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.

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

The lubrication performance of the slipper pair in aviation fuel piston pumps under extreme operating conditions such as high temperature, high pressure, high rotational speed and low-viscosity medium directly affects the service life and reliability of the pump. We investigate the mixed hydrostatic-hydrodynamic lubrication mechanism to reduce frictional losses. A transient lubrication model based on the hydrodynamic effect is proposed. We derive an asymmetric oil-film thickness expression, and solve the Reynolds equation and dynamic force-balance equations using finite volume and Newton-Raphson methods. This approach reconstructs oil film squeeze and tilt behaviors. We analyze the effects of pressure and rotational speed on film thickness, the maximum value of oil film pressure and frictional power loss. The results show that the squeeze effect dominates in the discharge-oil region, and the hydrodynamic effect dominates in the low-pressure region. In the transition region, film thickness and the degree of overturning are minimal. Meanwhile, significant pressure fluctuation occurs, with the pressure peak reaching 19.5 MPa. Rotational speed has the most significant impact on power loss. Increasing speed from 1500 r/min to 3500 r/min raises peak power loss by 50.4 W. Consequently, high rotational speed primarily causes aggravated slipper overturning and reduced mechanical efficiency.

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.

To address the difficulty in achieving consistent damping force before and after the large-and-small inerter switching of a switching-type inerter-based suspension under high-impact driving conditions, a technical scheme featuring a poppet valve in parallel with a long straight hose is proposed. By adjusting the throttling area of the poppet valve, its damping force is made to follow in real-time in the long straight hose. Through analysis of the pressure differential-flow rate characteristics for both the poppet valve and the long straight hose, the required real-time valving element displacement of the poppet valve for achieving consistent damping force between the poppet valve flow path and the long straight hose flow path is obtained. A following strategy for the poppet valve to follow the damping force of the long straight hose is constructed, and its key parameters are optimized. Simulations are conducted using AMESim for both sinusoidal high-impact conditions and actual high-impact driving conditions. The suspension's velocity-damping force characteristic curves are obtained under the sinusoidal high-impact condition, and the suspension's damping force versus time curves are obtained under the actual high-impact driving condition. Experimental validation under the sinusoidal high-impact condition is conducted. The results indicate that the damping force error between the poppet valve flow path and the long straight hose flow path is reduced from 29.36% (with a fixed orifice) to 5.85% under the sinusoidal high-impact condition, and from 16.15% to 2.22% under the actual high-impact driving condition.

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.

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%.

Binder jetting additive manufacturing technology provides new ideas for the design of hydraulic flow channel due to its unique advantage in manufacturing complex internal structures. Aiming at the problem of excessive pressure loss in hydraulic flow channel caused by traditional subtractive manufacturing, we focus on typical two-way channel and T-shaped three-way channel. By using finite element simulation and topology optimization methods, with the minimization of pressure loss as the optimization objective, the optimal channel topologies is obtained, followed by printing and experimental validation. The results show that when the inlet velocity is 6 m/s, the pressure loss of the optimized two-way flow channel is reduced by approximately 50%. For the T-shaped three-way flow channel, the pressure loss is reduced by about 59.6% under the flow splitting condition and 67% under the flow combining condition, showing a significant optimization effect. Moreover, the experimental data are consistent with the simulation results. The research results provide a reference for the development of lightweight hydraulic flow channel with low pressure loss.

The internal pre-stress generated by the interference fit connection is studied, focusing on the vibration characteristics of the separable armature component of the electro-hydraulic servo valve under interference fit conditions. Firstly, a dynamic model under pre-stress conditions is established based on the structure model of the separable armature component. A three-dimensional simulation model is created using the finite element analysis method, and modal analysis of the armature component is performed and compared using four different simulation methods. To verify the reliability of the simulation results, the natural frequencies of the separable armature component are determined by applying a sweep frequency signal from an electric actuator to a torque motor, which validated the feasibility of the simulation analysis. Based on this, the impact of the interference fit on the vibration characteristics of the separable armature component is studied. The results show that the interference fit affects the modes of the armature component. As the interference fit increases, the natural frequencies corresponding to the first mode, third mode, and fourth mode decrease with increasing interference fit, but the change is minimal. In contrast, the natural frequency corresponding to the second mode gradually decrease. These research findings provide technical support for the structural optimization design of electro-hydraulic servo valves.

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.

To address the issues of low working efficiency, significant worktable vibration, and poor energy utilization efficiency in conventional hydraulic presses, a novel high-low pressure servo pump-driven high-speed hydraulic system is proposed, along with a systematic design theory for high-speed and high-precision hydraulic systems. To investigate the static and dynamic characteristics of key hydraulic components—specifically the bladder accumulator and cartridge valve—mathematical and simulation models are developed, and their optimal operating parameters are determined through comprehensive analysis. Based on the operational principles of the high-low pressure servo pump system and the established component models, an AMESim physical simulation model and an experimental platform for the YGM315 high-speed hydraulic press are constructed. The working performance and energy distribution characteristics of the proposed high-speed system and the conventional system are systematically analyzed and compared. Furthermore, guided by the high-speed high-precision hydraulic system design theory, a parametric design software for the hydraulic system of high-speed hydraulic presses is developed. Simulation and experimental results demonstrate that, compared to the traditional system with a cycle time of 9.7 seconds, the new high-speed hydraulic press achieves a reduced cycle time of 4.5 seconds, thereby doubling the operational efficiency from 6 cycles per minute to 12 cycles per minute. Additionally, during the transition from fast approach to working feed, the slider vibration amplitude is reduced by 70%. In a single operation cycle, the total energy input is decreased by 35.6 kJ, and the energy utilization efficiency is improved by nearly 10%.

Based on the dynamic equilibrium mechanism of hydraulic system contamination control, this paper explores the design modeling method and design implementation approach for the filtration ratio of hydraulic filter elements. It establishes a design calculation model with initial contamination level, contamination generation rate, required contamination level and working flow as the main variables. Aiming at the technical principle of hydraulic system contamination control balance, it advocates constructing a verification system for contamination control dynamic balance test verification around the concept of equilibrium cleanliness level, elaborates on the test processes and procedures of contamination level “from high to low” and “from low to high”, and clearly lists the evaluation principles for the correctness and adaptability of filtration ratio design, providing theoretical support and guidance for the scientific and reasonable design of the filtration ratio of hydraulic filter elements.

To mitigate the impact of shock forces on the launch frame and ammunition box during the firing process, an electro-hydraulic servo system for ammunition box sliding, based on a hydrostatic actuator, is proposed. The system configuration, operational modes, and working principles of the electro-hydraulic follow-up system for container sliding are described. A hydraulic circuit model of the system is established, and the influences of structural parameters such as system pipeline length, pipeline diameter, and orifice diameter on performance metrics (including follow-up time, reset time, and contact impact force) are investigated. The results indicate that the orifice diameter affects the contact force between the ammunition box and the baffle. As the size of the orifice diameter decreases, the contact force reduces correspondingly, while the follow-up time increases significantly. When the orifice diameter increases to 3.6 mm, the contact force exhibits approximately 20% oscillation, and the reset time of the ammunition box decreases. Therefore, within the structure of the follow-up container sliding system, the orifice diameter can be adjusted according to the requirements of rocket launch to achieve the tailored follow-up characteristics during the launcher's operation.

As a new type of propulsion system, the water ramjet engine has broad application prospects in fields such as underwater weapons and unmanned underwater vehicles. To ensure a stable water-to-fuel ratio and accurately obtain the performance parameters of water ramjet engines, a ground direct-connect test system for water ramjet engines with axial water intake is designed. By employing axial plunger pump pressurization and pneumatic three-way valve technology for mainline bypass switching, stable flow output from the water supply system is achieved. During testing, it is observed that when the engine ignits, the flow rate of the water supply system decreases as the back pressure in the engine's afterburner chamber increases. The operating principles of the plunger pump and the mechanisms of flow leakage are analyzed. The water supply system piping is modeled by using AMESim software. The reliability of the simulation model is proved by experimental data, which confirms the primary cause of flow loss during testing is internal leakage within the plunger pump. A compensation strategy for flow loss is proposed and validated through testing, which provides valuable insights for future experimental work.