Design and Analysis of PM Machines for personal Mobility Applications Considering Safety Regulations

This paper presents the design and development of a permanent magnet (PM) traction machine for electric kick scooters (e-scooters). The research work starts with a benchmarking study of an existing commercial model to identify areas for improvement. The benchmarking study revealed that the traction machine used in the commercial e-scooter is overdesigned and its maximum speed is limited by software threshold. Following the benchmarking study, the tractive forces of an e-scooter were calculated to identify design specifications taking into account safety regulations and typical performance requirements. Then, the design process of an outer-rotor PM machine that meets the required design specifications is presented. This PM machine is designed for a maximum vehicle speed of 25 km/h without using a reduction gear. The proposed design process utilizes the characteristic current of the PM machine as a key constraint to efficiently search for an optimal solution. The optimal solution is found by using a surrogate-based metaheuristic optimization algorithm. Finally, simulation results show that the torque density of the proposed gearless design was found to be 39% higher than the benchmark design while meeting performance requirements and safety regulations.