Integrated Pumping and Direct Energy Recovery in a Digital Hydraulic Boom Drive System for Excavators

Conventional valve-controlled hydraulic excavator boom drive systems suffer from low energy conversion efficiency and severe throttling losses. To address this issue, this paper proposes a pump-controlled digital hydraulic drive system based on a Direct Energy Recovery Digital Pump (DERDP). The DERDP integrates hydraulic pumping and boom potential energy recovery within a single unit, enabling both energy recuperation and precise flow regulation. An AMESim simulation model of the system is developed and validated against experimental measurements from a dedicated hardware-in-the-loop test bench. Using the validated model, the operational characteristics are investigated under varying boom load pressures, pump displacement fractions, and motor displacement fractions; the drive and energy recovery efficiencies are systematically evaluated across different operating conditions. Simulation results show that the accumulator stores 2834 J per lowering cycle and releases 2756 J per lifting cycle, reducing motor energy consumption from 5413 J to 2317–2903 J. The system-level energy recovery efficiency reaches 50–60%. These findings offer practical guidance for implementing digital hydraulic solutions in construction machinery.