The time optimal slewing problem for flexible spacecraft is considered. We study single-axis rotational maneuvers for a simple flexible system, consisting of a rigid hub with an elastic appendage. The equations of motions are derived by Hamilton’s Principle, and a discrete nonlinear model is obtained by the assumed modes method. The problem is first solved in a discrete linearized space by parameter optimization. Optimality is verified by Pontryagin’s Maximum Principle. The linear solutions are then used to obtain time optimal solutions for the non-linear problem by a multiple-shooting algorithm. Although this approach is applicable to arbitrary boundary conditions, this work is confined, almost exclusively, to rest-to-rest maneuvers. These maneuvers are shown to possess some interesting symmetric and asymptotic properties. The problem is further analyzed in infinite-dimensional space, and the convergence of the finite-dimensional approximations is studied. Finally, a soft version of the time optimal slewing problem is considered, where the control is bounded only by a penalty term in the cost functional. A perturbation technique is applied to further simplify this problem. / Ph. D.

Thesis submitted in compliance with the requirements for the Master's Degree in Technology: Department of Mechanical Engineering, Durban University of Technology, 2008. / The development of an evolutionary optimisation method and its application to the design of an advanced composite structure is discussed in this study. Composite materials are increasingly being used in various fields, and so optimisation of such structures would be advantageous. From among the various methods available, one particular method, known as Evolutionary Structural Optimisation (ESO), is shown here. ESO is an empirical method, based on the concept of removing and adding material from a structure, in order to create an optimum shape. The objective of the research is to create an ESO method, utilising MSC.Patran/Nastran, to optimise composite structures. The creation of the ESO algorithm is shown, and the results of the development of the ESO algorithm are presented. A tailfin of an aircraft was used as an application example. The aim was to reduce weight and create an optimised design for manufacture. The criterion for the analyses undertaken was stress based. Two models of the tailfin are used to demonstrate the effectiveness of the developed ESO algorithm. The results of this research are presented in the study.

Vehicle system analysis models are becoming crucial to automotive designers wishing to better understand vehicle-level attributes and how they vary under different operating conditions. Such models require substantial planning and collaboration between multidisciplinary engineering teams. To improve the process used to create a vehicle system analysis model, the broader question of how to plan and develop any model should be addressed. Model-Based Systems Engineering (MBSE) is one approach that can be used to make such complex engineering tasks more efficient. MBSE can improve these tasks in several ways. It allows for more formal communication among stakeholders, avoids the ambiguity commonly found in document-based approaches to systems engineering, and allows stakeholders to all contribute to a single, integrated system model. Commonly, the Systems Modeling Language (SysML) is used to integrate existing analysis models with a system-level SysML model. This thesis, on the other hand, focuses on using MBSE to support the planning and development of the analysis models themselves. This thesis proposes an MBSE approach to improve the development of system models for Integrated Vehicle Analysis (IVA). There are several contributions of this approach. A formal process is proposed that can be used to plan and develop system analysis models. A comprehensive SysML model is used to capture both a descriptive model of a Vehicle Reference Architecture (VRA), as well as the requirements, specifications, and documentation needed to plan and develop vehicle system analysis models. The development of both the process and SysML model was performed alongside Ford engineers to investigate how their current practices can be improved. For the process and SysML model to be implemented effectively, a set of software tools is used to create a more intuitive user interface for the stakeholders involved. First, functionality is added to views and viewpoints in SysML so that they may be used to formally capture the concerns of different stakeholders as exportable XML files. Using these stakeholder-specific XML files, a custom template engine can be used to generate unique spreadsheets for each stakeholder. In this way, the concerns and responsibilities of each stakeholder can be defined within the context of a formally defined process. The capability of these two tools is illustrated through the use of examples which mimic current practices at Ford and can demonstrate the utility of such an approach.

Thesis (Master of Engineering in Electrical Engineering)--Cape Peninsula University of Technology, 2018. / The purpose of this paper was to design and develop an electrical power train for an Urban Concept electric vehicle geared to complete the Shell Eco-Marathon Africa in 2019. Various technologies which make up the electrical drive train of an electrical vehicle were also reviewed which include the battery pack, the battery management system, the motors, the motor management system and the human interface. Upon completion of this, the various topologies best suited for this project were selected, designed, constructed and developed. Two motors were re-designed and constructed for this vehicle and the motor drive was also constructed to control these motors. A Lithium-Ion battery pack was constructed and developed to drive the motors and an off-the-shelf battery management system was purchased and developed to suit the requirements for the Shell Eco- Marathon competition rules. A human interface was also developed in order for the driver to see various parameters of the electric vehicle defined by the Shell Eco-Marathon competition rules. After each component of the drive train was constructed, they underwent various testing procedures to determine the efficiency of each individual component and the overall efficiency for the complete drive train of this electric vehicle was ascertained. The Product Lifecycle Management Competency Centre group developed the chassis for this vehicle. For this reason, only the electric subsystems were evaluated and a simulation was completed of the complete drive train. After the complete drive train was constructed and all the individual subsystems evaluated and simulated, a vehicle with an overall efficiency of about sixty percent was expected and the completed drive train should be adequate enough to complete the entire Shell Eco-Marathon Africa circuit.

After describing the development of the ISDV, this thesis studies the energy management which can improve the energy efficiency. It is shown that the traditional electric vehicle (EV) is not capable of managing the energy required for one driving cycle because it has only a single traction motor. This thesis proposes and examines a new way to manage electrical energy in which torque is distributed among different in-wheel motors to achieve a higher level of overall energy efficiency, which has been enhanced and demonstrated in various driving cycles. / Thereafter, the thesis studies two aspects of benefits the ISDV can bring to parking. One is in space efficiency, defined as the ratio of the total space occupied by the vehicle in its final parked state over the whole area covered by the parking lot. Comparison of the ISDV and traditional vehicles in parking proves that the ISDV afford a higher level of space efficiency. The other aspect is the parking time. It is tested experimentally in the hardware-in-loop (HIL) system, and the motions of traditional vehicles, the zero radius turning motion, and the free motion of the ISDV are compared. The less time for parking demonstrates the easiness to steer the ISDV. / Throughout the history of human civilization, vehicles have played a significant role by connecting people in various locations. They have thus boosted the progress of civilization and made our lives more convenient. However, as the number of vehicles on the road has increased, the convenience, which vehicles provide, has gradually turned into inconvenience in three respects: 1) the energy consumed by vehicles accounts for a large proportion of total energy consumption, which is in an ever-increasing trend; 2) more parking space is needed, a significant proportion of which is not for parking itself but for enabling the vehicle to be navigated to its final parking slot; 3) the effort required to park a car is also troublesome, causing the driver to spend much more time in a crowded parking lot. / To alleviate these three problems, I develop a methodology to design an independent steering and driving vehicle (ISDV). It brings together the robotic technologies of steer-by-wire, drive-by-wire, four-wheel-independent-steering, and four-wheel-independent-driving. All four wheels of the ISDV can be steered independently, so that vehicle rotation and translation can be decoupled from each other. Omni-directional motions such as zero radius turning (ZRT) and lateral parking (LP) are realized, thereby enhancing the agility of the vehicle. In contrast with omni-directional wheeled mobile robots, this vehicle is targeted at serving as a human carrier or even as a vehicle carrier in the future. / Qian, Huihuan. / Adviser: Yangsheng Xu. / Source: Dissertation Abstracts International, Volume: 73-03, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 149-159). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Titanium matrix composites have been extensively evaluated for their potential to replace conventional superalloys in high temperature structural applications, with significant weight-savings while maintaining comparable mechanical properties. The purpose of this investigation is the evaluation of a gamma titanium aluminide alloy with nominal composition Ti-46.5Al-4(Cr,Nb,Ta,B)at.% as a matrix material for use in intermediate temperature applications (400-800㩠in future aerospace transportation systems, as very light-weight structures are needed for cost and weight reduction goals. Mechanical characterization testing was performed over the potential usable temperature range (21-800㩮 Thermal expansion behavior was evaluated, as thermal mismatch of the constituents is an expected problem in composites employing this matrix material. Monotonic testing was conducted on rolled sheet material samples to obtain material properties. The alloy exhibited good strength and stiffness retention at elevated temperatures, as well as improved toughness. Monotonic testing was also conducted on specimens exposed to elevated temperatures to determine the degradation effects of high temperature exposure and oxidation. The exposure did not significantly degrade the alloy properties at elevated temperatures; however, room temperature ductility decreased. Analytical modeling using AGLPLY software was conducted to predict the residual stress state after composite consolidation as well as the potential mechanical behavior of [0]4 laminates with a 㭍ET matrix. Silicon carbide (Ultra-SCS) and alumina (Nextel 610) fibers were selected as potential reinforcing materials for the analysis. High residual stresses were predicted due to the thermal mismatch in the materials. Laminates with Nextel 610 fibers were found to offer the better potential for a composite in this comparison as they provide a better thermal match. Coupons of SCS-6/㭍ET were manufactured with different volume fractions (10% and 20%). Both manufacturing attempts resulted in transverse cracking in the matrix from the residual thermal stress.

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Thesis (MScEng (Mathematical Sciences. Applied Mathematics))--University of Stellenbosch, 2007. / During the design or acquisition of missile systems the effectiveness of the system needs to be evaluated. Often actual testing is not possible and therefore mathematical models need to be constructed and solved with the aid of software. The current simulation model is investigated, verified, and a mathematical model to aid in the design of the detonic payload, developed. The problem is confined to the end-game scenario with the developed simulation model focusing on the last milliseconds before warhead detonation. The model, that makes use of the raytracing methodology, models the warhead explosion in the vicinity of a target and calculates the probability of kill for the specific warhead design against the target. Using the data generated by the simulation model, the warhead designer can make the necessary design changes to improve the design. A heuristic method was developed and is discussed which assists in this design process. There is, however, a large population of possible designs. Meta-heuristic methods may be employed in reducing this population and to help confine the manual search to a considerably smaller search area. A fuze detection model as well as the capability to generate truly random intercept scenarios was developed as to enable employment of meta-heuristic search methods. The simulation model, as well as design optimising technology, has successfully been incorporated into a Windows based software package known as EVA (The Effectiveness and Vulnerability Analyser).