Investigação de uma nova metodologia para ensaios de suscetibilidadeeletromagnética em veículos automotivos

Abstract

The study of electromagnetic compatibility has won importance through the years, due, mainly, to the growth of using electric energy, electronic equipments and telecommunications. This happens because many types of devices, present in the same environment, need to work properly. Thus, an equipment must be robust, to keep a good functioning even, in environments with a high level of electromagnetic field, and also must radiate the minimum field possible, for don't cause interferences in another equipments in its nearness. The technological development and the consequent increase of the electronic on-board systems in vehicles, made the question of electromagnetic compatibility a notable feature also in the automotive industry. There are several international rules which regulate the working of automobiles and its electronics components, establishing the test procedures and reference levels to electromagnetic fields. New products, before to be launched in the market, must obey these rules. The susceptibility (or immunity) electromagnetic tests verify the capability of a vehicle work properly in presence of an intense electromagnetic field. These tests became more important since is increasing the number of safety related functions controlled by electronic systems. To use its Laboratory of Antennae and Electromagnetic Compatibility to making susceptibility tests in vehicles, in its factory, in Betim, the FIAT Automobiles propose a new test methodology, only using the vehicle front part and reducing the distance between antenna and car. To investigate this proposal feasibility it's necessary to deep know the electromagnetic phenomena that happen during the tests, to evaluate the impact of the reduced distance in the coupling between antenna and car, and the effect introduced by the changing in the vehicle structure due to the split. The main objective of this thesis is experimentally investigate the feasibility of the presented proposal. This requires in depth knowledge of the electromagnetic phenomena that occur during a test, assess the impact of reducing the distance in the coupling between the antenna and the car and the effect introduced by the change in the structure of the vehicle due to the cut. Initially, it was held a series of experiments in a small Semi-Anechoic Chamber (CSA) in order to characterize the electromagnetic field generated by an antenna, about the changes in distance, the condition of reflection of the chamber and form of objects two-dimensional and three-dimensional, with different kinds of openings. Following, several experiments were conducted in an Open Area Test Site (OATS), using prototypes of vehicles in natural scale, and real vehicles, whole and cut as the proposal. In these experiments the electric field inside the object under test was mapped observing the change of distance and the comparison of results for objects intact and cut. Finally, the fields were measured inside vehicles for the condition of test standard, in a large CSA, and the condition of CSA testing proposal, in a small one, with the aim of verifying the existence of direct correlation between the quantities observed.