Design of a Highly Integrated Electric-Hydraulic Machine for Electrifying Off-Highway Vehicles

Off-highway vehicles represent a major portion of US energy consumption and greenhouse gas emissions. Electrifying or hybridizing these systems has the potential to yield substantial fuel savings through both efficiency improvements and energy recovery over the drive cycle. However, the extreme power density and transients of these systems pose unique challenges to electrification that have so-far prevented broad commercial success. To overcome these challenges, this paper proposes an integrated electric-to-hydraulic conversion machine. Three novel topologies are proposed which combine the rotor of radial and axial flux machines with an eccentric ball piston hydraulic pump. Design objectives for use in off-highway vehicles are defined, a sizing analysis is performed on each topology, and one topology is selected and optimized to investigate its suitability for meeting the unique requirements of an off-highway vehicle.