GEMCAR - Guidelines for electromagnetic compatibility modelling for automotive requirements
Overview
Background & policy context:
Future vehicle electronic systems will provide many more safety related functions to aid the driver, as well as advanced telematics facilities to support activities such as traffic management. In addition, more sophisticated control systems will be used to optimise vehicle performance and emissions. Thus, electromagnetic compatibility (EMC) represents an increasingly significant issue for the function, safety and reliability of modern vehicles.
The success of future vehicle technologies which aim to improve transport and to minimise its environmental impact will therefore be critically dependent on the efficient and successful handling of automotive EMC issues. This was recognised by the automotive industry’s CO2perate Programme, which provided a letter of support for the GEMCAR proposal.
Automotive EMC engineering has traditionally been an experimental activity. However, the advent of electric and hybrid-electric vehicles, and the increasingly wide range of systems and frequencies which are used in vehicles, are expected to make automotive EMC an increasingly onerous burden to vehicle manufacturers in future. It is considered that the adoption of numerical modelling techniques will provide the most cost effective approach for improving the efficiency of future automotive EMC engineering.
Although tools and techniques have been developed which are suitable for this purpose, further research was required to establish practical modelling issues such as:
- the requirements for EMC modelling in automotive applications;
- the level of model detail that is required;
- the uses and potential benefits of automotive EMC modelling;
- how to maximise the efficiency of vehicle scale simulations.
Objectives:
The project aimed to develop a comprehensive set of guidelines for practical electromagnetic modelling in automotive applications, based on detailed validation of models of real vehicles.
This was to be achieved by critical comparison of model results and measurements. A range of modelling techniques and vehicle test cases were used for this purpose. The test cases were derived from production vehicles, and were staged at three levels of complexity. The wiring harness and vehicle structure were also considered, both individually and in combination.
The guidelines were intended to be widely disseminated with the aim of speeding the adoption of EMC modelling techniques within the European automotive industry, thus improving competitiveness. It was also expected that the guidelines would be of value in other transport sectors, most notably the rail and aerospace industries.
Methodology:
The core of the project was concerned with the critical evaluation of numerical predictions against measured results obtained for a range of generic test objects. Only available modelling tools were used in this project, which was concerned with establishing the basis of a practical modelling process rather than the development of new tools and techniques. Tool development has already been the subject of considerable research activity, and efforts were considered necessary to capitalize on this work by promoting the practical use of existing modelling capabilities. A range of suitable analysis techniques was therefore used by the partners, to enable the relative merits of these different tools to be assessed.
This work was based on an initial requirements specification generated in the first few months of the project, which aimed to identify the type of information which would be required for various automotive EMC engineering activities. The test cases were based on a production vehicle, and the model validation activities were staged at different levels of complexity corresponding to various build stages of the vehicle.
For EMC purposes it is also necessary to integrate the modelling of complex structures and wiring harnesses. Thus, these two elements were considered both independently and in combination, at each stage of complexity. Three levels of complexity were investigated, and at each stage an extensive comparison between models and measurements was made. This resulted in a total of 9 test cases to be evaluated in considerable detail during the project.
The use of increasingly complex test cases ensured that the modelling approach was progressively refined, taking account of knowledge obtained from work at the lower levels of complexity. In the final stage of the validation activity a second vehicle, obtained from a different manufacturer, was introduced at the highest level of complexity. The aim of this was to ensure that the knowledge gained in work on the first vehicle was transferable. In parallel with this, studies were also carried out to investigate issues such as how and where to integrate electromagnetic modelling within existing vehicle engineering processes, and how best to carry out such simulations in an efficient manner
The results of this work formed the basis of the GEMCAR guidelines, which were developed and augmented over the duration of the project. In the final months of the project, one of the partners,
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