Liejiang Wei

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.

To address the variation in operating length that arises across different grading strokes, where conventional sine acceleration/deceleration algorithms cannot simultaneously satisfy motion efficiency and smoothness requirements, this paper proposes a length-adaptive sine acceleration/deceleration trajectory planning method. By adaptively adjusting velocity, acceleration, and phase durations, the method improves overall motion performance. Focusing on planar grading and slope grading, a kinematic model is established to determine the bucket pose-cylinder displacement mapping, enabling accurate bucket tip tracking. A length-adaptive simulation model is developed for long and short trajectory studies, with experimental validation on a 1-ton excavator. Results demonstrate that the algorithm maintains maximum average velocity under long trajectory conditions for efficiency, while adaptively tuning key parameters to enhance motion smoothness under short trajectory conditions. This method meets intelligent excavation requirements and provides a valuable reference for related research.

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.

With the continuous advancement of modern industrial equipment and the increasing severity of service conditions, the demand for high-performance sliding bearings with enhanced reliability, load-be...

Traditional Reynolds-averaged Navier–Stokes (RANS) models struggle to accurately predict nonlinear damping in wide-Reynolds-number (Re) oscillatory flows due to dynamic response lag caused by linear vortex–viscosity constitutive relations and time-averaged frameworks. To address this limitation, this paper proposes an instantaneous Re dynamic partitioning damping model (IRDP-Damping). The core innovation lies in establishing the instantaneous Re as an external criterion independent of turbulence variables. This approach enables synchronization of the damping mechanism with the local flow state and adaptive application of nonlinear physical friction laws, thereby fundamentally overcoming the inherent limitations of traditional models. By coupling the IRDP-Damping model with the shear stress transport (SST) turbulence model via a user-defined function, the model is integrated within a computational fluid dynamics framework. Using gas–liquid coupled oscillations in a vertical U-tube as a validation case, the performance of the IRDP-Damping model in free-decaying and forced-resonance oscillations is systematically evaluated. Results demonstrate that, compared to the SST model alone, the IRDP-Damping model improves damping ratio prediction accuracy by 24%–47% and significantly enhances numerical robustness under strongly nonlinear resonance conditions within the validated Re range (up to ∼9000). It also exhibits good agreement with classical U-tube oscillation experiments. This study presents a physically consistent and computationally robust damping modeling approach, validated for oscillatory flow in a U-tube system involving complex flow regime transitions. The framework shows promise for broader applications in oscillatory flows.

The mainstream Rotating Cell Culture System (RCCS) simulates microgravity via three-dimensional dynamic rotation, which differs from true space microgravity in physical mechanisms. In this context, the present investigation innovatively proposes a new microgravity simulation strategy based on Einstein’s equivalence principle—establish a stable and controllable quasi-free-fall flow field environment by constructing a gas-liquid coupled oscillatory system inside the U-tube. Based on the analysis of the physical modeling of the oscillating flow field in the vertical U-tube and the CFD-VOF gas-liquid coupling simulation experiments with parameters (D = 15 mm, R/D = 1.3) shown that in each oscillation period, 71% of the liquid will lose weight in two vertical sections, and when the liquid at the maximum volume ratio the average weight loss peak value is 0.02 g, achieving spatial low microgravity (10⁻²g), and the dynamic characteristics of the pressure and shear stress of the flow field meet the mechanical boundary conditions of cell culture. This approach is expected to establish a new paradigm for ground-based simulation of microgravity effects in space, offering novel technical/theoretical support.

A digital proportional valve is constituted by the main spool and a high-speed on/off valve bridge acting as the pilot stage. However, the main spool will generate oscillation during movement under the control of the pilot stage. This results in poor stability, slow response speed, low control accuracy, and even the potential loss of control of the valve. To tackle this issue, an oscillation suppression method based on fuzzy intelligent proportional-integral-derivative (PID) control is put forward. The movement state of the main spool is determined in accordance with its movement position and velocity. Thereafter, the fuzzy control parameters of the controller are calculated on the basis of the determined movement state of the main spool. Different PID parameters are adopted to eliminate the control effect difference caused by the structural asymmetry of the two pilot control chambers of the main valve. The performance and robustness of the proposed control method are verified by comparison with the PID controller based on full-bridge and half-bridge control. The results demonstrate that the proposed control method can effectively suppress the oscillation of the main spool of the digital proportional valve, improve the control accuracy, and reduce the response time. When the excitation signal takes the form of a step signal, the overshoot of the control method put forward in this paper is diminished by 26.2% in comparison with that of the PID control. Under stable operating conditions, the maximum tracking error is less than 3.1%. Moreover, compared with simply using the PID control method, this error is reduced by 41%.

The conventional hydraulic system of excavators suffers from significant valve throttling losses and inadequate matching between the hydraulic power source and the load, which substantially impact the system’s overall energy consumption and severely impede the trend toward electrification and energy efficiency in construction machinery. To address this issue, a pump-controlled hydraulic cylinder system has been implemented to replace the original valve-controlled hydraulic system that utilizes a single pump with multiple actuators. The influence of energy conversion efficiency and the speed between the motor and the hydraulic pump under varying load-power conditions has been determined through experimental investigations. Based on these findings, a compound-control strategy is proposed that adjusts the displacement of the hydraulic pump to achieve precise control over the position of the hydraulic cylinder and facilitates both the speed and displacement coordination while ensuring optimal motor speed matching with the load power. This strategy is implemented in the boom pump’s hydraulic cylinder control system. The research findings indicate that this combined-control approach enhances efficiency by approximately 18.9% compared with traditional variable-speed pump-controlled hydraulic cylinder systems. Furthermore, energy consumption is reduced by about 39% compared with the conventional valve-controlled hydraulic system.

The conventional hydraulic system of excavators suffers from significant valve throttling losses and inadequate matching between the hydraulic power source and the load, which substantially impacts the overall energy consumption of the system and severely impedes the trends toward electrification and energy efficiency in construction machinery. To address this issue, a pump-controlled hydraulic cylinder system has been implemented to replace the original valve-controlled hydraulic system that utilizes a single pump with multiple actuators. Focusing on a specific model of electric-driven excavator arm as the research subject, we completed parameter matching design for the pump-controlled hydraulic cylinder system. Based on typical operating conditions of the boom, experimental results revealed how energy conversion efficiency and hydraulic pump speed are influenced by varying load power.Furthermore, control over hydraulic cylinder position was achieved by adjusting pump displacement. A combined control strategy involving both displacement adjustment and motor speed modulation to align with load power is applied within this boom's pump-controlled hydraulic cylinder system. Research findings indicate that this combined control approach enhances efficiency by approximately 18.9% compared to traditional variable speed pump-controlled hydraulic cylinder system, while the energy consumption is reduced by about 39% compared with the traditional valve-controlled hydraulic system. under the hydraulic pump pressure of p=16 MPa and a working flow demand of Q=85 L/min, the efficiency of the hydraulic pump increases first and then decreases, that is, the efficiency spaceΔη=26.7% can be improved in the speed range.This study holds both theoretical and practical significance for enhancing energy utilization efficiency across entire excavator systems as well as optimizing their configurations.