Integrated hub gear motor for heavy-duty off-road working machines - interdisciplinary design

Abstract

This doctoral dissertation studies solutions that meet the demands made for the propulsion motors of off-road working machines. It has been shown that in a hybridization process, without a mechanical gear, it is not possible to cover all the required torque-speed operating points set by the driving conditions of the traditional off-road working machine without largely overdimensioning the electrical components. The dissertation presents a novel solution, which combines a two-step planetary gearbox and a tooth-coil permanent magnet synchronous machine with embedded magnets to solve the problem. The important boundary conditions in terms of the electromagnetic design, mechanics, and cooling are discussed. The high design flexibility offered by permanent magnet synchronous machines is utilized to the full to find a feasible integrated design. Furthermore, the dissertation presents a solution for a gear change mechanism, which is located inside an integrated electric motor gear assembly. The designed and measured performance of the integrated system meets the needs of many off-road working machines. The prototype motor has about 40 kW power and could be adapted for instance on each wheel of a farming tractor, bucket loader, or harvester. The same technology could also be used in on-road applications, such as buses or trucks, intended for difficult terrains.