Most domestic diesel generator sets in China use mechanical-hydraulic governors for throttle control. Analyzing the operating principles and characteristics of this mature and reliable governor provides critical reference for domestic independent design initiatives. This study constructs component models such as centrifugal flyweight of the governor in AMESim, and develops a diesel generator set dynamical model in Simulink based on the engine load, throttle opening and speed characteristics. Through AMESim/Simulink co-simulation, the study investigates the dynamic behavior of hydraulic buffer compensation in closed-loop speed regulation and its impact on performance. The results indicate that adding hydraulic buffer compensation effectively reduces both the settling time and speed oscillations of diesel generator sets under diesel generators load variations. This design concept not only applies to mechanical-hydraulic governors but also provides critical insights for the autonomous development of digital electronic governors.

Due to the inherent structure of hydraulic transformer, its piston pairs are more complex during operation. In order to prevent the problems such as jamming or low volumetric efficiency during the operation of hydraulic transformers, the lubrication characteristics of the piston pair for hydraulic transformer are studied. The transformer ratio of hydraulic transformer and the Reynolds equation of piston pair are derived and solved by using ANSYS. The results show that the oil film pressure, leakage and axial viscous friction of piston pair are complex due to the influence of hydraulic transformer structure, which are related to the piston movement speed, piston cavity pressure and rotation speed. Through the orthogonal test, it is found that the main factors affecting the lubrication characteristics of piston pair are fit clearance and A-port pressure.

By analyzing several methods for characterizing filtration rating, the importance of filtration rating in evaluating the performance of hydraulic filters is pointed out. Based on the commonly used filtration rating of hydraulic filters, several nominal opening corresponding to them are selected for experimental research on fully wrapped dense woven wire cloth with slanting weave. The research results indicate that the dense woven wire cloth can be characterized by the mean flow pore size and corresponding particle size under filtering ratio β_x(c) 100. Through fitting analysis, it is confirmed that there is a good correlation among the nominal opening, the mean flow pore size and corresponding particle size under filtering ratio β_x(c) 100 of the dense woven wire cloth. Using fitting equations to directly derive the mean flow pore size or corresponding particle size of the dense woven wire cloth through the nominal opening. The research results can provide useful references for design and selection of metal wire weaving dense woven wire cloth hydraulic filters.

To address the dynamic and efficient supply-demand matching between fully-mechanized-mining-equipment and fluid supply systems in fully mechanized coal mining faces, this study proposes a digital flow control technology to achieve on-demand fluid supply in pump stations. Firstly, the working principle of digital flow control technology is elaborated, and an actuator work strategy compatible with the flow distribution characteristics of a 5-plunger pump is formulated. Secondly, digital flow control schemes are systematically summarized. Finally, the optimal control scheme is selected, and its reliability is verified through simulation. The results indicate that the 5-plunger emulsion pump has 7 possible digital flow control schemes, with the number of engaged actuators exhibiting a negative correlation with flow pulsation rates. Depending on the scheme, the control intervals are either [0, π] or [0, 3π/5), enabling a flow adjustment range of 38%~100%. This approach not only meets on-demand fluid supply requirements but also minimizes flow pulsation, providing valuable insights for intelligent constant-pressure liquid supply technologies in fully-mechanized-mining-equipment.

The pilot solenoid valve regulates the internal oil flow of the shock absorber by controlling the main valve pressure, thereby affecting the damping force. A reasonable design of pressure-flow characteristics can broaden the range of damping adjustment to meet the needs of different working conditions. In this study, the pressure-flow characteristics of the pilot solenoid valve for an automobile continuous damping control shock absorber are optimized. Firstly, the hydrodynamic model and steady state force model of the oil flowing through each damping hole are established based on the fluid dynamics theory. The relationship between the electromagnetic force and the input current is determined with the electromagnetic magnetic circuit model of electromagnetic theory, and then the hydraulic simulation model is established. Subsequently, with the help of the solenoid valve performance test bench, experimental comparisons are carried out to verify the accuracy of the simulation model. Finally, the key structural parameters affecting the pressure-flow characteristics of the pilot solenoid valve were analysed to determine their importance using full factorial analysis of experimental design, and the key dimensions were optimised using a genetic algorithm, with the optimisation effect improved by 10.14%.

The vibration and noise of the bent-axis axial piston motor is investigated by a combination of test and simulation. Firstly, the vibration and noise excitation sources of piston motor are investigated and analyzed according to its structural composition and working principle. Secondly, the modal analysis and harmonic response analysis and calculations are carried out by using the simulation software to get the intrinsic frequency of the piston motor and the frequency curves of vibration-related parameters, and the accuracy of the simulation model and test method is verified with vibration tests. Finally, the noise radiation analysis and simulation of the piston motor is carried out by acoustic-vibration coupling method, and the reasonableness of the simulation results is verified with noise test. It is concluded that the peak frequencies of vibration and noise tests are around 700 Hz, which is highly consistent with the theoretical value of excitation frequency 700 Hz, and also close to the first-order intrinsic frequency 704 Hz of the piston motor shell. It proves that the piston motor system is in resonance at this frequency, and proposes optimization directions for vibration reduction and noise reduction of piston motor structure. This study reveals the main mechanism of the vibration noise of the piston motor and provides a basis for its vibration reduction and noise reduction.

To solve the problems of poor response speed, insufficient dynamic positional stiffness, and low system stability in mechanical hydraulic servo devices for marine controllable pitch propellers, a mathematical model of the servo device is established. The analysis identifies the factors affecting its performance as the geometry and number of throttle grooves, main control valve's underlap and hydraulic cylinder's diameter. Based on the AMESim simulation platform, the quantitative relationships between these parameters and performance indicators are systematically investigated. The results show that K-shaped throttle grooves exhibit superior performance in both response speed and dynamic positional stiffness compared with other groove configurations. Increasing the number of throttle grooves enhances response speed and dynamic positional stiffness but degrades system stability. A larger underlap of valve improves response speed but reduces dynamic positional stiffness. Enlarging the diameter of hydraulic cylinder sacrifices response speed but improves dynamic positional stiffness and system stability. Based on a comprehensive comparison of the optimization effects brought about by different degrees of changes in influencing factors and the adaptability under different working conditions, an optimization plan is finally proposed: A combined design of six circumferentially arranged K-shaped throttle grooves with a 0.6 mm underlap and a 600 mm cylinder diameter is adopted. The verification demonstrates that the optimized device achieves a 3.94% reduction in response time, a 1.28% increase in dynamic positional stiffness and significant overall performance improvement while maintaining system stability. The research results provide an important theoretical basis for the performance optimization of hydraulic servo devices for marine controllable pitch propellers.

To address the challenge in the domestic substitution of high-pressure hydraulic pumps, this paper proposes a tandem dual-output hydraulic pump power source. By connecting a secondary pump in series to the outlet of the primary pump, the system achieves stage-by-stage pressurization, fulfilling high-pressure requirements without modifying low-performance pumps. The tandem structure significantly reduces the pressure difference across single pumps, extends their service life, and isolates load impacts through accumulators. SimulationX-based analyses on flow pulsation and energy efficiency performance reveal the following results: Under conditions of 20 MPa and 1500 r/min, the flow pulsation rate is reduced by 37% compared to single-stage gear pumps. The system energy efficiency for driving high and low-pressure load hydraulic cylinders reaches 61% when adopting the proposed tandem power source, substantial improvement over the 36% efficiency of a single-stage variable displacement axial piston pump. These findings provide innovative insights for the design of power sources in complex high-pressure hydraulic systems.

It is crucial to select appropriate control parameters to improve the motion control accuracy of the pneumatic sliding table. However, the traditional trial-and-error method is inefficient and heavily reliant on experience of parameter adjusters. Therefor, a novel improved particle swarm optimization algorithm is presented. This algorithm applies an improved Gaussian-sine chaotic mapping technique to generate initial particles so as to enrich the diversity of the population. It introduces sine disturbance and Lévy flight strategy to help particles escape local optima. Additionally, it integrates the sine-cosine algorithm and an improved slime mold algorithm to improve search accuracy. The experimental results from linear active disturbance rejection motion control tests on the pneumatic sliding table show that the proposed novel particle swarm optimization algorithm can effectively improve control accuracy. Compared with the trial and error method,it reduces the maximum steady-state error by 15.9% and 23.4% respectively when tracking sinusoidal trajectories with an amplitude of 150 mm and frequencies of 0.25 Hz and 0.5 Hz. And it reduces the maximum steady-state error by 13.5% when tracking multi frequency curves.

Aiming at the challenges of poor road conditions, complex environments, this study proposes an active vibration reduction scheme using a tractor electro-hydraulic suspension based on digital valves in order to improve stability and comfort during tractor transportation. Highly responsive digital hydraulic valves are used to adjust the speed and displacement of the implement hitch cylinder in real time to counteract vibration. Firstly, a dynamics model of tractor vibration system with suspended implements is derived. A sliding mode controller is designed, and a simulation model is developed to investigate the active vibration reduction performance under random road, sinusoidal road, and pulse road conditions. The results demonstrate that effective vibration suppression is achieved under all three road conditions. Specifically, under a 20 km/h random road excitation, the peak vertical acceleration of the tractor can be reduced by the active vibration reduction system of electro-hydraulic suspension from 2.13 m/s² to 1.01 m/s², and the root mean square value decreases from 0.84 m/s² to 0.28 m/s², achieving a 63% reduction compared to passive vibration reduction systems, which results in excellent vibration reduction.

Sticking may occur in drilling different coal rocks for a coal mine anti-impact drilling robot, and it may lead to drilling failure, which seriously affects the safety of drilling pressure relief operations, the quality and efficiency of anti-impact pressure relief hole formation. To this end, an anti-sticking electro-hydraulic control strategy is proposed for coal rock drilling system. The mechanism of sticking is analyzed based on the variation of drilling parameters during drilling, and the drilling state is judged by combining support vector machines. The electro-hydraulic control strategy of anti-sticking based on sliding mode variable structure is designed. A joint simulation model of AMESim and MATLAB/Simulink is established, and the control characteristics of the anti-sticking is analyzed. The designed anti-sticking electro-hydraulic control experimental platform is executed for verification. The results indicate that the proposed anti-sticking electro-hydraulic control strategy can effectively identify the drilling status and reduce the risk of sticking, and can improve drilling efficiency and safety under different coal rock conditions.

The aircraft landing rollout scenario is one of the critical scenes in the overall flight mission process, involving disciplines such as mechanics, fluid dynamics and aerodynamics. Using traditional system modeling approaches for this scenario is complex and cumbersome. Utilizing the Modelica unified modeling language, this study focuses on constructing component-level and system-level models for a specific aircraft's landing gear and its landing rollout scenario. Key parameters at the component-level and the braking performance of the aircraft system during the landing rollout are simulated and analyzed. A general virtual experimentation based on this model can verify the correctness and rationality of the design parameters.

Aimed at the problem that it is difficult to levelling the lifting heavy-duty automatic guided vehicle and there exists the “floating leg” issue during leveling, a four-point support heavy-duty automatic guided vehicle hydraulic leveling system is designed and a position compensation mathematical model of hydraulic leveling system is established. The model consists of a highest-point chasing leveling mathematical model and a position compensation mathematical model. The highest-point chasing leveling model is used to execute the leveling process, and the position compensation mathematical model is used to solve the “floating leg” issue in the process. Based on the designed model, the conventional fuzzy PID control strategy is improved, and an enhanced fuzzy PID controller considering floating legs is proposed. A Simulink-AMESim co-simulation platform is built to validate the proposed strategy. The results show that compared with the conventional fuzzy PID method, the improved controller reduces the maximum tracking error of the lowest-point hydraulic cylinder by 86.59%, effectively alleviating the “floating leg” phenomenon.

Multi-degree-of-freedom hydraulic manipulators prominently exhibit strong joint coupling characteristics and large dynamic model errors, which leads to degraded control performance. To achieve high-precision pose control, a dual robust integral of sign error controller with prescribed performance function is proposed. Based on the prescribed performance function, the transformed error signal is obtained, simultaneously limiting the rate and range of error convergence. Combined with the backstepping method, a dual robust integral of sign error controller is designed to suppress both matched and unmatched uncertainties, enhancing the robustness of system. The semi-global stability of the system and the boundedness of all signals are proved by Lyapunov stability theory. The results show that the proposed control strategy significantly improves the joint tracking accuracy and error convergence rate of multi-degree-of-freedom hydraulic manipulators, fully verifying the effectiveness of this control strategy.