O sistema de suspensão de um veículo desempenha papel fundamental na isolação das vibrações provenientes da pista e de outras fontes de excitações e tem como alguns de seus objetivos: melhoria do conforto dos passageiros, manutenção da integridade das cargas e das vias (asfalto), aumento da segurança, proporcionando melhores condições de aderência pneu-piso, etc. A predição do desempenho de um sistema de suspensão veicular antes da construção de um protótipo físico, permite o dimensionamento prévio dos componentes que o integram com maior precisão, otimizando-se, desta forma, o custo final do produto bem como custos e prazos decorrentes de modificações para solucionar problemas que seriam detectados somente na experimentação do protótipo físico. Este trabalho apresenta um comparativo entre os resultados analíticos obtidos utilizando-se as funções transferências de um modelo simplificado (ou clássico) linear de uma suspensão automotiva de 1/4 de veículo (quarter-car); dos obtidos através da utilização de um protótipo virtual do mesmo modelo simplificado (ou clássico) de 1/4 de veículo e, por fim, dos obtidos utilizando-se um protótipo virtual de um sistema de suspensão do tipo MacPherson, sendo que os protótipos virtuais podem trabalhar com não-linearidades. São obtidas as respostas dinâmicas no domínio da frequência (0 a 30 Hz) e também no domínio do tempo, neste último caso utilizando-se como entrada um pulso no pneu, que simula a passagem do veículo sobre um obstáculo a 18 Km/h. Os resultados são comparados objetivamente e conclui-se sobre as limitações de utilização do modelo simplificado (ou clássico) de 1/4 de veículo. / The performance of the suspension system of a vehicle is fundamental to isolate the vibrations from road and from other sources and has the following objetives: improve the comfort of passengers (ride), protect the cargo and the road (asphalt), improve vehicle handling, etc. The prediction of the performance of a vehicle´s suspension system prior to the real prototype construction, allows the previous optimization of the design of the suspension´s components, obtaining a low cost product, in a shorter timming, with lower development costs, by solving problems that would be evident only during the tests with the real prototype. This study presents a comparison between analitycal results obtained by the use of transfers functions of a plain or classical linear model of a automotive suspension system named quarter-car; the results obtained from a virtual prototype of the same plain or classical model and, finally, the results obtained from a virtual prototype of a Macpherson suspension system, considering that the virtuals prototypes are be able to work with non-linearities. The dynamic response are obtained in the frequency domain (0 a 30 Hz) and in the time domain too, in this last case, with a pulse input in the tire, that simulates the car passing over a bump with a speed of 18 Km/h. Through the comparison of the results is possible to conclude about the limitations of the classical model.

The quantity of cell phone applications or mobile apps have seen an upsurge at an exponential rate in under a decade. Many have been created for a variety of industries, including transportation. The advent and subsequent commercialized implementation of near-instant transport by a middleman-type of app is now known as a Transportation Network Company or TNC. Examples of the more renowned TNCs are Uber, Lyft and Sidecar. In recent years, TNCs have cultivated a tremendous following, to the degree of taxicab desertion. Moreover, the massive success of TNCs led to expansion of its capacities into public transportation. The TNC’s expeditious popularity has garnered the attention of government and transit agencies. Without fail, TNCs can complement, supplement or compete with transit. However, sparsely has there been any deep discussion about a TNC potentially supplanting transit. The aim of this paper is to show how TNCs could replace public transportation in the United States if subsidized at the same level of transit agencies. Austin, Texas was analyzed as the case study city. A comparison of subsidization between Austin’s transit agency: Cap Metro, the local TNCs, and on a national aggregate level was conducted. The evidence herein clearly shows that TNCs are highly competitive when in revenue service operating at full capacity, potentially replacing public transportation.

This study aims to evaluate the use of mathematical optimisation algorithms for the optimisation of a vehicle’s spring and damper characteristics, with respect to ride comfort and handling. Traditionally the design of a vehicle’s suspension spring and damper characteristics are determined by a few simple planar model calculations, followed by extensive trial-and-error simulation or track testing. With the current advanced multi-body dynamics computer software packages available to the design engineer, the integration of traditional mathematical optimisation techniques with these packages, can lead to much faster product development. This, in turn results in a reduction of development costs. A sports utility vehicle is modelled by means of a general-purpose computer programme for the dynamic analysis of a multi-body mechanical system. This model is validated against measurements from road tests. The mathematical model is coupled to two gradient-based mathematical optimisation algorithms. The performance of the recently proposed Dynamic-Q optimisation algorithm, is compared with that of the industry-standard gradient based Sequential Quadratic Programming method. The use of different finite difference approximations for the gradient vector evaluation is also investigated. The results of this study indicate that gradient-based mathematical optimisation methods may indeed be successfully integrated with a multi-body dynamics analysis computer program for the optimisation of a vehicle’s suspension system. The results in a significant improvement in the ride comfort as well as handling of the vehicle. / Dissertation (MEng (Mechanical Engineering))--University of Pretoria, 2006. / Mechanical and Aeronautical Engineering / unrestricted

The world faces human-made hazardous weather events such as heat waves, droughts, floods andwildfires in dimensions which have never been seen before. A crucial contributor to this negative trendis the constantly growing transportation sector. In addition, most urban regions suffer from trafficcongestions which lead among others to local emissions, the loss of time and noise pollution. Onepromising approach to reduce the amount of transport related emissions is ride-sharing. This paperfocuses on the possibilities and barriers of ride-sharing for the daily commute to and from work. To gainreliably results, a real-life test trial was implemented at a Swedish corporation. The gatheredquantitative and qualitative datasets were analysed with the framework of Social Practice Theory, whichsplits up the practice into its three elements of materials, meanings and competences and therebydevelops revealing insights. The reason for the low participation rate during the test trial can be tracedback to the potential loss of flexibility. Despite a high environmental awareness and a deep trust relationto colleagues, the potential loss of flexibility was for most participants the crucial factor to not start ridesharing.Even though individuals’ opinions were very positive towards the idea of ride-sharing, theparticipation rate during the real-life study shows that the perception of ride-sharing highly derivatesfrom the action.

The efficient optimisation of vehicle suspension systems is of increasing interest for vehicle manufacturers. The main aim of this thesis is to develop a methodology for efficiently optimising an off-road vehicle’s suspension for both ride comfort and handling, using gradient based optimisation. Good ride comfort of a vehicle traditionally requires a soft suspension setup, while good handling requires a hard suspension setup. The suspension system being optimised is a semi-active suspension system that has the ability to switch between a ride comfort and a handling setting. This optimisation is performed using the gradient-based optimisation algorithm Dynamic-Q. In order to perform the optimisation, the vehicle had to be accurately modelled in a multi-body dynamics package. This model, although very accurate, exhibited a high degree of non-linearity, resulting in a computationally expensive model that exhibited severe numerical noise. In order to perform handling optimisation, a novel closed loop driver model was developed that made use of the Magic Formula to describe the gain parameter for the single point driver model’s steering gain. This non-linear gain allowed the successful implementation of a single point preview driver model for the closed loop double lane change manoeuvre, close to the vehicle’s handling limit. Due to the high levels of numerical noise present in the simulation model’s objective and constraint functions, the use of central finite differencing for the determination of gradient information was investigated, and found to improve the optimisation convergence history. The full simulation model, however, had to be used for the determination of this gradient information, making the optimisation process prohibitively expensive, when many design variables are considered. The use of carefully chosen simplified two-dimensional non-linear models were investigated for the determination of this gradient information. It was found that this substantially reduced the total number of expensive full simulation evaluations required, thereby speeding up the optimisation time. It was, however, found that as more design variables were considered, some variables exhibited a lower level of sensitivity than the other design variables resulting in the optimisation algorithm terminating at sub-optimal points in the design space. A novel automatic scaling procedure is proposed for scaling the design variables when Dynamic-Q is used. This scaling methodology attempts to make the n-dimensional design space more spherical in nature, ensuring the better performance of Dynamic-Q, which makes spherical approximations of the optimisation problem at each iteration step. The results of this study indicate that gradient-based mathematical optimisation methods may indeed be successfully integrated with a multibody dynamics analysis computer program for the optimisation of a vehicle’s suspension system. Methods for avoiding the negative effects of numerical noise in the optimisation process have been proposed and successfully implemented, resulting in an improved methodology for gradient-based optimisation of vehicle suspension systems. / Thesis (PhD)--University of Pretoria, 2008. / Mechanical and Aeronautical Engineering / unrestricted

Master thesis titled “Analysis of selected manoeuvres of bicyclists” in the first part deals with the history of bicycles, construction, division of bicycles and introduces–traffic accidents of cyclists and national legislation. Practical measurements with bicyclists is in the second part of this thesis. Cyclists performed deceleration on three surfaces, acceleration and a manoeuver, in which cyclist looked behind himself before changing the direction. The evaluation of all measurements and comparison with other similar works has been made in the last chapters.

Diploma work named Selected measurements of motion of bicycles starts with history and development of bicycle. There are components of bicycles described and analysis accidents with cyclist. There is a goal organise and realize measurement of ride in the curve and tranverse movement. The outputs are going to be use by experts in sphere of transport accident analysis. There will be exists data analysis then starts maeasurement. After then compile sources from measurement – break testing, ride in the curve testing and tranverse movement on the most frequently road surfaces with part of enaugh cyclist and bycicles. The end of work is already existing data with hold of measurement data comparison.

The topic of this master’s thesis is design of ride-on scrubber-dryer. The thesis concerns own design, which is based on findings from the analysis of the current state of knowledge.

Diploma thesis is oriented at suspension of commercial vehicle and tractor cab. It describes current state-of-art suspension systems, methods of measuring and evaluating ride comfort. Developed multibody model of tractor is used to compare different suspension concepts and a sensitivity analysis of parameters related to ride comfort is made.

The dynamics of demand responsive ride pooling (DRRP) systems is considered in a mean-field framework. The relevant dimensionless quantities determining the performance and viability of the system are identified. In the presence of an already established dominant market participant with comparable service quality (like, e.g., the private car), the mutual interaction of the actors (i.e., the customers sharing rides) by virtue of the route assignment algorithm gives rise to a discontinuous transition between two strongly different modes of operation. One of them represents the typical (unfavorable) performance of current ride pooling systems, while the other represents a new mode of operation in which virtually all customers use DRRP.