For the electric hydrostatic pump unit (EPU), which is a crucial component in the electro hydraulic servo pump control system (EHSPCS), nonlinear flow modelling is a key challenge to achieve high performance operation, especially in position control. For the nonlinear flow of EPUs, simple linearization combined with compensation has become a popular control method recently. However, the control performance is constrained by the reliance on deviation correction. This paper proposes utilizing the Gauss Newton iterative method to investigate the nonlinear flow modeling in the EPU, aiming to obtain the mapping relationship between the load flow and operating parameters in the EPU, thereby directly improving the control performance. A nonlinear flow model is built by utilizing the Gauss Newton iterative method based on test data obtained from various operating conditions, and the mapping relationship is presented accordingly. Experimental studies show that compared to well-established methods, this model exhibits high accuracy and practicality in improving the control performance, particularly in position control of the EPU.

An independent pump-controlled hydraulic system based on a variable speed variable displacement power source (VSVDPS) can eliminate throttle losses of the electric loader boom and recover gravitational potential energy. However, challenges arise in efficiently and rapidly solving for the optimal speed and displacement due to severe load fluctuations, model inaccuracies, and the coupling of the two variables. This paper proposes an energy-efficient optimization method based on the model search combined method (MSCM), which leverages the advantages of the model-based method for fast solution finding and the search-based method for high precision. Initially, the model-based method is used to determine the suboptimal speed. Subsequently, based on this speed, the initial speed search interval containing the optimal speed is calculated, enabling the VSVDPS to quickly operate near optimal efficiency during the early stages of the search. Finally, the search-based method is employed to swiftly determine the optimal speed and displacement. The experimental results demonstrate that the MSCM achieves significant energy efficiency improvements with short convergence times. In the hydraulic system of the loader boom, the VSVDPS employing the MSCM reduces energy consumption by 9.38 and 11.27% compared with a variable speed fixed displacement power source and a fixed speed variable displacement power source.

The lubrication performance of a straight-line conjugate internal meshing gear pump is poor under the low-speed, high-pressure operating conditions of the volumetric servo speed control system, and it is difficult to establish a full fluid lubricating oil film between the gear ring and the housing. This leads to significant wear and severe heating between the gear ring and the housing. The lubrication performance of the interface moving pair of the electro-hydraulic actuator pump gear ring housing can be improved by designing a reasonable lubrication bearing structure for the gear ring housing. In this study, a multi-field coupling multi-objective optimization model was established to improve lubrication performance and volumetric efficiency. The whole model consists of the dynamic model of the gear ring components, the fluid lubrication model of the gear ring housing interface, the oil film formation and sealing model considering the influence of temperature, and the multi-objective optimization model. The comprehensive performance of the straight-line conjugate internal meshing gear pump was verified experimentally using a test bench. The results show that the lubrication performance is improved, the mechanical loss is reduced by 31.52%, and the volumetric efficiency is increased by 4.91%.

High-speed on/off valve (HSV) is widely used in fields, such as construction machinery, marine equipment, and aerospace, due to its advantages of strong anti-pollution and low energy consumption. The dual solenoid sliding HSV, which dynamic performance is rarely affected by fluctuations in pressure, simplifies flow control. However, under the current drive methods, the dual solenoid HSV exhibits poor dynamic performance, which limits control accuracy and the range of applications. Thus, this paper proposes a high dynamic drive method for dual solenoid HSV. First, the spool dynamic model of the dual solenoid HSV is established. Then, the mapping between phase difference and response time is obtained, and a phase difference modulation method is proposed. On this basis, the phase-duty cycle compound modulation (PDCM) guiding law is designed by combining the current dynamic model. Subsequently, the optimal phase difference and duty cycle are determined through the simulation according to the designed modulation guiding law. Finally, a series of comparative experiments are carried out and the results demonstrate that the proposed PDCM reduces the closing response time by 41.9% and expands the controllable range of flow rate by 100%, which enhances control precision and expands the range of applications for dual solenoid HSV.

For permanent magnet synchronous machines (PMSMs), accurate inductances are critical to achieve high performance control, but inductance estimation can be affected by machine nonlinearities and the coupling with other machine parameters. Hence, this article presents the inductance estimation from a new perspective by using the derivative of the voltage to current angle (VCA) to improve the estimation accuracy especially for the d-axis inductance. The idea is to derive the derivative of VCA based inductance estimation model from the machine model, which is decoupled from the machine parameters such as permanent magnet (PM) flux linkage and improves the estimation performance. To consider magnetic saturation, nonlinear inductance variation is modeled in a local region of interest to improve the estimation performance. To avoid the influence from winding resistance and inverter distortion, the voltage variation under two speeds is employed to construct the estimation model. To reduce the influence from the measurement noise, the derivatives of VCA are modeled and estimated from the measurements using nonlinear polynomials. Hence, one can use measurements under low speeds for inductance estimation, which can reduce the influence of nonlinearities such as core loss in using high-speed data. The proposed approach is validated with extensive simulations, experiments, and comparisons on a test PMSM drive.

The hydraulic spool valve (HSV) represents the core control element in the fluid power system by virtue of its precise flow and pressure regulation abilities. Unbalanced radial flow force (RFF) is a major contributor to spool instability and friction-induced failure in HSVs, particularly in open-neutral configurations where flow field asymmetry is prominent. Conventional assumptions often overlook RFF due to structural symmetry, yet practical designs constrained by standard port layouts frequently induce asymmetrical pressure and velocity distributions. To address this issue, a novel through-hole design is proposed and integrated into the mid-shoulder of the HSV spool. Specifically, the study employs a combined approach of computational fluid dynamics-based numerical simulations and experimental bench testing to evaluate RFF generation and suppression mechanisms. The Realizable k–ε turbulence model is used to capture turbulent flow features and assess the contribution of pressure and viscous forces. Various through-hole angles are analyzed to determine the optimal configuration. Results indicate that RFF is predominantly pressure-driven (accounting for over 85% of total force), with significant asymmetries localized around the mid-shoulder region. Incorporating a 15° inclined dual through-hole structure reduces RFF on the mid-shoulder by 45.5% and total spool RFF by 29.9%, improving flow symmetry and minimizing pressure gradients. The optimized structure also enhances performance stability under varying spool displacements, achieving a maximum total spool RFF reduction of 55.5% at −1.5 mm displacement.