Featured Project

# Wireless Charging Table Supporting Multiple Devices with Arbitrary Placement

# Problem

While more and more device manufacturers adopt wireless charging into their smartphones and headphones, most currently available wireless charging pads only support a single device and require strict alignment between the device and the coil. Misalignment can negatively influence both user experience and charging efficiency. In certain scenarios such as cafeterias, a table that can simultaneously charge multiple devices with arbitrary placement can be useful and COOL, allowing the users to sit wherever they like and to arbitrarily place their devices.

# Solution Overview

We intend to design and manufacture a table with multiple mobile coils placed in an intermediate layer below. Driven by step motors, a tool grabber attaches the coils using electromagnets and drop them in the right place. Computer vision will be used to recognize devices (phones, AirPods, etc.) and guide the chargers to corresponding locations. Once the coil is in place, it will first communicate with the device (Qi protocol) to verify whether the device can be charged wirelessly. If yes, the charging process will start. Otherwise, the coil will be moved back to its original location. The scheduling algorithm ensures the wires get separated and neat.

# Solution Components

* Mechanical subsystem. The main moving component of the system is a large-scale X-Y moving mechanism under the table. The coils will be placed between two panels above the moving mechanism and will be caught and dropped to the right place by the moving tool head. The tool head will be developed with electromagnets or magnets with Z-axis moving capability.


* Vision detection subsystem. This includes a camera and a processing unit. It detects the locations of phones and other chargeable devices and send their positions to the control unit. In real-world settings, pre-installed surveillance cameras may be used as the video source so that no additional camera is required. Embedded GPU (NVIDIA Jetson Nano as a candidate) or cloud service can be used for image processing.

* Power supply control. It is used to control wireless chargers and supply power to devices if and only if the handshake between charger and device is successful. Status will be reported to the central control unit.

* Central control unit and embedded software. According to the output given by the vision detection system or the feedback from the power supply system, the central control unit should move the chargers with proper scheduling algorithm to pair chargers with devices and keep wires of coil separated and neat.

# Criterion for Success

* The vision detection system can localize chargeable device at an accuracy of over 80% and response within 2s.

* The power system can supply powers when a chargeable device is present, and not supply power when the misdetection happens. Correct feedback can be sent to the central control system.

* The mechanical system moves correctly according to the commands given by the central control system.

* The central control system can send correct commands to the mechanical system given the position information from the vision system and the feedback from the power supply system. It should be able to keep wires of charging coil separated.

# Evaluations on Alternative Solutions

The technology of wireless charging emerged some time ago, but its inclusion in commercial devices doesn’t take off until recent years. Intuitively, wireless charging doesn’t bring much additional convenience compared to the wired charging, but its adoption by major manufacturers has proven its value. Similarly, in certain settings such as the cafeteria, charging without alignment may significantly increase user experience, comparing to having only a few fixed charging locations.

An alternative solution to enable table-scale wireless charging is to deploy multiple coils covering the whole table. But it doesn’t solve the alignment problem unless the coils are heavily overlapped, which has been proven to be difficult by already canceled Apple AirPower.