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.

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.

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.

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.

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.

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 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.

This study focuses on the bolted connection structure between the pump flange and the housing, and establishes a finite element model of the piston pump. The model is validated through both modal analysis experiments and vibration response experiments. Based on the validated model, the influence of four design parameters—bolt position, installation radius, bolt quantity, and bolt size—on modal frequencies and vibration responses is systematically analyzed. The results indicate that a symmetrical bolt arrangement increases certain modal frequencies by up to 12.7% and reduces vibration velocity by up to 21.5%. The installation radius has a relatively minor effect on vibration characteristics. An increase in bolt size leads to higher modal frequencies, but has limited effectiveness in suppressing vibration. Increasing the number of bolts significantly improves the modal frequencies, with a maximum increase of 10.7%, and reduces vibration velocity by as much as 36.1%. An orthogonal experimental design is used to evaluate the relative significance of each parameter. The analysis confirms that bolt position and bolt quantity have the most substantial impact on the modal characteristics and vibration response of the piston pump. Bolt size has a moderate influence, while installation radius has the least effect.

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 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.

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.

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 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 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%.

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.

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 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.

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.

A finite time prescribed performance neural network control strategy is proposed to address the need for control strategies that balance both transient and steady-state performance in the electro-hydrostatic actuator (EHA). A nonlinear mathematical model of the EHA is established, and a barrier Lyapunov function is constructed by incorporating a finite time prescribed performance function for the tracking error. Based on the backstepping control framework, a neural network-based position tracking controller is designed. The stability and theoretical performance of the controller are rigorously proven using Lyapunov analysis. A co-simulation model is built using MATLAB and AMESim, and comparative simulations are conducted with a PI controller and a neural network controller without prescribed performance. The results demonstrate that the proposed controller achieves significantly higher tracking accuracy. Compared to the PI controller and the neural network controller without prescribed performance, it improves sinusoidal trajectory tracking accuracy by 85% and 47%, and point-to-point trajectory tracking accuracy by 85% and 55.9%, respectively. Furthermore, the tracking error converges below the predefined steady-state bound within a finite time and remains within the prescribed performance constraints throughout the operation.

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.

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.

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.

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.

As a key driving component in hydraulic systems, the dynamic performance of negative flow pumps directly influences the steady-state and response characteristics of the system. To improve system performance, it is essential to study the influence of internal structural parameters on the outlet pressure pulsation rate. An AMESim simulation model is established based on the operating principle of a negative flow pump. Model validation shows that the maximum relative errors between simulated and experimental values for the front and rear pump pressures are 9.35% and 9.12%, respectively, both within the 10% acceptable threshold. The influence of the control valve and variable mechanism on the outlet pressure pulsation rate at different temperatures is analyzed. The results indicate that the outlet pressure pulsation rate is negatively correlated with the left-side distance of the servo valve orifice and the orifice diameter. However, the outlet pressure pulsation rate is positively correlated with the power valve spool diameter, spool outer diameter, lug diameter, and slot diameter of the swing arm. The results provide a theoretical basis for optimizing the design of the control valve and variable mechanism in negative flow pumps.

Hydraulic axial piston pumps are core power components in hydraulic systems, so effectively diagnosing faults in axial piston pumps is crucial for ensuring the safe and reliable operation of hydraulic equipment. This paper proposes an improved fault diagnosis method that combines an auxiliary classification generative adversarial network and a model migration strategy. A fault diagnosis framework and adopts a pre-training-fine-tuning strategy to improve the model's generalisation ability in the target domain task is proposed. This method solves the problem of traditional deep learning diagnostic methods having a poor effect, or even failing, in the actual operation process of normal and fault data due to data imbalance and insufficient quantity. Experimental results show that this method increases the structural similarity value by 20.4% and the peak signal noise ratio value by 5.4% when samples are imbalanced. The three datasets achieve F1 scores of 96.3%, 94.4% and 92.5%, respectively, effectively improving the quality of production samples and the fault recognition rate of axial piston pumps.

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.

The 6-DOF platform has been widely applied in various fields due to its exceptional performance characteristics including high precision, high load capacity, and high rigidity. To meet the spatial motion and positioning requirements of proton knife surgical beds, a 6-DOF motion positioning platform is developed. Firstly, based on workspace usage requirements, a reasonable structural design for the 6-DOF platform is implemented. Secondly appropriate hardware selection for the control system is carried out, along with programming design for the STM32 controller and the LabVIEW-based host computer. Subsequently, a prototype of the 6-DOF platform is fabricated, and control algorithm parameters are debugged. Finally, experiments are conducted to investigate the adaptability of the BP-PID control algorithm and nonlinear PID algorithm to different load cases, the real-time tracking error of slave cylinders under a master-slave cooperative control strategy, and the overall structural positioning error of the 6-DOF platform. Experimental results demonstrate that, for position control of a single electro-hydrostatic actuator under varying load cases, the BP-PID algorithm outperforms the nonlinear PID algorithm in terms of response speed and adaptive capability, while both algorithms exhibit almost no overshoot; During platform motion, the real-time cooperative error of slave cylinders remains within 0.43 mm, and the positioning accuracy of the 6-DOF platform is better than 0.05 mm/0.1°.

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.

The openly-reported researches on mechatronic safety valves in aerospace applications show that the failure of solenoid valves will cause functional incapacitation of the safety valves. In view of this situation, we propose a valve terminal controlled mechatronic safety valve with the advantage of fault redundancy function, as well as the control strategy. The principle verification experimental investigations are carried out. The valve terminal is composed of three normally open two-position three-port solenoid valves. It is shown that by applying the valve terminal to control the switch of the passage between its back-pressure chamber and the pressure vessel or the atmosphere, combining with the proposed strategy, the main valve can operate normally under normal working mode and failure modes that DCF1 or DCF2 does not operate when power is on or off. The principle verification experimental results show that the control function of the solenoid valves by the controller, the action function of the solenoid valves and the opening pressure of the safety valve all meet the design requirements. The research results provide theoretical guidance and engineering application foundation for the subsequent application of the mechatronic safety valve in the pressurize transportation system of launch vehicle.

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.

In order to enhance the linear regulation capability of solenoid high-speed switching valves and achieve precise control of brake fluid flow, an influence factor characterizing the radial force on axial force of valve core is proposed. The numerical simulation of the internal flow field in the apply valve is carried out, additionally, it is found that the existing structure of valve seat and spool significantly affects brake fluid jet characteristics under Coanda Effect, coupled with asymmetric outlet geometry. These factors collectively increase the vortex probability and instability of flow field in the throttling region, which inducing substantial radial force during the opening and closing cycles. Structure optimization is implemented by reducing the spool spherical throttle ineffective area, implementing of variable-cone-angle surfaces on the valve seat and incorporating symmetrical supplementary outlet ports to improve flow field symmetry. The results show that the flow field of throttle area in new structure is more stable, the radial force on the spool is 0.1 N or less, which is with the opposite direction of the bias and is conducive to self-alignment of the spool. Finally, the new structure effectively weakening the radial force's impact on the linear regulation, reliability and life of the solenoid valve.

The existing luffing hydraulic system of cranes exhibits significant throttling losses and insufficient control precision during fine operations with low flow rates. To address these limitations, A double spool parallel pump-valve synergistic system is proposed. However, the dynamic response mismatch between the pump and double spool valves in the system induces flow fluctuations at mode transition points, resulting in impact vibrations. To resolve these technical challenges. Firstly, the theoretical analyses of the dynamic characteristics of the double spool valves and hydraulic power source is conducted. Building upon these analyses, a multi-mode segmented control strategy based on handle control signals is developed. Subsequently, co-simulation is implemented using AMESim and MATLAB/Simulink platforms. Experimental results demonstrate that the proposed double spool parallel pump-valve synergistic system achieves high-precision micro-motion control with a minimum stable flow rate of 5 L/min. Moreover, the implemented control strategy effectively mitigates flow fluctuations during mode transitions, reducing flow variation amplitude at switching points by 56.7%.

A new configuration of plate pilot pressure control for two-stage flow distribution hydrostatic-balanced high-pressure radial piston motor is proposed to address the problems of the large lateral forces on the piston pair lead to large transmission shocks at start/stop moments, serious leakage of the flow distribution and piston gap and low volumetric efficiency of traditional radial piston motors under high-pressure working conditions. This new model adopts composite pistons assemblies and pilot pressure control two-stage flow distribution method to achieve high-pressure power oil circuit sealing and high-efficiency flow distribution. In addition, the hydraulic floating support structure is adopted for the pilot stage flow distributor to compensate for mechanical wear and improve the reliability of long-time continuous operation. Based on AMESim, the dynamic simulation model of the whole motor is established. The thesis analyzes the correspondence between motion of single piston and its distribution valve, the influence of diameter of damping hole of distribution valve, the working pressure and main stage supply flow rate on the volumetric efficiency of the motor, and also analyzes the output characteristics of the motor with different transmission structures. The simulation results show that the motor has a volumetric efficiency of 89.74% at high pressure of 35 MPa. The pulsation rate of the output speed is reduced by 60% compared with that of the crankshaft linkage motor. It also has good low-speed stability and wide load adaptability. The results show a theoretical basis for the design and optimization of the high-pressure hydrostatic balance radial piston motor prototype is provided.

The non-circular planetary gear hydraulic motor has great application potential due to its compact structure and high torque output, but it suffers from severe gear impact, serious wear of the valve plate, and low volumetric efficiency. Based on computational fluid dynamics and dynamic analysis, a three-dimensional flow field model of the motor is established. Through numerical simulation and experimental testing, the impact characteristics, valve plate wear mechanism, and structural optimization are systematically investigated. The results show that appropriately enlarging and reshaping the port geometry can effectively reduce the impact peak of the gears and extend the stable operation period by about 55%. Increasing the through-hole diameter of the planetary gear significantly decreases the local axial force and impulse, reducing end-face wear by up to 66.7%. Prototype tests verifies the accuracy of the simulation results, confirming that the proposed optimization scheme improves valve plate wear resistance and motor volumetric efficiency. This study provides theoretical support and experimental evidence for the structural optimization and engineering application of non-circular planetary gear hydraulic motors.

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.

To investigate the friction and wear characteristics of slipper pairs in high-pressure and large-displacement radial piston pumps under impact loading, this study established a transient friction wear model for the stator-slipper contact surface using ANSYS Mechanical software with ANSYS parametric design language programming. The dynamic friction wear of stator-slipper pairs is analyzed under varying working pressures, impact pressure amplitudes, and impact pressure times, supplemented by experimental validation. Key findings reveal that during the 0~0.6 s transient phase, wear primarily occurs between the central oil reservoir and pressure-equalizing groove on the slipper surface, accompanied by uneven wear patterns and stress concentration near the pin hole. The average error of relative value between simulation and experimental results is 8.99%. Through orthogonal experiment analysis and Kriging interpolation fitting, the sensitivity hierarchy of wear factors is determined as impact times, impact pressure amplitude and working pressure. Experimental results under three impact times within 60 minutes show a wear volume of 824.1379 mm³, demonstrating significant structural degradation caused by impact loading and validating the predictive capability of the proposed simulation model for slipper pair wear assessment.

To study the impact of different dynamic sealing forms on dynamic characteristics of solenoid valve, based on the application cases of high-pressure solenoid valve, an AMESim model of pilot-operated solenoid valve is established. Three typical dynamic sealing forms, retaining ring, O-ring, and variseal are selected to investigate their respective impacts on the dynamic characteristics of solenoid valve. The result shows that the fact that the poor sealing effect of retaining ring leads to the opening and closing action of main valve of solenoid valve easily affected by environmental temperature results in negative impact on dynamic characteristics; Better sealing properties of O-ring leads to worse dynamic characteristics of solenoid valve, therefore a solution of cutting a pressure relief groove on sealing area is proposed; The sealing performance of variseal under normal and ultra-low temperature conditions is markedly different. Therefore the measures that should be considered in the design of the system are put forward to avoid affecting the dynamic characteristics of solenoid valve.