SAE Blog Text

Standardizing EV Alignment SAE J2954, the final step for commercializing Wireless Charging (Part 2)

Published: September 18, 2024 

Guest Post by Jesse Schneider, ZEV Station; Ky Sealy, WiTricity; Maximilian Hollenbach, ifak; Mike Böttigheimer, Timo Lämmle, Simon Joos MAHLE Powertrain; Ivo Teerlinck, Toyota Motor; Bastian Rappholz, Siemens; Andreas Wendt, Electreon

(Note: This is a continuation of a post authored by the taskforce on their process in finalizing SAE J2954. Read Part 1 here.)

SAE J2954 Alignment Witness Tests

The UWB and DIPS alignment systems were integrated into vehicles chosen by the technology providers and setup in accordance to SAE J2954 requirements for parking spaces. Three independent witnesses chosen by the SAE J2954 taskforce conducted the tests scheduled by the taskforce’s alignment sub team. Due to the positive results and outcome of the taskforce’s review, only the DIPS test is shown exemplarily.

Both systems were integrated into an electric vehicle (with a VA). The test setups were conducted in realistic environments.  For the exemplary case of DIPS, the testing was performed in an underground garage of a building. Three GAs were setup in adjacent parking spaces placed in accordance with the SAE J2954 Standard.

Parking Garage setup for Alignment testing in Stuttgart, Germany (courtesy of ifak).

Test Plan

Testing consisted of three blocks: basic tests, environmental tests and other tests. Basic tests included approaches of the GA from different directions, at different speeds and from several distances. For the environmental tests the GA was either covered (minimum thickness 5mm) with materials or surrounded by them, depending on the case. Other tests included verification of the frequencies being used with a spectrum analyzer and measurement of the magnetic flux emitted by the DIPS.

DIPS Alignment testing with environmental and metallic obstacles (courtesy of ifak).

Final Alignment Comparison Test Results

Both UWB and DIPS systems passed the basic requirements of the tests. The window shown below is illustrating the EV alignment tolerance limits related to EV parking within the SAE J2954 tolerance zone.

SAE J2954 DIPS test results as documented by ifak

SAE J2954 UWB test results as documented

From the driver’s perspective, a key difference was the visualization inside the car. Inside the E-Smart vehicle equipped with the DIPS, the screen gave fast and intuitive information to the driver about steering direction and distance or error if the driver overshot the target. The responsiveness of the guidance allowed the driver to approach the GA at all requested velocities, enabled the driver to correct the angle of steering, and gave brake signals in time to reach the SAE J2954 tolerance zone. The visualization of the UWB ranging system inside the other car had sporadic behavior and offered limited help for the driver. Therefore, the UWB system’s directions during parking did not help to reach the tolerance zone.

Another difference between the two systems witnessed was the multi-GA scenario. The DIPS showed sufficient performance with active GAs on the adjacent parking spaces. It also enabled the driver to switch the GA (with visualization) by driving the car to another parking space, without any interaction.

Voting Decisions: DIPS is clear winner for the standard

The SAE J2954 WPT Taskforce had the following four pieces of information available to them in order to make the decision between the two alignment methodologies for the next SAE J2954 standard:

  1. A draft SAE J2954 alignment section update in the standard based on the two technologies.
  2. A detailed technology description for each of the UWB and DIPS methodologies
  3. An open industry survey (subjective/ objective) with scoring results for both technologies
  4. Detailed witness testing reports for each of the UWB and DIPS technologies

The SAE WPT Taskforce, with this comprehensive set of data and information, carried out a decision poll with the following results:

As per the figure above, the SAE J2954 Wireless Power Transfer & Alignment Taskforce voted with 75% of the members in favor of DIPS as the common alignment method for public infrastructure in the light-duty vehicle standard. The choice was based on these test results, technology readiness level, and industry feedback. Therefore, the latest SAE J2954 standard published in August of 2024 includes DIPS as the common standardized alignment methodology for WPT.

“With over two decades of experience in wireless power transfer, ifak e.V. was enlisted by the task force to carry out the SAE J2954 alignment witness tests for their standard. We were honored to assist in this crucial step in helping to harmonize global standardization of WPT for EVs,” stated Maximilian Hollenbach, Research Associate, for ifak (Institut für Automation und Kommunikation e.V) of Magdeburg Germany. “As a result of the field testing, data taken and feedback from the SAE WPT-TF, it was found that the differential inductive positioning system (DIPS) has proven to be a mature technology capable of satisfying all requirements of the SAE J2954 alignment. DIPS gives fast and precise feedback to the driver while being resilient against numerous extreme environmental conditions.”

“The next generation of EV charging can be as simple as parking in a spot, with automated wireless charging using SAE J2954.” stated Jesse Schneider (ZEV Station), chair of the SAE WPT Task Force. “The SAE WPT Taskforce has extensively tested wireless power transfer and alignment from the lab to the field, allowing safe wireless power transfer up to 11kW with efficiencies up to  93%.The new standard gives consistent alignment to an exact parking spot with the DIPS System. This will enable a seamless wireless charging & parking, even for autonomous vehicles in rain and snow. With the new J2954 standard, the team has solved the missing link, enabling the start of commercialization of wireless charging for EVs, a gamechanger.”

Though it took more than a decade to arrive at the point of decision to determine an alignment method for WPT, SAE has carried out a transparent and data-based consensus process leading to a clear direction for standardizing the alignment method as well as wireless charging. This groundbreaking publication of the SAE J2954 Standard will lay the framework for commercialization of light duty wireless charging worldwide for plug-in electric vehicles as well as autonomous vehicles.

Looking to the future, the SAE J2954 Taskforce is currently working on higher WPT power classes up to 500kW in the heavy-duty recommended practice SAE J2954/2 and Dynamic WPT in SAE J2954/3.

Find this document in Mobilus.

 

 

X