Design and optimization of a direct-drive in-wheel electric motor for automotive applications

The topic of direct-drive electric machines for in-wheel applications is interesting because the placement of the primary vehicle drives in the wheels allows for additional vehicle functions and designs. It is the premise of this research that the specific boundary conditions presented by the actual homogeneous integration of such a drive in all four wheels of a vehicle presents a solution which differs from previous research in this area. The research also seeks to differentiate the specific advantages and challenges of the direct-drive variation of individually-controlled electric all-wheel-drive vehicles. During the design of the machine, typical parameters are discussed and three machine topologies which are commonly used in literature for this application are scientifically and neutrally compared. The result is that when comparable electromagnetic assumptions are used, electric machines of several types are approximately equivalent. Once the comparison is completed, a machine type is chosen to be produced as a full-scale prototype to be used to validate the methodology presented in the research. Extensive measurement details are presented to show the accuracy of the modeling as well as discuss development topics which would need to be addressed when designing an electric machine for this application. The measurements validate that a direct-drive machine with high torque density, when properly designed, can achieve comparable drive cycle efficiency when compared with a geared drive.