Magnetic gears transmit torque via non-contact electro-magnetic coupling, which eliminates mechanical contact and significantly reduces wear, backlash, and noise compared to traditional mechanical gears. These benefits make magnetic gears particularly appealing for high-precision, high-reliability applications. However, achieving both high torque density and high gear ratios necessitates an optimized structural design that promotes efficient magnetic flux distribution while minimizing leakage and saturation. This study focuses on a hollow-type magnetic gear for collaborative robots that offers a high gear ratio. It employs topology optimization in conjunction with finite element analysis (FEA) to enhance torque density and efficiency. Key design variables, such as the geometry of the ferromagnetic core and the arrangement of permanent magnets, were optimized to increase average torque and reduce torque ripple and electro-magnetic losses. A prototype based on the optimized model was fabricated, and its performance was validated using a conventional direct torque measurement system. Experimental results were compared with simulation predictions to evaluate accuracy and analyze loss characteristics. The findings demonstrate the effectiveness of the proposed optimization approach and provide practical guidelines for designing high-efficiency magnetic gears suitable for advanced drive systems, including electric mobility and renewable energy applications.

The aim of this paper is to investigate the improvement of surface characteristics of Stellite21 deposited layer by powder feeding type of direct energy deposition (DED) process using a plasma electron beam. Re-melting experiments of the deposited specimen is performed using a three-dimensional finishing system with a plasma electron beam. The acceleration voltage and the travel speed of the electron beam are chosen as process parameters. The effects of the process parameters on the surface roughness and the hardness of the re-melted region are examined. The formation of the re-melted region is observed using an optical microscope. Results of these experiments revealed that the re-melting process using a plasma electron beam can greatly improve the surface qualities of the Stellite21 deposited layer by the DED process.