A Series-Parallel Hydraulic Hybrid Mini-Excavator with Displacement Controlled Actuators

Abstract

A displacement-controlled (DC) prototype mini-excavator built at the Maha Fluid Power Research Center at Purdue University, had previously demonstrated 40% fuel savings over a standard mini-excavator with load-sensing architecture, in independent side-by-side testing. A DC series-parallel (DC S-P) hydraulic hybrid architecture has since been conceptualized where the braking energy of the swing can be stored in an accumulator. This architecture promises further efficiency gains over the DC architecture by taking advantage of four–quadrant operation enabled by DC actuation, swing kinetic energy storage capability, and enables 50% reduced engine power, through load-leveling and power management, while exploiting the cyclical nature of excavator work cycles. In simulation, feasibility studies for the DC S-P hybrid excavator with reduced engine power, showed 51% fuel savings over the standard excavator without loss of performance for an expert truck-loading cycle. Conservative power management was used for these studies, with the downsized engine operated efficiently at a single point (maximum governed speed and torque). This work will focus on: a) the high-fidelity co-simulation model used to model dynamic behavior and evaluate various power management strategies, b) working hydraulic schematics for the series-hybrid swing drive, c) the controller in use on the prototype, and d) measurements for proof-of-concept.