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Accurate measurement of a vehicle's resistance to motion on a road (the 'road load'), and the separation of this resistive force into its contributory components is of fundamental importance to generate the data required for vehicle performance assessment, the calibration of a modem chassis dynamometer and for comparing the drag of different vehicles or vehicle configurations. Established methods of determining road load on a test track are the coastdown and steady state torque tests, but environmental variability (largely due to ambient wind) and differences in the vehicle operating conditions cause wide variation in the results. This thesis describes a comprehensive study into methods of acquiring and analysing road load data at a test track. A mathematical model of the vehicle travelling in a straight line, in the presence of ambient wind, is developed and may be applied to measured data obtained in both the coastdown and the steady state test modes. The model includes the aerodynamic drag, tyre losses, transmission and un-driven wheel losses and the variation of aerodynamic drag with yaw angle. Experimental data obtained at a test track, using advanced instrumentation (including on-board anemometry and wheel torque meters) are analysed to obtain estimates of the coefficients in the road load equation. The results from an initial study demonstrate the importance of measuring the local wind at the test vehicle and the transmission losses if the total drag is to be accurately measured and separated into its contributory components. The coastdown method is shown to be more accurate and repeatable than the steady state method, and is therefore used as the basis of an advanced test procedure. Up to four coefficients can be determined from the coastdown data using a parameter optimisation routine. This routine fits the mathematical model to the measured coastdown profile to obtain estimates of the road load coefficients including the variation of aerodynamic drag coefficient with yaw angle. Results using this analytical method show that all four coefficients can be determined from coastdown data if there is sufficient ambient wind, and hence lay the basis for an advanced test method using only data from track tests. Constrained methods, where one or more of the parameters is fixed, can be used to investigate a single source of drag. The reduction in the total number of tests required to achieve an acceptable level of accuracy in the variable coefficients when using the constrained method is demonstrated.

This research develops a conceptual model of freight modal choice in which the basic unit of analysis is the socio-organisational group. Research into freight modal choice at the level of the firm has tended to disregard the nature of human choice and to assume that modal choice can be explained in terms of technological phenomena or cost relationships. There is also a tendency to equate the modal choice of organisational members with the modal use of firms. The approach adopted in this work is to accept that there are different interest groups within shipper firms and that such groups may not necessarily form a consensus of opinion about freight model choice. It is assumed that different socia-organisational groups may form different implicit theories about transport systems. Such an approach is called the social perceptual approach. The conceptual modal is converted into an operational model and an empirical investigation is undertaken into the area of modal choice between air freight transport end surface less than full load freight transport from the United Kingdom to Western Europe. In particular, the standpoint of shipping managers (managers responsible for arranging international freight transport in exporting companies) is examined vis-a-vis certain normative approaches such as the through transport concept.

In this work. an attempt has been made to develop a programming package for ride analysis of off-road vehicles based upon a finite-element formulation of vehicle suspension systems. Mathematical modelling of generalised suspension systems has been carried out with several non-linear aspects being investigated and implemented in the programming package. such as large deflection. non-linear characteristics of springs and dampers. bump stops and wheel separation. Different types of soi 1 have been considered together with an appropriate modelling of vehicle tracks. Several methods for time integration of dynamic equations have been investigated so as to deal wi th numerical instabi 1 i ty problems expected for off-road suspension systems which often have 'stiff' differential equations of motion. Three ride analysis criteria have also been considered in the programming package. Several case studies have been analysed using the developed programming package. They consist of two simple case studies with known analytical solutions. an existing wheeled off-road vehicle with published analog computer resul t s , and an off-road tracked vehicle wi th known experimental results. The package has been validated and proved to be an acceptable tool for the ride analysis of off-road vehicles. within the approximating assumptions considered. Several measures for future development have also been suggested.

This thesis documents a study into the effects of various parameters on the performance of Framed Child Seats (FCS) for automobiles. The work investigated the effect of three different sets of parameters: FCS design parameters, vehicle design parameters and occupant biomechanical parameters. The work was conducted at Middlesex University using a combination of experimental crash testing and computerised crash simulations. The experimental crash tests were conducted using the Road Safety Engineering Laboratory, Middlesex University impact test rig and the computerised simulations were conducted using MADYM03D software. The performance of the FCS configuration was assessed in terms of the potential injury to a child occupant in a 50 km/h frontal impact to ECE R44 test specification. All the FCS design parameters examined were shown to have a potential effect on the performance of the FCS. In particular FCS footprint area was shown in the experimental tests to have a significant affect on the performance. A large flat footprint was observed to reduce chest acceleration by 33%, although this was at the expense of a large increase in forward head excursion. Various vehicle design parameters were shown, by MADYM03D simulation, to have a considerable affect on FCS performance. A standardised semi-rigid or rigid anchorage system is recommended to overcome such problems in real vehicles. The biomechanical work was largely based around the potential for injury to the occupant's neck. An improved MADYM03D representation of the dummy neck was developed for this work and several factors were examined. Chin-chest contact, head mass and neck fulcrum for bending were all shown to have a potential affect on the likelihood of injury. Limitations of both experimental crash testing and computerised simulations were identified during this work and are discussed in this thesis.

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The thesis describes modelling methods that are being developed to support the design and evaluation of intelligent railway braking control systems. A particular feature is that the models include higher order vehicle and train dynamics, the effects of which are expected to become important as the performance of braking systems improve. The thesis describes mathematical techniques for modelling braking systems starting with braking of a single wheelset on its own, then a single braked wheelset in a bogie, followed by a single braked wheelset in a complete vehicle and finally four wheelsets braked in a complete vehicle. The mathematical model for the braking system combines the non-linear creep laws governing the braking forces generated between wheel and rail with the suspension dynamics of a typical high speed railway vehicle.

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No description available.