The deflector jet valve commonly serves as the pilot stage of two-stage electro-hydraulic servo valves, and its cut-off load pressure characteristics directly affect the starting ability of the main valve of the electro-hydraulic servo valve. To quickly and accurately obtain the cut-off load pressure characteristics of the deflector jet valve, the deflector jet flow field is divided into four regions: primary jet, deflector pressure recovery, secondary jet, and receiving chamber pressure recovery. Considering the three-dimensional jet and boundary layer effects in the primary jet zone of the nozzle, the pressure characteristic equation of the deflector jet valve is established by using jet impact theory. Compared with the conventional plane jet theoretical model that does not consider boundary layer effects, the velocity distribution of the jet flow field obtained from the proposed model is more consistent with the CFD calculation results. The experimental testing of the cut-off load pressure characteristics of the deflector jet valve shows that the maximum deviation between the results obtained by the proposed model and experimental data is 9.7%. This model provides a solid theoretical foundation for further analysis of the deflector jet servo valve.

The support and friction characteristics of the valve plate pair in piston pumps are crucial for reliability and lifespan. Various micro-texture models are constructed, and the entire pump flow field is simulated using Fluent software to compare the dynamic pressure characteristics and support forces of different micro-textures. The study further investigated the effects of slanted rectangle texture angle and rotational speed on oil film performance. Results show that all micro-textures improve dynamic pressure and support force, with slanted rectangle textures outperforming others. The dynamic pressure characteristics increase with pump speed but initially increase and then decrease with larger slanted rectangle texture angles, peaking at 0.1455 MPa. The minimum oil film support force occurres at 75° angle, while the maximum friction is at 15°. The larger angles have a greater impact on friction coefficient at speeds above 2000 r/min, whereas below 2000 r/min, smaller angles have more significant effect.

On the basis of considering the return pressure and radial clearance, mathematical models of dimensionless pressure characteristics for both matching and mismatching symmetric underlaps spool valves are established. The dimensionless pressure characteristics curves of the spool valve are obtained and compared with experimental results. The effects of valve matching, return pressure and radial clearance on the accuracy of the mathematical models are analyzed. The results indicate that when the mathematical model is set to neglect the mismatch of the spool valve, the return oil pressure and the radial clearance, the maximum calculation errors are 27%, 16% and 6.5% respectively, while the zero position calculation errors are 27%, 7% and 2%. Specifically, neglecting the radial clearance leads to increasing pressure calculation errors at ports A and B when the spool displacement exceeds 75% of the underlaps. Neglecting the return pressure and the mismatching characteristics of the spool valve also increases the pressure calculation errors at ports A and B within the range of positive opening, with the maximum errors of 78% and 50% respectively. The zero position's calculation errors at the working ports are significantly increased when the mismatching characteristics of the spool valve are not considered. The model can provide theoretical support and reference for the design of symmetric spool valves.

To investigate the friction and wear characteristics of slipper pairs in high-pressure and large-displacement radial piston pumps under impact loading, this study established a transient friction wear model for the stator-slipper contact surface using ANSYS Mechanical software with ANSYS parametric design language programming. The dynamic friction wear of stator-slipper pairs is analyzed under varying working pressures, impact pressure amplitudes, and impact pressure times, supplemented by experimental validation. Key findings reveal that during the 0~0.6 s transient phase, wear primarily occurs between the central oil reservoir and pressure-equalizing groove on the slipper surface, accompanied by uneven wear patterns and stress concentration near the pin hole. The average error of relative value between simulation and experimental results is 8.99%. Through orthogonal experiment analysis and Kriging interpolation fitting, the sensitivity hierarchy of wear factors is determined as impact times, impact pressure amplitude and working pressure. Experimental results under three impact times within 60 minutes show a wear volume of 824.1379 mm³, demonstrating significant structural degradation caused by impact loading and validating the predictive capability of the proposed simulation model for slipper pair wear assessment.

The ultra-high-pressure large-diameter quick-opening valve, is the core component of an ultra-high-pressure gas release device, its flow characteristics and gas flow force play a decisive role in the system performance. A mass flow model of the quick-opening valve is established, and numerical simulations are carried out based on CFD technology. The flow coefficients under different valve port openings and opening pressures are calculated, and the reason why the flow coefficient decreases as the valve port opening increases is analyzed, which is the formation of non-choked flow and the energy loss caused by eddies. Numerical simulations of the gas flow force acting on the quick-opening valve are conducted. The steady-state gas flow force acting on the conical surface and end face of the quick-opening valve core are quantitatively calculated, and it is analyzed that their values fully meet the requirements for quick-opening. A mathematical model of the gas flow force acting on the valve port is obtained through numerical fitting. The research results provide theoretical support for the optimal design and experimental verification of the quick-opening valve.

The existing on/off high pressure large-flow electromagnetic unloading valves suffer from issues such as pressure regulation difficulty and discontinuous fluid supply, which struggle to meet the requirements of rapid response and on-demand adjustment of high-pressure pump output pressure in pumping station fluid supply systems. To address these challenges, an unloading valve utilizing proportional pilot valve control for main valve spool displacement regulation is developed, enabling on-demand rapid fluid supply and multi-range pressure modulation. A simulation model of the unloading valve is established using AMESim simulation software to investigate the influence patterns of main valve spring cavity, spring stiffness, spring preload, and damping hole diameter on the dynamic characteristics of the main valve, with subsequent experimental validation. The results demonstrate: Reduced spring cavity shortens both pressure build-up and relief times; Spring stiffness and preload primarily affect residual pressure and pressure relief duration; Damping hole diameter mainly impacts residual pressure and pressure rise time. Through prototype testing with optimized structural parameters, the experimental data revealed pressure rise time is 388 ms, pressure relief time is 436 ms, and residual pressure is 1.88 MPa.

In response to the failure issues of the piston-slipper ball joint in high-speed axial piston pumps, dynamic characteristic analysis of the piston-slipper assembly is systematically conducted. Piston cavity dynamics model of the piston-slipper pair is established. The pressure variation within the piston chamber is analyzed by using computational fluid dynamics simulations. Subsequently, the interaction forces between the piston and slipper are quantified through multi-body dynamics simulation. Finally, the augmented Lagrangian method integrated with the steady-state structural analysis module of finite element software is employed to evaluate the deformation and stress distribution in both components. The results reveal that with increasing the load pressure, swash plate angle, and rotational speed leads to elevated negative pressure in the piston cavity, higher discharge pressure, and amplified interaction forces within the piston-slipper assembly. The maximum stress reach 80.4 MPa and deformation of the piston is 0.0213 mm respectively. For the slipper, the peak stress (168.4 MPa) and deformation (0.0057 mm) are localized at its closure. These findings provide critical insights for optimizing the design of piston-slipper ball joints in high-speed axial piston pumps.

To study the impact of different dynamic sealing forms on dynamic characteristics of solenoid valve, based on the application cases of high-pressure solenoid valve, an AMESim model of pilot-operated solenoid valve is established. Three typical dynamic sealing forms, retaining ring, O-ring, and variseal are selected to investigate their respective impacts on the dynamic characteristics of solenoid valve. The result shows that the fact that the poor sealing effect of retaining ring leads to the opening and closing action of main valve of solenoid valve easily affected by environmental temperature results in negative impact on dynamic characteristics; Better sealing properties of O-ring leads to worse dynamic characteristics of solenoid valve, therefore a solution of cutting a pressure relief groove on sealing area is proposed; The sealing performance of variseal under normal and ultra-low temperature conditions is markedly different. Therefore the measures that should be considered in the design of the system are put forward to avoid affecting the dynamic characteristics of solenoid valve.

To address the needs of deep-sea hydraulic systems under complex multi-actuator working conditions, this study investigates hydraulic power unit (HPU) technologies and proposes an externally mounted, integrated outboard HPU configuration. The design integrates a compensation oil tank, motor, and hydraulic pump into a unified structure which provides many capabilities like providing flow, pressure and power. To adapt to diverse hydraulic drive requirements. The HPU delivers a rated pressure of 21 MPa and a maximum flow rate of 90 L/min, meeting the demands for high-pressure and high-flow hydraulic power in deep-sea operations. This study conducts a series of performance validation tests, including land-based functional tests and pressure chamber tests. The test results demonstrate that the integrated deep-sea HPU operates stably under high-pressure conditions, with all performance indicators meeting design requirements. This provides an efficient and reliable solution for the hydraulic system of deep-sea manned platforms.

The magnetorheological (MR) fluid transmission device offers advantages such as high controllability, rapid response, and low power consumption. By incorporating the squeeze-strengthening effect, the power of the transmission device can be significantly enhanced. Through analyzing the magnetic energy of the MR fluid under squeeze-shear compound mode, the expression for the torque transmission of MR fluid under compound mode is derived. It is found that reduction in particle distance induced by squeeze leads to an increase in yield stress. A novel compound mode transmission method based on hydraulic squeezing is proposed, and a disc-type transmission device with axial pressure regulation capability is designed, of which the transmission performance is tested. The results show that under an excitation current of 2 A and a squeeze stress of 306 kPa, the output torque of the device reaches 174 N·m, representing an 85% improvement compared to the shear mode, with a transmission efficiency of 87% and a dynamic response time of 372 ms. The squeeze effect enhances the transmission torque of the MR fluid device without affecting the zero-field torque, static characteristics, or dynamic response time. This study provides theoretical and technical solutions for the design of high-power-density MR transmission devices.

The stretching ratio is a crucial factor affecting the lubrication state of reciprocating seals. Traditional axisymmetric models oversimplify the problem by neglecting the influence of circumferential stretching, leading to insufficient accuracy in handling nonlinear issues. Additionally, the microscopic morphology of the sealing surface affects the fluid flow at the sealing interface. Therefore, a lubrication model incorporating the microscopic morphology of O-rings along with a three-dimensional simulation model is proposed. The study investigates the distribution patterns of macroscopic contact stress and oil film thickness under different stretching ratios. The results indicate that as the stretch ratio increases, the maximum contact pressure during both extension and retraction gradually decreases, while the oil film thickness increases. The simulation results closely match the experimental data, with the calculated friction force deviating from the experimental results by approximately 12.65%.

To investigate the dynamic characteristics of the working process of a helical tube hydraulic inerter, a numerical model of the helical tube hydraulic inerter is established. The dynamic mesh technique and User-defined Function are employed to simulate the dynamic changes in the internal flow field of the hydraulic inerter. The velocity and pressure field distributions at different time points are obtained, and the dynamic characteristics of the internal flow field are analyzed. Through bench tests, three excitation conditions—uniform speed input, square wave input, and sinusoidal input—are applied to the hydraulic inerter to explore the influence of excitation forms and impact velocity on the pressure drop, flow velocity, and friction coefficient of the helical tube. The results show that the hydraulic oil converges and diverges at the helical tube interface, forming significant vortices in the hydraulic cylinder. As the buffering progresses, the vortices intensify and the velocity distribution becomes uneven. The pressure drop is the largest under square wave excitation, followed by constant velocity excitation, and the smallest under sinusoidal excitation. The impact velocity is directly proportional to the pressure drop of the helical tube and inversely proportional to the friction coefficient. The findings provide a theoretical basis for the optimal design of hydraulic inerter devices.

The existing luffing hydraulic system of cranes exhibits significant throttling losses and insufficient control precision during fine operations with low flow rates. To address these limitations, A double spool parallel pump-valve synergistic system is proposed. However, the dynamic response mismatch between the pump and double spool valves in the system induces flow fluctuations at mode transition points, resulting in impact vibrations. To resolve these technical challenges. Firstly, the theoretical analyses of the dynamic characteristics of the double spool valves and hydraulic power source is conducted. Building upon these analyses, a multi-mode segmented control strategy based on handle control signals is developed. Subsequently, co-simulation is implemented using AMESim and MATLAB/Simulink platforms. Experimental results demonstrate that the proposed double spool parallel pump-valve synergistic system achieves high-precision micro-motion control with a minimum stable flow rate of 5 L/min. Moreover, the implemented control strategy effectively mitigates flow fluctuations during mode transitions, reducing flow variation amplitude at switching points by 56.7%.

The 6-DOF platform has been widely applied in various fields due to its exceptional performance characteristics including high precision, high load capacity, and high rigidity. To meet the spatial motion and positioning requirements of proton knife surgical beds, a 6-DOF motion positioning platform is developed. Firstly, based on workspace usage requirements, a reasonable structural design for the 6-DOF platform is implemented. Secondly appropriate hardware selection for the control system is carried out, along with programming design for the STM32 controller and the LabVIEW-based host computer. Subsequently, a prototype of the 6-DOF platform is fabricated, and control algorithm parameters are debugged. Finally, experiments are conducted to investigate the adaptability of the BP-PID control algorithm and nonlinear PID algorithm to different load cases, the real-time tracking error of slave cylinders under a master-slave cooperative control strategy, and the overall structural positioning error of the 6-DOF platform. Experimental results demonstrate that, for position control of a single electro-hydrostatic actuator under varying load cases, the BP-PID algorithm outperforms the nonlinear PID algorithm in terms of response speed and adaptive capability, while both algorithms exhibit almost no overshoot; During platform motion, the real-time cooperative error of slave cylinders remains within 0.43 mm, and the positioning accuracy of the 6-DOF platform is better than 0.05 mm/0.1°.

The independent control of power sources and power transmission components in positive control flow excavator transmission systems, and the unified control strategy for hydraulic systems under all operating conditions, lead to poor coordination between vehicle powertrain system and suboptimal fuel economy utilization. To improve overall fuel efficiency, this study focuses on 90° truck loading operations by analyzing the entire operational process. Based on hydraulic pilot pressure signals, the operational cycle is divided into four distinct phases. By examining the performance of the engine and hydraulic pump, this study analyzes load variation characteristics and responsiveness requirements across different phases. At the same time, based on the driver's operation, this study analyzes the evaluation indicators that affect the fuel economy of excavator vehicles, clarifies the influencing factors of fuel economy, and proposes a vehicle control strategy for excavator 90° loading operation conditions.Compare with the original vehicle test data, the results show that adopting a collaborative control strategy can make the engine and hydraulic pump tend to work in the optimal state. Compare to the pre optimized gears, the fuel efficiency can be improved by 10.2% to 12.1% while maintaining comparable efficiency.