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.

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

The effectiveness of digital twin systems relies on the dynamic consistency between virtual models and physical entities. As the core power component of hydraulic systems, hydraulic pumps exhibit strongly non-stationary operating signals, such as pressure pulsations and vibration shocks. Traditional consistency assessment methods based on mean squared error or frequency-domain statistics struggle to effectively capture structural dynamic deviations like transient impacts and parameter drifts. To address this, a consistency assessment method integrating continuous wavelet transform and a multimodal large model is proposed. This method involves collecting simulation and measured signals from the hydraulic pump, constructing residual and real noise signals, and converting them into time-frequency images via continuous wavelet transform to highlight dynamic features. Subsequently, the image encoder of a domain-adapted multimodal large model is utilized to extract deep semantic features, and consistency is quantified using feature cosine similarity. Experimental results demonstrate that the proposed method possesses a significant ability to discriminate differences in non-stationary dynamic responses, outperforming traditional evaluation metrics. It can accurately identify model structural deviations under working conditions such as internal leakage and bearing wear, providing reliable technical support for the verification, optimization, and engineering application of hydraulic pump digital twin models.

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

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

A novel limit-type solenoid valve structure is proposed to address the issues of overheating and low efficiency in traditional limit-type solenoid valve under continuous power operation. An accurate magnetic-circuit modeling method considering magnetic saturation effects is established. By analyzing and accounting for core saturation at the stator tip and the central hole, the precision of the theoretical mathematical model is significantly enhanced. Finite element simulation and experimental platform testing are employed to systematically verify the structural performance and magnetic force output. The results indicate that the limit-type solenoid valve model, which considers saturation effects, achieves a high degree of fit with the simulation curve within a stroke range of 0~10 mm, with a maximum relative error of only 5.86%, representing a substantial improvement in computational accuracy compared to traditional models. Moreover, the design maintains attractive force performance while significantly reducing copper power consumption to only 19.9 W, approximately 75% lower than existing limit-type solenoid valve structures, demonstrating excellent thermal stability and continuous operation capability. This study provides theoretical support and engineering design references for electromagnetic valve structures intended for low-speed, long-duration operation scenarios.

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

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.

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.

The multi-way valve is a critical component in engineering machinery for flow distribution and actuator coordination. Its performance directly affects the machine's controllability. To address insufficient flow control accuracy and multi-parameter coupling in existing multi-way valves, this study focuses on a 16-diameter load-sensing multi-way valve. An electro-hydraulic-mechanical multidisciplinary co-simulation model is developed and validated through experiments. The research examines how the compensator spool flow force, spring parameters, damping holes, and the load-holding throttle edge influence the main valve static and dynamic flow characteristics. The results reveal that in static performance, flow force on the compensator is the main cause of flow error. This can be compensated by matching spring stiffness, though improper compensated stiffness may lead to flow “make a big bends”. In dynamic performance, appropriately increasing the damping hole diameter and spring stiffness of the compensator improves flow response speed. Although the load-holding throttle edge enhances safety and control accuracy, it also limits flow capacity and introduces pressure loss, requiring a trade-off in design.

The hydraulic manipulators provide high thrust/torque, making it suitable for handling heavy-payload objects. However, compared with electric drives, the hydraulic systems equip with more complex structures and respond more slowly. The hydraulic systems exhibit nonlinear characteristics, such as flow/pressure variations in servo valves and friction. Nevertheless, PID control remains the most widely used method in engineering practice. But PID performances negatively under system nonlinearities and heavy load disturbances, this study focused on the pipe-gripping manipulator and took the hydraulic nonlinearities, friction, and load disturbances into consideration. A dynamic model using the Lagrange method to describe the system response and designed two nonlinear controllers is established. A fuzzy PID controller and a fuzzy sliding-mode controller based on backstepping are designed. The simulation results showed that the latter could effectively handle system nonlinearities and heavy-load disturbances, limiting the manipulator's position error to within 1%. Additionally, the thesis adopts a saturation integral function and fuzzy sliding-mode control to mitigate the chattering problem common in sliding-mode control.

The existing on/off high pressure large-flow electromagnetic unloading valves suffer from issues such as pressure regulation difficulty and discontinuous fluid supply, which struggle to meet the requirements of rapid response and on-demand adjustment of high-pressure pump output pressure in pumping station fluid supply systems. To address these challenges, an unloading valve utilizing proportional pilot valve control for main valve spool displacement regulation is developed, enabling on-demand rapid fluid supply and multi-range pressure modulation. A simulation model of the unloading valve is established using AMESim simulation software to investigate the influence patterns of main valve spring cavity, spring stiffness, spring preload, and damping hole diameter on the dynamic characteristics of the main valve, with subsequent experimental validation. The results demonstrate: Reduced spring cavity shortens both pressure build-up and relief times; Spring stiffness and preload primarily affect residual pressure and pressure relief duration; Damping hole diameter mainly impacts residual pressure and pressure rise time. Through prototype testing with optimized structural parameters, the experimental data revealed pressure rise time is 388 ms, pressure relief time is 436 ms, and residual pressure is 1.88 MPa.

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

The pressure-flow characteristic is a key performance indicator for hydraulic valves, among which spool valves represent one of the three most widely used types of hydraulic control valves. Typical hydraulic spool valves include L-type, U-type, and V-type configurations. To refine the theoretical framework for their pressure-flow characteristics, this study firstly develops a universal hydraulic model based on the structural features and fluid dynamics principles of typical spool valves. MATLAB programs are written to analyze how spool opening influences different hydraulic models. Furthermore, commercial CFD simulation software is employed to conduct numerical calculations of the flow field inside a typical hydraulic spool valve. The analysis focuses on the variation patterns of the velocity and pressure fields, the pressure-flow characteristics, and factors influencing the flow coefficient of the valve port. The results indicate that both the equivalent diameter and the flow area of typical hydraulic spool valves increase synchronously with the spool opening. Under identical boundary conditions, the L-type spool valve exhibits the smallest pressure loss and the lowest flow coefficient. The variation of the flow coefficient depends solely on the spool structure and the spool opening, decreasing as the opening increases.

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

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

The ultra-high-pressure large-diameter quick-opening valve, is the core component of an ultra-high-pressure gas release device, its flow characteristics and gas flow force play a decisive role in the system performance. A mass flow model of the quick-opening valve is established, and numerical simulations are carried out based on CFD technology. The flow coefficients under different valve port openings and opening pressures are calculated, and the reason why the flow coefficient decreases as the valve port opening increases is analyzed, which is the formation of non-choked flow and the energy loss caused by eddies. Numerical simulations of the gas flow force acting on the quick-opening valve are conducted. The steady-state gas flow force acting on the conical surface and end face of the quick-opening valve core are quantitatively calculated, and it is analyzed that their values fully meet the requirements for quick-opening. A mathematical model of the gas flow force acting on the valve port is obtained through numerical fitting. The research results provide theoretical support for the optimal design and experimental verification of the quick-opening valve.

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

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

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.

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

The support and friction characteristics of the valve plate pair in piston pumps are crucial for reliability and lifespan. Various micro-texture models are constructed, and the entire pump flow field is simulated using Fluent software to compare the dynamic pressure characteristics and support forces of different micro-textures. The study further investigated the effects of slanted rectangle texture angle and rotational speed on oil film performance. Results show that all micro-textures improve dynamic pressure and support force, with slanted rectangle textures outperforming others. The dynamic pressure characteristics increase with pump speed but initially increase and then decrease with larger slanted rectangle texture angles, peaking at 0.1455 MPa. The minimum oil film support force occurres at 75° angle, while the maximum friction is at 15°. The larger angles have a greater impact on friction coefficient at speeds above 2000 r/min, whereas below 2000 r/min, smaller angles have more significant effect.

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%.

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.

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.

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 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.

The use of aluminum honeycomb as the energy-absorbing medium in automotive sideimpact simulation devices has inevitable drawbacks, including uncontrollable buffering performance, non-reusability and high cost. To improve the consistency, controllability, and reproducibility of tests, this study proposes a novel porous hydraulic buffer applied to the FMVSS 213a standard simulated side impact for child restraint systems. Based on the damping principle of the proposed device, a mathematical model and an AMESim simulation model of the automotive sideimpact process are established. Structural parameters designing of the buffer's pressure-relief orifices are optimized through simulation and subsequently validated by physical experiments. The results demonstrate that the designed 14-stage gradient pressure-relief orifice array, combined with a 0.1 mm annular clearance, can stably control the peak acceleration of the sliding seat within 24±1 G, which meets the required acceleration range of 18.5~25.5 G for the test. Furthermore, the relative velocity waveform between the sliding seat and the door assembly exhibits the desired characteristics—remaining stable initially and then linearly decreasing within the collision duration—satisfying the FMVSS 213a waveform requirements. The proposed optimized hydraulic buffer is reusable and reduces testing costs by more than 95% compared with aluminum honeycomb, demonstrating good potential for engineering applications.

With the rapid development of sensor technology and low-power electronic devices, environmental energy harvesting has become a primary research direction to replace traditional chemical battery power supplies. A symmetrical stacked piezoelectric energy harvester is proposed, offering a new approach for efficiently capturing energy in pipelines through structural innovation. A simulation analysis is conducted on the structure of the energy harvester and piezoelectric disk, exploring the velocity distribution, pressure changes, and mechanical response of the static structure inside the energy harvester, as well as the effects of static pressure, frequency, amplitude and resistance on the energy harvesting performance. The performance of series, parallel and hybrid connection methods for different piezoelectric elements is studied, and their output voltage, power and power density are compared. The results indicate that the difference in power generation between the two channels is small and generally consistent. It proves that an increase in the number of piezoelectric disks leads to an increase in output voltage and power, but the power density may decrease.

This thesis proposes design approach of a biomimetic soft telescopic in-pipe robot that addresses the poor environmental adaptability and the insufficient active steering capability in current systems. The robot integrates flexible air chambers and pneumatic artificial muscles to construct a support-extension composite motion structure inspired by earthworm locomotion, adopting a multi-muscle coordinated actuation strategy and a continuous multi-segment locomotion method. The design includes both forward and inverse kinematic models, with system behavior verified through MATLAB simulations. An experimental platform enables performance tests in inclined and curved pipelines. The robot achieves an average crawling speed of 3.25 mm/s in a 30° inclined pipe and performs active steering in a 135° curved pipe, demonstrating strong adaptability and effective motion performance.

Due to the inherent structure of hydraulic transformer, its piston pairs are more complex during operation. In order to prevent the problems such as jamming or low volumetric efficiency during the operation of hydraulic transformers, the lubrication characteristics of the piston pair for hydraulic transformer are studied. The transformer ratio of hydraulic transformer and the Reynolds equation of piston pair are derived and solved by using ANSYS. The results show that the oil film pressure, leakage and axial viscous friction of piston pair are complex due to the influence of hydraulic transformer structure, which are related to the piston movement speed, piston cavity pressure and rotation speed. Through the orthogonal test, it is found that the main factors affecting the lubrication characteristics of piston pair are fit clearance and A-port pressure.

In response to the failure issues of the piston-slipper ball joint in high-speed axial piston pumps, dynamic characteristic analysis of the piston-slipper assembly is systematically conducted. Piston cavity dynamics model of the piston-slipper pair is established. The pressure variation within the piston chamber is analyzed by using computational fluid dynamics simulations. Subsequently, the interaction forces between the piston and slipper are quantified through multi-body dynamics simulation. Finally, the augmented Lagrangian method integrated with the steady-state structural analysis module of finite element software is employed to evaluate the deformation and stress distribution in both components. The results reveal that with increasing the load pressure, swash plate angle, and rotational speed leads to elevated negative pressure in the piston cavity, higher discharge pressure, and amplified interaction forces within the piston-slipper assembly. The maximum stress reach 80.4 MPa and deformation of the piston is 0.0213 mm respectively. For the slipper, the peak stress (168.4 MPa) and deformation (0.0057 mm) are localized at its closure. These findings provide critical insights for optimizing the design of piston-slipper ball joints in high-speed axial piston pumps.

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.

To address the limitations in control precision and robustness of hydraulic position servo systems, an intelligent adaptive control strategy combining the deep deterministic policy gradient algorithm with sliding mode control is proposed. A coupled electro-hydraulic asymmetric cylinder system model is established on the AMESim-Simulink platform, and the integration of the sliding mode control module with the reinforcement learning module is validated. The designed controller, combining deep deterministic policy gradient and sliding mode control, enables online self-tuning of sliding surface gains and chattering suppression factors. Simulation scenarios under three typical operating conditions—step input, sinusoidal input, and composite disturbances—are constructed. Results show that the proposed strategy achieves rise and settling times of 0.82 s and 0.83 s, respectively, in step tracking, outperforming radial basis function-based sliding mode control and conventional sliding mode control; under disturbance conditions, the maximum tracking error remains below 0.003 m, effectively suppressing system chattering. These findings demonstrate the proposed method's superior dynamic response and robustness in complex environments, providing significant implications for enhancing the intelligence and control performance of hydraulic servo systems.

The noise generated during the operation of hydraulic pumps seriously affects the physical and mental health of operators. To study the influence of different rotational speed conditions on the sound quality of their radiated noise, a composite evaluation index for the sound quality of hydraulic pumps suitable for constant-speed and variable-speed conditions is constructed, which is based on four psychoacoustic parameters:loudness, sharpness, roughness and articulation index. Using the hemispherical measurement method, constant-speed and variable-speed noise tests are conducted on the hydraulic pump in a semi-anechoic chamber. The variation laws of psychoacoustic parameters and sound quality indicators under different conditions are analyzed and compared. The experimental results show that as the rotational speed increases, the composite evaluation index shows a fluctuating deterioration trend. The change rate of variable-speed has a relatively small impact on the psychoacoustic parameters. In the high-speed range, the loudness, sharpness and total sound energy under constant-speed conditions are all lower than those under variable-speed conditions at the same rotational speed. At the same time, the composite evaluation index of the sound quality for hydraulic pumps shows stronger fluctuations in the high-speed range, and the fluctuation amplitude intensifies with the increase of rotational speed. The above research results provide theoretical support and evaluation basis for the optimization of hydraulic pump operating conditions and noise control strategies.

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.

To address the needs of deep-sea hydraulic systems under complex multi-actuator working conditions, this study investigates hydraulic power unit (HPU) technologies and proposes an externally mounted, integrated outboard HPU configuration. The design integrates a compensation oil tank, motor, and hydraulic pump into a unified structure which provides many capabilities like providing flow, pressure and power. To adapt to diverse hydraulic drive requirements. The HPU delivers a rated pressure of 21 MPa and a maximum flow rate of 90 L/min, meeting the demands for high-pressure and high-flow hydraulic power in deep-sea operations. This study conducts a series of performance validation tests, including land-based functional tests and pressure chamber tests. The test results demonstrate that the integrated deep-sea HPU operates stably under high-pressure conditions, with all performance indicators meeting design requirements. This provides an efficient and reliable solution for the hydraulic system of deep-sea manned platforms.

On the basis of considering the return pressure and radial clearance, mathematical models of dimensionless pressure characteristics for both matching and mismatching symmetric underlaps spool valves are established. The dimensionless pressure characteristics curves of the spool valve are obtained and compared with experimental results. The effects of valve matching, return pressure and radial clearance on the accuracy of the mathematical models are analyzed. The results indicate that when the mathematical model is set to neglect the mismatch of the spool valve, the return oil pressure and the radial clearance, the maximum calculation errors are 27%, 16% and 6.5% respectively, while the zero position calculation errors are 27%, 7% and 2%. Specifically, neglecting the radial clearance leads to increasing pressure calculation errors at ports A and B when the spool displacement exceeds 75% of the underlaps. Neglecting the return pressure and the mismatching characteristics of the spool valve also increases the pressure calculation errors at ports A and B within the range of positive opening, with the maximum errors of 78% and 50% respectively. The zero position's calculation errors at the working ports are significantly increased when the mismatching characteristics of the spool valve are not considered. The model can provide theoretical support and reference for the design of symmetric spool valves.

Aiming at the challenges of poor road conditions, complex environments, this study proposes an active vibration reduction scheme using a tractor electro-hydraulic suspension based on digital valves in order to improve stability and comfort during tractor transportation. Highly responsive digital hydraulic valves are used to adjust the speed and displacement of the implement hitch cylinder in real time to counteract vibration. Firstly, a dynamics model of tractor vibration system with suspended implements is derived. A sliding mode controller is designed, and a simulation model is developed to investigate the active vibration reduction performance under random road, sinusoidal road, and pulse road conditions. The results demonstrate that effective vibration suppression is achieved under all three road conditions. Specifically, under a 20 km/h random road excitation, the peak vertical acceleration of the tractor can be reduced by the active vibration reduction system of electro-hydraulic suspension from 2.13 m/s² to 1.01 m/s², and the root mean square value decreases from 0.84 m/s² to 0.28 m/s², achieving a 63% reduction compared to passive vibration reduction systems, which results in excellent vibration reduction.