To address issues such as uncontrollable pressure difference, limited flow regulation range, and low flow control precision in pre-compensated multi-way valves, a principle of active pressure-difference control is proposed. By using a proportional pressure-reducing valve to regulate the force on the compensator spool to achieve proportional control of pressure-difference, actively adjusting according to working conditions, and improving the flow-control range. Additionally, a variable gain control strategy is developed, integrating closed-loop main spool position control, flow gain adjustment, and flow force compensation to mitigate adverse factors, match target flow curves, and enhance flow-control precision. Results show that adjusting the pressure-reducing valve allows the main valve pressure-difference to be continuously regulated within 0~1.28 MPa, increasing the flow-control range to 0%~131% of the original valve's capacity. Closed-loop control of the spool position improved accuracy, reducing flow hysteresis from 4.6% to 2%, a decrease of over 50% compared to the original valve. This method enables multiple flow gain configurations with the same main valve without altering the spool structure. By using the pressure-difference control unit to balance hydraulic forces on the compensator, disturbances from flow forces on the pressure-difference are eliminated, further enhancing flow-control precision.

Steering gear is the linchpin of hydraulic power steering system, critically impacting vehicle comfort and handling stability. Rotary valve, as a key component of the steering gear, determines its performance. A profound comprehension of the rotary valve's operating principles and the influence of its parameters on assisted characteristics is paramount for enhancing the performance of the steering system. Initially, this study introduces the composition of the hydraulic power steering system and elucidates its operational principles during straight-line driving and steering maneuvers. Subsequently, based on these operational principles, an AMESim model is developed to investigate the effects of various parameters, including torsion bar stiffness, engine speed, short cut length, axial length of pre-opening gap, width of pre-opening gap, and groove widths, on the power assist characteristic curve. Finally, experimental validation is conducted on the optimized steering gear. The results demonstrate that following structural optimization, the input hand torque of the steering gear decreased by 15.5%, with an overall inward shift observed in the assist characteristic curve, ultimately leading to improved comfort of vehicles.

In order to reduce the pressure loss of hydraulic control logic valve, improve the flow efficiency of the oil, a simulation model of the flow field in the logic valve is established based on CFD, and considering the influence of fluid cavitation. The flow characteristics of the hydraulic oil and the flow-pressure characteristics of the valve are analyzed, and the test is carried out. Finally, the influence of different structural parameters of valve port on the pressure loss is explored. The results show that when the inlet flow rate is greater than 60 L/min, the simulation results and test errors of whether to consider cavitation are 4.16% and 22.41%, respectively. The pressure loss can be reduced by using a smooth transition at the sharp edge, increasing the valve sleeve aperture and reducing the diameter of the valving element, which can provide reference for the optimal design of the logic valve.

This study introduces a modeling method based on digital twins in pneumatic manipulator systems to achieve simulation, control, and monitoring of pneumatic manipulators, and provide more intuitive teaching demonstrations for beginners. Using the Unity 3D platform to configure the twin environment, create a digital twins model of physical entities, establish communication, and achieve real-time updates of motion status and data, thereby accurately mapping the twin model. Multiple control methods are adopted for the pneumatic manipulator. Analyze the motion state of the pneumatic manipulator gripping a cube in ANSYS Workbench transient structure; Perform secondary development on its results in Unity 3D, display gradient cloud maps of the analysis results, and provide intuitive visualization models for beginners. The research presents a digital twins system for motion simulation of pneumatic robotic arms, synchronization of virtual and real states, and secondary development of finite element analysis.

The thrust reverser actuation system is used to control and drive the aircraft thrust reverser deployment and retraction, thereby enhancing landing safety. The synchronization of the actuation has a direct bearing on the efficiency of the aircraft reverse thrust and landing safety. Through a comprehensive analysis of the synchronization requirements of the hydraulic thrust reverser actuation system and an exploration of synchronous actuation architectures, a scheme of the hydraulic thrust reverser synchronous actuation system is proposed. Subsequently, the system mathematical and AMESim simulation models are established. These models are utilized to simulate and analyze the impact of various operating conditions, asynchronous loads, and flow control valves on the displacement synchronization of the system. The results reveal that, in comparison to the synchronous scheme of diversion valve and throttle valve, the flow rate of the speed control valve scheme is less affected by the system operating conditions. Furthermore, the load has lesser impact on the synchronization of the system operation. Consequently, the adoption of a speed control valve scheme based on constant flow control can achieve the thrust reverser actuation system deploying and stowing synchronously under different operating conditions.

This paper proposes a new type of lifting oil-gas buffer structure which meets both the buffering function and the demands of aircraft loading and unloading cargoes, and the performance parameters of this structure are analyzed through virtual simulation technology. Based on the working principle of this new type of lifting oil-gas buffer, its mathematical model and simulation model are constructed. The results show that, within a certain range, the lifting and buffering performance of this oil-gas buffer is positively correlated with the initial pressure of the air cavity and negatively correlated with the initial volume of the air cavity, however, when the initial pressure of the air cavity increases to 7.5 MPa or the initial volume of the air cavity decreases to 0.01 m³, the system will appear a jitter phenomenon. The results provide a reference for the structural design of oil-gas buffers for lifting landing gear in engineering applications, enhancing both design efficiency and quality.

To address the challenges of gait control in obstacle crossing and crawling for pneumatic biomimetic robots, this paper designs a four-legged pneumatic soft crawling robot modeled after the red-eared slider turtle. The robot consists of four two-segment pneu-net actuator, which mimic the structure and movement of turtle legs. Finite element analysis is conducted to optimize the structural parameters of the soft actuators. Performance tests are carried out on a single leg under different timing control conditions. The robot's mobility performance is tested in straight-line crawling, turning, and obstacle crossing scenarios. The results show that the soft robot exhibits excellent adaptability and stability, with a maximum straight-line crawling speed of 50 mm/s, a turning speed of 45 (°)/s on rigid surfaces, and the ability to cross obstacles up to 25 mm in height. Its outstanding adaptability and stability suggest significant practical application potential in fields such as search and rescue, detection, and inspection.

Flow pulsation is an inherent property of the delivery oil of axial piston pumps. The pressure pulsation induced by flow pulsation affects the working quality and service life of axial piston pumps and even the entire hydraulic system. To clarify the causes and components of flow pulsation, a three-dimensional transient CFD model of an axial piston pump is established, a test platform for pressure pulsation at the outlet of an axial piston pump is built to verify the numerical model experimentally. In addition, the pressure pulsation components due to geometric pulsation, backflow pulsation, leakage pulsation and dead zone pulsation are obtained by adjusting the geometrical structure parameters of the simulation model. The verified simulation model is employed to analyze the amplitude contributions of each flow pulsation component under different operating conditions. The simulation results indicate that geometric pulsation and backflow pulsation have positive contributions to the flow pulsation, while leakage pulsation and dead zone pulsation have negative contributions to the flow pulsation. The geometric pulsation, backflow pulsation, dead zone pulsation,and leakage pulsation account for 9%, 214%, -35% and -88%, respectively, of the total delivery flow pulsation at a discharge pressure of 10 MPa and a rotational speed of 1000 r/min. The research results provide an important theoretical basis for the formation mechanism and suppression methods of the delivery flow pulsation in axial piston pumps.

The downhole flow control system, as the central component of intelligent completion systems, is crucial for intelligent downhole mining. The downhole high-temperature solenoid valve, as a vital component of the electronic-controlled hydraulic drive flow control system, significantly impacts the system's performance. This paper introduces the structure and working principle of the solenoid valve developed an electromagnetic model using finite element simulation, analyzes the effects of static core cone angle, static core protrusion, coil position, magnetic shielding ring inclination, and magnetic shielding ring length on electromagnetic force characteristics, and performes an electromagnetic-thermal coupled simulation analysis. This study uses an orthogonal experimental design to investigate the primary and secondary relationships between electromagnetic force structural parameters, and it optimizes the electromagnet's structural parameters using the optimization concept of combining the response surface method with the improved particle swarm algorithm. Following optimization, the electromagnetic force at 0 mm increases by 16.68%, at 0.5 mm by 29.62%, and at 1 mm by 31.06%. This study provides a theoretical foundation for the design of an electronic-controlled hydraulic drive flow control system.

Deflector jet servo valve fault signals are limited and easily affected by noise under complex conditions, resulting in difficult feature extraction. This paper presents a fault diagnosis method combining starfish optimization algorithm-based variational mode decomposition, temporal convolutional network, and a self-attention bidirectional gated recurrent unit network. The starfish optimization algorithm selects variational mode decomposition parameters to improve decomposition accuracy and robustness. Main features are extracted from key intrinsic mode functions based on minimum envelope entropy. These features are entered into a temporal convolutional network and a self-attention-based bidirectional gated recurrent unit network to enhance fault classification. A fault simulation platform and dataset are built, with experiments under typical fault conditions. Results show that the fault recognition accuracy of the method achieves 97.33%, demonstrating strong robustness and high diagnostic performance.

Current valve electromagnets face issues of large size, heavy weight, and high cost. A linear force motor scheme using electrically-heated NiTi shape memory alloys wire to electrically heat and drive the valve core is proposed. Based on Brinson's one-dimensional constitutive equation, a thermodynamic model of shape memory alloys is established. MATLAB Simulink is used to simulate shape memory alloys wire electro-thermal behavior under varying currents, and the heat-induced effects on linear force motor actuation are analyzed. When the spring stiffness is 20 N/mm, the maximum displacement and driving force of three different lengths of shape memory alloys wires with a diameter of 0.5 mm are calculated theoretically. Finally, a test bench is built. When 6 A current is applied at 22 ℃, the three different lengths of shape memory alloys wires reach the maximum displacement of 1.8, 2.1, 2.5 mm respectively at about 0.5 s. The corresponding driving forces are 58.4, 61, 80 N. Compared with the simulation results, the displacement and driving force errors are both within 10%. The natural cooling response time after power-off is 5 s, and the total response time is 5.5 s. The results show that it is feasible to use shape memory alloys linear force motor to drive the hydraulic valve with a frequency response below 0.2 Hz.

As the core actuator in the turbine governing system, the main distributing valve is prone to a series of problems such as local high pressure, uneven force on the valving element, and vibration under different operating conditions. During the research process, CFD is employed to analyze the internal flow field characteristics of the main distributing valve of a turbine governor under start-up and shutdown conditions. Numerical simulation is carried out on the valve models with different valving element openings to obtain the opening-flow characteristic curve, and the adjustment strategies of the valving element position under different operating conditions are analyzed. The research founds that the annular structure of the valve body causes a large number of backflow and vortex areas in the main distributing valve. Ths results in significant uneven force distribution on the valve core, compromising the main distributing valve's safe and stable operation. Furthermore, the flow characteristic curve of main distributing valve exhibits a single-hump pattern, with the 25%~40% opening range constituting the primary hump zone.

Aimed at the problem that it is difficult to accurately control the spool valve under the influence of flow force, the internal flow field of the spool valve is simulated by using Fluent software, and the influence of the opening and flow rate changes on the pressure distribution of the spool wall is analyzed and verified by experiments. From the point of view of balancing the force on the wall surface of the spool, the optimized structure of the spool is proposed. The results show that he pressure distribution on the wall of the external flow valve calculated by simulation is the same as the experimental results. The radial pressure distribution on the inlet wall is basically equal, while the pressure distribution on the outlet wall is large at the valve root and small at the orifice. The peak value of wall pressure increases with the increase of flow rate and decreases with the increase of the opening of the valve port. The steady-state flow force is caused by the uneven pressure integral of the wall caused by the oil flow. The optimized spool structure can effectively reduce the flow force, and the average flow force compensation effect of different flow rates can reach 75%.

Most domestic diesel generator sets in China use mechanical-hydraulic governors for throttle control. Analyzing the operating principles and characteristics of this mature and reliable governor provides critical reference for domestic independent design initiatives. This study constructs component models such as centrifugal flyweight of the governor in AMESim, and develops a diesel generator set dynamical model in Simulink based on the engine load, throttle opening and speed characteristics. Through AMESim/Simulink co-simulation, the study investigates the dynamic behavior of hydraulic buffer compensation in closed-loop speed regulation and its impact on performance. The results indicate that adding hydraulic buffer compensation effectively reduces both the settling time and speed oscillations of diesel generator sets under diesel generators load variations. This design concept not only applies to mechanical-hydraulic governors but also provides critical insights for the autonomous development of digital electronic governors.

The steam turbine at a power plant exhibited an increase in rotor eccentricity and serious leakage after prolonged operation, resulting in a significant decline in efficiency. This research proposes a distributed steam curtain self-sealing system to address the issue by employing multiple independent steam sealing modules. The steam flow characteristics and sealing effectiveness of the system are analyzed using numerical simulation. The results show that a steam pressure of 200 Pa represents the minimum threshold for ensuring effective sealing. Supplying steam at multiple positions can guarantee the sealing effect and reduce the proportion of air in the mixed gas to 10^-6. When the pressure reaches or exceeds 20 kPa, supplying steam at any position can meet the sealing requirements; however, the steam consumption will increase by 13.6%. This research also discusses the single-side supplying steam on sealing effect, which can lead up to a 40.5% saving in steam.

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.

Dynamic seals in hydraulic slide valves play a crucial role in reducing oil leakage. However, their sealing performance is significantly influenced by environmental temperature, medium temperature and oil pressure, which alter the seal clearance during operation. A finite element analysis model is developed to analyze the combined sealing structures commonly used in slide valves. The model is used to evaluate the effects of varying environmental and medium temperatures, as well as pressure conditions on the clearance and friction behavior of dynamic seals. Based on the Stribeck curve, a mathematical expression describing the relationship between seal clearance and the friction coefficient is introduced. Experimental validation confirmed the accuracy of the theoretical model. The results indicate that the gap between the fluoroplastic sealing ring and the valve sleeve decreases with increasing temperature, accompanied by a corresponding change in the dynamic friction coefficient. Furthermore, both the theoretical analysis and experimental data reveal that the friction force of the dynamic clearance seal increases with temperature.

Electro-hydrostatic actuator has the advantages of large power to weight ratio, high efficiency, high integration and easy maintenance, and has broad application prospects in the field of large robots. This paper presents a electro-hydrostatic actuator for quadruped robot joint, and the mathematical model is derived and its aracy accuracy is verified through experiments. Aimed at the low-frequency response bandwidth of electro-hydrostatic actuator and unclear dynamic response factors, frequency-domain analysis is applied to the electro-hydrostatic actuator system to analyze the influence of key parameters on response speed. Based on the results of frequency-domain analysis, it is determined that the key factor affecting electro-hydrostatic actuator response speed is the displacement of the piston pump and the effective area of the hydraulic cylinder. The concept of electro-hydrostatic actuator response velocity sensitivity parameter is proposed, and the design optimization method to improve the response bandwidth of the electro-hydrostatic actuator system is proposed. It provides a theoretical basis for improving the response speed of electro-hydrostatic actuator system.

This article proposes a hydraulic system modeling language based on transmission line modeling method, elaborates on the method of using this modeling language for program implementation, and develops a system oriented graphical modeling and simulation tool. The component model based on transmission line method can be decoupled through time delay and solved in a distributed manner, and the simulation environment is suitable for distributed simulation. Numerical errors will not be introduced during simulation, and the combination of efficient simulation algorithms significantly improves design and analysis efficiency. Finally, the correctness and effectiveness of the modeling description language are verified through the simulation process of the hydraulic displacement servo system. The results indicate that the graphical modeling language based on transmission line modeling method can accurately and efficiently simulate hydraulic systems.

During the operation of a hydraulic excavator, the swing system will experience large inertia and high-frequency braking. During the braking process, a large amount of kinetic energy is converted into thermal energy and dissipated through the relief valve port, resulting in serious energy waste. This study proposes integrating a variable displacement hydraulic pump/motor and accumulator into the positive flow control swing system to recover and reuse braking energy. A mechanical-hydraulic integrated simulation model of a 38 t hydraulic excavator was developed to simulate braking energy recovery under various working conditions, with a focus on analyzing accumulator pressure changes. By leveraging the independently adjustable displacement of the variable motor, the accumulator output flow is controlled to align with the power demands of the original system. The impact of variable pump/motor displacement on the swing system's performance under different loads and speeds was also investigated. The results indicate that during the startup phase, the displacement adjustment of the variable hydraulic motor decreases as the excavator's speed increases and increases with higher moments of inertia. This approach reduces the energy consumption of the swing system by 41.6% to 52.4% compared to the original system, significantly enhancing energy efficiency.

The local temperature of the swash plate increases close to the tempering temperature of the material under the swash plate axial pistion pump slipper pair working condition of high speed and large load. As a result, the residual austenite phase transformation causes the material surface expansion, the formation of static pressure support oil film, the surface hardness and durability decrease and other problems. Based on the premise of improving the friction and wear performance of the axial piston pump friction pair under high speed operation. A comparative analysis between the substitute material and the finished sample through composition analysis, high temperature treatment, friction and wear experiments is conducted. The results show that the average surface hardness of B material is increased by 17.7% compared with the original finished material at room temperature. After being stored at 400 ℃ for 10 h, the surface hardness of B material can still remain above 700 HV, the average maximum surface deformation of no more than 1 μm on the surface, and the average wear is reduced by 5.9% compared to the finished sample. The possibility of substitute material selection for swash plate axial piston pump under high speed operation is verified, which provides a reference for the follow-up research on material selection of swash plate axial piston pump.

In order to solve the problems of difficult on-site testing and poor reproducibility of the control system of fully electronically controlled large-scale hydraulic excavators, and to provide a testing platform for the verification of control strategies, a semi-physical simulation system for hydraulic excavators is established. Firstly, establish an overall model of the excavator power system, hydraulic system, and mechanical system in AMESim. Secondly, in response to the poor real-time performance caused by factors such as rigid equations and multiple implicit variables in the AMESim model, the system is simplified while ensuring the accuracy and real-time performance of the model. Afterwards, the AMESim model is encapsulated into a real-time FMU and loaded into the dSPACE SCALEXIO. The controller input/output and CAN communication system are modeled in Simulink, and the hardware in the loop of the controller is implemented. Finally, a 3D real-time visualization platform is developed based on Unity, which communicates with the dSPACE SCALEXIO through the MAPort interface to visually display the 3D virtual excavator operation scene and process, improving the human-computer interaction effect. Taking a certain ultra large excavator as the research object, the results show that after simplification, the simulation solving speed is increased by more than 10 times, and the deviation from the non simplified model simulation results is less than 5%, which verifies the real-time, accuracy, and human-computer interaction of the semi-physical simulation system.

During underwater operations, it is difficult to install contact force sensors for electro-hydrostatic actuator and design direct force feedback controllers. Therefore, a contact force control scheme for underwater electro-hydrostatic actuator is proposed based on force estimation and model compensation. We establish a hydraulic cylinder pressure flow model, design a flow model feedforward compensation scheme, and achieve precise pressure control of underwater electro-hydrostatic actuator based on oil chamber pressure sensors.We establish a friction model and design a friction compensation scheme based on an extended observer to estimate and control the contact force.Finally, the performance of contact force estimation and control was verified using a hydraulic test bench. The tests showed that the accuracy of force estimation and control was 2%FS, which is superior to using pressure sensors for contact force control in terms of control performance.

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.

To improve the anti-eccentric dynamic performance of constant pressure hydrostatic bearings in electro-hydraulic servo actuators, a dynamic model for bearing anti-offset is developed. The effects of orifice, annular gap, and bearing cavity size on dynamic performance are systematically analyzed. The research results indicate that the maximum bearing capacity occurs when the initial bearing cavity pressure is 50% of the supply pressure. This leads to the derivation of the matching relationship between fixed damping holes and variable gap damping. A correlation between fixed damping orifice and variable annular gap orifice is derived. Under the conditions of a piston rod diameter of 40 mm and a radial offset force of 2000 N, using a damping hole with a diameter of 0.3 mm and a length of 10 mm, and a sealing surface with a unilateral clearance of 43 μ m, the flow loss of the actuator static pressure system at 15 L/min can be controlled at 12%. Furthermore, the study reveal a positive correlation between rod eccentric overshoot and the ratio of bearing cavity volume to non-eccentric flow. When this ratio exceeds 11%, increasing the risk of seal failure and creeping phenomenon. The research results provide theoretical guidance and design reference for optimizing the hydrostatic bearing of electro-hydraulic servo actuator.

Based on an relief boost valve, the high-pressure structure design is carried out, and the three-dimensional model of the high-pressure relief boost valve is established. The velocity distribution, pressure change and steady flow force change of the flow field in the valve are analyzed by CFD software. The simulation results show that the velocity and pressure gradient in the conical valve port area are large, and the undesirable phenomena such as small vortices are easy to appear at the right angle near the oil outlet of the main valve body. In addition, when the valve displacement reaches 0.5 mm, the steady flow force reaches the maximum. In order to further verify the performance of the high-pressure relief boost valve, a sample of the relief boost valve with rated pressure of 45 MPa is developed. The test results show that under the condition of an inlet pressure of 42 MPa, the high-pressure overflow oil replenishment valve has a fast dynamic response, with an overshoot of 2.5 MPa and a response time of 0.047 s. When the oil replenishment flow rate increased from 10 L/min to 80 L/min, the pressure loss increased from 0.073 MPa to 0.15 MPa. This study provides a quantitative analysis basis for the optimization design of high-pressure overflow oil replenishment valves.

The pilot solenoid valve regulates the internal oil flow of the shock absorber by controlling the main valve pressure, thereby affecting the damping force. A reasonable design of pressure-flow characteristics can broaden the range of damping adjustment to meet the needs of different working conditions. In this study, the pressure-flow characteristics of the pilot solenoid valve for an automobile continuous damping control shock absorber are optimized. Firstly, the hydrodynamic model and steady state force model of the oil flowing through each damping hole are established based on the fluid dynamics theory. The relationship between the electromagnetic force and the input current is determined with the electromagnetic magnetic circuit model of electromagnetic theory, and then the hydraulic simulation model is established. Subsequently, with the help of the solenoid valve performance test bench, experimental comparisons are carried out to verify the accuracy of the simulation model. Finally, the key structural parameters affecting the pressure-flow characteristics of the pilot solenoid valve were analysed to determine their importance using full factorial analysis of experimental design, and the key dimensions were optimised using a genetic algorithm, with the optimisation effect improved by 10.14%.

The wear of the piston pairs in the axial piston pump causes changes in the temperature of the drain port, and the research on the law of change is carried out. This study established an AMESim simulation model of axial piston pump with 9 pistons,and built a piston experimental platform for verification. The results show that under the condition of 1000 r/min speed and full displacement, when comparing the temperature differences between the drain port and the inlet port of the piston pump, the temperature difference of the piston pump with one piston pair suffering from severe wear is about 6 ℃ higher than that of the normal piston pump. However, there is no significant difference in the temperature of the pump case. The simulation model shows that the oil temperature at the drain of the pump increases with the increase of the rotational speed of the piston pump, and the temperature of the drain port increases with the increase of the clearance of the piston pair. The research indicates a positive correlation between the wear clearance of the piston pair of the axial piston pump and the temperature difference between the pump's drain port and inlet port, and it provides a basis for predicting the wear of the piston pair based on the temperature difference between the drain port and the inlet port.

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.

Addressing the issue of the unstable output and low accuracy issues of single-rod hydraulic cylinders under heavy load, high stiffness, and dynamic disturbances, a nonlinear model of the hydraulic system is established based on the analysis of force-bearing process and structural characteristics. Then an adaptive control method based on an asymmetric barrier Lyapunov function is proposed to performance steady tracking under output force constraints. The controller integrates adaptive parameter, extended state observer, and dynamic surface control and handles the system's parameter uncertainties, unknown states estimation and time-varying disturbances, and complexity explosion caused by high-order derivatives. The output force boundaries are constrained by the constructed asymmetric barrier Lyapunov function. Lyapunov-based analysis proves the system's asymptotic stability. Co-simulation verifys control effectiveness. The results show that the proposed method can accurately estimate and compensate for uncertainties, ensure the output remains within safe boundaries during loading while achieving high-precision actuator's position tracking.

The vibration and noise of the bent-axis axial piston motor is investigated by a combination of test and simulation. Firstly, the vibration and noise excitation sources of piston motor are investigated and analyzed according to its structural composition and working principle. Secondly, the modal analysis and harmonic response analysis and calculations are carried out by using the simulation software to get the intrinsic frequency of the piston motor and the frequency curves of vibration-related parameters, and the accuracy of the simulation model and test method is verified with vibration tests. Finally, the noise radiation analysis and simulation of the piston motor is carried out by acoustic-vibration coupling method, and the reasonableness of the simulation results is verified with noise test. It is concluded that the peak frequencies of vibration and noise tests are around 700 Hz, which is highly consistent with the theoretical value of excitation frequency 700 Hz, and also close to the first-order intrinsic frequency 704 Hz of the piston motor shell. It proves that the piston motor system is in resonance at this frequency, and proposes optimization directions for vibration reduction and noise reduction of piston motor structure. This study reveals the main mechanism of the vibration noise of the piston motor and provides a basis for its vibration reduction and noise reduction.

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.

The butterfly bleed valve is widely used to release part of the air from the outlet of an axial flow compressor, preventing engine surge. During aircraft operation, particulate contaminants in the air may infiltrate critical valve clearances, leading to increased torque resistance and mechanical seizure. Based on the valve's working principles and operational environment, computational fluid dynamics (CFD) is applied to evaluate the flow field under various conditions. According to the flow field conditions and particle properties, this study uses CFD combined with the discrete element method (DEM) to analyze, particle trajectories and clearance intrusion behaviors within the valve. The results indicate that as temperature increases, the inlet mass flow rate gradually decreases, while the inlet velocity rises. In fully closed condition, contaminant particles are expelled through the clearances on both sides of the valve plate, while in fully open condition, particles are discharged through the main channel. Additionally, smaller diameter and lower density particles exhibit better following behavior in the valve's flow field. An anti-contamination spacer ring design is proposed to prevent particle contaminants from invading sensitive gaps, providing a theoretical basis for improving the anti-contamination performance and structural optimization of the butterfly bleed valve.

Air springs have significant application prospects in quasi zero stiffness system, and their stiffness characteristics are the key to analyzing their performance. A single-convolution bellows type air spring is studied as the research object, and its static and dynamic characteristics are systematically investigated through a combination of theoretical analysis, numerical simulation, and experimental research. A stiffness calculation model for the single-convolution bellows type air spring is established based on gas dynamics theory, and expressions for vertical stiffness and natural frequency are derived. A finite element model of the G40/60 type air spring is constructed by ABAQUS software, and the influence of initial internal pressure on stiffness characteristics is analyzed. Static tests are conducted on a WDW-100 testing machine, where force-displacement characteristic curves under different air pressures are obtained. Load-bearing capacity and static stiffness expressions are derived through polynomial fitting. Dynamic tests are performed on an MTS 831 testing machine, and the effects of air pressure, frequency, and amplitude on stiffness and damping characteristics are studied. Theoretical foundations and design bases are provided for the application of air springs in quasi zero stiffness system.

Different pilot control strategies for proportional valves induce varying extents of cavitation and vortex phenomena within the main valve control cavity, culminating in distinct oscillatory behaviors of the main spool. This study integrates CFD flow field simulations with visualization experiments to explore the flow characteristics of the control cavity when employing either a high-speed on-off valve bridge or a proportional pressure-reducing valve as the pilot stage. The influence mechanism of the pilot approach on main valve oscillations is elucidated by analyzing the flow field characteristics and vortex structures. A method to optimize the control cavity flow field is proposed, namely, chamfering the geometric corners and improving the wall smoothness. The results reveal that vortex generation and dissipation within the control cavity are intimately linked to spool oscillations. When the high-speed on-off valve bridge is utilized as the pilot, the flow field demonstrates significant fluctuations, intricate vortex structures, and periodic vortex variations, all contributing to pronounced main valve oscillations. Conversely, employing the proportional pressure-reducing valve as the pilot yields a more stable flow field, with uniform pressure distribution and simple vortices confined to geometric corners, where the interplay between pressure differentials and flow velocity further mitigates spool oscillations. This study offers a theoretical foundation for optimizing control cavity design and mitigating oscillations.

Emergency rescue vehicles need to adapt to various complex terrains with higher requirements for reliability and redundant safety. In response to the operational requirements of heavy-duty articulated all-terrain vehicles, a distributed hydraulic drive system with 4 variable displacement pumps and 4 variable displacement motors has been designed. An AMESim simulation model of the distributed hydraulic drive system is established, and data on engine speed and load rate, vehicle speed, as well as the inlet and return pressure and flow rate of the distributed hydraulic drive system under typical operating conditions are obtained. The influence of the variable motor displacement on the speed regulation performance of the distributed drive system for all-terrain vehicles has been investigated. The heavy-duty articulated all-terrain vehicle has undergone real vehicle testing, and its distributed hydraulic drive system is stable and reliable. The vehicle's rapid acceleration time is 25 s, the maximum speed is 34 km/h, which basically meets the parameter design requirements.

In conventional hydraulic systems, machined integrated valve blocks are commonly used to consolidate hydraulic valves with diverse functions. However, the presence of numerous process orifices and cutter-tip cavities within these blocks leads to substantial local pressure losses and frictional losses, resulting in elevated energy consumption. In order to reduce energy loss, reduce weight, and save costs, this study uses casting to integrate the main functional valve body and oil circuit into one, and designs a new low-pressure loss integrated valve group. Through CFD simulations employing a liquid-gas two-phase flow model, we conducted comparative analyses of pressure losses between conventional and redesigned configurations. The results demonstrate that the optimized manifold design achieves over 50% reduction in pressure losses while maintaining full compliance with the original hydraulic system's operational requirements.

Small displacement high-speed piston pumps have the advantages of high working pressure and high power density, and are the core power components of deep-sea equipment. Unlike ground conditions, in the low-temperature and high-pressure environment of deep sea, the viscosity of oil increases significantly, leading to prominent problems of churning loss in high-speed rotating components inside the pump. Based on the analysis of the churning flow field in the cylinder block, a mathematical model of pump churning loss under deep-sea oil rheology was established, and the influence of sea depth and speed on pump churning loss was analyzed. The results showed that the churning loss of the pump varied in three stages at different speeds. Among the churning loss distribution of various components (bearings, cylinder block, gears, piston connecting rods) inside the pump, the bearing churning flow field contributed the most, followed by the cylinder block churning flow field, and the other parts had a smaller impact. Based on this, the pump support bearing structure was improved, and the total churning loss of the pump was reduced by about 11%.

Slipper wear is a common failure in piston pumps. Aimed at the failures of the flow rate decrease and excessive vibration of the pump caused by slipper wear in the fuel piston pump of a certain type of aero-engine, a comprehensive failure diagnosis method is proposed within the framework of multiple disciplines including dynamics, tribology, fluid lubrication, and structural strength. The calculation and simulation of the oil film thickness, structural strength, and pv value of the slipper of this type of fuel piston pump under multiple operating conditions are carried out, and the associated mechanism between each operating condition and the wear failure is analyzed. The research results show that the structural strength of the slipper of the fuel piston pump meets the requirements within the full operating condition range, and the oil film characteristics are favorable when the rotational speed is below 4500 r/min. However, when the rotational speed of the fuel piston pump gradually increases, the proportion of the axial inertial force and centrifugal force acting on the slipper pair in the contribution to the pressing force gradually increases. When the rotational speed increases to 5000 r/min, the supporting force cannot effectively compensate for the external pressing force, resulting in the rupture of the hydrostatic oil film of the slipper pair. The slipper and the swash plate change from the fluid lubrication state to the boundary lubrication state or the direct contact state. Moreover, the pv value of the material of the slipper pair is in an over-limit state under the high rotational speed operating condition, which ultimately leads to wear failure.

The disc spring hydraulic mechanism is a key equipment in the power system, and its performance directly impacts the reliability of the system. Dynamic characteristic analysis of its key components aims to enhance operational stability. The mechanism's structural composition and operational principles are analysed firstly. Subsequently, Fluent-based simulations investigate the pressure variation characteristics in both rodless and rod cavities of the working cylinder piston. These simulations reveal the intrinsic correlation between piston velocity and pressure fluctuations. Further research focuses on gas pressure dynamics in the arc-extinguishing chamber during circuit-breaking operations, employing pressure cloud diagrams to analyse the spatial-temporal pressure distribution patterns in both the disc spring hydraulic mechanism and the arc-extinguishing chamber. Experimental validation confirms the accuracy of this dynamic analyses, establishes a theoretical foundation for optimizing mechanism design and improving operational stability.