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.

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.

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%.

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.

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 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.

Once faults occur in the key friction pairs of hydraulic axial piston pumps, modulation phenomenon will be generated in their vibration signals. The fault modulation characteristics in the vibration signals establish a corresponding relationship with specific fault types. And fault characteristics can be extracted from the vibration signals through signal decomposition for fault diagnosis. In this paper, hydraulic axial piston pump is taken as the research object, variational mode decomposition and successive variational mode decomposition a utilized to respectively decompose and reconstruct different simulation signals under noisy conditions. The disparities in decomposition performance between the two algorithms a comprehensively compared. Eventually, the two algorithms a applied to the extraction of fault characteristics from the measured vibration signals of a hydraulic axial piston pump. The results indicate that both algorithms are suitable for extracting fault characteristics of hydraulic axial piston pump. Successive variational mode decomposition accurately reconstructs effective components highly related to the pump faults. And variational mode decomposition extracts effective component amplitudes with less attenuation, making it more sensitive to subtle fault characteristics.

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.

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.

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 view of the complexities and variability in the flow field of the hydraulic valve controlled system in high voltage circuit breaker operating mechanisms, this study focuses on the impact of valve opening on the dynamic characteristics of the flow field within the hydraulic cylinder, hydraulic valve, and return oil pipeline. Initially, the flow channel of a disc spring hydraulic operating mechanism is extracted and simplified by using ICEM software. Subsequently, the k-ε turbulence model in STAR-CCM+ software is employed to solve the flow field of the hydraulic valve controlled system of the high voltage circuit breaker operating mechanism, and the movement of the main valve spool is realized by the dynamic grid technology. The results demonstrate that the pressure at the lower end of the working cylinder calculated by simulation is consistent with the experimental data. The velocity of hydraulic oil increases rapidly when it passes through the valve port while forming two vortices between the bottom of the main valve spool and the valve body. Additionally, the pressure in the return oil pipeline fluctuates considerably with the movement of the main valve spool.

When the winche of automobile crane are lifting and lowering, the micro-motion characteristics of its hydraulic control circuits are closely related to the smoothness and safety of the whole machine. The winch hydraulic system is taked as the research object, and its micro-motion characteristics is analyzed, which is based on the parallel research method of system simulation, real-time joint simulation of the system and components, and experimental test. The results show that the original main valve stem experienced a throttling inflection point due to a sudden change in valve port area gradient. This study effectively improved the throttling characteristics of the main control valve by optimizing the structure of the throttle valve port and return valve port. The original large diameter three port valve exhibited a "quick closing, quick opening" response state due to excessive spring preload and relatively low stiffness. This study effectively improved the problem of pressure overshoot in the winch system circuit by scaling the three port valve diameter proportionally, reducing the preload force of the pressure reducing spring, and reasonably matching its stiffness parameters and optimizing its valve port area curve.

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.

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.

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.