Alvus: A Reconfigurable 2-D Wireless Charging System

Wireless charging pads such as Qi are rapidly gaining ground, but their limited power supply range still requires precise placement on a specific point. 2-D wireless power transfer (WPT) sheets consisting of coil arrays are one well-known counterpart to extend this range. However, these approaches require custom-made designs by expert engineers; what we need is a WPT system that can be reconfigured by simply placing ready-made modules on the intended surface (e.g., table, floor, shelf board, etc). In this paper, we present "Alvus", a reconfigurable 2-D WPT system which enables such simple construction of WPT surfaces. Our system is based on multihop WPT that composes "virtual power cords" and consists of three types of ready-made resonator modules: (i) transmitter, which outputs energy, (ii) relays, which pass energy down to the next module, and (iii) receivers, which receive energy and charge the loads. We show that power can be transferred efficiently (over 25%) within a range of 19.6 m2 using a single transmitter. We implemented an end-to-end WPT system and demonstrated that Alvus is capable of intuitive construction/reconfiguration of WPT surfaces, as well as automatically deciding the power routes based on the sensed information (e.g., receiver location, module placement, obstructive objects).