A Smart Autonomous WPT System for Electric Wheelchair Applications with Free-Positioning Charging Feature

Electric wheelchairs (EWs) are gradually replacing conventional wheelchairs as an assistive tool for people with disabilities who are unable to use the physical force to drive manual wheelchairs on their own. EW charging requires manipulating, plugging in, and unplugging an off-board charger, which can be challenging or impossible for people with severe disabilities. In this paper, a comprehensive solution to the problem of EW recharging is provided in the form of a smart, autonomous charging system, based on the wireless power transfer (WPT) technology. In this paper, a sufficiently large area of 0.75 m2 for a floor-charging pad involving multiple primary coils has been implemented while offering a free-positioning charging feature. A novel design methodology for primary and secondary charging pads' optimization has been developed, taking into account various complex real-life constraints. In addition, a novel 250-W WPT controller design has been employed to maximize misalignment tolerance up to 7 cm while maintaining high system efficiency. In this paper, a novel, comprehensive, system-level organization of a master controller design has been presented which manages continuous coordination between the WPT controllers and the autonomous docking controller, records important system data, maintains safe operation of overall system, and prevents hazardous exposure to potentially harmful magnetic field beyond 15\mu \text{T}. In addition, a novel design methodology for primary and secondary charging pads' optimization has been developed, which takes into account various real-life constraints, and provides a fair comparison between different designs in a multivariable environment. The proposed design is tested in laboratory conditions and later validated in a practical environment.