With the increasing severity of global warming, there is a growing need for eco-friendly vehicles to reduce greenhouse gas emissions. However, the expansion of charging infrastructure is struggling to keep up with the rising number of electric vehicles due to space constraints and installation costs. This paper aims to address this issue by proposing an autonomous driving algorithm for a mobile robot-based movable charging system for electric vehicles, as an alternative to traditional stationary charging stations. Our paper introduces a rule-based path planning algorithm for autonomous robot-based charging systems. To achieve this, we employ the A^* (A-star) algorithm for global path planning towards the charging request position, while utilizing the Dynamic Window Approach (DWA) algorithm for generating avoidance paths around obstacles in the parking lot. The avoidance path generation algorithm differentiates between dynamic and static obstacles, with specific algorithms formulated for each type of obstacle. Finally, we implement the suggested algorithm and verify its performance through simulation.

Toroidally-wound brushless direct-current (BLDC) machines are compact, highly efficient, and can work across a large magnetic gap. For these reasons, they have been used in pumps, flywheel energy storage systems and left ventricular assist devices among others. The common feature of these systems is a spinning rotor supported by a set of (either mechanical or magnetic) bearings. From the view point of dynamics, it is desirable to increase the first critical speed of the rotor so that it can run at a higher operating speed. The first critical speed of the rotor is determined by the radial stiffnesses of the bearings and the rotor mass. The motor also affects the first critical speed if the rotor is displaced from the rotating center. In this paper, we analytically derive the flux density distribution in a toroidally-wound BLDC machine and also derive the negative stiffness of the motor, based on the assumption that the rotor displacement perturbs the flux density distribution linearly. The estimated negative stiffness is validated by finite element analyses.