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.

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

The piston-cylinder interface, as a key friction pair in an axial piston pump, directly affects its reliability and service life. This paper establishes the Reynolds equation and force equation for the piston-cylinder interface, and solves them using discretization in MATLAB. A comparative analysis of the minimum film thickness, film pressure, friction, and leakage between the drum-shaped and conventional piston-cylinder interfaces under the same conditions is conducted. The results show that, compared to the conventional piston-cylinder interface, the drum-shaped piston-cylinder interface has a larger minimum film thickness, improving lubrication performance. It also exhibits distinct pressure peaks, with more significant squeezing effects on the film. The drum-shaped piston reduces axial and circumferential viscous friction, enhancing fluid flow efficiency, but increases leakage during motion, reducing sealing performance. These findings provide a theoretical basis for improving the lubrication performance of the piston-cylinder interface.

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

The electromagnet is the electromechanical conversion device of high-speed on/off valves, which achieves rapid response of high-speed on/off valves through the rapid opening and closing of valves. The performance of the electromagnet directly affects the dynamic characteristics of high-speed on/off valves. Therefore it is crucial to research the design and magnetic characteristics of the electromagnet. Based on this, this study carried out the structural design of high-speed on/off valve electromagnet, established the magnetic field model of the electromagnet, analyzed the magnetic field law of the electromagnet, and obtained the magnetic characteristics of the electromagnet. The results show that the maximum electromagnetic force of the electromagnet is about 28.0 N, the magnetic field establishment time is about 15 ms, and the magnetic field disappearance time is about 20 ms in the separated state. In the suction state, the maximum electromagnetic force is about 45.7 N, the magnetic field establishment time is about 15 ms, and the magnetic field disappearance time is about 50 ms. Under the separated and suction states, the steady-state electromagnetic force experiment and simulation average errors are less than 2.5%, and the experimental results are consistent with the design expectations. The structural gap has a significant impact on the performance of the electromagnet. Increasing the moving iron core and reducing the air gap can increase the electromagnetic force.

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.

To reasonably evaluate airtightness quality issues, the primary factors influencing airtightness quality a identified based on characteristics such as stabilization time, cavity volume, and temperature. Subsequently, a quality evaluation approach integrating the entropy weight method with fuzzy comprehensive evaluation is proposed. By analyzing the factors affecting airtightness, a factor set encompassing five relevant indicators, including temperature and cavity volume, is established. Determine the weight factors of each indicator according to the entropy weight method, use the ridge shaped membership function to obtain the membership matrix, and determine the evaluation results of air tightness quality. The results demonstrate that this method can accurately assess airtightness quality based on multiple factors, and has stability and effectiveness.

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

With the advantages of pressure self-compensating and high energy density, the hydraulic power supply system makes itself a good driver for deep-sea equipment. However, the deep-sea hydraulic power would be easily overheated to decrease the reliability of deep-sea equipment because of its large power, high integration and special working conditions. Aimed at the temperature control problem of deep-sea integrated hydraulic power supply, a novel thermal control method based on low temperature reflux heat dissipation under deep-sea environment is proposed and studied. Firstly, a coupled heat transfer model is established and analyzed to obtain steady-state heat transfer characteristics with Fluent. The result shows that steady state temperature of internal hydraulic oil is determined by the reflux oil temperature. Then, a passive thermal control system is proposed and its AMESim dynamic model and experimental facilities are constructed. The results show that the error between the simulation and experimental results of the thermal control system oil temperature does not exceed ±5%, and the final temperature of fluid can be controlled at 45 ℃ in normal temperature water. The proposed method can effectively control fluid temperature of integrated hydraulic power supply and improve the reliability of deep-sea equipment.

Taking a certain type of dual-chamber controlled hydraulic rock drill as the research object, this study aims to minimize the clearance energy losses between the impact piston and the cylinder. The lumped parameter modeling method is adopted to establish the mechanical models of the impact system, the damper system, the rock and the piston and cylinder clearance energy consumption model on the basis of considering the compressibility of the oil, the pipeline pressure losses and the leakage, and the corresponding AMESim graphical solving model is constructed. Under specified structural parameters, the motion curves of the piston and the spool valve, the transient process of the controlled chamber pressure and the characteristics of the clearance energy losses are calculated. The impact mechanism of size on clearance energy consumption is analyzed. The relationship of the piston-cylinder clearance and the working pressure are summarized when the energy loss of the gap is the smallest. It can provide a theoretical basis for the determination of the radial fit gap between the piston and the cylinder of a hydraulic rock drill.

Using ANSYS Workbench as the platform, a three-dimensional finite element model of a flared aviation hydraulic connector with a pipe diameter of 10 mm is established to systematically study the influence mechanism of sealing performance under different tightening torques. The relationship between tightening torque and sealing surface width, average contact stress distribution and maximum contact stress is revealed through calculation and simulation. The validity of the simulation results are verified through pressure test and coloring test. The results show that 37~40 N·m is the optimal assembly torque, which meets the working pressure and sealing performance requirements of the hydraulic system. The methods proposed in this study provide theoretical guidance and technical support for the high-precision assembly of aviation hydraulic system pipeline.

The synchronization operation of the hydraulic thrust reverser actuation system is one of the key functions to ensure the normal deployment/retraction of the thrust reverser device. Based on the working principles of throttling synchronization and mechanical synchronization, establish a mathematical model and system simulation model for system synchronization, and verify the effectiveness of the system synchronization simulation model through experiments. Based on the experimental boundary conditions, simulation parameters are set to study the effects of throttle valve opening size, actuator transmission ratio, and synchronous soft shaft stiffness on synchronization characteristics. The differences between throttle synchronization and mechanical synchronization are compared and analyzed. The results indicate that the throttle valve opening size, actuator transmission ratio, and synchronous soft shaft stiffness all have nonlinear effects on the system. Under the same load conditions, the mechanical synchronization accuracy is 68% higher than the throttling synchronization accuracy. The simulation model can simulate the synchronization changes during the system motion process, and can serve as an effective tool for studying the synchronization of hydraulic thrust reverser actuation system.

Single hydraulic system modelling leads to distorted predictions of system dynamic characteristics due to simplification of flow field in main control valve. Taking electro-hydraulic shift control system as object, a real-time co-simulation method for coupling transient flow field of main control valve with dynamic simulation of hydraulic system is proposed and realized, the synchronous operation data of electro-hydraulic control system model and its main control valve flow field model are communicated in real time through TCP/IP interface. The results show that this method can accurately capture the internal transient flow field parameters and transient flow force during the regulating process of the main control valve, and then give high precision parameters of the main control valve in the hydraulic system model in real time, reproducing system vibration and spool self-excited vibration. At the same time, it is found that the steady state value of the main control valve flow force is 12.53 N by real-time co-simulation of the system, while the value of the system simulation is only 0.50 N, which is greatly different from the traditional theoretical calculation value of 8.09 N. This difference is one of the main reasons for the difference in dynamic performance prediction.

The engine nozzle throat actuator cylinder regulates the nozzle throat area to control the engine's afterburner operation. To diagnose abnormal nozzle throat area control, we analyze the actuation system's working principles, establish a fault tree, and conduct bottom events. The malfunction is determined to result from the tilting of the piston coaxial sealing ring during pressure reversal, which caused a sudden surge in internal oil leakage between the rod and non-rod chambers of actuator cylinder. By adding oil-guiding grooves on the lateral surface of the piston coaxial sealing ring, and simulating pressure reversal conditions in rod and non-rod chambers of actuator cylinder, experimental validation is performed. Results demonstrate that the modified design significantly reduce internal leakage under pressure reversal, enhance the piston seal integrity, and resolve the nozzle throat area control anomaly. This improvement provides critical guidance for optimizing similar products and developing new-generation actuators.

This study focuses on addressing the issue of significant leakage under 32 MPa high pressure during clockwise rotation in a certain type of internal cam radial piston motor. By conducting finite element analysis simulations on the port plate, and based on the theory of radial laminar flow between parallel plates, it was determined that the substantial deformation (0.015 mm) of the port face of port plate at 32 MPa under clockwise rotation is the primary cause of the high leakage (3.5 L/min) on this side. By optimizing the port plate structure and upgrading the material grade, the deformation of the port face under clockwise 32 MPa high-pressure conditions is reduced to 0.0084 mm. Experimental validation revealed that the leakage of motor with optimized port plate reduced to 0.55 L/min at 32 MPa pressure under clockwise rotation, representing an 84% decrease compared to the original design. The results provide simulatio and theoretical guidance for optimizing the leakage in similar types of piston pumps and motors.