Abstract

Understanding how humans control a vehicle (cars, aircraft, bicycles, etc.) enables engineers to design faster, safer, more comfortable, more energy efficient, more versatile, and thus better vehicles. In a typical control task, the Human Controller (HC) gives control inputs to a vehicle such that it follows a particular reference path (e.g., the road) accurately. The HC is simultaneously required to attenuate the effect of disturbances (e.g., turbulence) perturbing the intended path of the vehicle. To do so, the HC can use a control organization that resembles a closed-loop feedback controller, a feedforward controller, or a combination of both. Previous research has shown that a purely closed-loop feedback control organization is observed only in specific control tasks, that do not resemble realistic control tasks, in which the information presented to the human is very limited. In realistic tasks, a feedforward control strategy is to be expected; yet, almost all previously available HC models describe the human as a pure feedback controller lacking the important feedforward response. Therefore, the goal of the research described in this thesis was to obtain a fundamental understanding of feedforward in human manual control."br/"First, a novel system identification method was developed, which was necessary to identify human control dynamics in control tasks involving realistic reference signals. Second, the novel identification method was used to investigate three important aspects of feedforward through human-in-the-loop experiments which resulted in a control-theoretical model of feedforward in manual control. The central element of the feedforward model is the inverse of the vehicle dynamics, equal to the theoretically ideal feedforward dynamics. However, it was also found that the HC is not able to apply a feedforward response with these ideal dynamics, and that limitations in the perception, cognition, and action loop need to be modeled by additional model elements: a gain, a time delay, and a low-pass filter."br/"Overall, the thesis demonstrated that feedforward is indeed an essential part of human manual control behavior and should be accounted for in many human-machine applications.

Abstract

Vehicle manufactures have adopted different strategies for improving the environmental performance of their fleet including lightweight design and alternative drivetrains such as EVs. Both strategies reduce energy during use but may result in a relative increase of the impact during other stages. To address this, a lifecycle approach is needed when vehicle design strategies are developed. The thesis explores the extent that such a lifecycle approach is adopted today and assesses the potential of these strategies to reduce the lifecycle impact of vehicles. Moreover it aims to contribute to method development for lifecycle considerations during product development and material selection. Current practices were explored in an empirical study with four vehicle manufacturers. The availability of tools for identifying, monitoring and assessing design strategies was explored in a literature review. The results of the empirical study showed that environmental considerations during product development often lack a lifecycle perspective. Regarding the use of tools a limited number of such tools were utilized systematically by the studied companies despite the numerous tools available in literature. The influence of new design strategies on the lifecycle environmental performance of vehicles was assessed in three case studies; two looking into lightweight design and one at EVs. Both strategies resulted in energy and GHG emissions savings though the impact during manufacturing increases due to the advanced materials used. Assumptions relating to the operating conditions of the vehicle e.g. lifetime distance or for EVs the carbon intensity of the energy mix, influence the level of this tradeoff. Despite its low share in terms of environmental impact EOL is important in the overall performance of vehicles. The thesis contributed to method development by suggesting a systematic approach for material selection. The approach combines material and environmental analysis tools thus increases the possibilities for lifecycle improvements while minimizing risk for sub-optimizations. "p"QC 20160920

Abstract

MIng (Mechanical Engineering), North-West University, Potchefstroom Campus, 2014 The Formula SAE is a student based competition organised by SAE International where engineering students from a university design, develop and test a formula-style race car prototype to compete against other universities. The competition car needs to satisfy the competition rules set out by the organisers. The competition strives to stimulate original, creative problem solving together with innovative engineering design practices. In any race environment, the primary goal is always to be as competitive as possible. Due to the competitive nature of motor sport, vehicle components need to withstand various and severe stresses. The components of a race car vehicle are responsible for the vehicle’s handling characteristics and reliability. The chassis is a crucial and integral component of a Formula SAE competition car, primarily responsible for the vehicle’s performance characteristics. The chassis is the structural component that accommodates all the other components. A Formula SAE chassis is a structure that requires high torsional stiffness, low weight as well as the necessary strength properties. In this study, multiple Formula SAE chassis were designed and developed using computer aided design software. Each concept’s torsional stiffness, weight and strength properties were tested using finite element analysis software. The different concepts consisted of different design techniques and applications. All the concepts were analysed and assessed, leading to the identification of an acceptable prototype. The prototype was manufactured for experimental tests. The designed chassis complied with the Formula SAE rules and regulations. The weight, torsional stiffness and strength characteristics of the designed chassis frame were also favourable compared to accepted standards for Formula SAE chassis frames. The manufactured chassis was prepared for experimental tests in order to validate the simulation results produced by the finite element analysis. The torsional stiffness, weight and strength were experimentally determined and the results were compared with the corresponding simulations results. The comparison of the experimental and simulated results enabled the validation of the finite element analysis software. The study draws conclusions about the use of computer aided design and finite element analysis software as a design tool for the development of a Formula SAE chassis. Closure about the study is provided with general conclusions, recommendations and research possibilities for future studies. Master

Abstract

Industrial companies supply products intended to satisfy customers’ needs and requirements. To be competitive and to maintain good economic performance, efficient systems are needed to communicate information and exchange knowledge. Such systems are often referred to as quality systems as they intend to support development as well as standardized work regarding the quality of the product and increase satisfaction of the company’s customers and other stakeholders (employees, owners, sub-suppliers, society). Many companies try to structure and improve their quality systems by applying the international quality standard ISO 9000, which can result in extensive documentation. The guidelines and instructions of quality management systems are traditionally documented and presented as paper documents, alternatively on an intranet (a company’s internal computer network) suitable for printouts. These however, do not correspond to some company’s requirements for usability in daily work and as support to interest and engage the personnel in development work. An assumption was that visualizing guidelines using different kinds of multimedia technologies such as hyperlinked and animated pictorial illustrations might be relevant to support quality control and design processes in industrial companies. Two objectives were set up: The first was to explore how the usability of guidelines could be improved by changing the interface design of the guidelines; The second was to explore how the visualization process of guidelines could support participative design by applying evaluations and interpretations in a dialogue form between two individuals or among a group of individuals. The methodology that has been used to generate research questions as well as methods is based on theories of action research and experiential learning. Various methods have been used and combined in order to collect information and to ensure the reliability of the findings based on it. Three industrial companies participated in a first case study. They had conventional quality systems, which they wanted to replace or improve. The companies set up design teams to establish principles for visualizations of their quality systems on their intranets. Cooperating with the author, the design teams created and evaluated computer supported prototypes. These prototypes were made available via the Internet and discussed within each design team. The teams exchanged ideas and comments to enhance their prototypes. The results showed that a quality system should be visualized by an overview of the physical production plant. Information about different processes and instructions are represented by hyperlinked symbols within or next to the plant layout. A second field study aimed to clarify how industrial companies with certified quality systems according to ISO 9001 visualized their guidelines and instructions of construction, production, and installation. The quality manager at each company evaluated the existing system and explained their needs of developing the system by means of computer supported visualization on their intranet. The information was collected through telephone interviews and on site visits. The results showed that the companies would like to improve the visualization of information by decreasing text and increasing pictorial descriptions, such as flowcharts and animations. They also experienced that a quality system on the companies’ intranets was or should be an enhancement in order to disseminate and update the information. A third case study performed in collaboration with Saab Automobile showed results that corresponded with the other studies. The company wanted to replace their conventional information system of ergonomic design guidelines for cars, and design a new system based on interactivity and multimedia. The results showed that a pictorial overview of the car with different areas hyperlinked to further information was preferred. The specific information in the ergonomic guidelines was illustrated with icons, pictures, animations, and some text. In a comparison with the conventional system, subjects performed working tasks faster and with a more positive attitude in the new system. A fourth case study was performed within the GM company group, which showed the need of a formalized working process throughout work with human simulation tools as well as possibilities to document the information generated. A human simulation system prototype was modeled in collaboration with the companies and was presented on an intranet. The results indicated a great potential to enhance the communication within and between the companies, increased accessibility to knowledge, and increased quality on performed work. To summarize, the studies in this thesis show a need among industrial companies to visualize guidelines in information and quality systems by means of multimedia and an interactive design process. Such an approach supports knowledge acquisition and communication, and has a potential to ensure high quality in a company’s processes and products. Furthermore, the users’ attitudes tend to become more positive to the information presented compared to a conventional system. För att tillverka produkter av hög kvalitet, behöver industriella företag strukturera arbetet med hjälp av instruktioner och riktlinjer som är lätta att förstå och komma åt. Dessa samlas ofta i en eller flera pärmar eller på internt datornätverk, ofta som en del av den internationella kvalitetsstandarden ISO 9000. Men detta fungerar sällan som ett välfungerande stöd för personalen. Däremot så finns det exempel på hur riktlinjer kan presenteras eller visualiseras med hjälp av olika slags tekniker inom multimedia som t.ex. hyperlänkade och animerade bilder och illustrationer, dvs ett väl anpassat gränssnitt mellan personal och den information som ska presenteras. Avhandlingen har haft två syften: Dels att utforska hur användbarhet av riktlinjer kan förbättras genom att förändra utformningen av riktlinjernas gränssnitt; dels att utforska hur visualiseringsprocessen kan stödja dialogen mellan användare som därmed görs delaktiga i utformningen av riktlinjer."br /" "br /" Resultaten från en första fältstudie visade att tre industriella företag föredrog ett system av riktlinjer som presenterar informationen utifrån en översiktsbild av den fysiska produktionslokalen. Information om processer och instruktioner representerades av hyperlänkade symboler inom eller vid sidan av lokalen. Resultaten från en andra fältstudie visade att industriella företag med kvalitetssystem certifierade enligt ISO 9000 skulle vilja visualisera informationen tydligare genom att minska omfattningen av text och istället använda mer bildmässiga beskrivningar, t.ex. flödesscheman och animeringar. Man upplevde även att ett kvalitetssystem på företagets interna datornätverk innebar eller skulle innebära en förbättring för att sprida och uppdatera informationen. I en tredje fältstudie genomförd i samarbete med Saab Automobil, ville företaget ersätta sitt konventionella informationssystem av ergonomiska designriktlinjer, och utforma ett nytt system baserat på interaktivitet och multimedia. Resultaten visade att man föredrog en översiktsbild av bilen där olika områden var länkade till vidare information. Den specifika informationen i riktlinjerna illustrerades med ikoner, bilder, animeringar och viss text. Vid jämförelse med det tidigare systemet visade det sig att arbetsuppgifter genomfördes både snabbare och med en positivare attityd i det nya systemet. En fjärde fältstudie genomfördes med en grupp företag inom GM koncernen. Studien visade på behovet av en tydlig process vid simuleringsarbete samt möjlighet att kunna dokumentera genererad kunskap. En prototyp av ett system för simuleringar och analyser av förarmiljöer, togs fram i samverkan med företagen och presenterades på ett datornätverk. Resultaten visade stora möjligheter till förbättring av kommunikationen både inom och mellan företagen, samt ökad kunskapsspridning och förbättrad kvalitet på utfört arbete."br /" "br /" Sammantaget visar studierna i avhandlingen på ett behov bland industriella företag av att visualisera riktlinjer med hjälp av multimedia och en ansats där användarna involveras i utformningen av dessa. En sådan ansats underlättar lärande och kommunikation samt har en potential att säkerställa en hög kvalitet på företagets processer och produkter. Dessutom tenderar användarnas attityd att bli mer positiv till den information som presenteras jämfört med tidigare.

Abstract

The target cascading methodology is applied to the conceptual design of an advanced heavy tactical truck. Two levels are defined: an integrated truck model is represented at the top (vehicle) level and four independent suspension arms are represented at the lower (system) level. Necessary analysis models are developed, and design problems are formulated and solved iteratively at both levels. Hence, vehicle design variables and system specifications are determined in a consistent manner. Two different target sets and two different propulsion systems are considered. Trade-offs between conflicting targets are identified. It is demonstrated that target cascading can be useful in avoiding costly design iterations late in the product development process. Copyright © 2001 Society of Automotive Engineers, Inc.

Abstract

This paper describes the concept development process of three vehicle design team projects carried out in successive years in our fourth year undergraduate studio course, in collaboration with industry. The problem areas for all three projects were unfamiliar to student teams, and our collaboration required close involvement of the firms, for their technical expertise and design feedback. Our framework and strategies for this process involved: user research conducted in the field; group discussions for analyzing the operations carried out by the users and mapping their relation to the functions of the related hardware; scenario building for describing the context within an activity based time-related process and searching for solutions at the same time; the generation of numerous ideas through the matching of alternative scenarios with the project dimensions; convergence of these ideas into alternative design proposals; and decision-making on the final project concepts. User research extended throughout the concept development process, supported with an intense 3D exploration and with class assignments that encouraged goal-oriented teamwork. Although we followed a similar design process in all three projects, the strategies used in the various stages were modified depending on the requirements of each project, and regarding the differences in the vehicle types involved, the users and the tasks. (C) 2016 The Authors. Published by Elsevier B.V.

Abstract

In this paper, we have used the differential evolution to optimize the design of a Micro Air Launch Vehicle and its launch trajectory. Since trajectory design of a launch vehicle requires prior knowledge of the masses and propulsion performance parameters of the Micro Air Launch Vehicle, whereas the vehicle design requires prior knowledge of the required velocity (ΔV) to insert the required payload into the target orbit, a two-step optimization cycle was adopted. A Micro Air Launch Vehicle was designed to launch a 20-kg payload into a 400-km circular polar orbit. The preliminary design of the Micro Air Launch Vehicle was conducted given the required ΔV, which was obtained from trajectory optimization, and then applied in mission analysis to obtain the initial masses. These initial masses were used in the vehicle design to get the performance and geometry parameters. The objective function of the Micro Air Launch Vehicle design optimization is to minimize the initial mass under specified constraints on the insertion orbit. The objective of trajectory optimization is to maximize the payload mass under constraints on orbit specifications and design variables. For the 20-kg payload mass, the optimal initial mass is 1267.8 kg and optimal payload is 20.6 kg, which slightly exceeds the mission requirements. Document type: Article

Abstract

Car body design in view of structural performance and lightweighting is a challenging task due to all the performance targets that must be satisfied such as vehicle safety and ride quality. In this paper, material replacement along with multidisciplinary design optimization strategy is proposed to develop a lightweight car body structure that satisfies the crash and vibration criteria while minimizing weight. Through finite element simulations, full frontal, offset frontal, and side crashes of a full car model are evaluated for peak acceleration, intrusion distance, and the internal energy absorbed by the structural parts. In addition, the first three fundamental natural frequencies are combined with the crash metrics to form the design constraints. The wall thicknesses of twenty-two parts are considered as the design variables. Latin Hypercube Sampling is used to sample the design space, while Radial Basis Function methodology is used to develop surrogate models for the selected crash responses at multiple sites as well as the first three fundamental natural frequencies. A nonlinear surrogate-based optimization problem is formulated for mass minimization under crash and vibration constraints. Using Sequential Quadratic Programming, the design optimization problem is solved with the results verified by finite element simulations. The performance of the optimum design with magnesium parts shows significant weight reduction and better performance compared to the baseline design. Document type: Article

Abstract

Tyre modelling is a major challenge when using time domain multibody simulation models to evaluate ride comfort on off-highway commercial vehicles. Further, parameters for these big tyres are difficult to obtain and thus, commercial car tyre models are difficult to apply. In this research work, a simple vertical tyre model for off-highway ride comfort evaluation is suggested. A displaced volume approach has been developed and combined with the slip theory to yield a tyre model that can be characterised by only three parameters. Full scale measurements on a dump truck have been carried out. Force responses from measurements are compared to the simulation results. Acceleration responses and the level of whole-body vibrations have also been compared.

Abstract

Computational human body models are widely used for automotive crashsafety research and design and as such have significantly contributed to a reduction of traffic injuries and fatalities. Currently crash simulations are mainly performed using models based on crash-dummies. However crash dummies differ significantly from the real human body and moreover crash dummies are only available for a limited set of body sizes. Models of the real human body offer some promising advantages including the prediction of injury mechanisms and injury criteria. In this paper, a review will be given of a number of developments in the field of occupant crash simulations in the past 40 years. Topics presented include history of occupant crash simulation codes, human body geometry, human body material modelling and model quality rating. A discussion on foreseen future developments in this field will conclude this paper. © 2005 Springer.