Efficiency modeling and experimental validation of a variable displacement linkage pump

The power density of hydraulic drive trains make variable displacement machines appealing to a wide range of applications such as mobile hybrid systems, displacement controlled actuation of heavy machinery, and hydrostatic transmissions for wind power. Current state of the art variable displacement pumps suffer from poor efficiencies at low displacements, thus limiting the potential benefits of hydraulic solutions. Here, a variable displacement linkage pump is presented as a promising method for achieving high efficiency across the full displacement range. In this paper, the linkage kinematics and dynamics are discussed, an energy loss model is presented and used to drive design decisions of a first generation prototype, and experimental results are presented to validate the model. It will be shown that this linkage-based, variable, positive displacement architecture shows promise as a highly efficient alternative to other axial piston machines across a wide range of displacements.