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In-wheel motors offer a promising solution for novel drivetrain architectures of future electric vehicles that could penetrate into the automotive industry by transferring the drive directly inside the wheels. The available literature mainly deals with the optimization of electromagnetically active parts; however, the mechanical design of electromagnetically passive parts that indirectly influence motor performance also require detailed analysis and extensive validation. To meet the optimal performance of an in-wheel motor, the mechanical design requires optimization of housing elements, thermal management, mechanical tolerancing and hub bearing selection. All of the mentioned factors have an indirect influence on the electromagnetic performance of the IWM and sustainability; therefore, the following paper identifies the hub bearing as a critical component for the in-wheel motor application. Acting loads are reviewed and their effect on component deformation is studied via analytically and numerically determined stiffness as well as later validated by measurements on the component and assembly level to ensure deformation envelope and functionality within a wide range of operations.

This work investigates the role of double row angular contact ball bearings as a vibration transmitter in shaft-bearing assemblies. In our analyses the double row bearings are represented as five dimensional stiffness elements (with associated damping) through an extension of the stiffness matrix concept described by Lim and Singh (1989) for single row bearings to double row angular contact ball bearings. In particular, the effects of bearing preloads on dynamic characteristics of double row angular contact ball bearings are first numerically explored. The dynamic responses of face-to-face, back-to-back and tandem arrangements are evaluated on a comparative basis under various preloads. The nature and extent of preloads significantly affect the vibration characteristics of the bearing assembly due to major changes in the diagonal and off-diagonal elements of the stiffness matrix, and these effects vary for alternate configurations. The dynamic effects of bearing preloads are then experimentally investigated for a wheel bearing assembly containing double row angular contact ball bearings (with back-to-back arrangement) under two different preloading mechanisms. Experiments show that the mechanism and amount of bearing preloads significantly affect the system natural frequencies, mode shapes and vibration amplitudes, thus altering the vibration behavior of the bearing assembly. Suggestions for further work and applications will be briefly mentioned.