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.

A school-enterprise cooperation “news broadcast style” class is proposed, in which teachers give theoretical explanations in class (similar to the infield hosting) and senior technicians of enterprises give live production broadcasts (similar to the outdoor hosting) to explain the physical objects of hydraulic components and production sites, so as to achieve the combination of theory and practice in the classroom. Through “news broadcast style” scenario interactive teaching, a class for schools and enterprises is created to educate people together, enhance students' understanding of knowledge from multiple dimensions, shorten the distance between books and the scene, and improve students' ability to use what they have learned to solve practical problems. This teaching mode has been rated as the most satisfactory classroom for students at Huazhong University of Science and Technology, with a 100% attendance rate for undergraduate students and an excellent performance rate of 86.4%.

As the core component of pneumatic proportional control system, pilot-operated pneumatic proportional valve has hysteresis characteristics in time response, which affects the control response speed of the system. Aiming at the problem, based on its internal structure and working principle, the dynamic characteristics of pilot-operated control stage, main valve spool and the gas flow process in the valve are modeled and analyzed, and the equivalent spring stiffness and Stribeck friction coefficient in the valve are identified by genetic algorithm. AMESim is used to simulate and analyze the pilot-operated pneumatic proportional valve, and the influence of the main parameters such as the upper chamber volume, equivalent spring stiffness and the entrapment area of the pilot-operated inlet channel on the response hysteresis and control accuracy is obtained. Aiming at minimum hysteresis, the optimal parameters are determined by quadratic programming algorithm. The results show that the dead-time is reduced from 0.041 s to 0.031 s, and the time to steady-state is shortened by 20.79% after the sequential quadratic planning design. By optimizing the proportional valves of different calibers, the response hysteresis is reduced by about 20% under the premise of ensuring the control accuracy. The research results can provide a theoretical basis for the parameter design of pilot-operated pneumatic proportional valve.

Torque pulsation stands as one of the principal causes of vibration and noise in cam lobe motors. A U-groove distributor plate has been designed to attenuate torque pulsation. Based on the flow-pressure pulsation of the motor's piston chambers, a theoretical model is established for the variation of damping slot distribution area and motor torque pulsation. Utilizing the AMESim platform, a dynamic simulation model of the cam lobe motor is established, and the response surface methodology is employed for parameter optimization of the U-groove. The results demonstrate that torque pulsation is influenced by multiple mechanisms associated with the structural parameters of the U-groove. Compared to the undamped slot, the optimized U-groove distributor plate has achieved a 44.55% reduction in torque pulsation level.

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.

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.

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 cylinder speed is controlled by the speed control valve in the circuit. The cushion valve affects the energy absorption of the cushioning device. For optimal cushioning and improved cylinder efficiency, two valves must be adjusted based on a specific openness relationship. A cylinder cushioning test bench is built to conduct experiments and find the corresponding relationship between the number of valve turns. An AMESim model simulates the cushioning effect at various valve openings. The sonic velocity discharge method measures the effective throttle area of pneumatic components, revealing the area matching relationship between the cushion valve and speed control valve when effective cushioning occurs. The results indicate that only certain openings of the speed control valve achieve effective cushioning, with the cushion valve adjustable within a narrow range, making precise adjustments difficult. The area matching relationship diagram helps enable quicker cushion adjustments.

With the goal of reducing the flow force acting on the valve spool during operation, and using the external structural parameters of the valve spool as optimization variables,the method of optimizing the structure of the hydraulic servo valve spool is studied. The SPEA2 algorithm is utilized to optimize the external shape of the spool. The Pareto-optimal designs of the spool shape are obtained. The flow field and pressure distribution of the spool before and after optimization are simulated using CFD software, and the optimization effect is verified. An experimental platform is built to test the hydrodynamic force of the spool before and after optimization. This platform is capable of calculating the steady-state flow force acting on the spool during operation. Experimental results show that the flow force of the optimized spool decreases under different opening displacements, with an average decrease of 14.86% in the steady-state hydrodynamic force. The change trend is consistent with the simulation calculation, and the optimization effect is maximized when the opening displacement of the spool is 0.6 mm, further verifying the feasibility of the optimization scheme.

To address the high precision temperature control requirements of semiconductor manufacturing equipment and other precision devices and instruments, a high precision temperature control system based on a temperature gradient attenuator is proposed. First, the heater is used as a temperature regulator to compensate for low-frequency temperature disturbances. Additionally, the flow mixing mechanism of the temperature gradient attenuator is employed to reduce high-frequency temperature disturbances in the fluid. Together, these components form a complementary high precision temperature control system. A simulation model is constructed using MATLAB/Simulink. Under model predictive control, disturbance attenuation analysis of the high precision temperature control system is conducted in both time and frequency domains. By comparing experimental and simulation results, it is found that the maximum temperature rise in the temperature control system using model predictive control is reduced by 24% during the temperature rise phase caused by thermal disturbances, compared to traditional PID control. The results validate the superior attenuation effect and disturbance rejection performance of the high precision temperature control system based on the temperature gradient attenuator.

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.

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.

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.

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.

With the development of hydraulic technology in the direction of high speed, high pressure and high power, the problem of vibration and noise of hydraulic components becomes more and more serious, and noise pollution becomes a “bottleneck” restricting the development of hydraulic technology. As a control element commonly used in construction machinery and other fields, proportional directional valve has important practical significance for the research on vibration and noise reduction. The flow-induced vibration problem of a certain type of proportional directional valve is analyzed, and the flow field pressure pulsation characteristics, vibration characteristics, vibration and noise reduction of the proportional valve are studied. The flow field in the valve under different openings is numerically simulated, and the flow characteristics of the proportional directional valve pressure pulsation, turbulence intensity, cavitation degree and other flow characteristics are analyzed. The main frequency range of flow-induced vibration is obtained by setting the monitoring points, and compared with the natural frequency under the prestress mode analysis. The fluid-structure interaction numerical simulation of the proportional directional valve is carried out to explore the main factors affecting the vibration energy level. The vibration mechanism of proportional directional valve is summarized, and the working reliability of proportional valve is verified.

Fluid-structure interaction vibration widely exists in hydraulic pipeline system. In order to study the influence of fluid flow and clamp constraint on the fluid-structure interaction vibration of pipeline, the pipeline is simulated by ANSYS Workbench software, and the experimental platform is established. The law between different flow rates and the vibration response of horizontal pipeline is analyzed by hammering method, and the influence of different clamp materials and constraint positions on the vibration characteristics of spatial pipeline system is studied. Simulation and experimental results indicate that as the fluid flow rate in the pipeline system increases, the inherent frequency of the system decreases. Changing the clamp materials and its constraint positions can effectively adjust the inherent frequency of the pipeline to avoid system resonance.

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.

To address the issue of large fluid-induced vibration force and even serious local cavitation erosion damage caused by cavitation during the suction and discharge process of axial piston pump, the dynamic motion process of the piston pump is simulated using user-defined function and the dynamic mesh method. By conducting experiments on the cavitation flow-induced vibration characteristics of piston pump, the response characteristics of cavitation flow-induced vibration in piston pump are compared and analyzed, and the mechanism of cavitation flow-induced vibration in axial piston pump is obtained. The results show that the volume fraction of gas in piston chamber oscillates periodically with the change of cylinder angle, and cavitation phenomenon is mainly concentrated in the suction area of the pump; When the cylinder angle is in the alternating zone of suction and discharge, a negative pressure phenomenon occurs in the pressure field inside the piston chamber, and bubbles diffuse in the direction of the fluid jet, forming a clear local cavitation cloud.The frequency spectrum of cavitation induced vibration of piston pump coincides with the frequency spectrum of fluid pulsating load, directly affecting the amplitude of piston pump shell vibration and becoming the main cause of piston pump shell vibration response.

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 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.

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%.

Under the environment of large-scale sea depth, the change of medium viscosity and the deformation of key parts of hydraulic system are obvious. For gear pump, the change of working medium viscosity and the deformation of parts will affect its volumetric efficiency. In order to study the change law of gear pump volume efficiency in deep sea environment, the mathematical model of sea depth and gear pump volume efficiency is established, and the volume efficiency of gear pump under different sea depth is analyzed by theory and simulation. The results show that the volumetric efficiency of gear pump increases with the increase of sea depth. When the sea depth reaches the limit of 11000 m, the influence of rotational speed and temperature on the volumetric efficiency of gear pump is more obvious than that on land. The research results provide a relevant theoretical basis for optimizing deep-sea gear pump and have a certain reference significance for the design of underwater hydraulic components and hydraulic system.

In order to compare the applicable scenes and the magnitude of static solenoid force generated by solenoid static iron core solenoid valve and pole static iron core solenoid valve. Firstly, the finite element model of the two types of static iron cores is established and the model is verified through experiments, and then the static solenoid force of the two types of structures is compared in different currents and under different air gaps. Through the calculation and analysis, it is concluded that in the same shape and volume, solenoid force generated by solenoidal static iron core steadily increases with the increase of coil current. Because the coil temperature is too high when the current is too high, under the working condition of 40 A current, the coil temperature reaches 186.2 ℃. It is suitable for small current and small stroke working situation. While the solenoid force generated by the pole static iron core solenoid valve rises faster and is also larger with the increase of the coil current, and the bare single-layer coil ensures heat dissipation, under the working condition of 40 A current, the temperature is only 51.1 ℃. It is suitable for large current and large stroke working situation. Meanwhile, the pole static iron core solenoid valve solenoid force increases first and then decreases with the increase of the number of poles. Under the same conditions, six-pole static iron core solenoid valve generates the largest solenoid force and it provides theoretical guides for the design of new high-speed solenoid valve static iron core.

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.

At present, the design or use of two-stage orifices are based on the flow calculation formula or empirical parameters of classic single-stage orifices, with significant selection errors. It is necessary to rely on on-site experiments to correct pressure loss parameters or use trial and error methods to replace orifices of different sizes for effect compensation. This research combines experiments and CFD simulations to investigate the influence of factors such as cavitation, different aspect ratios, and machining errors on the flow characteristics of two-stage thick orifices. The stable flow coefficients of orifices with or without cavitation are obtained for fixed length and different diameter sizes, providing a basis for the correct selection of two-stage thick orifices and the setting of characteristic parameters in mathematical modeling.

To enhance the conveying performance and force conditions of the pump, a new structure of an asymmetric rotor pump is proposed. The mathematical model of the asymmetric rotor is established, and the influence of the long-to-short radius ratio of the rotor pump on its performance is studied through CFD numerical simulation. The study indicates that the long-to-short radius ratio has a significantly affects on the fluid flow condition, flow pulsation characteristics, and rotor force within the pump cavity. With the increase of long-to-short radius ratio, the fluid flow velocity in the pump cavity gradually increases, the number of vortices initially decreases first and then increases, the radial force of main rotor gradually increases, when the long-to-short radius ratio is 1.52, the mean radial force increases by 26.9% compared with the ratio is 1.12, the volumetric efficiency increases gradually, the secondary pulsation of the export flow rate is effectively suppressed and the flow pulsation coefficient decreases first and then increases. When the long-to-short radius ratio is between 1.28~1.44, the volumetric efficiency of the pump is higher,the flow inside the pump ccavity is smoother, and the force on the rotor is better. This provides a theoretical basis for optimizing the design of rotor pumps by using an asymmetric structure and adjusting the long-to-short radius ratio.

The aviation propulsion system's pneumatic safety valve is affected by airflow during operation. Uneven internal loads induce deformation of the structure, affecting the dynamic performance of the aviation pneumatic safety valve. The working process of the aviation pneumatic safety valve's numerical simulation model was established by the two-way fluid-structure interaction theory. The accuracy of the simulation model was verified through pressure characteristic experiments. The aviation pneumatic safety valve's spool movement and the changes in pressure and velocity of the internal flow field were analyzed. The relationship between the internal flow field and structural deformation was explored. The results show that the valve spool tends to be stable after oscillation adjustment. The valve port opening is stable at 0.45 mm, and the gas flow rate changes significantly at the valve port. The maximum velocity is 325.9 m/s. The valve seat, shell, valve assembly, and seat plate undergo a certain degree of elastic deformation. The valve seat has a more extensive elastic deformation, with a maximum deformation of 6.554×10^-5 mm.

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.

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.

Traditional flow control valves have disadvantages such as complex structure, large mass, and low output flow, and are not suitable for special fields such as aerospace. A new type of flow regulating valve has been designed, which is a rotary direct drive type and has the advantages of large output flow, simple structure, and light weight. Using UG software to create a 3D model, the working principle of the flow control valve is introduced. Based on Workbench and Fluent software, strength verification models and fluid domain models for flow valves are established, and simulations of valve core and sleeve deformation and steady-state flow field are conducted. The experimental prototype is processed and the static characteristics of the flow control valve are tested. The results show that the total quality of this flow control valve is 375.5 g, when the inlet pressure is 4 MPa, and the outlet pressure is 3.5 MPa, the maximum outlet flow rate is 25.99 L/min, which meets the needs of light quality and large outlet flow rate.

Adding an energy recovery system is one of the important methods to improve the energy utilization efficiency of construction machinery. The feasibility of applying mechanical energy recovery systems in engineering machinery represented by hydraulic excavators are discussed from the perspective of usage conditions. As the core of the energy recovery system, the performance of energy storage components determines the performance of the energy recovery system. A comparative analysis is conducted on the performance of flywheels, batteries, supercapacitors and hydraulic accumulator, and the complementary effects between the characteristics of flywheels are further analyzed. It is concluded that the energy recovery system based on flywheel energy storage is suitable for energy recovery systems for excavators.

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.

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.

In response to the problems of poor reliability and outdated control technology of hydraulic controllable vibrator systems currently developed , the electro-hydraulic servo controllable vibrator is taken as the research object. ADAMS software is used to establish a system dynamics model, and MATLAB software is used to establish hydraulic and control system models, thus obtaining a co-simulation model of the system. The research uses iterative learning control method to improve the response performance of the system, improving the system's tracking accuracy of the desired signal. The simulation experiments show that the co-simulation model is correct and feasible, and the proposed control method can significantly improve the tracking performance and anti-disturbance robustness of the system.