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SAE International announces alignment methodology for wireless electric vehicle charging; “Differential Inductive Positioning System”

SAE International announced that the SAE Wireless Power Transfer & Alignment Taskforce has completed a lengthy consensus process and decided upon Differential Inductive Positioning System (DIPS) as the technology alignment methodology for the SAE J2954 standard.

The taskforce, consisting of automakers (OEMs), Tier 1s and wireless charging suppliers, were surveyed to determine minimum common methods for alignment (fine alignment, pairing, and alignment check) to be standardized and agreed upon DIPS as the alignment technology for the upcoming revision for SAE J2954, Wireless Power Transfer (WPT) for Light-Duty Plug-in/Electric Vehicles and Alignment Methodology.

EV charging should be as simple as parking in the right spot and walking away, SAE J2954 Standard enables this. The SAE J2954 Taskforce decided on the standardized alignment method DIPS, completing the standard, making a seamless and automated, all-weather wireless charging & parking. With this, the team has solved the missing link for wireless charging commercialization for EVs.

—Jesse Schneider, chair of the SAE Wireless Power Transfer Task Force (ZEV Station)

With this update to the standard, wireless automatic charging will become available to public infrastructure. I’m pleased to commend the excellent work of the SAE J2954 technical sub-committee for alignment and controls on the extended efforts to reach this result.

—Ky Sealy, co-chair of the SAE J2954 Alignment and Controls sub-team (WiTricity)

Wireless Power Transfer (WPT) following SAE J2954 enables fully automatic wireless charging solution for electric vehicles and promises highly efficient charging (up to 93%) of electric and plug-in-hybrid vehicles. The missing piece of standardization of light duty WPT has been finding an alignment methodology which works in all weather conditions and environments and is interoperable between many different types of applications. The next revision of SAE J2954 with DIPS enables automated parking and charging also for autonomous vehicles.

The new J2954 standard alignment system, DIPS, is described as a low-frequency, low-intensity magnetic field generated from the ground assembly with multiple coils that can evaluated by the vehicle assembly for positioning. A conformance test is done to ensure interoperability between vehicle and charging pad.

Ground and Vehicle WPT assembly manufacturers can develop and test their systems according to this interoperability specification. The DIPS transmitter and receiver coils can be fully integrated into the GA and VA.

The basic interoperability working principle of DIPS is comparable with that of the plug. The GA provides a H-field source description like the socket and the VA has therefore free choice like the connector. With that concept it is possible to develop the GA and VA independent from each other.

The H-field description is provided by a Test Station GA where a solenoid coil shown in yellow is wound around the ferrite and the litz wire from the power transfer coil to generate a horizontal field with a defined magnetic flux with 0.26 At_RMS (far below ICNIRP limit). This horizontal field allows the VA to evaluate the magnetic field early enough before reaching the Ground Assembly so that it is possible to provide the needed information about steering and braking for the driver in good time. The four red coils placed above the winding and the ferrite from the power transfer coil generate a vertical field, also with a defined magnetic flux. Since there are different frequencies, the VA can distinguish from which coil which signal level comes to calculate the position. As one example for the VA, the magnetic field can be evaluated by a crossed solenoid coil wound around the ferrite with 45° to driving direction (with only one turn each).


DIPS fine alignment/guidance solution for static charging in SAE J2954(courtesy of MAHLE)

The updated SAE J2954 light duty vehicle standard is expected to be published in the first quarter 2024 with a detailed specification. There will also be a data report presented at SAE World Congress in April 2024.


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