Current state of the art variable displacement pumps suffer from poor efficiency at low volumetric displacement. Additionally, their performance is strongly dependent on operating conditions. A new variable displacement linkage pump architecture has been developed which can achieve high efficiency across a wide range of operating conditions. Previous work has described the kinematics, energy loss modeling, and experimental validation of a low power single cylinder prototype as well as the design of a second generation prototype. The second generation pump employs roller element bearings in its joints to minimize friction losses and the three cylinder design reduces the pressure ripple. In this paper, experimental characterization is presented of the new 21 MPa, 6.75 cc/rev pump. High mechanical efficiency is achieved at low volumetric displacements at partial loads as low as 0.6% of maximum power. Poorly performing cartridge check valves result in low volumetric efficiencies at low displacements. Close agreement was obtained between the model and predicted work input using measured cylinder data as an input into the model. This work shows that the presented pump with properly functioning valves can achieve high efficiency across a wide range of operating conditions. Having such versatile pump performance can greatly improve the performance of hydraulic systems as well as expand their potential applications.

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