Hongfei Gao

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.

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 boom energy recovery efficiency reaches 50%–60%. These findings offer practical guidance for implementing digital hydraulic solutions in construction machinery.

There is a permanent and strong need for energy recovery to improve the efficiency of the hydraulic system in the field of the construction machinery. In addition, the digital pump will become powerful and versatile by employing different configurations and intelligent control of the flow distribution valves. Considering this case, we have proposed a novel digital pump in which every plunger is equipped with two flow distribution valves. By controlling these two valves, external hydraulic energy can be directly reused without other components. Based on the structure and working principle of the digital pump, the mathematical model is established and three working modes are detailed. To verify the feasibility and correctness of control methods, a performance simulation testing platform including a digital pump, load module, hydraulic energy to be recovered, and controller module was developed in AMESim R15 software. The pressure, flow rate, and torque simulations of the digital pump in three working modes were carried out. The simulation results have shown that the digital pump not only can be used as an ordinary pump but also has the function of recovery and immediate reutilization of another hydraulic energy. Meanwhile, the corresponding variable displacement control strategy is effective and the positive torque required to drive the digital pump can be reduced, which verified the energy-saving of this scheme. The ideas and contents in this paper can offer significant references for energy conservation technology of various engineering machineries and the intensive study of digital hydraulics.

The potential energy recovery of hydraulic excavators is very significant for improving energy efficiency and reducing pollutant emissions. However, the more common solutions for potential energy recovery require more energy conversion processes before these potential energies can be reused, which adds to the complexity and high cost of the system. To tackle the above challenges, we proposed a novel energy recovery system for hydraulic hybrid excavators based on the digital pump with an energy recovery function. The new system could operate in three different modes: pump, energy recovery, and direct reuse. Based on the descriptions of the working principle of the digital pump and the whole energy recovery system, the mathematical models of the digital pump, the excavator arm cylinder, and the accumulator were established and the AMESim simulation model (combining mechanics, hydraulics, and electrics) was developed. The dynamic characteristics of the energy recovery system were studied under no-load and full-load conditions. The simulation results showed that this scheme could achieve 86% energy recovery when the boom was lowered and reused the recovered energy directly when raised, which could decrease the system input energy by 78.1%. This paper can provide an optimized solution for construction machinery or off-road vehicles and presents a reference for the research on digital hydraulics.