Design and development of safety systems for high frequency inductive power transfer

Abstract

As wireless charging is gaining its popularity among consumer electronics, e.g., phones, smart wearables, electric toothbrushes, etc., there has been a trend of expanding this technology into a wider range of applications e.g. drones, robots, electric vehicles etc.. To achieve this, both the charging power and range need to be increased. This thesis discusses the limitations of widely used kHz inductive power transfer systems and emphasises the challenge of deploying into a wider range of applications. High-frequency inductive power transfer (HF-IPT) systems are then discussed with two real-world applications presented to showcase HF-IPT’s potential over kHz IPT systems. Some of the benefits of the HF-IPT, e.g., the large air gap and tolerance to misalignment, could increase the chances for live or other unintended objects to be coupled into the wireless charging system, which could cause safety hazards if the system was not designed carefully. This thesis, therefore, focuses on the safety systems design and development for HF-IPT systems. A number of existing and potential foreign and live object detection methods (FOD/LOD) including a new FOD/LOD method based on reflected impedance are introduced. The proposed method can operate without additional sensors, and without a communication link between IPT transmitter and receiver. A detection accuracy of 95% is achieved by implementing such FOD/LOD method. In addition, a FOD/LOD technique based on a mmWave radar sensor is also introduced. Differing from typical radar applications, the proposed method leverages machine learning techniques to perform object recognition to reduce the false detection rate. The developed FOD/LOD system could classify six different charging scenarios with an average accuracy of 96%. For applications that do not involve any live or unintended objects, this thesis also introduces a localisation technique based on the IPT system to help guide a drone or robot to a specific location e.g. a wireless charging point. Such a system was designed to reduce the risk of charging by minimising human’s involvement.