Research Trends and Results

Wireless Power Supply Technology for Running
Vehicles: Experiment Using a Model Vehicle
OBARA Hiroshi, Senior Researcher
TANIGUCHI Hisatoshi, Researcher, (Ph.D. Information
Information Technology Division, Research Center for Advanced Information Technology(keyword) electric vehicle, non-contact power supply, electricity supply in running state
1. Studies on wireless power supply

by doing so, we identified a set of essential factors for

The NILIM has been working, in partnership withwirelessly supplying power for a running vehicle. AtTokyo University, on developing and testing a

ITS World Congress Tokyo 2013, we presented ourtechnology that realizes power supply and battery

experiment as well as its result.

charging for running electric vehicles. Until last year,
our focus was to conduct some basic testing, such as
electricity transfer over a big gap, and supplying
electricity in a large area with an asymmetrical powertransmission and reception unit, to identify theessential elements to achieve this goal. Using a power

2. The Challenges: from bulb to motor
Transferring electricity to a bulb, as seen in ourexperiments last year, is a favourable condition forwireless power supply using magnetic field resonance.
With light bulbs, load is consistent, and the most of theenergy is turned into heat and light, not returning to thetransmission and reception unit, 35cm in diameter, wepower source. On the other hand, with electric vehicles,

have successfully transferred electricity over an

the load varies depending on conditions like theapproximately 80cm gap, which simulates the distancedriver’s control and the amount of power stored in thewhen transferring the power on an actual road.

battery. This is a critical issue in achieving wirelessAnother test using a model vehicle with a bulb

power transfer with a magnetic field resonance system,

attached has also proved it possible to supply power

resulting in situations like not being able to transfer

continuously, over 3m in distance, by employing

electricity at all, or unexpected voltages applied to thetransmission and reception units with different sizes

storage battery.

and shapes. (See Photo 1)

Many of the wireless power supply devices
currently in development for commercial use are forparked vehicles, and maintain optimal charging
conditions by passing load status information from thevehicle to the power transmission unit. However, thismethod is not valid when the vehicles are running. We
at The NILIM have achieved wireless electricity
supply for a running model vehicle, by implementing acontrol circuit where both the power source and thereceiver automatically maintain optimal conditions.

Photo 1 Experiment using a model vehicle
This year, we built a system where a model vehicle
can run continuously using transferred electricity, and,(See Photo 2)

Research Trends and Results

Photo 2 Experiment on power supply for a runningvehicle
In Photo 2, you can see that the red graph,
representing charging status, increases at the power
supply point (where the car is, in the photograph),
indicating that the battery is successfully charged
while the model vehicle is running.
3. Supplying electricity for running vehicles
The

test

with

themodelconfirms

whichtechnologies are required in order to supply electricity
for running vehicles. However, it is still essential totest at higher levels of electrical power, in order toapply these results to real electric vehicles. Thus, ournext step is to progress further with technicalverification, aiming for a life-sized experiment andtesting with greater power.