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Systems modelling and simulation in the product development process for automotive powertrains : executive summary

By Eng.D. Graham King


This submission is a summary of the ten submissions that form the Engineering Doctorate\ud Portfolio.\ud The aim of the portfolio is to demonstrate the benefit of applying systems modelling and\ud simulation in a modified powertrain product development process.\ud A description is given of the competitive pressures that are faced by motor manufacturers in\ud the global automotive business environment. Competitive pressures include a requirement for\ud reduced time to market, exacting product quality standards, manufacturing over-capacity that\ud increases fixed costs and compromises profit margins, and legislation that is increasingly\ud difficult to meet. High-level strategic responses that are being made by manufacturers to these\ud pressures are presented. Each strategic response requires organisational changes and\ud improved approaches to the way in which day-to-day business is conducted. Computer Aided\ud Engineering (CAE) is presented as an approach that can help to improve the competitiveness\ud of motor manufacturers by reducing product development time and the level of hardware\ud prototyping that is required.\ud An investigation in five engineering companies yielded a number of observations about the\ud use of CAE and its integration into product development. Best practice in the implementation\ud of CAE in the product development process is defined. The use of CAE by a leading motor\ud manufacturer in powertrain development is compared with the best practice model, and it is\ud identified that there is a lack of coherence in the application of CAE. It is used to tackle\ud specific problems but the use of CAE is not integrated into the product development process.\ud More importantly, it was found that there is limited application of systems modelling and\ud simulation, which is a critical technique for the effective integration of vehicle systems and\ud the development of on-board vehicle control systems.\ud Before systems modelling and simulation can be applied III powertrain development, an\ud appropriate set of tools and associated modelling architecture must be determined. An\ud appraisal of a range of different tools is undertaken, each tool being appraised against a set of\ud criteria. A combination of DymolaIModelica and MATLAB/Simulink tools is recommended\ud as the optimum solution. DymolaIModelica models of the vehicle plant should be embedded\ud into Simulink models that also contain controller and driver models. MATLAB should be\ud used as the numerical engine and for the creation of user environments.\ud Transmission calibration is selected as a suitable pilot example for applying systems\ud modelling and simulation in powertrain development. Best practice in CAE implementation\ud and the systems modelling and simulation architecture are validated using this example.\ud Simulation models of vehicles equipped with CVT and discrete ratio automatic transmissions\ud are presented. A full description of the operation of the transmission system, of the simulation\ud model itself, and of the validation of the model is presented in each case. The potential benefit\ud of the CVT model in transmission calibration is demonstrated. A Transmission Calibration\ud Simulation Tool (TCST) is described within which the discrete ratio simulation model is\ud encapsulated. The TCST includes a user environment in which the simulation model can be\ud parameterised, a variety of simulation runs can be specified, and simulation results are\ud processed. Development of the TCST requires an objective measure of driveability effects\ud that are influenced by the transmission shift schedule. A method for objective assessment of\ud driveability is developed, correlated, and implemented as an integral part of the TCST. This\ud element of the TCST allows trade-off exercises to be conducted between fuel economy and\ud driveability.\ud The development of a transmission calibration based on experimental testing is compared\ud with a similar exercise based on simulation testing. This study shows that, if the TCST is\ud properly integrated into the transmission calibration process, the vehicle test time taken to\ud optimise the calibration for fuel economy could be reduced by six weeks, and a week of\ud calibrator time could be saved. Thus, the aim of the submission is fulfilled, since the benefit\ud of applying systems modelling and simulation in the powertrain development process has\ud been demonstrated.\ud It is concluded that a consistent approach is required for effectively integrating systems\ud modelling and simulation into the product development process. A model is proposed that\ud clarifies how this can be achieved at a local level. It is proposed that in the future, the model\ud is applied whenever systems modelling and simulation is introduced into a powertrain\ud department

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