The influence of suspension and tyre modelling on vehicle handling simulation
A study has been carried out in order to investigate the influence of suspension and tyre modelling on the outputs predicted by vehicle handling simulations. The computer models have been generated using data for a Rover vehicle, for which instrumented track test measurements were also available. The results obtained from a high speed lane change manoeuvre have been used as a benchmark for comparison of the various computer modelling strategies. This investigation addresses two main areas. The first of these is the influence of suspension modelling on calculated outputs. The second and more complex area investigates the influence of models representing the effects of the tyres. In each case a primary aim has been to asess the accuracy of models which use a simplifed approach, reduce the number of model parameters and may hence be more amenable to vehicle and tyre design studies. Comparison of the results from this study indicate that for quite an extreme manoeuvre a relatively simple vehicle and tyre model can be used to carry out a simulation with a good level of accuracy. A sensitivity study has also been carried out to illustrate how the models respond to design changes for both vehicle and tyre parameters. The multibody systems analysis program ADAMS (Automatic Dynamic Analysis of Mechanical Systems) has been used to generate the models, formulate and solve the equations of motion, and postprocess the results. An initial literature survey has been carried out investigating this analysis discipline and its usage in vehicle dynamics. Previous work in the areas of vehicle handling sikulation, tyre theory, and computer modelling of both vehicles and tyres has also been studied. Initial investigations have been carried out looking at the modelling of the suspension systems and the steering system. Information from this phase has been used to provide inputs for a set of four full vehicle models ranging in complexity from a model where the suspensions are treated as lumped masses, a model where the suspensions are treated as swing arms, a model based on roll stiffness and a final detailed model which represents the suspension linkages as fitted on the vehicle. Of the three simple models it will be shown that the roll stiffness model is most suitable for further comparisons with the detailed linkage model, where aspects of tyre modelling are considered. Tyre testing has been carried out at SP Tyres UK Ltd. and at Coventry University. A set of FORTRAN subroutines, which interface with ADAMS, has been developed in association with a computer model of a tyre test rig to represent and validate the various tyre models. The provision of these tools forms part of a new system developed during this study and is referred to as the CUTyre System due to its origins at Coventry University. The tyre models compared include a well known and accurate model which requires up to fifty model parameters and a more simple model requiring only ten parameters. An interpolation method is also used as a benchmark for the comparisons. To the author's knowledge the work described in this thesis can be considered to make an original contribition to the body of knowledge involving the application of multibody systems analysis in vehicle dynamics by: (i) providing a detailed comparison of vechicle suspension modelling strategies with the ADAMS program, (ii) developing a tyre modelling and validation tool which can interface directly with the ADAMS software, (iii) providing a comparison between a sophisticated and a simple tyre model in ADAMS. Of particular significance is the assessment of the influence of the tyre models on simulation outputs and not just shape of the tyre force and moment curves.