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 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.

The variable regulator is an important control component of load-sensing variable displacement piston pump. Its function is to adjust the displacement of the piston pump based on the difference between the outlet pressure and the load pressure, thereby meeting the flow requirements of actual conditions and reducing power losses. To efficiently and conveniently design a load-sensing variable regulator that meets the static and dynamic characteristics of the system while shortening the development cycle as much as possible, a hardware-in-the-loop testing system for load-sensing variable regulators is established by combining AMESim and LabVIEW. Validation tests are conducted on the working characteristics of the load-sensing variable regulator. The tests verify the feasibility of the hardware-in-the-loop testing scheme and the accuracy of the simulation of the static and dynamic control characteristics of the load-sensing system. The study provides valuable engineering insights for hardware-in-the-loop testing of hydraulic components.

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 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.

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.

In lubricating system filtration, contaminating particles with sizes approaching the filter mesh aperture may exhibit blocking phenomenon. To investigate backwashing characteristics, a geometric model of tightly woven metal wire mesh is constructed, blocking and backwashing processes of contaminating particles with varying materials and shapes are simulated. The thesis analyzes single-particle retention in the filter mesh and pressure-driven dislodgement, evaluating material/shape effects on critical dislodgement pressure. Results demonstrate that identical-shaped particles of different materials generate distinct blocking stresses, equivalent elastic strains, and critical dislodgement pressures, while same-material particles with different shapes exhibit varied mechanical responses. Blocking-induced equivalent elastic strains shows positive correlation with stress, and increases particle hardness elevates filter mesh stress and equivalent elastic strains, which consequently raises required critical dislodgement pressure and intensifies backwashing difficulty.

To address the dynamic performance degradation of system caused by component's performance deterioration in control systems, we propose a design method for system's transfer function modeling and a compensation controller based on degradation state estimation. Firstly, a nonlinear Wiener process incorporating measurement errors is employed to describe the relationship between component measurements and the true degradation state. The Kalman filtering method is then applied to estimate the true degradation state. Secondly, the estimated degradation state is integrated into the control system model. Targeting the output of the non-degraded system as the control objective, we derive the transfer function of a compensator to counteract the impact of component degradation on system dynamic performance. Finally, the validation based on a pump-controlled electro-hydraulic servo system demonstrates that after compensation, the rise time, settling time and peak time of the degraded system are increased by only 1.79%, 2.30% and 2.15%, respectively, compared to the dynamic performance indices of the non-degraded system, while the overshoot is reduced by only 1.15%. This method effectively enhances the dynamic performance of systems experiencing component degradation, enabling the step response output of the degraded system to accurately track that of the non-degraded system.

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.

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.

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.

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.