Energy Efficient Excavator Hydraulic Systems With Digital Displacement® Pump-Motors and Digital Flow Distribution

Abstract Environmental and economic factors are driving the development of more fuel efficient off-highway vehicles. The pathway to fuel savings of greater than 50% in an excavator application through utilisation of system architectures unlocked by Digital Displacement technology is presented. Pump flow distribution using digital valves instead of traditional proportional control valves is demonstrated experimentally. The “Workbus” power distribution scheme is demonstrated on a small scale backhoe arm on a laboratory test rig. These tests do not include hydraulic energy recovery. A backward-facing simulation of an 18 tonne excavator is described. The simulation uses input data collected from grading and lorry loading duty cycles. Applying the workbus system architecture to the excavator in simulation, fuel savings of 31% to 48% are realized. With the addition of energy recovery capability via Digital Displacement Pump-Motors, simulated fuel savings are 53% to 58% compared to the original excavator hydraulic system.