This paper investigates the effects of self-inductance and mutual inductance on saggy coil magnetic resonant inductive coupling power transmission (IPT). The simulation of the saggy coil is conducted using a specialist tool called IPTVisual to visualise the phenomenon of saggy winding in the system. The results provide important intuitions for optimising saggy coil inductive coupling devices for better performance and reliability in a variety of applications. The setup of simulations and experimental shows a slight difference. The mutual inductance and coupling coefficient of two saggy coils are analysed and discussed. There is a difference of 1.74% in self-inductance in saggy coil with two fixed mounting point of 1 m distance when comparison is made between simulation and experimental results.

This paper presents a wireless power transfer (WPT) for a mid-sized inspection mobile robot. The objective is to transmit 100 W of power over 1 meter of distance, achieved through lightweight Litz wire coils weighing 320 g held together with a coil structure of 3.54 kg. The Wireless Power Transfer System (WPTS) is mounted onto an unmanned ground vehicle (UGV). The study addresses an investigation of coil design, accounting for misalignment and tolerance issues in resonancecoupled coils. In experimental validation, the system effectively transmits 109.7 W of power over a 1-meter distance, with obstacles present. This achievement yields a system efficiency of 47.14%, a value that is remarkably close to the maximum power transfer point (50%) when the WPTS utilises the full voltage allowance of the capacitor. The paper shows the WPTS charging speed of 5 minutes for 12 V, 0.8 Ah lead acid batteries.