Browsing by Subject "Radial Ball Piston"

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    A Study and Optimization of a Radial Ball Piston Pump for High-Speed Applications
    (2021-01) Bohach, Garrett
    Ever increasing concern and regulations related to climate change has prompted hydraulic research to focus on improving energy efficiency and reducing emissions, with electrifying hydraulic systems considered a promising solution. This thesis studies the radial ball piston hydraulic architecture, and its capability to efficiently and compactly be integrated with a high-speed electric motor. A combination of analytical, numerical, and empirical models are utilized to create a detailed model of a radial ball piston unit and its losses. The model is experimentally validated using an off-the-shelf radial ball piston pump. After updating the model parameters, the model predicted the efficiency within 3-10 percent across the range of operating conditions. The model is then implementing within a genetic algorithm optimization framework that predicts performance across multiple operating conditions. The preferred embodiment discovered by the optimization reached 12,500 rpm while maintaining 80 – 90 percent efficiency across four quadrants of operation and packaged a 20kW machine within approximately 100mm outside diameter. The work within this thesis represents the first computationally fast and accurate model of a radial ball piston unit that was utilized within an optimization framework for design purposes. The results of this optimization demonstrate that the radial ball piston is an acceptable hydraulic architecture for four quadrant operation and integration with a high-speed electrical motor. However, a challenge with the architecture is that the ball piston kinematics generate an uneven clearance around the ball that results in a nearly constant torque loss independent of piston-cylinder clearance, creating an upper bound on the efficiency.