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.

Pilot-operated electro-hydraulic proportional relief valve is a pressure control valve that is used to control the oil pressure in the system. It can control the electromagnetic force with electric signal according to the requirements of working conditions, so as to achieve the pressure control of the hydraulic system, and is composed of pilot valve, main valve and hand-adjustable safety valve. Due to the control valve port flow state is complex, the use of flow experience formula and the traditional hydrodynamic formula is difficult to accurately calculate the orifice flow and spool hydrodynamic force, resulting in large differences between the mathematical model calculations and the experiments. In order to accurately obtain the static characteristics of the relief valve, the Fluent software is used to simulate the flow field of the main valve and pilot valve to obtain the spool force and orifice flow under different orifice openings and differential pressures. The interpolation model is obtained by interpolating the spool force and orifice flow, according to which the static mathematical model is solved to obtain the static characteristic curve of the relief valve. The results show that the static characteristic curve obtained from the interpolation model is more consistent with the experiment curve.

The slide valve integrated into existing valve-controlled digital hydraulic cylinder usually adopts a full-circular opening, resulting in high flow gain and significant hydraulic forces on the valve spool, which seriously affect the dynamic response characteristics during startup and switching. This article focuses on six typical non-circular opening value structures, calculates the flow area of each valve spool throttle groove, and determines the structural parameters of one-section stage (U, V, K shape) and two-section stage (UU, UV, UK shape) throttle groove under the same flow area. The response of the digital hydraulic cylinder with different non-circular opening slide valve under step input signals and step load disturbance were studied and compared. The simulation and experimental results show that, compared to other valve port forms, the digital hydraulic cylinder has a better response to the step input signals when the throttle groove adopts K-shaped and UK-shaped structures. Compared to UK-shaped throttle groove, when the valve core adopts the K-shaped throttle groove, the load stiffness of the digital hydraulic cylinder controlled by the slide valve is better, and the speed impact is smaller, but the working pressure of the piston rodless cavity is slower. Additionally, with UK-shaped throttle groove, the digital hydraulic cylinder controlled by the slide valve exhibits faster response speeds under the same load interference.

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.

To meet the demand for high-precision coupled control of displacement and force in the electro-hydraulic servo systems of bidirectional hydraulic press, a kind of separate meter in and meter out electro-hydraulic servo system for bidirectional hydraulic presses is designed. A corresponding mathematical model is established, revealing the physical laws of the displacement-force coupled control system based on linear loads. A decoupling method for displacement-force coupled control of the bidirectional hydraulic press is proposed, simulation analysis and experimental validation are conducted based on linear loads. The results show that once the system stabilizes, the maximum overshoot of force is 1.42%, the maximum overshoot of displacement is 0.8%, the standard deviation of the force closed-loop tracking error is 447.5 N, and the standard deviation of the displacement closed-loop tracking error is 0.037 mm. This method not only achieves the high-precision coupled control requirements of displacement and force for the bidirectional hydraulic press but also enhances the system's degrees of freedom, offering a new approach to the study of decoupling methods in the displacement-force coupled control.

Online wear state recognition of key friction pairs in the axial piston pump is crucial for ensuring the stability and reliability of the whole hydraulic transmission and control system. However, wear state recognition performance is always hindered by strong noise interference in real working conditions. Although wear state recognition models can enhance noise robustness through adversarial training, their large number of parameters limits the application on edge computing devices. To balance noise robustness and model scale, a lightweight method based on adversarial distillation for online wear state recognition is proposed. A student model and a teacher model based on one dimension convolutional neural network are designed. The student model generates adversarial examples as a knowledge transfer dataset and learns robust feature knowledge from the teacher model through knowledge distillation. Through fault injection, comparison experiments, and ablation experiments, the proposed method demonstrates strong noise robustness and lightweight model structure advantages. Edge deployment and online verification experiments show that the proposed method can accurately recognize the wear state of the axial piston pump in real time.

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.

Underwater hydraulic manipulators are pivotal apparatuses for underwater special operations. Currently, the control of hydraulic manipulators for underwater operations mainly relies on visual feedback to determine the position. However, various operating errors can occur, such as camera distortion and water flow interference, which often result in sticking or jamming issues, severely impacting the efficiency and safety of operations. To address these, an active/passive compliant control system specifically designed for underwater hydraulic manipulators is proposed. By designing an end clamp, position and deflection errors are compensated to achieve passive compliance. Active compliance is achieved by the virtual decomposition control method, combined with a force observer and impedance control. Furthermore, the effectiveness of the active/passive compliant control method is verified through experiments, providing a reference for the design of safe and compliant control for underwater hydraulic manipulators.

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.

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.

Active suppression of pressure pulsation is the key technology to improve the control accuracy and reliability of digital hydraulic valve control system. However, the current active suppression method lacks an in-depth understanding of its characteristics when suppressing pressure pulsations, resulting in unsatisfactory suppression effects. Therefore, a pressure pulsation test bench was designed, and the changes of pressure pulsation at different positions in the system were analyzed. The influence of hydraulic pumps and high-speed on-off valves on pressure pulsation at different positions was further explored. The results show that the main pressure pulsation in the digital hydraulic valve control system comes from the water hammer phenomenon caused by the continuous on/off of the high-speed on-off valve, and the frequency of the pressure pulsation is always consistent with the on/off frequency of the valve. This study provides a new idea for the design of feedforward active suppression system, and also provides a reference for the development of more efficient pressure pulsation attenuator.

The film temperature distribution of the port plate pair in piston pump affects the lubrication, leakage, and friction. The test platform was constructed to measure the three-point film thickness and multi-point temperature of the port plate pair. The wedge-shaped oil film model was established according to the three-point film thickness test data. The axial force balance equation of the piston cylinder was derived regarding the static pressures in the piston chambers and in the film on the cylinder, and the force between the micro-convex surfaces of the port plate pair. The film heat balance model was developed considering the energy loss, the heat conduction, and the oil viscosity-temperature characteristics. The results indicate that the film maximum temperature increases with the rise of the loading pressure and the swash plate inclination angle. The maximum temperature point falls in the range of -20°~20° on both sides of the symmetric line of the high-pressure waist groove. The maximum temperature relative error between theoretical and experimental results is less than 8%.

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.

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 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.

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.

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.

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%.

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.

In order to investigate the internal basin cavitation characteristics of a novel low-speed high-torque internal curve piston pump, the internal drainage model of the fluid distribution of the internal curve piston pump is established. The cavitation distribution and generation in the fluid distribution basin are studied by CFD fluid simulation. The cavitation characteristics of the fluid distribution basin under different conditions are analyzed. The research findings demonstrate that cavitation mainly takes place at the oil discharge non-return valve port and the high-speed on-off valve port, and the gas phase volume fraction directly reflects the intensity of cavitation. Pump shaft speed and load pressure have an obvious effect on cavitation, however, too low oil suction pressure will cause the piston to suck air. The structure of fluid distribution internal basin is optimized by increasing the local inner diameter of the flow path and reducing the length of the flow path, thereby reducing the oil flow rate and weakening cavitation. The latter optimization method is superior to the former.

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 design of flow resistance characteristics of labyrinth channel is the key to achieving throttling and pressure reduction in labyrinth adjusting valve. However, the structure of the labyrinth channel is complex, and particle in the fluid can easily lead to clogging of the channel, affecting the throttling and pressure reducing performance. The flow resistance and anti-clogging performance of channels are studied, and the flow field and particle transport laws of different channels are analyzed. The Tesla-shaped is selected as the basic maze channel structure. Through orthogonal experimental design, the relationship between the structure parameters of Tesla-shaped channel and flow resistance coefficient and particle passing time is elucidated, and a multiple nonlinear regression model is established.Multi-objective optimization algorithm based on NSGA-II is used and the optimization design of labyrinth channel with high flow resistance and low clogging rate is carried out with the maximum flow resistance coefficient and the minimum particle passing time as the optimization objectives. The results show that reducing the width and depth of the Tesla-shaped channel can increase the flow resistance coefficient, reducing the length of the outlet section can decrease the particle passing time. After optimization, the flow resistance coefficient of the Tesla-shaped channel is increased by 55.3%, and the particle passing time is decreased by 1.58%, effectively improving the flow resistance characteristics and anti-clogging performance.

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.

When using a variable speed motor to drive a fixed pump as an electro-hydraulic power source, pressure control is achieved by controlling the speed, which is difficult to adapt to the rapidly changing load flow conditions. Using a servo motor to drive a fixed pump through direct torque control to achieve pressure control has the advantage of faster dynamic response compared to variable speed pressure control. However, due to the influence of nonlinear factors such as rotational speed, there is a non-linear correspondence between torque and pressure, which leads to significant pressure control deviation in open-loop control. Therefore, this research proposes to use a 2D chart of speed and pressure control deviation that can be iteratively generated offline for speed compensation in open-loop pressure control. Through theoretical analysis and digital simulation, the results show that under the same conditions, compared with the pressure control scheme using fitted curves for speed compensation, the pressure control error is reduced to 2%. This scheme can better achieve pressure control.

At present, it is difficult to further improve the matching characteristics of output force switching electromagnetic for mining by relying on the traditional electromagnet optimization design under the dual limitations of intrinsic safety and power. The electromagnet on the mine electromagnetic pilot valve is taken as the research object, aiming at the problem of poor matching between the output electromagnetic force and the load reaction, the influence of the structure parameters of the electromagnet on the output force characteristics is analyzed by finite element method, and the optimization idea combining finite element analysis and multi-objective genetic algorithm is adopted to correct the output force characteristic curve of the electromagnet. The experimentals show that the matching relationship between the inside diameter of the pole shoe and the outside diameter of the armature has a significant influence on the electromagnetic force characteristics. The horizontal section of the electromagnetic force displacement characteristic is doubled after optimization, and the matching with the load reaction force is obviously improved. The results have laid a foundation for improving the efficiency of mechanized mining face.

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.

The stable gripping of flexible container bags is an important part of the feeding process, and the gripping quality of container bags has a great impact on the subsequent packaging process. Therefore, the effect of vacuum sucker on the grab quality of container bags is studied. Using the principle of vacuum adsorption, by designing a pneumatic vacuum system and observing the numerical changes in the digital pressure gauge, establish an adsorption suspension theoretical model and conduct experimental measurements. Study the variation law of the number of vacuum generators, suckers, and vacuum degree, as well as determine the layout method of the critical parameters for axial and radial deformation failure of the suckers themselves. The final determination is that the vacuum degree during grasping must not be lower than 45 kPa, and the critical values for axial and radial deformation failure of the suckers are 4 mm and 5 mm, respectively, provides a reference for the same type of flexible grasping.

Aircraft fuel pipeline internal fluid flow characteristics are complex, the interaction between the oil and the pipe wall produces the fluid-solid coupling effect seriously affects the safety of the pipeline, in-depth study of the fluid-solid coupling characteristics of the pipeline to reduce vibration and wear of the pipeline is of great significance. The specific dimensions and mechanical parameters of the welded joint area are obtained through metallographic testing and microtensile testing, and the fluid-solid coupling model of the butt-welded fuel line with a 90° bend is established. Realizable k-ε turbulent flow model is adopted to carry out the study, and the effects of different inlet flow rates on the flow characteristics and the stress response law in the fluid domain and the response of the equivalent force in different regions are comprehensively analyzed under the constant velocity flow field and the results of the response of the equivalent force in different regions are also analyzed under the pulsating flow field. It is found that: under constant velocity flow field, the maximum equivalent force at the outlet bend section is significantly affected by the flow velocity; under pulsating flow field, the maximum equivalent force at the welded joint appears in the weld area and the stress level is more concentrated. This will provide an important reference for improving configuration design and system performance of aircraft fuel lines.

Cavitation phenomenon is a key factor affecting the performance of centrifugal pump, in order to study the effect of bionic microstructure on the cavitation performance of centrifugal pump. Taking the centrifugal pumps with a specific rotational speed of 112.4 as the research object, a class of mushroom-like pit microstructure blade is proposed based on the gas-entrapping microtextured surfaces of sea skaters. Numerical simulations of non-stationary cavitation is carried out on the model using CFD simulation software to study the effect of different pit depth ratios of the microstructure on the cavitation properties of centrifugal pump. The finding indicate that the bionic microstructure exerts a negligible influence on the hydraulic performance of centrifugal pump, with a marginal change of head: -1.42%~1.38%. Different depth ratios have a greater effect on the cavitation properties of centrifugal pump, when the depth ratio is 2.5, the best effect of inhibiting cavitation, the volume of vacuole in the incipient stage of cavitation is reduced by 54.75%, and the fracture head is increased by 17.07 m. The arrangement of bionic mushroom-like pits in front of the suction front at the first 1/3, reduces the distribution of low-pressure zone at the impeller inlet, reduces the cross-sectional area of the vacuole in the flow channel, and inhibits the incipient and development.

Regulating valves are widely used in the field of industrial automation, for precise control of fluid flow, pressure, temperature and other parameters. The thrust regulating valve applied to the thrust control system of reusable liquid oxygen/methane engine is a floating seat rectangular-opening ball valve, which regulates the power of the turbine pump by controlling the flow of methane and liquid oxygen into the gas generator, thereby achieving thrust regulation. Firstly, theoretical modeling of the flow characteristics of the regulating valve. A theoretical model is proposed to predict the flow coefficient of the regulating valve by parameterizing the flow characteristics of the valve seat and spool. The theoretical model is validated using CFD simulation and experimental measurement methods, and the theoretical values, simulation values, and measurement values are compared. The results show that the theoretical model can predict the flow coefficient well at medium opening, but there are deviations at very small and very large opening. Finally, further research and improvement directions are pointed out to improve the accuracy of the model at extreme opening.

Gas sealing technology is the main mechanism for maintaining the stability of the immersion flow field. The gas jet impinges on the wafer surface to prevent the leakage of the immersion liquid, which can lead to overlay errors and exposure defects. The interaction between the immersion flow field and the sealing gas flow and the behavior characteristics of the gas-liquid interface are necessary to investigate. The background oriented schlieren technique is used for observing the gas jet. The measurement principle and hardware construction of this visualization technology are introduced. Through the optimized optical path design, synchronous observation of both the gas-liquid and internal-external flow fields, enabling a comprehensive study of interface behavior characteristics. This study can offer valuable guidance for the application of non-contact measurement techniques such as background oriented schlieren technology in ultra-clean fluidics.

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.

Aimed at the serious energy losses caused by frequent lifting and start-stop braking of hybrid forklift, a combined recovery system of hybrid forklift potential energy and braking energy was designed, focusing on the key technologies of potential energy recovery of hybrid forklift and energy efficiency improvement of dual-power energy distribution control strategy. On the basis of improving and optimizing the original parallel hybrid system of traditional hybrid forklift, the simulation model is built by using forward modeling idea. In order to control the displacement of hydraulic cylinder accurately, a fuzzy PID adaptive control system is proposed. In order to optimize the working efficiency of engine and drive motor of hybrid forklift during driving and to recover braking energy, a control strategy of braking energy recovery based on the optimal working curve of engine is proposed. Finally, based on the JB/T 11988—2014, a variety of working conditions are formulated, and AMESim and Simulink are used to carry out simulation and comparative tests under various working conditions, which verifies the effectiveness of the proposed method and improves the energy recovery efficiency, and the combined recovery efficiency of potential energy and braking energy can reach up to 56.86%.

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 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.

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.