Wireless Power Transfer for Mobile Robots

Abstract

Mobile robots used in hazardous environments face challenges due to limited onboard battery capacity. Current solutions, such as manual battery replacement or tethering, result in downtime and mobility limitations. Integrating wireless power transfer (WPT) technology offers a promising alternative. Whilst existing WPT research focuses on high-power applications for electric vehicles and low-power applications for consumer devices, mid-range mobile platforms require an average of 100 W operating power and transfer distances of 1 to 20 metres. This thesis presents a study on magnetic resonant inductive coupling power transfer (IPT) through system implementation. The IPT system was evaluated to investigate the IPT coils with different geometrical shapes under lateral and angular misalignment to assess the system’s viability. The study of Power Transfer Efficiency (PTE) and transmitted power was assessed by comparing circular and octagon coils. It was found that the PTE of octagon coils performed similarly to circular coils of the same 1-metre diameter, with less than a 2% difference. The outcome of the research is a generalised simulation of IPT systems with experimental validations for the OC-WPT (Octagon Coil WPT) with a 1-metre aperture demonstrated a PTE of 47.14%, transferring 109.7 W across a 1-metre distance. In the coil misalignment study, PTE significantly dropped to 1.65% when the receiver coil was laterally displaced over 1 metre. Among various coil shapes under study, Square Coil WPT (SC-WPT) proved feasible. A novel retractable design of an inductive wireless power charging system is proposed, and a prototype with 5x size compression is implemented and tested. The experimental results show 116.5 W of output power at 68.72% PTE across a 1-metre distance. Compared to the OC-WPT system, there was an improvement in PTE, with a 21.58% increase. The development of the retractable coil led to an investigation into sagging coils. A study of the IPT system’s PTE, focusing on self-inductance and mutual inductance, was conducted through simulations and validated by experiments. A difference of 1.74% in self-inductance was observed for a sagging coil with two fixed mounting points at a 1-metre distance when comparing simulation and experiments. Through analysing the performance of the WPT system viable for the mobile platform, it is clear that wireless charging is one of the potential solutions to improve the mobile robot’s efficiency in reducing the time taken for task completion. This thesis demonstrated the wireless charging capabilities of mid-range mobile platforms and represents a critical step in advancing the integration of robots in challenging environments, implying that the combination of WPT and mechatronic systems can contribute to the improvement of mobile platform performance.

Date of Award	4 Mar 2025
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Gus Cheng Zhang (Co Supervisor) & Simon Watson (Main Supervisor)