Tokyo Engineers Shrink EV Wireless Charging Test Track to Tabletop Scale
Building a test track to study wireless charging for electric vehicles is expensive. Installing transmitter coils in a stretch of pavement, equipping a vehicle with a receiver unit, and running trials at realistic road speeds requires infrastructure that most universities and smaller research institutes simply do not have. As a result, much of the experimental work on dynamic wireless power transfer - charging EVs while they move - has been concentrated in a handful of well-funded national laboratories and corporate R&D facilities.
A team at Tokyo Metropolitan University has built a device that changes that arithmetic. The rotating tabletop system, designed by a group led by Assistant Professor Ryosuke Ota, fits on a standard laboratory bench and can replicate the electromagnetic conditions of an EV receiver coil passing over an embedded transmitter coil at highway-relevant speeds.
The Engineering Problem It Addresses
Dynamic wireless power transfer, or DWPT, works by embedding a transmitter coil beneath a road surface and mounting a receiver unit on the underside of a vehicle. As the car passes over the transmitter, inductive coupling between the two coils transfers power to the battery. The appeal is obvious: if EVs can be charged continuously while driving, they need smaller battery packs, reducing both cost and weight.
The fundamental challenge in studying this system is speed. The electromagnetic coupling between transmitter and receiver changes constantly as the vehicle moves, and the effect of misalignment - when the receiver is slightly off-center relative to the transmitter - needs to be characterized at realistic velocities. Doing that on a real road requires a real road. Until now.
How the Rotating Device Works
Ota's team mounted a receiving unit on a counterbalanced arm attached to a servo motor. The arm rotates in a horizontal plane above a bean-shaped transmitter coil installed below the arc of motion. As the arm spins, the receiver passes repeatedly over the transmitter in a pattern that mimics a vehicle traveling along a straight section of embedded charging road.
The design sounds simple, but making it work required careful electromagnetic simulation. The team used finite-element modeling to verify that the magnetic field produced by the bean-shaped coil closely approximates that of a standard linear track coil. They also analyzed mechanical stress in the rotating arm at high speeds to confirm structural safety.
The resulting system achieved power transmission of 3 kilowatts at conditions equivalent to a vehicle moving at 40 kilometers per hour - comparable to conditions achievable in dedicated track facilities. The coupling behavior under various degrees of receiver misalignment was measurable and consistent with theoretical predictions.
What This Opens Up
The device's practical value lies in access. Academic research groups that lack the space or budget for track infrastructure can now conduct DWPT experiments in a standard laboratory setting. The design principles and evaluation framework the team published provide a blueprint for replication at other institutions, which is the main pathway through which this kind of benchtop-to-track compression typically propagates through a research field.
There are important caveats. The rotating geometry is an approximation of linear travel, not an exact physical model, and the electromagnetic fields near the edges of the arc differ from those at the center of a straight track. High-speed performance above 40 km/h was not reported in this study. Real vehicle deployments also involve variations in ground clearance, lateral positioning tolerances, and power electronics that a bench device cannot fully replicate.
The work was partially supported by the TEPCO Memorial Foundation. The findings suggest that the bottleneck limiting DWPT research may be less about fundamental science and more about the practical barriers to building testbeds - barriers this work is designed to lower.