In March 2026, Academician JIAO Zongxia, a member of the Chinese Academy of Engineering, a professor at the School of Automation Science and Electrical Engineering at Beihang University, and a leading expert in airborne electromechanical systems and flight control systems, was invited to deliver a distinguished presentation titled“Discussion on Future Development of Airborne Electromechanical Systems” at the 14th National Conference on Fluid Power Transmission and Control held in Wuhan, Hubei Province. The report begins with an overview of aircraft composition and the positioning of airborne systems, highlighting the core role of electromechanical systems in aircraft energy flow, actuation and support functions. It then focuses on three major technological threads of high-temperature and high-pressure hydraulics, multi-electrification and intelligence, and analyzes the new requirements imposed by next-generation aviation platforms on power density, reliability, maintainability and intelligent control capabilities. Finally, from the perspective of the integration of “energy-information-control”, the report offers forward-looking insights into the development trends of airborne systems in the contexts of green aviation, unmanned operations, swarm cooperation, and extreme-environment applications. The following text has been transcribed and edited from Academician JIAO's lecture.

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.

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

The 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.

Piezoelectric ceramics are functional materials that convert electrical energy into mechanical energy, and vice versa. Piezoelectric proportional flow valves, driven by piezoelectric bimorphs, offer advantages such as fast response, low power consumption and high precision. However, the low output force of piezoelectric bimorphs limits their application in high-flow applications. To improve the output flow rate of the piezoelectric bimorph-driven proportional valve, we use ANSYS and COMSOL software to create three-dimensional and two-dimensional axisymmetric models of the piezoelectric valve and bimorph. The flow field characteristics of the valve and the fluid-structure coupling behavior of the piezoelectric element are analyzed. The effects of inlet and outlet positions, valve opening and chamber pressure on the output flow rate are also explored. The relationship between the force at the end of the piezoelectric bimorph and the output flow rate is studied, and its performance is compared with existing piezoelectric proportional valves of the same type. The results show that the optimized parameters significantly improve the valve's output flow rate. When the valve chamber's inlet pressure reaches 0.5 MPa (with an outlet radius of 1.1 mm), the output flow rate approaches 160 L/min, while the force on the free end of the piezoelectric bimorph is only 0.9 N. It provides guidance for designing nozzle-baffle pneumatic piezoelectric proportional valves and is expected to expand their application range.

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.

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.

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 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 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.

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.

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.

The stator surface roughness significantly alters the blade wall turbulence structure of the torque converter, thereby affecting its operational performance. Therefore, studying the influence of stator surface roughness on flow field evolution holds important research significance and application value. Considering manufacturing constraints, several groups of stator blade surface roughness levels are selected. Based on CFD, the internal flow field of the torque converter is numerically simulated using the SST k-ω turbulence model, and the three-dimensional vortex structures under different stator surface roughness levels are comparatively analyzed. The results indicate that: the variation in stator surface roughness significantly affects its blade wall turbulence structure. As the roughness increases, the area of the high-velocity region on the blade suction side at the inlets of the stator, pump, and turbine gradually shrinks, the velocity magnitude drops significantly, and the overall vortex system becomes more chaotic. Under stall conditions, with the progressive increase in stator blade surface roughness, the error between the torque converter's torque ratio and the experimental value decrease by approximately 2.7%, 3.6% and 1.24%, respectively, compared to the smooth blade. The pump torque coefficient decreased by approximately 1.6%, 2% and 4.45%, respectively. The research results can provide certain technical guidance for the flow field analysis and blade manufacturing of torque converters.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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 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.

In grain storage management, the curved surface structure of silo walls imposes stringent demands on the adhesion performance of wall-climbing robots. These robots must possess sufficient flexibility to adapt to curved surfaces while maintaining adequate rigidity to ensure stable support. We find that when a rigid suction cup is employed on walls with varying curvature, the limited deformation capacity of the suction cup body causes the sponge to adopt a “saddle-shaped” deformation during adhesion, which significantly diminishes the adhesion performance. To address this issue, we optimize the rigid suction cup structure, leading to the design of a semi-rigid suction cup with distributed rigid elements. The adhesion force experiments on various simulated substrates reveal that the rigid suction cup exhibit forces of 205.49 N, 307.56 N and 360.25 N on simulated substrates with curvature radii of 100 mm, 200 mm and 400 mm, respectively. In contrast, the semi-rigid suction cup exhibit slight fluctuations in adhesion force across different curved surfaces, yet maintain a stable overall value around 420 N. This solution achieves a significant enhancement in adhesion performance on complex curved surfaces, effectively reducing the risk of detachment during robot operation, which establishes a reliable foundation for expanding the application of wall-climbing robots in areas such as silos.

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.

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.

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.

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%.

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 a dual-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.

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 address the complex fault characteristics and low fault diagnosis accuracy of directional-control valves and hydraulic cylinders in hydraulic systems, a hybrid kernel support vector machine algorithm that combines a linear kernel and a Gaussian kernel is proposed. This algorithm can significantly enhance the classification capability of support vector machine for complex fault data. On this basis, the hybrid kernel support vector machine algorithm combines particle swarm optimization with a one-vs-one multi-classification strategy, enabling the hybrid kernel support vector machine algorithm to perform parameter optimization and multi-classification. To validate the algorithm's effectiveness, a fault experimental setup for directional-control valves and hydraulic cylinders is established to collect fault flow signal data. The data is then preprocessed through time-domain feature extraction and principal component analysis. Subsequently, the preprocessed data is input into the improved fault diagnosis model for training and validation. The classification results show that this method achieves an accuracy of 97.11% in the fault diagnosis of directional-control valves and hydraulic cylinders. Compared with other fault diagnosis models, this model demonstrates higher fault diagnosis accuracy and superior classification performance.

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.

Aimed at the scientific challenges in laboratory shock testing for deep sea vessel heavy long tubular components, a fully hydraulical shock testing apparatus based on hydropneumatic spring is developed. Firstly, fundamental principals and dynamic models of the shock response are established. The stored energy during the thermodynamic adiabatic process of the accumulator is expressed using the pressure ratio, and theoretical formulas for the natural frequency and acceleration are derived. Secondly, a simulation analysis is conducted on the feasibility of the shock testing principle with AMESim, revealing the influence laws of loading pressure, oil unloading pipeline diameter and accumulator precharge pressure on the stored energy and peak acceleration. The results show that peak acceleration increases with both higher loading pressure and larger oil unloading pipeline diameter; at three loading pressures of 5, 10 and 15 MPa, the variation trends of the stored energy and the peak acceleration with the precharge pressure exhibit the characteristics of increasing, increasing first and then decreasing and decreasing respectively.

The gas volume regulation of compressor is greatly affected by complex working conditions, and single fault identification cannot guarantee the accuracy of abnormal identification. In order to further improve the precision of compressor gas volume control, a self-healing control method of compressor gas volume regulation oriented to fault anomaly recognition is designed. Based on the analysis of the electro-hydraulic actuator system, the self-healing control strategy of gas volume regulation is given. A stepless gas coupling control model is established to eliminate the fault problem by actively controlling the load, and to ensure that the gas regulating system can complete the goal of online self-healing under the unstable condition. The results show that the error of network training results is less than 2% after adding two levels of pressure, and the ideal prediction target is reached. The self-healing control curve of the system is in good agreement with the simulation results, and the simulation process meets the requirements. The first-stage actuator is in a relatively constant vibration phase, and the stable load can be obtained by judging the first-stage adjustment process. The research can be applied to other fields of mechanical transmission fault diagnosis and has promotional value.

Axial piston pumps are the core power sources in aerospace equipment. The cylinder block is the most critical rotating component, and its tilt angle often responds to internal faults earlier than external signals such as pressure and vibration. However, due to the enclosed pump structure, the cylinder block tilt angle cannot be measured directly. It is therefore a key unobservable variable for reliability assessment and early risk identification. To address this issue, we propose a physics-informed neural network that incorporates cylinder block tilting dynamics. A moment-balance model is established by considering the clamping force, hydrodynamic film supporting force, and residual supporting force, and is embedded in the loss function as a physical constraint. By suppressing error amplification in weak-signal computation, the proposed physics-informed neural network achieves good generalization under multiple operating conditions and health states. Compared with the model without physical constraints, it reduces the average error by 17% while maintaining high prediction accuracy, with errors bounded within 5.71%. The proposed method provides an interpretable estimation of internal states in axial piston pumps and offers a reliable technical pathway for health monitoring, risk identification, and maintenance decision-making.