Car-key radio tech could line up EVs with wireless chargers to within millimetres
Wireless charging for electric vehicles promises that a driver can park over a pad in the ground and walk away, with no cable to plug in. The catch is alignment. If the receiving coil under the car sits a few centimetres off the pad, or the car is parked at an angle, efficiency drops and charging takes longer. Researchers in Japan and the United States now report a way to measure that alignment to within a few millimetres using the same radio technology found in some digital car keys.
The work comes from the University of Osaka, auto-parts maker Tokai Rika and the University of California San Diego. It was published in the IEEE Open Journal of Vehicular Technology.
Why existing guidance falls short
Current approaches have weak spots. Magnetic positioning systems work best when the car is already close to the pad, and cameras can be thrown off by rain, dirt on the lens or poor light. The Osaka team turned instead to ultra-wideband (UWB) radio, a short-range signal designed for precise distance measurement.
In their setup, four UWB devices are mounted around the vehicle's receiver coil and communicate with antennas next to the charging pad. Positioning happens in two stages. First, the time signals take to travel between the antennas gives a rough fix on where the car is. Then the system measures tiny phase differences in how the radio waves arrive at each of the four devices, which narrows down both position and heading. Signal distortions peculiar to each installation are measured ahead of time and subtracted out.
Millimetre-level results, in the lab
In laboratory tests with a scaled-down vehicle mock-up parked repeatedly at a fixed spot, the method's median error was 2.32 millimetres in position and 0.25 degrees in orientation. Without the correction for installation-specific distortions, the position error was about five times larger. The output can feed a display that guides the driver, or an automated parking system, into place.
The researchers see the clearest use in autonomous vehicles and robotaxis, which will need to recharge without a person on hand to plug them in.
"We hope this research will lead to a future where EVs charge simply by parking, much like smartphones placed on wireless chargers," said Ryotaro Hada, the study's first author.
The results come from a controlled indoor setup, not a working charger. The team says it still needs to test the system on full-sized vehicles, outdoors, and while power is actually flowing between pad and coil.
Source: Hada, R. et al., "Toward Precise Pad-to-Coil Alignment in EV Inductive Charging With UWB," IEEE Open Journal of Vehicular Technology (2026), doi:10.1109/OJVT.2026.3725689; University of Osaka news release.