Standardized Differential Inductive Positioning System for Wireless Charging of Electric Vehicles

Abstract

To shape future mobility MAHLE has committed itself to foster wireless charging for electrical vehicles. The standardized wireless power transfer of 11 kW at a voltage level of 800 V significantly improves the end user experience for charging an electric vehicle without the need to handle a connector and cable anymore. Combined with automated parking and autonomous driving systems, the challenge to charge fleets without user interaction is solved.Wireless charging is based on inductive power transfer. In the ground assembly’s (GA) power transfer coil, a magnetic field is generated which induces a voltage in the vehicle assembly (VA) power transfer coil. To transfer the power from grid to battery with a high efficiency up to 92% the power transfer coils are compensated with resonant circuits.In this paper the Differential-Inductive-Positioning-System (DIPS) to align a vehicle on the GA for parking will be presented. This system utilizes five standardized magnetic fields which are generated within the GA. On the VA induced voltages by the standardized magnetic fields are measured with two crossed coils. A dedicated coil in the GA provides the (magnetic) field for the steering and braking information. The stop signal for the vehicle is provided by an array of four coils in the GA. Additionally to private garages, the DIPS is designed for multi-GA parking spots as well. The special differential signal processing makes the procedure extremely robust against metallic foreign objects. The high accuracy of the DIPS allows the driver to align the vehicle at the first attempt. The automized pairing process enables a charging process without interaction of the driver.