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.

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.

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.

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.

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 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 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 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.

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.

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.

To address the severe wear and leakage of conventional combined seals in servo motors under dynamic sealing conditions, a novel combined seal configuration is proposed by exploiting the complementary characteristics of an X-ring, an O-ring and a rectangular ring. A two-dimensional axisymmetric finite-element model is established in ANSYS and used to compare the proposed design with the conventional structure under identical parameters. Based on the contact-stress distribution, the Reynolds equation is inversely solved to obtain the oil-film thickness distribution, from which the leakage rate and friction force are calculated. In addition, an L₉(3⁴) orthogonal design is conducted, with leakage rate as the response to quantitatively evaluate the effects of compression ratio, medium pressure and friction coefficient. The results indicate that the proposed structure yields a more reasonable stress distribution, with a 6.9% reduction in leakage and a 2.5% reduction in friction. The orthogonal analysis further shows that medium pressure is the dominant factor, followed by compression ratio, whereas the friction coefficient has the weakest influence.

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.

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.

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.

To meet the requirements of heavy-duty vehicle suspensions operating under complex road conditions—specifically high load-carrying capacity, wide-band damping, and tunable stiffness—this study investigates the dynamic characteristic modeling and structural parameter optimization of a dual-chamber hydro-pneumatic spring. Based on the operating mechanism of the hydro-pneumatic spring, a fractional-order Zener model is introduced. Frequency-domain representations of equivalent stiffness and equivalent damping are established, and the influence of different fractional-order derivatives on the system's dynamic response is analyzed. Building on this, a vehicle suspension model is developed, with ride comfort and handling stability selected as optimization objectives and dynamic suspension travel imposed as a constraint. Multi-objective optimization of key structural parameters of the hydro-pneumatic spring is performed using the particle swarm optimization algorithm. Bench tests of the hydro-pneumatic spring and quarter-vehicle suspension performance experiments are conducted to validate the proposed model and assess the optimization effectiveness through comparative analysis. The results indicate that the developed model effectively captures the wide-frequency dynamic characteristics of the dual-chamber hydro-pneumatic spring, and that the optimized parameter combination improves overall suspension performance while satisfying the prescribed constraints. This provides a feasible method and practical reference for the design and performance enhancement of hydro-pneumatic suspensions for heavy-duty vehicles.

A novel nonlinear active disturbance rejection control method is proposed for the constant tension control of hydraulic tensioner in wire stringing. Firstly, an adaptive-bandwidth extended state observer is designed, whose bandwidth adjusts automatically according to disturbance estimation errors. This effectively mitigates the noise sensitivity issue associated with conventional extended state observer caused by fixed high observer bandwidth. Secondly, to enhance transient tension control performance, an adaptive damping ratio function and an integral terminal attractor are incorporated into the controller. The damping ratio function enables the system to transition adaptively from underdamped to critically damped states, reducing settling time and eliminating overshoot. The integral terminal attractor further accelerates tension convergence and strengthens disturbance rejection, thereby relaxing the required extended state observer bandwidth and reducing noise sensitivity. Moreover, the mechanism by which the integral terminal attractor improves convergence speed and robustness is rigorously analyzed and proven using Lyapunov stability theory. Finally, a co-simulation platform is established using AMESim and Simulink. Comparative simulations with traditional active disturbance rejection and proportional-integral controllers demonstrate that the proposed adaptive-bandwidth extended state observer significantly reduces noise sensitivity, achieves smoother disturbance estimation, and novel nonlinear active disturbance rejection controller exhibits strong robustness against multiple disturbances including step, time-varying, and parametric uncertainties, the constant tension control performance is effectively improved.

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.

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 filtration performance test of hydraulic filter elements is a key step to ensure reliable contamination control in the main fluid system. There has long been a problem of unclear and inconsistent understanding regarding performance interpretation. Based on the multi-pass test standard for filter elements, this study systematically explains the basic test principles, performance concepts, and calculation formulas. It clarifies the internal relationships among filtration ratio, dirt holding capacity, and pressure drop. By analyzing actual test cases, three progressive interpretation methods are proposed: direct reading, analytical judgment, and in-depth decryption. These methods help extract more information from reports, prevent data manipulation, and evaluate filter performance. This work provides a useful reference for industry professionals to improve their interpretation skills.

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 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.

Insufficient control precision is caused by strong nonlinearity in vacuum butterfly valve pressure control systems. A dual-mode switching strategy fusing Active Disturbance Rejection Control (ADRC) and PID control is proposed. The controller utilizes an extended state observer to uniformly estimate and compensate for aggregated disturbances including gas temperature drift, sealing friction, and gas source fluctuations. A pressure error threshold triggering mechanism is designed to activate ADRC exclusively during dynamic processes for rapid overshoot suppression, while automatically switching to lightweight PID control during steady-state operation to maintain precision. Compared with conventional PID control, settling time of proposed method is significantly shortened and overshoot substantially reduced. Compared with single ADRC control, steady-state error is effectively minimized. Under flow disturbances, pressure recovery time is 67% faster than that of PID control, with a steady-state error below 25 Pa. This approach significantly enhances system response speed, precision, and robustness, fully leveraging the cost advantage of butterfly valves. And it provides a high-performance, low-cost vacuum pressure control solution for semiconductor, aerospace, and related fields.

A novel nonlinear integral sliding mode control method is developed to resolve the constant speed regulation challenge in closed-circuit hydraulic traction machine systems for power transmission cable deployment equipment. Firstly, a comprehensive mathematical model of the traction machine's constant speed control system is formulated through rigorous dynamic analysis. Moreover, to simplify controller complexity and facilitate engineering implementation, the model's order is systematically reduced following singular perturbation theory principles. Subsequently, a nonlinear integral sliding mode control scheme is developed through the strategic incorporation of nonlinear compensation terms, with its enhanced convergence properties and tracking accuracy being theoretically verified using Lyapunov stability analysis. Additionally, an uncertainty observer is developed to improve system robustness by observing and compensating for multiple uncertainties, including parametric variations and external disturbances. Finally, a high-fidelity multi-physics simulation platform is established using Simscape modeling toolbox for the traction machine's speed control system. Comparative simulations with traditional integral sliding mode control and proportional-integral control are conducted, and the results not only validate the effectiveness of the reduced-order model-based controller design, but also demonstrate that the designed uncertainty observer achieves accurate estimation under both step-type and sinusoidal time-varying loads. The traction machine's speed step response exhibits no overshoot, with a settling time reduced to 1.2 seconds. Under a 100 N·m static load, the speed drop is merely 0.0127 m/s. For a 100sin(πt) N·m dynamic load, the maximum speed steady-state error is 0.012 m/s. Even under the combined operating condition of simultaneous positive/negative parameter perturbations and a 100sin(πt) N·m time-varying load, the maximum speed steady-state error remains as low as 0.016 m/s. Consequently, the constant speed control performance of the traction machine is significantly enhanced by the proposed control method.

Porous graphite materials significantly influence the performance of porous restrictors, which are key components of aerostatic guideways. This study employs the compressible Darcy-Forchheimer equation to fit experimental data and determine the permeability and inertia coefficients of porous graphite with five different porosities (18%, 17%, 13%, 12%, 11%). A CFD model incorporating these coefficients is established, accurately predicting the flow velocity and pressure drop within the porous medium, with an error margin within 5%. Further analysis under various supply pressures and loading conditions reveals that restrictors made from low-permeability graphite materials exhibit superior load-bearing capacity and gas film stiffness. Specifically, under a supply pressure of 0.45 MPa, the stability of the aerostatic block is significantly enhanced. Based on this research, an experimental platform for an aerostatic guideway with an adjustable gas film thickness is constructed using low-permeability restrictors. The guideway surface straightness is verified using a Keyence laser sensor, achieving better than 2.5 μm/600 mm.

To enhance the suction performance of pneumatic jet pumps and improve drainage and gas production efficiency, we focuse on the single-tube jet pump structure in the Sulige Gas Field. Using ANSYS to establish a simulation model, we evaluate the pump's performance metrics by analyzing structural parameters. Based on the Box-Behnken Design in the response surface methodology, we develope a response surface model with nozzle diameter, nozzle-to-throat clearance, throat diameter and throat length as design variables, and jet pump efficiency as the optimization objective. Through variance analysis of pump efficiency and structural parameter correlation analysis on the response surface model, it is determined that the influence of each structural parameter on efficiency follows the order of: nozzle diameter> throat length> throat diameter> nozzle-to-throat clearance. The optimal parameter combination within the optimization range is determined as follows: nozzle diameter d_j 3.3 mm, nozzle-to-throat clearance L_c 4.3 mm, throat diameter d_t 4.7 mm and throat length L_k 25.76 mm. The simulation results and the experimental results are compared and analyzed, and the relative error is not more than 5%, which verifies the reliability and accuracy of the simulation model and the response surface model.

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.

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.

To address the challenges of leakage in the mechanical seal of high-pressure oil delivery pumps and the insufficient opening force of the seal face, a novel long-arc groove seal face is optimally designed, and its sealing performance is analyzed. Firstly, the L25(5⁶) orthogonal experiment is used to perform multi-objective optimization on five structural parameters, including the groove diameter ratio of the designed long-arc groove seal face. Then, based on the construction of a comprehensive scoring model, the optimal operating condition curve is fitted and the optimal parameter combination is obtained. Finally, the optimal parameter combination is verified under different operating conditions, including rotational speed, medium pressure, and liquid film thickness. Numerical tests show that when the groove diameter ratio, groove width ratio, groove depth ratio, arc radius, and groove number are 0.6, 0.6, 2.5, 5 mm, 8, respectively, the sealing performance of long-arc groove mechanical seal for the high-pressure delivery pump is optimal. Research shows that under the optimal parameter combination, the maximum stress in the flow field at the outlet of the groove area generally decreases, the overall stress distribution along the circumference is more uniform, and the fluid dynamic pressure effect is more significant, greatly improving the opening force of the end-face liquid film while effectively controlling the leakage rate.

This study investigates the overlap of the spherical port plate as a key parameter to reduce hydraulic shock and noise during high-to-low pressure transitions in a bent-axis piston motor. Using CFD simulations analyzes the effects of overlap from-0.5° to 4° (covering negative, zero, and positive overlap) on pressure pulsation, flow pulsation, and volumetric efficiency. The results show that increasing negative overlap improves transition smoothness, but significantly reduce the motor's volumetric efficiency. Conversely, positive overlap enhances volumetric efficiency; however, it intensifies pressure pulsation in the piston chambers. A detailed analysis within the 2°~3° range, combined with noise testing, identifies 2.8° as the optimal overlap. At this setting, both pressure and flow pulsation rates are significantly reduced. Measured noise decreases by 0.7 dB compared to the initial design, achieving an effective balance between low noise and high efficiency.

To address issues such as poor stability, low coordination, high labor intensity and significant drill pressure fluctuations associated with manual drilling operations in automatic drilling systems, we design a hydraulic drawworks system for automatic drilling. This system includes power, drive, execution and control units. It enables control over the drill string hoisting speed and surface drill pressure by adopting a composite controller that combines the conventional PID with self-adjusting fuzzy control. Using the AMESim-Simulink co-simulation platform, simulation tests verify that the hydraulic drawworks system can effectively control the hoisting speed and surface drill pressure. The controller improves the system's response speed, reduces overshoot and enhances its stability. The research shows that this composite controller delivers high accuracy in controlling the automatic drilling hydraulic drawworks system, enables real-time monitoring, improves both intelligence and drilling efficiency and reduces drilling costs. These findings hold practical application value for the future of automatic drilling operations.

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.

The oil-gas shock absorber strut plays a vital role in an aircraft's landing gear, its sealing performance directly impacts the shock absorption efficiency and safety during takeoff and landing. T-shaped sealing ring is commonly used for sealing the shock absorber struts of landing gear. A static sealing model of the T-shaped sealing ring is established using the MSC.MARC finite element software, simulating the assembly and compression process. This simulation produces detailed contours of the sealing ring's surface contact stress, Von Mises stress, and strain. The effects of changes in the seal's structure, compression ratio and working pressure on sealing performance are analyzed. The results show that: when the fillet radius where the T-shaped rubber meets the retaining ring is less than 0.9 mm, the rubber experiences self-extrusion; increasing the fillet radius to over 1.2 mm eliminates this issue and reduces Von Mises stress at that point. Changes in the fillet radius have minimal impact on the sealing's surface contact stress. Reducing the compression ratio from 26.84% to 19.82% decreases respectively the sealing's surface contact stress and effective sealing width by 9.22% and 23.15%. By lowering the sealing groove height while ensuring the retaining ring and T-shaped rubber could still be assembled, the minimum compression ratio achieved is 14.56%. Even as the operating pressure rises to 50 MPa, causing the maximum surface contact stress on the sealing surface to surge by 238.82% and the effective sealing width to drop by 8.45%, the seal remains effective in containing the oil.

Coal mining is a high-energy industry. Intelligent mining pursues both efficiency and low-carbon operation. The conveyor pushing and support moving process of hydraulic supports is the main energy-consumption stage in following shearer process. It represents a key issue for energy optimization. To address this issue, a mathematical energy-consumption model for hydraulic supports following shearer process is established. It uses response surface and correlation analyses to examine the effects of shearer traction speed, pushing-jack inlet pressure, flow rates of leg raising and lowering, and inlet-return pressure. It also analyzes single-factor effects and parameter interactions. A case study on the ZY21000/38/82D hydraulic support in a Shaanxi coal mine shows that traction speed is the dominant factor and has a nonlinear negative relation with both conveyor pushing and support moving energy-consumption. The pushing-jack inlet pressure, leg inlet pressure, and leg raising and lowering flow rates each show linear positive relations with conveyor pushing energy-consumption. The leg return pressure shows a linear negative relation with conveyor pushing energy consumption. Parameter interactions have a significant influence on total energy-consumption. This energy-consumption model provides a theoretical foundation for optimizing hydraulic support parameter configurations. It helps reduce following shearer consumption and promotes green low-carbon transformation in the coal mining industry.

A magnetorheological damper, known for rapid response, wide adjustment range of damping coefficient and low energy consumption, is a significant research direction in the field of vehicle engineering. By dynamically controlling the excitation current of the magnetorheological damper, we minimize the vibrations transmitted to the vehicle body, ultimately improving vehicle running smoothness. This research conducts a theoretical analysis of the hybrid-mode damping characteristics of a certain magnetorheological damper model. A multi-physics simulation model of the magnetorheological damper is developed using ANSYS to analyze the relationships among piston velocity, damping force and control current. A semi-active suspension and full-vehicle dynamics model is established, and a sliding mode control algorithm is applied in a Simulink numerical simulation to investigate the impact of control system on suspension and vehicle vibration performance. The research shows that the finite element analysis of the electromagnetic field provides a clear visualization of magnetic flux distribution, offering guidance for magnetic fluid flow path structural design. Additionally, the sliding mode control significantly enhances the performance of the semi-active suspension, effectively improving critical indicators such as vehicle body acceleration and suspension stroke. Ultimately the vibration characteristics, as well as ride smoothness and ride comfort of vehicles are significantly improved.

As an important component for regulating and protecting hydraulic systems, the performance degradation of relief valves will directly affect the stability and safety of the system. After a certain type of pilot operated relief valve has been in service in hydraulic systems of engineering equipment for a period of time, its performance often deteriorates due to wear of the main valve core. Therefore, it is urgent to evaluate its performance to provide a basis for subsequent service life assessment. A mathematical model for a pilot operated relief valve is established, and the impact trend of changes in the radial clearance and rounded corner radius between the main valve core and the valve sleeve on static and dynamic characteristics based on the model are qualitatively analyzed; a simulation model is established in commercial software, and the simulation model is validated using measured data to quantitatively analyze the influence of wear parameters on its static and dynamic characteristics. The results show that in the flow range of 0~7 L/min, the increase in radial clearance leads to a slower gain in the static characteristic curve, while the increase in rounded corner radius leads to a nonlinear change in the gain of the static characteristic curve; the increase of radial clearance and rounded corner radius will prolong the response time, increase the pressure overshoot and steady-state pressure, among which the increase of radial clearance has a more significant impact on the extension of dynamic response time of the relief valve, and the increase of rounded corner radius has a more significant impact on the increase of pressure overshoot. The research results can provide theoretical basis and tool support for the performance evaluation and fault prediction of relief valves.