Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The successful development of a three degree of freedom motion simulation platform, capable of simulating a vessel’s flight deck at sea, is presented. The motion simulation platform was developed to practically simulate and test an unmanned aerial vehicle’s capability of landing on a moving vessel, before practically being demonstrated on an actual vessel. All aspects of the motion simulation platform’s development are considered, from the conceptual design to its practical implementation. The mechanical design and construction of a pneumatic motion simulation platform, as well as the electronics and software to enable the operation of this motion simulation platform, are presented. Mathematical models of the pneumatic process and platform orientation are developed. A controller architecture capable of regulating the pneumatic process, resulted in the successful control of the motion simulation platform. Practical motion simulation results of one of the South African Navy Patrol Corvettes, demonstrate the motion simulation platform’s success. The successful development of the motion simulation platform can largely be attributed to extensive research, planning and evaluation of the different development phases. / AFRIKAANSE OPSOMMING: In hierdie studie word die suksesvolle ontwikkeling van ’n drie-grade-van-vryheid bewegingsimulasieplatform, wat in staat is daartoe om ’n skip se vliegdek ter see te simuleer, aangebied. Die bewegingsimulasieplatform is ontwikkel om ’n onbemande lugvaartuig se vermoë om op ’n bewegende skip te land, te simuleer en te toets, voor dit op ’n werklike skip gedemonstreer word. Alle aspekte van die ontwikkeling van die bewegingsimulasieplatform word in ag geneem – van die konsepontwerp tot die praktiese implementering daarvan. Die meganiese ontwerp en konstruksie van ’n pneumatiese bewegingsimulasieplatform word bespreek, sowel as die elektronika en programmatuur wat die werking van hierdie bewegingsimulasieplatform bemoontlik. Wiskundige modelle van die pneumatiese proses en platformoriëntering word ontwikkel. ’n Beheerderargitektuur wat in staat is daartoe om die pneumatiese proses te reguleer, lei tot die suksesvolle beheer van die bewegingsimulasieplatform. Praktiese resultate van die bewegingsimulering van een van die Suid-Afrikaanse Vloot se patrolliekorvette wys daarop dat die bewegingsimulasieplatform wel suksesvol is. Die geslaagde ontwikkeling van die bewegingsimulasieplatform kan grootliks toegeskryf word aan omvangryke navorsing, beplanning en evaluering van die onderskeie ontwikkelingsfases.

A 3D velocity model and 3D wave propagation code have been employed to simulate long-period ground motions in the upper Mississippi embayment. This region is exposed to seismic hazard in the form of large earthquakes in the New Madrid seismic zone and observational data are sparse, making simulation a valuable tool for predicting the effects of large events. These simulations were undertaken in order to estimate ground-motion characteristics and to investigate the influence of the 3D embayment structure and finite-fault mechanics. There are three primary fault zones in the New Madrid seismic zone, each of which was likely associated with one of the three main shocks of the 1811-1812 earthquake sequence. For this study, three simulations have been conducted on each major segment, evaluating the effects of different epicentral locations and rupture directions on ground motions. The full wave field up to a frequency of 0.5 Hz was computed on a 200 × 200 × 50 km3 volume, and up to a frequency of 1.0 Hz on a 100 × 100 × 50 km3 volume, using a staggered-grid finitedifference code. Peak horizontal velocity, bracketed durations, and pseudospectral accelerations were calculated at the free surface. Animations showing the evolution of peak horizontal velocity through time at the free surface were also generated. The New Madrid seismic zone simulations indicate that for the considered bandwidth, finite-fault mechanics such as fault proximity, directivity effect, and slip distribution exert the most control on ground motions. The 3D geologic structure of the upper Mississippi embayment also influences ground motion, with indications that the bedrock surface acts as a wave guide, trapping waves in shallow, low-velocity parts of the embayment.

The goal of this thesis was to get familiar with the basics of mathematical description of the thermal motion of particles in a given media, and with other possibilities of the software package COMSOL Multiphysics. A model for viscous and viscoelastic environments was created, a uniform and user friendly system for simulation and calculation of MSD and system for data conversion from FCS to MSD. Furthermore, the possibilities of the model for use in microrheology were assessed and another procedure in the implementation of the COMSOL program in the characterization of gels was proposed.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21461号 / 工博第4536号 / 新制||工||1707(附属図書館) / 京都大学大学院工学研究科建築学専攻 / (主査)教授 松島 信一, 教授 竹脇 出, 教授 池田 芳樹 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Mathematical modeling and realistic human simulation of human jogging motion is a very challenging problem. Majority of the current literature is focused on studying walking or running. This work is aimed at bridging the gap in literature due to the lack of research work in three main areas: (1) simulations and experiments on running at speeds lower than 3 m/s, (2) Kinetics of fore-foot strike pattern in jogging and running and (3) the existence of a double support phase in running at slower speeds and its effects. Formulations to simulate natural human jogging are studied and developed. The digital human model used for this work includes 55 degrees of freedom, 6 for global translation and rotation and 49 for the revolute joints to represent the kinematics of the body. Predictive Dynamics methodology is used for dynamic analysis where the problem is formulated as a nonlinear optimization problem. Both, displacement and forces are considered as unknowns and identified by solving the optimization problem. The equations of motion are satisfied by applying them as equality constraints in the formulation. Kinematics analysis of the mechanical system is performed using the Denavit-Haretneberg (DH) method. The zero moment point (ZMP) condition is satisfied during the ground contact phase to achieve dynamic stability. The joint angle profiles are discretized using B-spline interpolation method. The joint torque squared, also termed dynamic effort, and the difference between predicted motion and motion capture data are used as performance measures and minimized in the optimization formulation. The formulation also includes a set of constraints to simulate natural jogging motion. Two formulations are discussed for jogging on a straight path: (1) one-step jogging formulation and (2) one-stride jogging formulation. The one-stride formulation is discussed for clock-wise and counter clock-wise jogging along a curved path. Cause and effect is shown by obtaining simulation results for different loading conditions. The proposed formulation provides realistic human jogging motion and is very robust.

Future generations of unmanned spacecraft, aircraft, ground, and submersible vehicles will require precise relative navigation capabilities to accomplish missions such as formation operations and autonomous rendezvous and docking. The development of relative navigation sensing and control techniques is quite challenging, in part because of the difficulty of accurately simulating the physical relative navigation problems in which the control systems are designed to operate. A hardware testbed that can simulate the complex relative motion of many different relative navigation problems is being developed. This testbed simulates near-planar relative motion by using software to prescribe the motion of an unmanned ground vehicle and provides the attached sensor packages with realistic relative motion. This testbed is designed to operate over a wide variety of conditions in both indoor and outdoor environments, at short and long ranges, and its modular design allows it to easily test many different sensing and control technologies. / Master of Science

Fatigue analysis is essential for the optimization of products subjected to dynamic loads. However, a number of fatigue analysis theories have been developed, how to apply an established method in real-world product designs is not a trivial task. Most of small or medium sized enterprises (SMEs) still rely heavily on the experiments to evaluate the fatigue lives of products. Among existing fatigue design methods (i.e., experiments, analytical methods, and simulations), the simulation-based methods have the advantages of low cost, low risk environment and enable a designer to determine the accuracy and performance of a product design without building physical prototypes. Regarding the methodologies for fatigue analysis, some identified challenges are (1) the characterization of dynamic loads, (2) the formulation of finite element models which can be aligned with applications or testing scenarios, and (3) the verification and validation of simulations. To make a simulation-based fatigue analysis more practical for real-world product designs, the solutions to the aforementioned problems must be found. This thesis aims to establish a systematic methodology to perform the fatigue analysis for product design with any material, carbon steel material is used for the present case study to illustrate and verify the proposed methodology for fatigue analysis. Major tasks involved in this thesis study are: 1).The method for the characterization of dynamic loads. It is a numerical method to simulate the kinematic and dynamic behaviors subjected to the given motion, and it is expected to extract interacting dynamic forces of components to be analyzed. 2).The systematic method and procedure to formulate the problem of fatigue analysis as a finite element analysis model and find the solution of fatigue life of product.3).The procedure and approaches are developed to verify and validate fatigue analysis models and procedure used for the present case study.4).The parametric studies with a set of design variables to show the feasibility and flexibility of using simulation methods to evaluate the influence of multiple design variables on wheel products.<br>

Assessment of potential ground motions in seismically active regions is essential for purposes of seismic design and analysis. Peak ground motion intensity values and frequency content of seismic excitations are required for reliable seismic design, analysis and retrofitting of structures. In regions of sparse or no strong ground motion records, ground motion simulations provide physics-based synthetic records. These simulations provide not only the earthquake engineering parameters but also give insight into the mechanisms of the earthquakes. This thesis presents strong ground motion simulations in three regions of intense seismic activity. Stochastic finite-fault simulation methodology with a dynamic corner frequency approach is applied to three case studies performed in D&uuml / zce, L&rsquo / Aquila and Erzincan regions. In D&uuml / zce study, regional seismic source, propagation and site parameters are determined through validation of the simulations against the records. In L&rsquo / Aquila case study, in addition to study of the regional parameters, the limitations of the method in terms of simulating the directivity effects are also investigated. In Erzincan case study, where there are very few records, the optimum model parameters are determined using a large set of simulations with an error-minimization scheme. Later, a parametric sensitivity study is performed to observe the variations in simulation results to small perturbations in input parameters. Results of this study confirm that stochastic finite-fault simulation method is an effective technique for generating realistic physics-based synthetic records of large earthquakes in near field regions.

Nonlinear dynamic analysis is a required step in seismic performance evaluation of many structures. Performing such an analysis requires input ground motions, which are often obtained through simulations, due to the lack of sufficient records representing a given scenario. As seismic ground motions are characterized by time-varying amplitude and frequency content, and the response of nonlinear structures is sensitive to the temporal variations in the seismic energy input, ground motion non-stationarities should be taken into account in simulations. This paper describes a nonparametric approach for modeling and prediction of non-stationary ground motions. Using Relevance Vector Machines, a regression model which takes as input a set of seismic predictors, and produces as output the expected evolutionary power spectral density, conditioned on the predictors. A demonstrative example is presented, where recorded and predicted ground motions are compared in time, frequency, and time-frequency domains. Analysis results indicate reasonable match between the recorded and predicted quantities.

The vestibuloocular reflex can be manually elicited by tilting or rotating the head. Manual techniques serve their purpose well and is the golden standard in the clinical work, but they lack control of velocity and movement pattern. However, motion simulation platforms enable automatic control of both velocity and movement pattern. One motion simulation platform, named BIRGIT, has been built at the Department of Clinical Neurosciences at Karolinska Institutet but has not yet been in service and require a performance evaluation. The objectives with this thesis is to evaluate the accuracy and precision of BIRGIT and evaluate how bodyweight and movement direction impact the performance. The thesis also evaluate whether it is possible to stabilize the head of the patient during the acceleration phase. Repeated measurements of acceleration with different loads, desired ac- celeration, direction and motion type (rotational and translational), are per- formed. Dummies are used to simulate bodyweight in the performance study and real persons are used in the head stabilization study. Analysis of variance (ANOVA) is the main statistical tool. The results suggest that the platform does not perform equally at dif- ferent load or directions and that there is a bias between desired and true acceleration. The main problems are an inclination of the rails, upon which the chair is mounted, that causes differences between directions and an un- desirable performance characteristic for rotational motions. The stabilization study suggest that the head can be stabilized. / Den vestibulo-okul ̈ara reflexen kan framkallas genom att manuellt rotera eller rycka p ̊a huvudet. Att manuellt framkalla reflexen fungerar i de flesta sam- manhang va ̈l och a ̈r standard i m ̊anga underso ̈kningar. Dock g ̊ar det inte att till fullo kontrollera vare sig hastighet eller ro ̈relsebana perfekt. Emellertid g ̊ar detta att kontrollera genom att anva ̈nda sig av en s ̊a kallad ro ̈relsesimu- leringsplatform. En s ̊adan platform, d ̈opt till BIRGIT, har byggts vid Institutionen f ̈or kliniska neurovetenskaper vid Karolinska Institutet. Denna har ej bo ̈rjat anva ̈ndas ̈annu d ̊a dess prestanda fo ̈rst beho ̈ver utv ̈arderas. Syftet med denna uppsats ̈ar att utva ̈rdera precision och noggrannhet hos BIRGIT. Dessutom, att utv ̈ardera hur kroppsvikt och ro ̈relseriktning inverkar p ̊a prestandan. I arbetet ing ̊ar ̈aven att testa om det a ̈r m ̈ojligt att stabilisera huvudet under accelerationsfasen. Repeterade ma ̈tningar av sann acceleration med olika last, riktning, bo ̈rac- celeration och r ̈orelsetyp (rotation eller sidledes) genomfo ̈rdes. Testdockor anva ̈ndes fo ̈r att simulera lasten i prestandatesterna och riktiga testpersoner anva ̈ndes i huvudstabiliseringsdelen. Variansanalys (ANOVA) var det hu- vudsakliga statistiska verktyget. Resultatet antyder att last och ro ̈relseriktning inverkar p ̊a acceleratio- nen och prestandan och att den sanna accelerationen alltigenom a ̈r la ̈gre a ̈n bo ̈raccelerationen. Det finns tv ̊a sto ̈rre problem hos plattformen, det fo ̈rsta a ̈r att uppha ̈ngningen till stolen lutar och detta resulterar i en skillnad mellan riktningarna (det g ̊ar fortare nedf ̈ors). Det andra problemet a ̈r ett cykliskt uppfo ̈rande na ̈r flera rotationsr ̈orelser skall fo ̈lja p ̊a varandra. Stabiliseringsstudien visade att det g ̊ar att stabilisera huvudet.