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.

A hierarchical control strategy with adaptive neuro fuzzy inference system compensation is proposed for heavy-duty automatic guided vehicle on unstructured roads. It improves posture control performance under severe nonlinear conditions. The strategy addresses hydro-pneumatic suspension nonlinearity and electromagnetic valve force inaccuracies. The upper layer uses linear quadratic regulator for optimal vertical body control. A fuzzy PID controller suppresses roll motion. Desired active suspension forces are generated. The lower layer applies adaptive neuro fuzzy inference system for force tracking error compensation. It maps force errors to electromagnetic valve control signals. High-precision force tracking is achieved. Simulation results validate the proposed strategy. Under class C road excitation, root mean square vertical and roll accelerations decrease by 30.4% and 38.9%. Under single-side step excitation, peak roll angle decreases by 44%. The strategy shows strong robustness under complex conditions.

Traditional passive hydro-pneumatic suspensions, limited by their ride comfort and handling stability, becomes a performance bottleneck for mining trucks. A semi-active hydro-pneumatic suspension model predictive control strategy based on whale algorithm optimization is proposed, aiming to achieve rapid convergence and optimize control system performance. A system model including a double-chamber hydro-pneumatic suspension model, a 7-degree-of-freedom dynamic model and a model predictive controller is established, and the stiffness and damping are equivalent. The whale algorithm optimizes the controller weight matrix under various road excitations. It then builds the optimization algorithm model predictive controller. The semi-active hydro-pneumatic suspension based on whale algorithm optimization is compared and analyzed with passive hydro-pneumatic suspension and traditional model predictive control semi-active hydro-pneumatic suspension on different roads. The simulation results demonstrate that the proposed model predictive control strategy optimized by the whale algorithm significantly enhances the ride comfort and handling stability of mining trucks. It also effectively reduces the dynamic load impact on road surfaces, offering considerable engineering significance for efficient mining area operations.

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.

Due to the limitations of factors such as on-site space and economic, the sample acquisition size of certain fault type of each component is very small, and thus a fault dataset of extreme long-tail distribution is formed, which makes the traditional decoupled supervised contrastive learning model unable to conduct effective diagnosis. Therefore, an improved decoupled supervised contrastive learning model is proposed, namely contrastive distillation type equilibrium decoupled supervised contrastive learning mode. Firstly, the synthetic minority oversampling method is introduced to generate tail samples appropriately to alleviate the problem of dataset imbalance; secondly, the parameter contrastive learning is introduced to construct a double contrast mechanism to increase the contribution of the tail and the diagnosis accuracy, solving the problem of sparse feature distribution of the tail type; finally, the type balanced self-distillation is introduced to solve the problem of insufficient representation of tail features through knowledge transfer. The experimental analysis of two extreme distribution forms of measured fault samples from the hydraulic pump, the gear and the rolling bearing shows that the proposed model can effectively solve the problem of extreme long-tail distribution, with diagnostic accuracies reaching up to 90.93% and 98.61%, respectively. In addition, the accuracy of the proposed method is 40.99% higher than that of the original method, and 76.97% and 35.83% higher than those of the traditional wide parameter contrastive learning and balanced contrastive learning methods.

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 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.

High-precision control of excavator electro-hydraulic servo systems is significantly hindered by difficulties in accurately identifying parameters for nonlinear friction models. To address this, a hybrid optimization algorithm is developed by integrating genetic algorithm selection and crossover operations into a particle swarm optimization framework, enhanced with adaptive strategies for inertia weight and learning coefficients. This proposed algorithm demonstrates superior performance in identifying parameters for the LuGre friction model, achieving a maximum friction force error of only 1.70 kN—a 40.68% improvement in solution quality over a standard genetic algorithm. Subsequently, an adaptive friction compensation controller is designed based on the identified model. The experimental validation on a 23 t excavator shows that the proposed controller achieves a maximum trajectory tracking error of 11.56 mm for a sinusoidal input, significantly outperforming traditional PID and feedforward compensation controllers. The proposed controller effectively compensates for friction and disturbances, eliminating stick-slip phenomena and improving system robustness and tracking accuracy.

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.

Modeling electro-hydraulic actuators is challenging due to their strong nonlinearities and unobservable internal states. To address issues such as low modeling accuracy and poor generalization, we propose an improved physics-informed neural network modeling method. First, a one-dimensional convolutional neural network module is employed to extract temporal features from sensor data. Subsequently, the force balance equation derived from electro-hydraulic actuator dynamics is embedded into the loss function as a physical constraint. This mechanism compensates for the poor interpretability of pure data-driven models and accelerates convergence. Furthermore, to mitigate the interference of sensor noise on physical constraint calculations, a signal smoothing strategy based on local linear fitting is designed. The multi-condition experiments demonstrate that this method effectively balances data fitting with physical consistency. Compared with traditional models, the proposed approach significantly improves prediction accuracy and robustness under limited data conditions.

The use of aluminum honeycomb as the energy-absorbing medium in automotive sideimpact simulation devices has inevitabledrawbacks, 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.

To address the low energy efficiency of hydraulic excavator valve-controlled systems and the insufficient dynamic performance of single-pump-controlled differential cylinder systems, this study proposes adual-pump-controlled differential cylinder system driven by a single servo motor with two fixed-displacement pumps. A composite controller integrating velocity feedforward compensation and linear active disturbance rejection control is designed. The controller employs a linear extended state observer to estimate and compensate for internal and external disturbances in real time, while incorporating velocity feedforward to compensate for position errors in advance. A model of the dual-pump-controlled cylinder system is established in MATLAB/Simulink, and simulations under constant load conditions verify the feasibility of the proposed controller for position control. A multi-body dynamics model of a mini hydraulic excavator is established, with dual-pump-controlled cylinder systems equipped for the boom, arm, and bucket. Comparative simulations of typical digging cycles are conducted using three different controllers. Results show that under constant load, the maximum position tracking error with the proposed method is reduced from 4 mm to 2 mm compared to linear active disturbance rejection control alone. In typical digging cycles, the maximum position error of the boom is 3.78 mm, with an energy efficiency of 61.33%. The arm and bucket also demonstrate higher positioning accuracy and energy efficiency compared to PID and linear active disturbance rejection control. The results verify that the method effectively improves both the energy efficiency and dynamic performance of the dual-pump-controlled cylinder system.

The space station's environmental control and life support system requires pressure-reducing valves with high sealing integrity, pressure stability and mechanical environmental adaptability. A diaphragm type pressure-reducing valve is designed to meet these demands. A micron-scale filter is integrated at the valve's inlet and outlet, which enhances the anti-pollution capability and prevents seal failure caused by foreign objects. The throttling pair employs a titanium alloy-fluororubber edge seal structure with a hard stop design, achieving long-term reliable sealing under low sealing force. The optimized diaphragm structure and fine-thread adjustment mechanism improve outlet pressure control precision. The mechanical simulation analysis confirms that all three primary natural frequencies exceed 2200 Hz, meeting space station mechanical design standards. After random vibration, shock and other mechanical tests, along with helium mass spectrometry leak detection and zero-flow pressure rise sealing tests, the product demonstrates excellent performance consistency before and after mechanical environmental testing. The external leakage rate is not more than 8.0×10^-7 Pa·m³/s, with a 0.5 h pressure rise not more than 0.63 kPa. All metrics exceed design requirements. The valve has been successfully deployed in orbit, providing a reference for designing high-precision pressure-reducing valves in the aerospace field.

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.

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 mitigate the impact of sticking in aviation hydraulic slide valves on flight safety, we adopt EDEM-Fluent coupling—Fluent simulates fluid flow while EDEM models contaminant particle motion and interactions—since traditional flow field analysis is insufficient. We adjust boundary parameters like opening to explore particle effects on pressure output and sticking evolution, and analyze particle distribution as well as transient flow area changes caused by particle accumulation. Regional particle accumulation correlates with particle size distribution, flow field jets, vortices and wall friction; sticking leads to pressure and mass flow rate oscillations. The coupled simulation reveals sticking mechanisms and provides technical support for health-oriented lifecycle green design of hydraulic slide valves.

The pneumatic grinding system faces challenges such as nonlinearity, disturbance sensitivity, and modeling issues. The thesis proposes a model-free adaptive control strategy based on reinforcement learning, using the twin delayed deep deterministic policy gradient. This approach is named twin delayed deep deterministic policy gradient-model-free adaptive control. We build a model of the pneumatic loading system in MATLAB/Simulink, design the proposed control strategy, and define state-action and composite reward functions. Simulations show that the proposed control strategy is the optimal controller. Under constant force loading, the proposed control strategy exhibits no significant overshoot and achieves a 0.94 s settling time. Under disturbance loading, the two disturbance peaks are limited to 3.0 N and 3.2 N. For sine force loading, the proposed control strategy tracks the reference with an error of 0.16 N. Under varying angular loading, the proposed control strategy reduces error by 0.4 N. In conclusion, the proposed control strategy exhibits higher control accuracy, faster response, and greater robustness in complex nonlinear pneumatic systems, proving its potential for engineering applications.

The paths optimized by the traditional ant colony algorithm have the problem that “the distance is the shortest but the energy consumption is not the lowest.” In order to ensure that the search path of the underwater vehicle in the complex marine environment meets the requirements of the lowest energy consumption and the shortest path, it is necessary to analyze the energy consumed by the buoyancy regulation system, pitch regulation system and depth-stabilized propulsion system of the underwater vehicle during their operation, and add energy consumption constraints to the ant colony algorithm. By establishing a grid-based environment map, we simulate and analyze the differences in results under the two optimization methods. The simulation results show that although the path length and the number of turning points under the energy consumption constraint are slightly higher than those under the shortest path constraint, but the energy consumption level is decreased by 22% to 24%, which is more conducive to the navigation of underwater vehicles. Since the buoyancy regulation system accounts for a large proportion of energy consumption, it is necessary to optimize the buoyancy regulation system into a dual-loop system consisting of the surface circuit and the underwater circuit, in order to avoid the problem of inconsistent oiling efficiency points of the initial single-pump design at different depths. The experiment shows that the energy consumption level and the maximum current of the dual-circuit buoyancy regulation system on both the surface and underwater are significantly improved, and the energy consumption of the optimized buoyancy regulation system is decreased by 63% to 65.2%, which reduces the risk of damage to the internal circuit components of the underwater vehicle.

Variable displacement hydraulic motors can achieve adaptive flow control based on load changes, featuring high efficiency, fast response and low power consumption. However, they also face key technical issues such as a large starting dead zone, low-speed oscillation and significant high pressure internal leakage. To improve the control accuracy and robustness of the variable displacement PDU, we propose a control law design method that combines PID control with feedforward anti-interference. By Simulink modeling simulation and test verification, the proposed control law algorithm can significantly improve dynamic speed response characteristics of the PDU. The test results demonstrate that under the hydraulic condition of 35 MPa and the aerodynamic load of 240 N·m, the flow consumed by the variable displacement PDU is 60.1% lower than that of the same fixed displacement PDU, while the driving efficiency is increased by 100.8% and the total power consumption is reduced by 17.34 kW.

As an important part of the thrust reverser system, the hydraulic thrust reverser actuation system is used to control the deployment and stowage of the thrust reverser device, and the thrust reverser force is generated during the plane to reduce the speed of aircraft. In order to investigate the movement characteristics of system, the experimental method is adopted to conduct experimental measurement research on the development of the hydraulic thrust reverser actuation system at different operating conditions, and the performance changes of different external forces and environmental temperatures. Based on the experimental boundary conditions, the hydraulic thrust reverser actuation system is carried out numerical simulation research, including simulation tool selection, model establishment, parameter settings, etc. The results of the study show that at the design conditions, the hydraulic thrust reverser actuation system can be deployed within 2 s and stowed within 3 s. At the end of the movement, the fierce impact effect of the operator can be weakened, and the speed is reduced to less than 150 mm/s. Different external forces seriously affect the synchronization exercise accuracy of deployment and stowage. The greater the external force, the worse the synchronous exercise accuracy. When the oil pressure and temperature are changed, the system movement performance deviates from the design point. And increasing pressure and temperature can effectively shorten the running time. In addition, except for different external forces (greater than 1500 N), the simulation and experiment have a good consistency, and this simulated model can be used as an effective tool for system operation evaluation.

In the full authority digital control system of aero-engines, the hydraulic servo actuator serves as the core executive mechanism for thrust vector control. It is dedicated to regulating the direction, magnitude, and dynamic characteristics of thrust. To enhance the mission reliability of the engine, an innovative integrated high-speed solenoid valve is adopted to construct a pulse width modulation balanced duty cycle control architecture. This architecture not only improves the system compatibility and anti-contamination capability but also achieves the design goal of low cost. However, the stability of the system is compromised due to the nonlinear output control of the high-speed solenoid valve. To address this issue, an in-depth investigation into the pulse width modulation balanced duty cycle control strategy of the high-speed solenoid valve is conducted to enhance system compatibility and mitigate the influence of hydraulic characteristic variations on the system. Utilizing the AMESim modeling and simulation platform, a double closed-loop hydraulic actuation system model based on high-speed solenoid valve control is developed. Based on this system model, simulations and analysis of system stability are performed under the 50%±5% pulse width modulation balanced duty cycle signal condition. The simulation results indicate that increasing hydraulic damping can effectively reduce the fluctuations in the system caused by nonlinear outputs; appropriately setting throttling can lessen flow regulation gain, thereby diminishing the impact of external factor variations on the system. These research findings provide significant theoretical foundations and technical support for product development and prototype creation.

To address the issues of low efficiency in calculating unbalanced forces on pneumatic control valving element and the difficulty in accurately predicting dynamic characteristics. Applying a physics-informed neural network to calculations of valving element unbalanced force is proposed. By analyzing the working principle of pneumatic control valves and the generating mechanism of valving element unbalanced forces, the neural network model integrating fundamental fluid mechanics equations and simulation data is constructed. This enables efficient prediction of valving element unbalanced forces, with the method's validity ultimately verified through CFD simulations. Research findings demonstrate that the physics-informed neural network predictions closely match CFD simulations, with computation time reduced to under 10 seconds. The maximum error (<8%) occurs at the valve's critical closing point. This approach overcomes the high computational costs of traditional methods, enabling real-time, precise prediction of dynamic unbalanced forces. It provides a novel technical pathway for intelligent design and dynamic characteristic optimization of pneumatic control valves.

Setting an embedded weapon bay is an effective means of avoiding radar detection for modern stealth warplanes. In the allowable time and flow range, in order to ensure that the weapons bay doors are in place, a system model is established in AMESim, and closed loop control of the system is achieved by a three loop control strategy. The effects of design parameters such as displacement tolerance, low speed range on the dynamic characteristics of the system are analyzed. After analysis, if the displacement tolerance is too large, it will cause system jitter on the premise of ensuring the system in place time; if the displacement tolerance is too small or the low speed range is too long, it will result in excessive system flow consumption. If the low speed range is too short, it can make the system's end speed excessive. Finally, the control strategy and design parameters, such as displacement tolerance and low rotation speed range, are verified by the material object of weapon bay door drive system. The results show that the design of the three loop control strategy is reasonable, and the system can operate stably by the choose of suitable design parameters. At the same time, the theory and method involved in this study can also be extended to hydraulic actuators and hydraulic pumps and other fields, with important practical significance.

To improve the friction performance of the valve plate pair in axial piston pumps under high-speed and high-pressure conditions, triangular, square, and cylindrical surface textures are constructed on the valve plate. A one-way fluid-structure interaction simulation model of the piston pump is establishedy using ANSYS. The effects of different rotational speeds and pressures on the oil film load-carrying capacity, friction coefficient, and structural deformation are analyzed and compared between textured and non-textured valve plates under full film lubrication. Results show that, compared to non-textured valve plate pair, the textured pair exhibits increases oil film load-carrying capacity and reduced friction coefficient as speed and pressure rise. However, solid domain deformation increases. Within a broad range of high-speeds and high pressures, the triangular texture demonstrates superior comprehensive performance compared to square, cylindrical, and non-textured surface. Under high-speed and high-pressure boundary conditions, the oil film load-bearing capacity of the valve plate pair with triangular texture is increased by 22.51% compared to that of the non-textured surface; the friction coefficient is reduced by 18.24%; and the maximum deformation of the cylinder block and the valve plate increases by only 10.9% and 1.6%, respectively, compared to those of the non-textured surface, demonstrating significant performance advantages.

This study focuses on PTFE lip seals for aircraft fuel pumps. A three-dimensional finite element model is developed in MSC MARC software to simulate the full sequence of seal assembly, fluid pressurization, and shaft rotation. Additionally, an experimental test platform is built to measure the friction torque of PTFE lip seals. Experimental results demonstrate that at the majority of rotational speeds, the simulation error of the friction torque does not exceed 5%, validating the effectiveness of the simulation model. The simulation analysis reveals that the primary seal lip experiences much higher contact stress than the secondary lip and plays a dominant role in sealing performance. The peak stress consistently occurs at the edge region of the lip contact zone and remains relatively stable during rotation. As the inclination angle of the primary seal lip increases, the maximum contact stress rises by 15.37%, while the contact width varies slightly within 8.94%. When the thickness of the primary seal lip increases from 0.5 mm to 0.9 mm, the maximum contact stress surges by 345.65%, whereas the contact width shows negligible variation. Furthermore, interference between the primary and secondary seal lips after assembly can be effectively avoided when the primary seal lip thickness is less than 0.6 mm.

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 flap system's rapid response is prone to speed loop overshoot, which degrades system stability and shortens equipment life. To address this, a composite control method featuring “speed loop adaptive control and position loop smooth planning” is proposed. Firstly, a dynamic model of the flap system is constructed through an in-depth analysis of its components' working principles. Secondly, a theoretical mathematical model of the system under a loading environment is established to accurately characterize its dynamic behavior under actual operating conditions. Finally, to ensure stability and reduce start-up overshoot, the dynamic performance of the composite method is compared with traditional PID control in the speed loop. Based on the system performance specifications, the position loop performance of the composite control method is comprehensively verified under both no-load and load conditions. Simulation results demonstrate that, compared to the traditional PID control, the proposed method effectively reduces start-up overshoot, suppresses oscillation, and enhances system stability while meeting the system's rapidity requirements.

Rope-hook recovery is a primary retrieval method for small fixed-wing unmanned aerial vehicles. To enhance its applicability, a dedicated recovery device is developed, incorporating a combined energy absorption mechanism of “recovery rope and elastic deformation”. The dynamic equations of the system are derived using the Lagrange method and an equivalent spring-damper model is established. Using the MATLAB platform, the response characteristics are solved. And key parameters of the recovery rope are prioritized based on static tensile tests. Furthermore, finite element analysis is carried out on all components of the device, and the method for calculating the overturning load is elaborated. The development process and key design aspects provide practical guidance for the engineering development of similar devices. Finally, recovery tests are conducted in ascending order of energy levels to validate the device's performance. The test results demonstrate that the device achieves a maximum recovery energy of 32.4 kJ (measured), exceeding the theoretical value of 28.9 kJ for certain RQ21 unmanned aerial vehicle system. The maximum recovery overload remains below 7.5 g.

To tackle the high energy consumption and control complexity in traditional electric forklift hydraulic systems, this study proposes a novel control strategy for pump-valve coordinated system. The strategy employs a linear active disturbance rejection controller to enhance dynamic performance and utilizes an improved greater cane rat algorithm for adaptive parameter optimization. Firstly, a mathematical model of the electro-hydraulic servo system is established. Then, the control strategy is designed: linear active disturbance rejection controllers are applied to both the pump and valve subsystems, and a pressure command controller is developed for coordination. Subsequently, the improved greater cane rat algorithm tunes the controller parameters. Finally, verification is conducted through a co-simulation model built in AMESim and MATLAB/Simulink. Simulation results demonstrate that the proposed strategy effectively regulates the servo valve opening and the pump's output flow and pressure. Compared with a PID-controlled system, it achieves faster response, higher accuracy, and maintains a position error within 0.003 m. Moreover, it significantly reduces throttling and overflow losses compared to traditional valve control systems, yielding an energy-saving rate of 41.78%.

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.

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 curveof main distributing valve exhibits a single-hump pattern, with the 25%~40% opening range constituting the primary hump zone.

The hydraulic breaker is a commonly used operating tool, which is installed on main machines such as excavators for crushing and demolition operations. To study the efficiency characteristics of the hydraulic system during the operation of the hydraulic breaker, modeling, simulation, and experimental testing are conducted on the hydraulic system of a small hydraulic breaker. Firstly, the working principle of the small hydraulic breaker is analyzed. Then, a model of the hydraulic breaker's system is established based on Simulink, and simulations are carried out. Through this, the pressure curve of the nitrogen chamber in the hydraulic breaker and the instantaneous efficiency curve of the system are obtained. In addition, experimental tests are performed on the operation of a mini-excavator with a small hydraulic breaker. The pressure signals of the nitrogen chamber of the breaker and the hydraulic system are collected, and the instantaneous efficiency and average efficiency of the breaker are derived. This research provides a reference for the study on the efficiency of hydraulic breaker system.

For high-power hydrogen fuel cell systems, a large-flow hydrogen pressure-reducing valve with a reverse-unloading tapered valve core is designed. The structural design and working principle of the product are introduced. A static mathematical model is established, and its pressure and flow characteristics are studied using AMESim software. Analysis reveales that increasing the valving element angle, reducing spring stiffness and enlarging piston area can improve the output pressure accuracy of the pressure-reducing valve. A test platform for the pressure-reducing valve is built to evaluate its static characteristics under actual operating conditions. The results demonstrate that this valve exhibits stable output pressure accuracy which is ±8.1%. The adjustment accuracy is ±0.61%, and it has large output flow rate and minimal lock-up pressure, indicating excellent operational performance. Moreover, the theoretical calculations, simulation analyses, and experimental test results show close agreement.

The digital inlet valve serves as a critical hardware foundation for implementing digital flow control technology. Targeting the design requirements of digital inlet valve, a steady-state flow force analysis and calculation are conducted for the inlet valve of emulsion pumps. Firstly, the operational principles of digital flow control technology are expounded, and the feasible operating range of the actuator for the digital inlet valve is determined. Secondly, hydrodynamic forces acting on the inlet valve spool are rigorously analyzed, with the steady-state flow force acting on the spool within the feasible operating range is calculated. Finally, the visualization analysis results of the internal flow field in the pump chamber are obtained through CFD simulation. The simulated flow force values are calculated and comparatively validated against theoretical predictions. Depending on the scheme, maintaining the inlet valve spool in normally open position at crank angles θ ∈[60°,240°] is essential for goal of digital flow control technology. Feasible operating range flow force are computed via momentum theorem-based CFD simulations. Peak steady-state flow force occurred at θ=80°, with theoretical and simulated values of 6.68 N and 6.19 N respectively. The maximum deviation between theoretical and simulated results across the entire feasible operating range is 0.57 N, which provides a fundamental basis for determining design parameters of digital inlet valve in subsequent studies.

A subsea hydraulic stepping actuator is the core equipment for flow control in deep-sea Christmas trees, and its dynamic performance directly influences the safe and stable operation of subsea production systems. To address the difficulty in accurately characterizing the subsea hydraulic stepping actuator's nonlinear dynamic response in deep-sea high-pressure and low-temperature environment, a high-precision modeling method based on the design and analysis software of subsea-control system is proposed. Using a component-based modeling concept, a simulation model of this actuator is established. It integrates the Stribeck friction model, deep-sea pressure compensation mechanism and hydraulic-mechanical coupling characteristics. Innovatively, the Gevrey function is adopted to smooth the mechanical friction link. It effectively optimizes the numerical stability and response speed of the solver. Through the parameter sensitivity analysis, typical working condition simulation and demonstration project application verification, it is verified that during the opening process of the production choke valve, the deviations of key indicators such as actuator piston displacement and oil supply pressure are all less than 2%, and the nonlinear dynamic response of the actuator can be accurately reproduced. This modeling method provides a reliable technical means for the design optimization and performance prediction of subsea hydraulic stepping actuators, and also lays a modeling technical foundation for achieving independent and controllable development of deep-sea equipment.

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.

Hydrostatic non-contact mechanical seals are widely used under high-pressure and high-speed hydraulic pump applications due to a stable liquid film, low wear and long service life. The inclination of the stationary ring breaks the symmetry of the film, shifting the pressure field, sharply increasing the leakage rate and reducing the opening force. We establish a combined hydrostatic and hydrodynamic lubrication model with the consideration of the cone angle of the rotating ring and the inclination angle of the stationary ring, and use the finite element method to compare parallel and convergent gaps. The results show that for a parallel gap without inclination, the leakage rate scales cubically with film thickness while the opening force remains nearly constant. Once the inclination is introduced, a local low-pressure region expands rapidly and the opening force drops markedly; increasing film thickness alleviates pressure nonuniformity but cannot prevent sealing performance degradation. In contrast, a convergent gap uses the cone angle convergence effect to raise load carrying capacity and partially counteract stationary ring inclination. The inclination still degrades the pressure field in the convergent gap, with weakened high-pressure regions and expanded low-pressure regions, and the opening force decreases as the inclination angle increases. Even so, the convergent gap retains higher load capacity than the parallel gap, exhibits lower sensitivity to inclination, and is less prone to local instability. These findings clarify how gap topology and film thickness govern responses to stationary ring inclination and provide guidance for structural optimization and assembly tolerance control.

As a critical component for fluid control in hydraulic systems, the proportional pressure relief valve plays a pivotal role in dynamic regulation. Investigating and optimizing its pressure drop characteristics are significant for improving system control accuracy and energy efficiency. We focus on a specific proportional relief valve. A simulation model is established using AMESim to analyze pressure drop characteristics. A multi-parameter collaborative optimization method based on experimental design and response surface methodology is proposed to balance valve port pressure drop and dynamic response. Results indicate that damping orifice diameter is the dominant factor affecting pressure drop. Reducing the diameter from 0.5 mm to 0.2 mm decreases the minimum pressure drop by 39.8%, while the maximum pressure drop changes slightly. Response surface model validation shows low sensitivity of pressure drop to half-cone angle and spring stiffness. This method effectively resolves the conflict between "low pressure drop" and "fast response" in traditional designs, providing a theoretical basis for developing high-performance proportional pressure relief valves.

To study the influence of helical spring characteristics on the sealing performance of spring-energized sealing rings under normal temperature and low-temperature low-pressure conditions, a three-dimensional cyclic symmetrical structure finite element model of such sealing ring is established. The influences of the presence of spring, as well as spring installation interference, structural stiffness, installation position and material on the sealing performance of sealing rings under low-pressure conditions of 20 ℃ and -100 ℃ are systematically studied. The results show that the energy storage spring plays a key role in sealing under low-pressure, especially zero pressure conditions. At 20 ℃ and zero pressure, when there is a spring, the maximum contact stress of the inner lip is approximately 11.0 MPa, and it is only 2.1 MPa without a spring. At -100 ℃, when there is no spring, the contact stress of the outer lip drops to 0.4 MPa, causing the seal to fail, when there is a spring, it can still maintain an effective seal at 1.1 MPa. The installation interference has a significant impact on the contact force. The greater the spring stiffness, the wider the range of interference available. The two installation forms have no significant impact on the sealing performance. With the increase of radial stiffness, the contact stress at the lip of the polytetrafluoroethylene sheath shows an increasing trend. Under the working conditions of -100 ℃ and 0.1 MPa, the contact stress of the inner and outer lips of the 3J21 elastic alloy spring is approximately 67% and 134% higher than that of the 304 stainless steel spring respectively, and its leakage suppression effect on the outer sealing surface is particularly significant.

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.