Error Characteristics of Passive Position Sensing via Coupled Magnetic Resonances Assuming Simultaneous Realization With Wireless Charging

Recently, wireless charging via coupled magnetic resonances has gained attention because it offers the possibility of efficient midrange wireless charging. However, recent studies have shown that the use of a position sensor is helpful in realizing efficient power transmission. In response, we have proposed a passive position sensing method that shares a common structure with a wireless charging system, enabling cost reduction, and space reduction because of integration of multiple functions into a single system and batteryless and cost-effective transponders because of passive sensing. The sensing method is useful for efficient wireless charging or even long-range navigation for mobile robots such as automated guided vehicles. However, the error characteristics of the sensor have not been previously studied. Therefore, the error characteristics of the position sensing were derived through error analysis in this paper. Moreover, the first actual experiment of 3-D position estimation was conducted to demonstrate the appropriateness of the position sensing method and to analyze the error characteristics.

I. Introduction

In recent years, wireless charging via coupled magnetic resonances has gained attention because it is effective for near-field usage [1]–[6]. This type of charging has a wider transmission range than electromagnetic induction charging [7] and ideally higher transmission efficiency than microwave [8] or laser charging [9]. Recent studies have shown that the ideal transmission efficiency is realized when the target is at a certain relative position from the power transmitter [2]–[6].