballaire, Frederic [Verfasser]. "Dynamic, Continuous, and Center of Gravity Independent Weighing with a Loader / Frederic Ballaire." München : Verlag Dr. Hut, 2015. http://d-nb.info/1080754288/34.
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Cheng, Quan Jia. "A WLAN location estimation system using center of gravity as an algorithm selector." HKBU Institutional Repository, 2013. http://repository.hkbu.edu.hk/etd_ra/1513.
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Poullet, Julie(Julie M. ). "Leveraging machine learning to solve The vehicle Routing Problem with Time Windows." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/127285.
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Thesis: S.M., Massachusetts Institute of Technology, Sloan School of Management, Operations Research Center, May, 2020Cataloged from PDF version of thesis.
Includes bibliographical references (pages 111-125).
The Vehicle Routing Problem with Time Windows (VRPTW) has been widely studied in the Operations Research (OR) literature given its increasingly widespread applications, ranging from school bus scheduling to packages delivery. In the last decades, and in large part due to the surge in e-commerce and shortened promised lead times, the scale of the highly constrained VRPTW instances encountered in real-world applications has significantly increased. Simultaneously, various Machine Learning (ML) methods have been developed to tackle combinatorial problems and to leverage complex data structure, but little research has been done on applying these techniques to the VRPTW. In light of this research gap, our thesis develops a process to solve large-scale VRPTW without classical OR routing by proposing a two-stage algorithm. In the first stage, we design a clustering algorithm leveraging Optimal Classification Trees (OCT), which aims at dividing customers into smaller subsets. In the second stage, we present an actor-critic Reinforcement Learning (RL) approach to solve the VRPTW on these smaller customers clusters. Subsequently, we explore the interactions between ML and OR and develop a framework to overcome the difficulties linked to the differences between the train and test sets, as well as the adversity created by the OR algorithm. We also study the generalization limitations of RL methods. Results show that the clustering approach is competitive with regards to a k-means-based clustering, yielding improvements up to 5% in terms of number of vehicles, and that a RL approach can successfully solve medium-size VRPTW instances, providing optimality results similar to state-of-the-art industrial solvers.
by Julie Poullet.
S.M.
S.M. Massachusetts Institute of Technology, Sloan School of Management, Operations Research Center
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Burnham, Katherine Lee. "Information fusion for an unmanned underwater vehicle through probabilistic prediction and optimal matching." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/127297.
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Thesis: S.M., Massachusetts Institute of Technology, Sloan School of Management, Operations Research Center, May, 2020Cataloged from PDF version of thesis.
Includes bibliographical references (pages 89-92).
This thesis presents a method for information fusion for an unmanned underwater vehicle (UUV).We consider a system that fuses contact reports from automated information system (AIS) data and active and passive sonar sensors. A linear assignment problem with learned assignment costs is solved to fuse sonar and AIS data. Since the sensors operate effectively at different depths, there is a time lag between AIS and sonar data collection. A recurrent neural network predicts a contact's future occupancy grid from a segment of its AIS track. Assignment costs are formed by comparing a sonar position with the predicted occupancy grids of relevant vessels. The assignment problem is solved to determine which sonar reports to match with existing AIS contacts.
by Katherine Lee Burnham.
S.M.
S.M. Massachusetts Institute of Technology, Sloan School of Management, Operations Research Center
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Ebert, Rebecca L. "Bridging Grammar and Speech Acoustics: Effects of Morpheme Status on Duration and Center of Gravity." Bowling Green State University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1616618286162091.
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Lashore, Michael. "Mathematical Model Validation of a Center of Gravity Measuring Platform Using Experimental Tests and FEA." DigitalCommons@CalPoly, 2015. https://digitalcommons.calpoly.edu/theses/1467.
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This thesis sets out to derive an analytical model for a center of gravity (CG) measuring platform and examines its validity through experimental testing and Finite Element Modeling. The method uses a two-stage platform tilting process to first locate the planar CG coordinates and then find the third CG coordinate normal to the platform. An uncertainty model of the measuring platform was also developed, both CG and uncertainty models were implemented in the form of a MATLAB code. A load cell sizing task was also added to the code to assist the Integration Engineers at Jet Propulsion Laboratory in selecting load cells to design their own version of the CG Platform. The constructed CG Platform for this project used an array of six strain gauges, four C2A-06-062LT-120 Tee Rosettes and two C2A-06-031WW-120 Stacked Rosettes. They were bonded onto the legs of three truss shaped bipods. Results from the Platform Tilting Tests could not be used to validate the CG model as the measured CG and weight values found from the experimental tests contained a considerable amount of error. The errors in the Platform Tilting Tests are believed to stem from the initial errors observed during the bipod rod and strain gauge calibration tests. As an alternative, an FE model of the CG measuring platform was created as another means of validation. The math model of the CG measuring platform was successfully validated by showing that there was less than a 0.01% different between the bipod loads predicted from the MATLAB code and the FE model. Using the FEM generated loads as inputs into the CG code to calculate a CG matched the initial point mass or CG created in the FE model within a 0.01% difference. To validate the CG model even further, another test should be performed using a CG Platform prototype instrumented with load cells to generate new experimental data and compare them with the results from the FE model.
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Sridhar, Siddharth. "Spacesuit and Portable Life Support System Center of Gravity Influence on Astronaut Kinematics, Exertion and Efficiency." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1447690750.
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Roush, Grant Corwin. "Finding Cadaveric Human Head Masses and Center of Gravity: A Comparison of Direct Measurement to 3D ing." Wright State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=wright1282766380.
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Chiraphadhanakul, Virot. "Large-scale analytics and optimization in urban transportation : improving public transit and its integration with vehicle-sharing services." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/82190.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Sloan School of Management, Operations Research Center, 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 (pages 143-154).
Public transportation is undeniably an effective way to move a large number of people in a city. Its ineffectiveness, such as long travel times, poor coverage, and lack of direct services, however, makes it unappealing to many commuters. In this thesis, we address some of the shortcomings and propose solutions for making public transportation more preferable. The first part of this thesis is focused on improving existing bus services to provide higher levels of service. We propose an optimization model to determine limited-stop service to be operated in parallel with local service to maximize total user welfare. Theoretical properties of the model are established and used to develop an efficient solution approach. We present numerical results obtained using real-world data and demonstrate the benefits of limited-stop services. The second part of this thesis concerns the design of integrated vehicle-sharing and public transportation services. One-way vehicle-sharing services can provide better access to existing public transportation and additional options for trips beyond those provided by public transit. The contributions of this part are twofold. First, we present a framework for evaluating the impacts of integrating one-way vehicles haring service with existing public transportation. Using publicly available data, we construct a graph representing a multi-modal transportation service. Various evaluation metrics based on centrality indices are proposed. Additionally, we introduce the notion of a transfer tree and develop a visualization tool that enables us to easily compare commuting patterns from different origins. The framework is applied to assess the impact of Hubway (a bike-sharing service) on public transportation service in the Boston metropolitan area. Second, we present an optimization model to select a subset of locations at which installing vehicle-sharing stations minimizes overall travel time over the integrated network. Benders decomposition is used to tackle large instances. While a tight formulation generally generates stronger Benders cuts, it requires a large number of variables and constraints, and hence, more computational effort. We propose new algorithms that produce strong Benders cuts quickly by aggregating various variables and constraints. Using data from the Boston metropolitan area, we present computational experiments that confirm the effectiveness of our solution approach.
by Virot Chiraphadhanakul.
Ph.D.
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Vaněček, Michal. "Měření polohy těžiště motocyklu." Master's thesis, Vysoké učení technické v Brně. Ústav soudního inženýrství, 2012. http://www.nusl.cz/ntk/nusl-232692.
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My diploma thesis deals with measuring the center of gravity (CG) the motorcycle. The first part is outlined with legislation and the types of motorcycle division. I mention the theoretical types of measuring the CG the motocycle there too. These methods are applied to the issue of motor vehicles. The chosen one way of measuring the center of gravity which is used for practical measurements of gravity the motocycle. The practical part included the weighing of the different types of motorcycles with a different occupancy. These values are then processed and the resulting CG are calculated for each motorcycle. The values of CG were compared by experiment with the program for the analysis of road accidents and reconnoitred the measured results with this program results. In the last chapter is the evaluation of individual CG motorcycle and the influence of changes in occupancy due to a motorcycle.
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Ballaire, Frederic [Verfasser], Steffen [Akademischer Betreuer] Müller, and Christian [Akademischer Betreuer] Schindler. "Dynamic, Continuous, and Center of Gravity Independent Weighing with a Loader / Frederic Ballaire. Betreuer: Steffen Müller ; Christian Schindler." Kaiserslautern : Technische Universität Kaiserslautern, 2015. http://d-nb.info/108082264X/34.
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Deng, Shengfu. "A Spatial Dynamic Approach to Three-Dimensional Gravity-Capillary Water Waves." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/28254.
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Three-dimensional gravity-capillary steady waves on water of finite-depth, which are uniformly translating in a horizontal propagation direction and periodic in a transverse direction, are considered. The exact Euler equations are formulated as a spatial dynamic system in which the variable used for the propagating direction is the time-like variable. The existence of the solutions of the system is determined by two non-dimensional constants: the Bond number b and λ (the inverse of the square of the Froude number). The property of Sobolev spaces and the spectral analysis show that the spectrum of the linear part consists of isolated eigenvalues of finite algebraic multiplicity and the number of purely imaginary eigenvalues are finite. The distribution of eigenvalues is described by b and λ.
Assume that C1 is the curve in (b,λ)-plane on which the first two eigenvalues for three-dimensional waves collide at the imaginary axis, and that the intersection point of the curve C1 with the line λ=1 is (b0,1) where b0>0. Two cases (b0,1) and (b,λ) â C1 where 0< b< b0 are investigated. A center-manifold reduction technique and a normal form analysis are applied to show that for each case the dynamical system can be reduced to a system of ordinary differential equations with finite dimensions. The dominant system for the case (b0,1) is coupled Schrödinger-KdV equations while it is a Schrödinger equation for another case (b,λ) â C1. Then, from the existence of the homoclinic orbit connecting to the two-dimensional periodic solution (called generalized solitary wave) for the dominant system, it is obtained that such generalized solitary wave solution persists for the original system by using the perturbation method and adjusting some appropriate constants.Ph. D.
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Bendapudi, Srinivas, and Mayil Murugan Shiva Kumar Patchai. "Design of Station for Calculating Centre of Gravity of Truck Cabin : A Product Design Project." Thesis, Linköpings universitet, Maskinkonstruktion, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-148599.
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As a part of Linköping University’s master program course curriculum, current thesis is performed at Tools and fixtures department (MPCT) of Scania, Oskarshamn. The aim of this master thesis project is to develop a complete construction of the station in CAD which calculates the weight and center of gravity of all the different cabs produced in Scania CV AB. To accomplish this project a generic product development process described in product development textbook by Ulrich and Eppinger (2012), fifth edition and The mechanical design by David G Ullman, fourth edition were extensively used. The whole function from a black box is decomposed into several sub functions and different solutions were identified for these individual functions. By using morphology matrix and proper combinations from these solutions five different concepts were developed and presented to Scania CV AB. The team along with technical design experts in the MPCT department evaluated all the concepts and one concept was chosen for further development. Protecting the weighing scales during loading of cab from forklift onto the station and safety for the cab during tilting are the two main challenges faced during detail design phase. We were able to achieve these operations by incorporating a lifting table into the station design. Thanks to the custom made multi-tasking lift table which is manufactured and supplied by HYMO. With the help of sensors, speed of the lifting table can be controlled with two operating speeds-High & Low. Lifting table moves in its lowest speed whenever it approaches the weighing scales. Incorporation of Jacob safety into the lifting table allows the table to always operate in low speed when the lift link is in action. These sensors ensure high safety for the cab and weighing scales. Apart from this, an emergency stop has been provided to stop the entire operation in case of emergencies. In this proposed design, the center of gravity values will be determined in two stages and the weight readings are recorded in computer during these stages. For determining the longitudinal and transverse distances of CG, weight readings from all the weighing scales is essential once the cab is loaded on the station from the forklift. For determining the vertical distance of CG, two weight readings and measured tilt angle is required. A calculation module will allow the user to enter these values and obtain the result in no time. This developed 3-D CAD model with 2-D drawings are presented to Scania and the obtained results of this work fulfilled the set of requirements set for this master thesis.
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Pitcher, Paige(Paige Marie). "Hit the deck : impacts of autonomous vehicle technology on parking and commercial real estate." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/113471.
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Thesis: S.M. in Real Estate Development, Massachusetts Institute of Technology, Program in Real Estate Development in conjunction with the Center for Real Estate, 2017Cataloged from PDF version of thesis.
Includes bibliographical references (pages 54-60).
The United States has a large supply of parking and with the adoption of autonomous vehicles, the demand for these spaces could change dramatically. Parking is among the most prevalent land uses occupying up to 31% of urban area. It is estimated that there are 3.4 to 8 parking spaces for each car in the US yielding 800 million to 2 billion spaces that could cover an area the size of West Virginia (Chester, Horvath, & Madanat, 2010). With fully autonomous vehicles expected on the consumer market by 2020, the $30 billion parking industry will experience enormous changes as cars evolve. This thesis models the effects of autonomous vehicles on the financial performance of urban parking garages. The future of parking and autonomous vehicles will be anything but smooth or certain, and this work harnesses the power of uncertainty through repeated random number simulation in financially modeling autonomous vehicles' impacts on parking garages. The results indicate that parking in the short term is a risky investment and in the longer term may not be a viable asset. As the only class of real estate explicitly built for vehicles, they have a high degree of exposure to changes created by autonomous vehicles. This is illustrated by significantly negative net present values and minimal returns of the simulation outputs. This exposure will continue to grow as the stock of parking spaces increases with minimum parking requirements for new construction. Recommendations from this research would be to limit new supply of parking to allow for greater utilization of existing stock, more beneficial use of urban land, and better use of construction and financial resources.
by Paige Pitcher.
S.M. in Real Estate Development
S.M.inRealEstateDevelopment Massachusetts Institute of Technology, Program in Real Estate Development in conjunction with the Center for Real Estate
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Turco, Andrew. "After the gas station : redevelopment opportunities from rethinking America's vehicle refueling infrastructure." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/90111.
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Thesis: M.C.P., Massachusetts Institute of Technology, Department of Urban Studies and Planning, 2014.Thesis: S.M. in Real Estate Development, Massachusetts Institute of Technology, Program in Real Estate Development in conjunction with the Center for Real Estate, 2014..
Page 93 blank. Cataloged from PDF version of thesis.
Includes bibliographical references (pages 89-92).
Gas stations are found throughout the US, but their ubiquity causes them to go largely unnoticed. Because their purpose - refueling vehicles - is so uniform and so integral to the existing automotive transportation system, stations share extensive siting and design similarities across many contexts. Recent corporate, market, and regulatory pressures have led to the closure of tens of thousands of these stations in the past few decades. Increasingly stringent Corporate Average Fuel Economy (CAFE) standards will likely continue the trend of station closures. CAFE standards are expected to reduce future US gasoline consumption and spur the production of alternative powertrain vehicles. Of these new powertrain technologies, electric vehicles (EVs) demand particular attention because their introduction has been quite strong and because their adoption has the potential to significantly change the location and physical environment in which vehicles are "refueled." EVs differ from other propulsion systems in that they rely on electricity for power. Unlike liquid fuels, which are most efficiently distributed from centralized facilities, electric power can be obtained from a number of dispersed outlets. This thesis seeks to rethink the physical infrastructure that is and has been necessary to fuel the US's vehicles by exploring the most effective deployment of EV charging systems and by proposing potential reuses for unneeded gas station sites. After studying vehicle travel patterns and EV charging requirements, at-home suburban charging systems emerge as the most effective way to support electric vehicles. In addition to the environmental benefits to the transportation system, solar and smart-meter components of this charging system enable the greening of the power grid as well. As such, this thesis posits that the most effective deployment of EVs and their associated chargers would be in suburban areas that currently have dirty energy profiles and high solar capacity. Another promising place for EV charger deployment would be at centralized stations along major transportation routes that could be co-located with uses that actively take advantage of the extended time it takes to recharge an EV battery. Especially in EV target regions, reduced demand for gasoline can be expected to further unlock opportunities for gas station property redevelopment. Challenges to reuse include environmental remediation costs and liabilities, but this thesis explores strategies for overcoming these obstacles, as well as redevelopment functions that take advantage of gas stations' small and distributed characteristics
by Andrew Turco.
M.C.P.
S.M. in Real Estate Development
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Bendall, William Bryson. "Retrospective Analysis of Injuries Sustained In Vehicle Front‐ and Back‐Overs in a Level I Pediatric Trauma Center." Thesis, The University of Arizona, 2017. http://hdl.handle.net/10150/623628.
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A Thesis submitted to The University of Arizona College of Medicine - Phoenix in partial fulfillment of the requirements for the Degree of Doctor of Medicine.Motor vehicle accidents involving pedestrians are some of the most common and lethal forms of injury for children in the United States. Among younger children, a common mechanism of action for severe trauma is when a vehicle runs over the child in a forward or backward motion at low speed resulting in a blunt crush injury. This typically occurs in non‐traffic settings including driveways, sidewalks, and roadways. Such incidents have been referred to in many different ways in the literature but for the purposes of this paper will be referred to as low speed vehicle run‐overs. This is a retrospective chart review carried out at Phoenix Children’s Hospital in affiliation with the University of Arizona College of Medicine‐Phoenix that categorizes and examines the injuries sustained by patients involved in low speed vehicle runovers occurring between December 2007 and August 2013. Fifty‐five pediatric patients were included with a median age of 24 months and 6 of these patients were fatally injured. Internal injuries were common overall and significantly more common in children ≤24months. Over half of the cohort sustained fractures, with a 24% incidence of skull fractures. All fatalities were the result of traumatic brain injury. Twenty percent of victims required operative intervention. It was concluded that the severity of these types of incidents varies from minimal to life threatening and best care requires close and thorough evaluation by the trauma and emergency department teams.
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Atkins, Brad Matthew. "Mars Precision Entry Vehicle Guidance Using Internal Moving Mass Actuators." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/50648.
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Many landing sites of scientific interest on Mars including most of the Southern Hemisphere at elevations above 2km Mars Orbiter Laser Altimeter reference are inaccessible due to current limitations in precision entry guidance and payload deceleration. Precision guidance and large payload deceleration is challenging due to the thin Martian atmosphere, large changes in free stream conditions during entry, and aerothermal and aerodynamic instability concerns associated with control systems with direct external flow field interaction. Such risks have descoped past Mars missions to unguided entry with the exception of Mars Science Laboratory's (MSL) bank angle guidance. Consequently, prior to MSL landing ellipses were on the order of 100's of km. MSL has approached the upper limit of payload deceleration capability for rigid, blunt body sphere cone aeroshells used on all successful Mars entry missions. Hypersonic Inflatable Aerodynamic Decelerators (HIADS) are in development for larger payload deceleration capability through inflated aeroshell diameters greater than rigid aeroshells constrained by the launch rocket diameter, but to date there has been limited dynamics, control, and guidance development for their use on future missions.
This dissertation develops internal moving mass actuator (IMMA) control systems for improving Mars precision entry guidance of rigid capsules and demonstrating precision guidance capability for HIADs. IMMAs provide vehicle control moments without direct interaction with the external flow field and can increase payload mass delivered through reducing propellant mass for control and using portions of the payload for the IMMAs. Dynamics models for entry vehicles with rotation and translation IMMAs are developed. IMMA control systems using the models are developed for two NASA vehicle types: a 2.65 m, 602 kg Mars Phoenix-sized entry capsule and an 8.3 m, 5.9 metric ton HIAD approaching payload requirements for robotic precursor missions for future human missions. Linear Quadratic controllers with integral action for guidance command tracking are developed for translation and rotation IMMA configurations. Angle of attack and sideslip guidance laws are developed as an alternative to bank angle guidance for decoupling range and cross-range control for improved precision entry guidance. A new variant of the Apollo Earth return terminal guidance algorithm is implemented to provide the closed-loop angle of attack range control commands.
Nonlinear simulations of the entire 8 degree of freedom closed-loop systems demonstrate precision guidance to nominal trajectories and final targets for off-nominal initial entry conditions for flight path angle, range, cross-range, speed and attitude. Mechanical power studies for IMMA motion show rotation IMMA require less total mechanical power than translation actuators, but both systems have low nominal mechanical power requirements (below 100 Watts). Precision guidance for both systems to terminal targets greater than 38 km down-range from an open-loop ballistic entry is shown for low mechanical power, low CM displacement, (< 4.5 in) and at low internal velocities (< 2 in/s) over significant dynamic pressure changes. The collective precision guidance results and low mechanical power requirements show IMMA based entry guidance control systems constitute a promising alternative to thruster based control systems for future Mars landers.Ph. D.
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Grould, Marion. "Études d'effets relativistes au Centre Galactique à l'aide de simulations d'observations d'orbites d'étoiles par l'instrument GRAVITY." Thesis, Paris Sciences et Lettres (ComUE), 2016. http://www.theses.fr/2016PSLEO013/document.
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Le Centre Galactique abrite en son cœur un objet compact de plusieurs millions de masses solaires. L'hypothèse faite à l'heure actuelle est que cet objet serait un trou noir supermassif décrit par la relativité générale. L'instrument de seconde génération du Very Large Telescope Interferometer, GRAVITY, va permettre d'apporter des réponses quant à la réelle nature de cet objet. Grâce à sa précision astrométrique de 10 microsecondes d'angle, il va pouvoir sonder l'espace-temps en champ fort via l'observation des étoiles et du gaz situés à proximité de l'objet central.Au cours de ma thèse j'ai mis au point un modèle permettant de simuler les observations d'orbites d'étoiles de GRAVITY, l'objectif étant d'extraire à l'aide de celui-ci les paramètres fondamentaux du candidat trou noir central ainsi que les effets relativistes. Pour cela, j'ai utilisé le code de tracé de rayons GYOTO développé à l'Observatoire de Paris. Ce code permet de calculer des trajectoires d'étoiles et de photons obtenues en présence d'un objet compact. Il est alors possible de simuler les positions apparentes d'étoiles en orbite autour du Centre Galactique en calculant leur image relativiste.J'ai d'abord validé le calcul des trajectoires des photons effectué dans GYOTO. Grâce à des tests effectués en déflexion faible et forte, j'ai pu démontrer que GYOTO était hautement satisfaisant pour simuler les observations GRAVITY. En effet, j'ai montré que l'erreur sur le calcul des géodésiques de genre lumière était inférieure à environ 10^-2 microseconde d'angle, et cela même pour de grandes distances d'intégration.Je me suis ensuite intéressée à l'étude d'une étoile appelée S2 qui a contribué à fortement contraindre la masse de l'objet central. Sa proximité au Centre Galactique fait d'elle une cible idéale pour sonder l'espace-temps en champ fort. En particulier, j'ai estimé quels étaient les temps minimaux d'observation nécessaires pour détecter des effets relativistes à l'aide de mesures astrométriques et spectroscopiques obtenues sur l'étoile S2. Pour cela, j'ai mis en place plusieurs modèles d'orbites prenant en compte chacun un certain nombre d'effets relativistes. Le modèle le plus précis est obtenu en relativité générale complète avec le code GYOTO. Néanmoins, puisque l'étoile S2 est suffisamment éloignée de l'objet compact, ce modèle néglige certains effets de lentilles gravitationnelles telles que les images secondaires et l'amplification des images primaires. Par ailleurs, je me suis également intéressée à la contraindre du moment cinétique du candidat trou noir central avec cette étoile. En particulier, j'ai déterminé, grâce au modèle le plus précis mis en place ici, qu'il était possible de contraindre la norme et la direction du moment cinétique avec une incertitude d'environ 0,1 et 20 degrés, respectivement, et cela en considérant des observations obtenues sur trois périodes de S2 et des précisions de 10 microsecondes d'angle et 10 km/s.En vue de la possible détection d'étoiles plus proches du Centre Galactique par GRAVITY, j'ai développé un modèle prenant en compte les effets de lentilles négligés dans le modèle précédent. Néanmoins, afin de minimiser le temps de calcul demandé par celui-ci, j'ai déterminé une zone de l'espace dans laquelle il était tout de même possible d'utiliser ce dernier.Enfin, j'ai étudié l'influence de corps du Système Solaire sur les mesures astrométriques de GRAVITY, c'est-à-dire sur la séparation angulaire entre deux sources du Centre Galactique. Cette étude a montré que ces mesures différentielles n'étaient déviées que de quelques microsecondes d'angle par la perturbation gravitationnelle engendrée par le Soleil. Cependant, celles-ci sont modifiées de plusieurs centaines de microsecondes d'angle par l'effet d'aberration induit par le mouvement de la Terre par rapport aux sources du Centre Galactique. Il sera donc nécessaire de prendre en compte cet effet lors de l'interprétation des données obtenues par GRAVITYDecades of studies have demonstrated the presence of a compact object of several million solar masses at the center of the Galaxy. Nowadays, the assumption is that this compact object is probably a supermassive black hole described by general relativity. The second generation instrument at the Very Large Telescope Interferometer, GRAVITY, is expected to better constrain the nature of this central object. By using its astrometric accuracy of about 10 microarcseconds, it will probe spacetime in strong gravitational fields by observing stars and gas located near the compact object.During my PhD I have developed a stellar-orbit model in order to interpret the future GRAVITY observations. By using this model it will be possible to extract the central black hole candidate parameters and relativistic effects. To implement the model, I used the ray-tracing code GYOTO developed at Observatoire de Paris. This code allows computing star and photon trajectories obtained in the vicinity of a compact object. It is thus possible to simulate apparent positions of stars orbiting the Galactic Center by computing relativistic images.My work started by validating the photon trajectories computed in GYOTO. By doing tests in both weak- and strong-deflection limits, I have shown that the GYOTO code is highly qualified to simulate GRAVITY observations. Indeed, the error made on the photon trajectories is inferior to 10^-2 microarcsecond, even when integrating over large distances.Then, I was interested in studying a star called S2 that contributed to importantly constrain the mass of the central object. This star is the second closest star to the Galactic Center and has an orbital period of about 16 years. Nowadays, we do not know whether closer-in stars will be discovered by GRAVITY. It is thus important to extract as much information as possible from this star. In particular, I have estimated the minimal observation times needed to detect relativistic effects by using astrometric and spectroscopic measurements of S2. To do so, I have developed different stellar-orbit models taking into account a certain number of relativistic effects. The more accurate model is obtained by using the ray-tracing code GYOTO and considering all relativistic effects. However, as the S2 star is sufficiently far from the compact object, this model neglects certain gravitational lensing effects such as the secondary images and the primary images amplification. Besides, I was also interested in the possibility of constraining the angular momentum of the central black hole candidate with the S2 star. In particular, I have shown that with a model which does not use ray-tracing, the norm and the direction of the angular momentum can be constrained with an uncertainty of about 0.1 and 20 degrees, respectively, by using observations obtained during three periods of S2 and with accuracies reaching 10 microarseconds and 10 km/s.Since closer-in stars could be detected by GRAVITY, I have developed a more accurate stellar-orbit model taking into account the lensing effects neglected in the previous model. However, in order to minimize the computing time required by this model, I determined a volume in which it is possible to neglect both the secondary images and the primary images amplification.Finally, I have studied the impact of different components of the Solar System on astrometric positions measured by GRAVITY. This study has shown that those measurements are deviated by an amount of a few microarcseconds by the gravitational perturbation generated by the Sun. However, those apparent positions are shifted by several hundred microarcseconds by the aberration effect due to the movement of the Earth with respect to the Galactic Center. It is thus necessary to take into account this effect in future interpretations of GRAVITY observations
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Chai, Sonny T. "Landing gear integration in aircraft conceptual design." Thesis, This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-09182008-063506/.
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Mlynár, Adam. "Konstrukční návrh tříkolového vozidla." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-445160.
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The goal of this diploma thesis is to create structural design of reverse trike vehicle. With use of vehicle dynamics simulations in software MSC Adams Car 2019 is examining suitability of double wishbone suspension with different roll centre heights and effect of longitudinal position of Centre of mass on ride properties and limits. Selected concept of reverse trike vehicle is structurally designed using Solidworks 2016 and stress is inspected with FEM software Ansys Workbench 2019.
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Náglová, Katarína. "Konvenční a adaptivní metody nastavení parametrů regulátoru pro řízení letové výšky letadla s pohyblivou pozicí těžiště v prostředí MATLAB - Simulink." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2013. http://www.nusl.cz/ntk/nusl-219931.
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The thesis is focused on aircraft flight level control in case when the location of center of gravity changes during flight. The theoretical part of the thesis describes basics of aerodynamics, which are necessary to understand airplane's behavior and its control theory. Basics of state theory and stability of systems, as it is used for design of linear model. This part also mentions mathematical equations of nonlinear model of business jet and discusses conventional and adaptive methods used to design autopilot parameters. Several autopilots were designed in practical part of the thesis. The most important part is the logic used to determine location of center of gravity of the airplane. The models use nonlinear model of an airplane that better represents the real environment and conditions.
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Dvořák, Karel. "Měření setrvačných charakteristik těles pro účely matematického modelování dynamiky vozidel." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2008. http://www.nusl.cz/ntk/nusl-227970.
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The aim of the diploma thesis is to create a concept of methods that can be used for measurement of important mechanical inertia properties of bodies -- the coordinates of center of gravity and the the moment of inertia tensor, in case we don't have 3D model of these bodies. The thesis divides this problem into several sub-problems and suggests the solutions for each of them. Required equipment was created and measurement was carried out. At the end the measured values are compared with the teoretical ones and accuracy of this method is determined.
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Yang, Feng. "On the estimation of center of gravity height of arbitrarily loaded articulated freight vehicle." Thesis, 2005. http://spectrum.library.concordia.ca/8569/1/MR04206.pdf.
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The accurate prediction of an impending rollover threat of a heavy vehicle forms the essential basis for developing a rollover prevention system. The vehicle roll stability and the rollover predictors are most significantly related to the center of gravity height of the trailer sprung mass, which tends to vary considerably. The developments in the rollover warning devices have been mostly limited due to extreme complexities associated with the onsite measurement of the center of gravity height of an arbitrarily loaded vehicle. In this study, the system identification techniques are applied to obtain an estimate of the c.g. (Center of Gravity) height on the basis of the measured response under a controlled directional maneuver. A simulation model of a five-axle tractor-semitrailer is analyzed in the TruckSim environment to identify the desirable response measure, which is most sensitive to variation in the c.g. height, and the test maneuver for deriving the desired response. A 10 D.O.F. (degree-of-freedom) analytical model of the vehicle is developed and linearized to derive the analytical transfer function relating the steer angle to the desired semitrailer sprung mass roll angle response. A model reduction technique is further applied to obtain a reduced-order analytical transfer function to facilitate its implementation.
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Skonieczny, Krzysztof. "Centre-of-gravity control for a Mars Rover chassis with multiple degrees of freedom." 2006. http://link.library.utoronto.ca/eir/EIRdetail.cfm?Resources__ID=450289&T=F.
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Li, Jeng-Shing, and 李政興. "Gravity Turn and Attitude Control of Launch Vehicle." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/85959818765602254887.
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碩士國立交通大學
電機與控制工程系所
98
To put a payload into orbit, a launch vehicle must meet altitude, speed and flight path angle specifications. Usually the flight path angle is near zero, which means the vehicle must turn from its vertical or near vertical launch attitude. The turning of vehicle is usually achieved by a thrust vector control system. Due to the large dynamic pressure during atmospheric flight, one of the control objective during this phase of flight is to prevent the induced bending moment from damaging the vehicle structure. Hence most vehicles adopt the so called gravity turn during the early atmospheric part of flight, that is, to maintain zero angle o attack and zero sideslip angle. This thesis investigates gravity turn control system design. Nonlinear and time-varying nature of aerodynamic model makes it inconvenient for control system design. This thesis proposes a method that construct approximate linear model and use it for control system design. Vertically launched vehicles need attitude control to achieve a certain pitch angle before gravity turn. There numerical examples are used to demonstrate the design attitude control system and gravity turn control system. Simulation results show that the designed control systems yield stable flight and achieve attitude and gravity turn design objectives.
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li, Hsien-Chang, and 李憲昌. "PSO algorithm with Center of Gravity and Dimension Searching." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/05230620070585377343.
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碩士國立中央大學
電機工程學系
101
In this thesis we have presented an improved algorithm for Particle Swarm Optimization (PSO) named Standard Dimension Searching with Center of Gravity PSO algorithm (SDGPSO). The SDGPSO algorithm needs to have a special experience-sharing mechanism to coordinate with single-dimensional searching mechanism. These mechanisms cause the faster convergence ability in the pre-convergence and have less computing time than SPSO. However, The ability to escape local optimal solution is worse than SPSO in the post-convergence. Because of this shortcoming, we further proposed a hybrid version named SDGPSO-MSP which takes advantages of fast and excellent convergence ability from SDGPSO and obtaining the better convergent solution from SPSO. The performances of SDGPSO and SDGPSO-MSP are fairly demonstrated by applying sixteen benchmark problems and compared it with several popular PSO algorithm. The simulations of results show that our proposed methods are effective and gain better performance than other compared PSO algorithms.
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Tung, Yen-Chun, and 董彥均. "Center of Gravity Adaptation of a Bicycle-riding Robot." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/80029828902581373684.
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碩士國立清華大學
動力機械工程學系
104
This thesis develops an adaptive controller for a bicycle-riding robot that can provide consistent balancing and steering performance under uncertain center of gravity. The adaptive controller contains two parts: the adaptation part and the PD control part. While the adaptation part estimates the roll angle associated with the uncertain center of gravity, the PD control part uses the estimated roll angle and the measured roll rate to stabilize the bicycle laterally. The design of the adaptive controller is based on a linearized third-order model which contains the roll angle, the roll rate and the steering angle as the states. The input of the model is a fictitious quantity that once it is determined by the controller, the actual steering angle input to the bicycle is obtained by low-pass filtering the fictitious input. Simulations and experiments verify that the adaptive control can automatically steer the bicycle in a straight line even if mass imbalance exists.
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Wu, Chun-lung, and 吳俊龍. "Development of Vehicle Controls based on the Gravity-Shifting Signals." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/09490286173708742497.
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碩士國立臺南大學
機電系統工程研究所碩士班
98
In the last years, most motion controls for vehicles have been developed for people and improving the traditional systems with special needs. For example, by using joystick to control assistant robot system, for disabled persons, has been developed. However, the traditional methods, using joystick, steering wheel, or keyboard, between humans and machines still can not match the requirement of those with severe disabilities. In order to satisfy this requirement, the new method is developed like Brain-Computer Interfaces (BCI), visual information and voice recognition. For example, using voice recognition to control some wheelchair or applications by means of basic voice commands, writing a text in “speech and spell” applications etc... On the other hand, the other options, likely based on visual information for detecting gesture or eye movements with an on-board computer, are inconvenient and difficult to control for the elderly or the handicapped. Besides, they are high cost. The purpose of this study is to design and develop a new controller for solving above problems. First, the steering motion control by using gravity shift signals is proposed. Here, the angle of body slope can be measured by tilts as the input signals for control. The control concept is possible to be developed in the use of military, entertainment, and society welfare etc... Second, in order to simplify the transmission mechanism, a wheel motor, also called hub-in motor, which is directly mounted inside the wheel so that the transmission gears and differentials are eliminated with associated energy loss. In addition, it is difficult to build up the dynamic model of wheel motor, and install rotational speed sensor, the neural-network (NN) is adopted to the instead of the dynamic model of wheel motor for sensorless motor control. To detect angles by using tilt sensor, but outputs of tilt sensor are different according to the variation of environment. In [27], for the fuzzy controllers, with stable and reliable output performance, are suitable for real-time speed control, it is used as an input signal processor of this system. The implements of system setup include designing the A/D converter, motor driver circuit and the main body of the system, a tricycle with two front wheels and one rear wheel (2F/1R). Most of the methods concerning with sensorless estimation need to use the Digital Signal Processor (DSP), and large number of mathematic computation. For above reasons, the microcontroller for sensorless estimation method is proposed in this study to reduce system complexity and costs. The effectiveness of this proposal has been confirmed through simulation study and experimental implementation. The mean absolute percentage error is about 1.05%.