Mechanical Impact on In-Wheel Motor's Performance

Abstract

In-wheel motors offer a promising solution for novel drivetrain architectures that could penetrate into the automotive industry by locating the drive where it is required, directly inside the wheels. As obtainable literature mainly deals with optimization of electromagnetic active parts, the mechanical design of electromagnetically passive parts that indirectly influence motor performance should also be reviewed and characterized for its effect on performance. The following study uniquely evaluates the impact of mechanical design and its dimensional variations to air-gap consistency between on rotor glued magnets and on stator fitted winding, for the most commonly used layout of an in-wheel motor. To meet the optimal performance of an in-wheel motor, the mechanical design requires optimization of housing elements, thermal management, geometrical and a dimensional tolerance check, and proper hub bearing selection to assure consistent electromagnetic properties. This article covers the correlation between desired electromagnetic parameters and required geometrical limitations for ensuring functionality and high performance operation. Major mechanical contributors have been analyzed with analytical calculations, numerical simulations, and verified with different sets of measurements. The relative change of motor physical air-gap size, between the stator and rotor was correlated with electromagnetic flux density.

In-Wheel Motor Drive Systems for Electric Vehicles: State of the Art, Challenges, and Future Trends

“…Hub bearings are recognized as a critical component for IWM application in various studies, such as [125][126][127][128]. These studies analyze acting loads and their effects on component deformation, using analytically and numerically determined stiffness, and validated through measurements at the component and assembly level to ensure functionality under a wide range of operations.…”