▲ Assistant Professor Kim Seon-hee of Sangmyung University is introducing FOD and P2PS technologies.


“FOD technology can prevent fire and burns during wireless charging”
P2PS, Subsystem Integration Trend for Charging Efficiency and Time Reduction

Research on FOD and P2PS technologies is being actively conducted to prevent accidents that may occur in electric vehicle wireless charging systems where the power transmitter and receiver are separated and to improve charging efficiency.

The Korean Institute of Electromagnetic Engineering and Science held a three-day summer academic conference in Jeju Island from the 17th to the 19th, providing a venue to share the latest technological trends in the field of radio waves.

Among them, in the workshop on the topic of wireless charging for electric vehicles, experts such as Assistant Professor Kim Seon-hee of Sangmyung University, CEO Lee Ja-hyeon of Byenergy, and CEO Lim Yong-seok of Byonever took the stage as presenters.

CEO Lee Ja-hyeon cited safety, efficiency, and convenience as examples of why wireless charging for electric vehicles is becoming a hot topic.

In terms of safety, since the wired charging method involves directly connecting the cable, there is a risk of electric shock due to wear and tear on the contact area or damage to the cable caused by foreign substances. However, in the case of wireless charging, the cable is discharged, so there are no exposed wires, reducing the risk of electric shock.

In terms of efficiency, an electric bus can charge its battery at 1.6 kW for 30 seconds at a stop. This can extend the battery life by continuously charging small amounts, enough to drive about 1.3 km.

In the case of wired charging, the shape of the charging port varies from company to company. In the case of wireless chargers, standardization is in progress to ensure uniformity, and they are being developed to be compatible regardless of the type of vehicle, so they also have an advantage in terms of convenience.

Wireless charging hardware consists of a 'ground pad' that is installed on the floor and transmits wireless power (transmitter) and a 'car pad' that is installed on the underside of the car and receives electromagnetic fields (receiver).

This is a form of collecting energy by generating a magnetic field through a coil in the transmitter and inducing a current in the receiver by receiving this magnetic field.

The unique feature of wireless charging for electric vehicles is that the transmitter and receiver are separate. The wireless charger developed by BMW is also about 8cm away.

Here's where the problem arises.

Assistant Professor Kim Seon-hee said, “High-power power is exposed between the ground pad and the car pad, and if there are foreign substances such as living organisms or metal objects, it can cause serious problems.”

If there is a metal object between the two hardware, the current will be induced in this object as well, and over time, the temperature will rise, which can cause fatal burns or fire.

Cats and chewing gum lying under a car can also be dangerous, and because the magnetic field is invisible, you can get burned if you put your hand in without thinking.

For this reason, FOD (Foreign Object Detection), a technology that detects foreign substances, is attracting attention in the electric vehicle wireless charging sector.

The Wireless Power Consortium (WPC)'s FOD standard aims to detect foreign substances by measuring the Quality Factor value before charging begins or by the amount of power loss during charging.

For SAE J2954, the goal is to prevent foreign matter exposed on the surface of the transmitter from becoming hot enough to ignite or to damage the surface of the transmitter.

FOD technology is divided into LOD technology for detecting living things and MOD technology for detecting non-living things, and is classified into electrical and non-electrical methods depending on the method.

A typical non-electrical method is to attach sensors such as image and thermal cameras. It is also possible to determine the presence of foreign substances by applying deep learning technology.

Additionally, when it rains or snows, the camera's field of view can be compromised, so the importance of pressure, weight, and temperature sensors is emerging to compensate for this.

The electrical method is typically judged by power efficiency, as in the WPC standard mentioned above. Voltage, current, and phase are measured at the transmitter.

If there is a foreign substance, the resonance relationship between the transmitter and receiver is disturbed, and the phase changes along with the voltage conversion and current change, and this is detected.

P2PS technology is being studied for alignment between ground pads and car pads and for communication between transmitters and receivers in wireless charging systems.

To put it simply, when a wireless charging electric vehicle is input to charge, it guides it to a location where charging is possible.

Alignment between the transmitting and receiving pads is very important to increase wireless charging efficiency and reduce charging time.

The importance of P2PS technology is increasing as technology for guiding and autonomously adjusting drivers when parking cars to ensure alignment between the two pads increases.

P2PS also relies on camera image processing.

It allows electric vehicles to park autonomously, guiding them to be more accurately aligned through a ground-facing camera.

Kim Seon-hee, a professor at Sangmyung University, said, “The standard requires electrical methods over image processing, but non-electrical methods are still dominant,” adding, “Research is also being conducted by integrating subsystems into one.”