Optimization of the coupling factor curve for lateral offset of a coil pair for contactless inductive charging to generate positioning tolerance

Abstract

Electric Vehicles can become more interesting for prospective customers as soon as existing disadvantages, as for instance range and comfort for the charging process, can be improved. Beside the increase of the battery capacity, the contactless inductive charging can help to raise the acceptance in the population. Inductive contactless charging can be used to charge a vehicle while the driver does not even have to leave it. If short parking and waiting times can be used for inductive charging, the practical range and the comfort are being increased. In the future, when cars will drive without a human driver, also the parking process should happen autonomously and thereby an electronic parking assistant will take care of the correct positioning of the secondary to the primary coil. Until the transition to a standard equipment of vehicles with parking assistants, it is necessary to develop positioning tolerant systems for the inductive charging. Moreover, it can become possible that small vehicles are equipped with an inductive charging system without a parking assistant due to cost benefits. For those cases, it is necessary to develop an inductive charging system which allows a principally caused large positioning tolerance. In this paper, a procedure is being developed to achieve a flat curve of the coupling factor against a lateral offset through small modifications in the coil pair. Measurements for various coil pairs are presented. For a given example, an inductive charging system will be optimized for high positioning tolerance.