Wireless Charging enables the customer the ability to have “transparent” recharging of plug-in electric vehicle—EV, combustion engine (IC) PHEV, fuel cell (FC) PHEV—through a seamless connection to the EVSE charger and automated charging process. For WPT [wireless power transfer], essentially the customer does not have to do anything except park the vehicle in the right spot. The integration of DSRC communications (specified by SAE Hybrid/DSCR committees) allows WPT increased interconnect ability over present conductive communications with V2Infrastructure assisting in location of available chargers, an automated secure charging and billing and options such as connectivity with smart grid.

—Jesse Schneider, Chair SAE J2954

Since launching in late 2010, the taskforce has now grown to comprise six subteams: Alignment and communications (in coordination with SAE Hybrid Communications and SAE DSRC committees and the US Department of Transportation (DOT)); Testing and validation; Verification of wireless charging regarding performance, safety, interoperability and communication; interoperability; WPT frequency determination; and Bus wireless charging.

There are a number of topics under the aegis of J2954, including:

• Classification of different charging types and minimum efficiency per charging type;
• Interoperability including center operating frequency of charging ;
• Communications & software (harmonize with SAE conductive charging);
• Validation testing (vehicle, charger, system);
• Parking alignment beween the vehicle secondary coil and the primary coil of the wireless charging unit (EV Supply Equipment, EVSE);
• Location on vehicle and orientation of charger;
• Safety items, including obstacle detection, both organic and inorganic; magnetic field levels; charging battery state of charge levels and rate; temperature development tests; and electric shock; and
• Design validation test and wireless charging verification test.

The taskforce is taking a six-point approach to these issues:

1. Determine minimum performance criteria for charging (efficiency) through team consensus with input from industry studies;
2. Develop safety criteria also by coordinating with data gathering;
3. Develop testing protocol for safety and performance of wireless charging;
4. Create a matrix of available wireless charging technologies with EVSE supplier input and determine frequency of charging with input from industry groups (SAE/ IEEE) and government agencies (FCC/FDA);
5. Develop a common interface for vehicle primary coil; assist in interoperability of wireless charging; and
6. Develop protocol and determine means of communication.

In addition, SAE J2954 is working together with UL (Underwriters Laboratories) to create a validation test and link the efforts for design validation (SAE J2954) to verification of safety and performance (UL 2750) of wireless charging. A jointly developed test fixture is under planning to provide a means for verification of performance (such as minimum efficiency with alignment) while keeping within safety limits (ICNIRP magnetic field levels, temperature limits).

Communications for wireless charging will use DSRC (Dedicated Short Range Communications) (earlier post). This is a coordinated effort between US DOT, SAE DSRC Committee as well as the SAE Communications Committee, and will open up numerous opportunities also for electric vehicle communications (V2Grid, V2V) as well as billing and smart grid, Schneider notes.

As part of its work on specifying the center operating frequency for WPT, the taskforce has issued a request for information on interference frequencies (e.g., automotive, communications, medical, clock, etc.), in order to determine which frequencies are open for wireless charging. This is necessary before a determination of charging frequency can be standardize and should include the second and third harmonic possibilities.

The taskforce has taken recommendations from JARI and developed a draft concept of charging categories per power level, static charging (e.g., residential; public parking; on-site static such as stop lights or bus stops) but not on-road dynamic charging:

Concept only types of charging, locations and efficiencies. Source: J2954. Click to enlarge.

To choose the minimum efficiency level, power level and frequency, the taskforce is investigating the ideal method to specify interoperable coil geometries. The taskforce is evaluating a number of options to accomplish this from specifying coils to creating a “magnetic coupling” performance test.

Proposed alignment methods that are being investigated include triangulated RFID positioning; magnetic coupling positioning; or combination positioning. The general principle of RFID positioning is to use signal strength by multiple RFID readers and tags to triangulate vehicle position.

One possibility for magnetic coupling positioning is to send a magnetic ping; the most sensitive secondary resonant circuit component is measured for voltage or current. Coupling coefficient estimation or “sweet spot” detection is used to determine relative magnetic alignment.

Another possibility is combination positioning which uses RFID to determine vehicle proximity or relative position, while magnetic coupling is used to help determine magnetic “sweet spot”.

Industry involvement. There is heavy involvement from industry and government in the effort. WPT suppliers include Conductix-Wampfler; Evatran; HaloIPT; KAIST (Korea); Momentum Dynamics; LG; OLEV; Qualcomm; Samsung; SEW; and WiTricity. Other infrastructure companies include Better Place, NRG Energy and Southern California Edison.

Auto OEMs participating include Audi; BMW; Chrysler; Coda; Daimler; Fisker; Ford; GM; Honda; Mitsubishi; Nissan; Phoenix; and Toyota. Bus manufacturers Volvo and Proterra are also participating. Tier 1 suppliers in the mix include Delphi; Magna; Maxwell; Panasonic and Yazaki.

Finally, government and research organizations involved include US Department of Energy (DOE) and its national labs (ANL, INL, ORNL, etc.); US Environmental Protection Agency (EPA); US Department of Transportation (DOT); and Energy Dynamics Laboratory (EDL), a government research institution and technology provider owned by the Utah State University Research Foundation. JARI (Japan); EPRI; KAIST (Korea); University of Tennessee; Underwriters Laboratories; TÜV North America; and the California Department of Transportation are also involved.

The J2954 taskforce has objectives to align the industry on minimum performance and safety targets for Wireless Power Transfer (WPT) of PHEVs. Determining a common center operating frequency and means of magnetic interoperability and alignment are critical for the wide scale success of WPT. The frequency and magnetic coupling are essentially equivalent to the conductive charging “plug”, so that a vehicle can go from its charging station in the garage to work or shopping mall with the same charging ability without any action on behalf of the customer except confirming correct parking. The OEMs also have to choose general common vehicle locations. These are no easy tasks. J2954 will offer the first industry wide guideline to make interoperability between suppliers and OEMs to enable the first phase of pre-commercial applications.

—Jesse Schneider, Chair SAE J2954

Resources

• SAE J2954 Overview And Path Forward (SAE International website)