Multi-MHz In-Motion Capacitive Wireless Power Transfer System for Mobile Robots

This paper presents a multi-MHz in-motion capacitive wireless power transfer (WPT) system for mobile robots. Unlike conventional WPT systems, the presented system is placed in an upside-down manner, allowing the robots to get charged by going underneath the charging pads attached to the bottom of a low-lying surface and thereby minimizing risk of human exposure to high fringing fields. This arrangement also reduces installation cost by eliminating the requirement of any major alteration of existing facilities. The proposed system can automatically turn on and off by detecting the proximity of the robot using an infra-red (IR) based sensing technique. A control methodology is proposed for choosing the turn on and turn off instants in a way that maximizes the energy transferred to the robot over a single pass. Furthermore, the multiplicity of the sensors is selected optimally to maximize the detection angle while avoiding the risk of premature detection. The proposed approach is validated through a GaN-based 6.78-MHz 12-cm air gap prototype capacitive WPT system designed to charge a Rumba robot.