Dynamic seals in hydraulic slide valves play a crucial role in reducing oil leakage. However, their sealing performance is significantly influenced by environmental temperature, medium temperature and oil pressure, which alter the seal clearance during operation. A finite element analysis model is developed to analyze the combined sealing structures commonly used in slide valves. The model is used to evaluate the effects of varying environmental and medium temperatures, as well as pressure conditions on the clearance and friction behavior of dynamic seals. Based on the Stribeck curve, a mathematical expression describing the relationship between seal clearance and the friction coefficient is introduced. Experimental validation confirmed the accuracy of the theoretical model. The results indicate that the gap between the fluoroplastic sealing ring and the valve sleeve decreases with increasing temperature, accompanied by a corresponding change in the dynamic friction coefficient. Furthermore, both the theoretical analysis and experimental data reveal that the friction force of the dynamic clearance seal increases with temperature.

A new configuration of plate pilot pressure control for two-stage flow distribution hydrostatic-balanced high-pressure radial piston motor is proposed to address the problems of the large lateral forces on the piston pair lead to large transmission shocks at start/stop moments, serious leakage of the flow distribution and piston gap and low volumetric efficiency of traditional radial piston motors under high-pressure working conditions. This new model adopts composite pistons assemblies and pilot pressure control two-stage flow distribution method to achieve high-pressure power oil circuit sealing and high-efficiency flow distribution. In addition, the hydraulic floating support structure is adopted for the pilot stage flow distributor to compensate for mechanical wear and improve the reliability of long-time continuous operation. Based on AMESim, the dynamic simulation model of the whole motor is established. The thesis analyzes the correspondence between motion of single piston and its distribution valve, the influence of diameter of damping hole of distribution valve, the working pressure and main stage supply flow rate on the volumetric efficiency of the motor, and also analyzes the output characteristics of the motor with different transmission structures. The simulation results show that the motor has a volumetric efficiency of 89.74% at high pressure of 35 MPa. The pulsation rate of the output speed is reduced by 60% compared with that of the crankshaft linkage motor. It also has good low-speed stability and wide load adaptability. The results show a theoretical basis for the design and optimization of the high-pressure hydrostatic balance radial piston motor prototype is provided.

As the core control component in hydraulic systems, the three-stage electro-hydraulic servo valve has problems such as large energy loss at the valve port and nonlinear flow control in practical applications. In response to these issues, this study uses flow field simulation analysis software to establish a three-dimensional mesh simulation model of the main valve of a certain three-stage electro-hydraulic servo valve. By simulating the internal flow field of the main valve, the velocity, pressure and turbulent energy dissipation rate distribution characteristics of the fluid inside the valve cavity under different opening degrees of the main spool are analyzed. The simulation results show that under the condition of a valve port pressure difference of 7 MPa, as the opening degree of the main valve increases, the fluid flow velocity at the valve port significantly increases, and the maximum flow velocity always appear in the valve port area. At the same time, it is found that the fluid would generate strong vortices at the throttle and sudden changes in flow direction, leading to significant energy dissipation phenomena. In addition, the flow coefficient of the valve port shows a non-linear decreasing trend with increasing opening, which directly affects the control accuracy of the valve. The research results reveal the energy loss mechanism and flow control nonlinearity of the three-stage electro-hydraulic servo valve, providing important basis for its structural optimization design and control strategy improvement.

There are problems of unstable control accuracy and imperfect matching of various types of equipment in current proportional control valve drivers, which cannot meet the flexibility, rapidly and localization requirements of modern electro-hydraulic control systems a digital-analog hybrid proportional control valve driver based on the GD32F450ZKT6 control chip is developed. The designed driver integrates a main control module circuit, power amplification circuit, ADC sampling circuit, and CAN/USB communication circuits, thereby enabling the realization of multiple command signal inputs, host computer parameter configuration, and output precision control functions. A test platform is further established to conduct the performance of the hybrid proportional control valve driver. The results show that the developed driver achieves an output accuracy of less than 2% under diverse signal command inputs, incorporates comprehensive control parameter configuration capabilities, and effectively satisfies the electro-hydraulic control requirements across multiple operational scenarios.

The swashplate serves as a critical structural component for flow regulation in axial piston pumps. To investigate the fracture cause of the swashplate and propose effective improvement measures, we examine its fracture cause based on physicochemical analysis and finite element simulations results conducted using software such as ANASYS Workbench. The analysis results indicate that the swashplate fails due to high-cycle fatigue fracture, with fatigue cracks originating from the root transition area of the lower step of the trunnion. Stress concentration at this location significantly influences the initiation and propagation of fatigue cracks. With the application of a fillet treatment to the largest root of the swashplate, the stress concentration situation near the root of the step is significantly improved. The study found that machining tool marks on the surface near the root of the step substantially weakened structural strength of the swashplate. In conclusion, enhancing fillet requirements at the step root and controlling its surface machining quality can effectively improve the fatigue resistance of the swashplate.

Accurate measurement of the speed of sound in hydraulic systems is essential for performance prediction and optimization. However, since the speed of sound is sensitive to the system state, conventional methods often fail to provide reliable measurements under varying conditions. To address these challenges, we propose a novel bidirectional progressive search algorithm for calculating the speed of sound in rigid pipelines. First, we establish a physical model of sound speed based on the pressure wave's propagation characteristics in pipelines. Next, data processing techniques are optimized, and a high-precision calculation is achieved through an improved bidirectional search algorithm. Pressure fluctuations under different operating conditions are measured using a dedicated experimental setup. We validate the accuracy of the proposed method by comparison with conventional approaches. The experimental results show that the proposed method significantly outperforms existing techniques in terms of computational accuracy across a range of conditions, with an average improvement of 4.5% in the calculated speed of sound. Notably, under a pressure of 15 MPa and in turbulent flow conditions with secondary source interference, the improvement reaches up to 7.8%. These findings demonstrate that the proposed approach can offer higher accuracy and broader applicability in dynamic hydraulic environments.

Environmental pollution site investigation and risk assessment are particularly important for land security. Currently, full-hydraulic direct-push sampling rig is applied widely in sampling operations. The drill tool is rigidly connected to the integrated frame and vehicle body. So the deviation of integrated frame and vehicle body will cause the deviation of drilling direction. In order to ensure initial direction of drill tool and realize deviation correction control of integrated frame and vehicle body, a deviation correction control strategy based on triaxial tilt angle is proposed. Concurrently, we establish models of each system and simulate under different initial conditions. The simulation results show that the control strategy has excellent control performance, high leveling accuracy, and single-direction adjustment time is not exceeding 6 s, which is suitable for full-hydraulic direct-push sampling rig.

The extended supply and return pipelines of the comprehensive working face result in high-pressure loss along the hydraulic support system, and the supply strategy of the emulsion pump station is incompatible with the operation of hydraulic supports. These result in a slow dynamic response of the key actuators for hydraulic supports, which limits the automatic following speed. According to above problems, on the basis of the current intelligent integrated liquid supply system, we add a high-pressure small-displacement pump as a centralized liquid supply and pressurization system for the column lifting action. And a mathematical model of the column-pushing hydraulic cylinder for the hydraulic support group in the comprehensive working face is established. Then, an automatic following strategy for hydraulic supports with rapid fluid supply and pressurization of the lifting column is proposed. Additionally, a simulation model of the fluid supply system for a comprehensive working face, based on independent pressure compensation, is established by using AMESim. The effectiveness and superiority of the proposed automatic machine following control strategy are studied, and the fluid supply schemes of hydraulic supports under different flow conditions are compared. The research demonstrates that the proposed system and its control strategy can enhance the following speed of hydraulic supports by 30.11% and reduce the pressure-building time of the column initial support pressure by 76%. We offer a novel solution to problems such as the unsmooth flow channel of the lifting column, insufficient initial support pressure and excessive back pressure during the process of lowering the column.

Shear thickening fluid is a kind of intelligent material, and when applying the shear thickening fluid to the damper, we obtain the shear thickening fluid damper. Based on the reason that shear thickening fluid damper will be subjected to huge resistance due to the existence of velocity gradient when the fluid flows through small pores or gaps, the shear thickening fluid damper plays a key role in energy absorption and shock absorption. Through the way of Fluent simulation, the shear thickening fluid which is made of 20% mass fraction of nano-silica-polyethylene glycol solution is used as the working medium of the shear thickening fluid damper, and the flow of the shear thickening fluid in the damping holes is used to simulate the working process of the damper, and then draw the force-displacement hysteresis curves at different frequencies. The energy produced by the resistance force during the working process of the shear thickening fluid damper is calculated according to the results of the hysteresis curve to analyze the energy absorption effect. From the results, it is known that under the condition of the low-frequency working environment (f≤2 Hz), the force-displacement curve shows a good characteristic of symmetry, and the energy consumed in the retraction process of the damper is almost equal to that in the process of extension. But with the increase of frequency (f>2 Hz), the symmetric characteristic of the force-displacement curve becomes worse, and the energy consumed in the retraction process of the damper and the extension process are quite different.

The torque converter serves as the hydraulic transmission system core. Engine power transmits entirely through it to the transmission system. Torque converter efficiency directly impacts overall vehicle fuel economy. Operating immersed in oil, its high-speed rotation agitates viscous fluid. This generates oil churning loss, affects power transmission system efficiency. Simulation and experimental research address torque converter oil churning loss. A particle-based method simulation model establishes the torque converter oil churning flow field. It calculates torque and power losses under different rotational speeds and oil temperatures. A fully-enclosed oil shield designs for the torque converter to suppress oil churning loss. Experiments verify simulation model accuracy and feasibility and verify oil churning suppression method feasibility. Results show that torque converter oil churning torque increases approximately linearly with rotational speed. Oil level height significantly impacts oil churning torque loss. Higher oil levels cause greater churning losses. Adding the oil shield effectively suppresses oil churning torque loss. Suppression efficiency exceeds 83% across different oil level heights. Research findings provide an oil churning torque numerical calculation method and form a basis for hydraulic transmission gearbox oil pan oil level design.

Insufficient control precision is caused by strong nonlinearity in vacuum butterfly valve pressure control systems. A dual-mode switching strategy fusing Active Disturbance Rejection Control (ADRC) and PID control is proposed. The controller utilizes an extended state observer to uniformly estimate and compensate for aggregated disturbances including gas temperature drift, sealing friction, and gas source fluctuations. A pressure error threshold triggering mechanism is designed to activate ADRC exclusively during dynamic processes for rapid overshoot suppression, while automatically switching to lightweight PID control during steady-state operation to maintain precision. Compared with conventional PID control, settling time of proposed method is significantly shortened and overshoot substantially reduced. Compared with single ADRC control, steady-state error is effectively minimized. Under flow disturbances, pressure recovery time is 67% faster than that of PID control, with a steady-state error below 25 Pa. This approach significantly enhances system response speed, precision, and robustness, fully leveraging the cost advantage of butterfly valves. And it provides a high-performance, low-cost vacuum pressure control solution for semiconductor, aerospace, and related fields.

Aiming at the nonlinear control of multiple hydraulic joint system of hydraulic quadruped robot, an interactive force control strategy for floating base operation by force control is proposed. The control strategy transforms the basic motion, robot end motion, leg motion, interaction force control, joint constraint and friction cone constraint into a quadratic programming optimization problem, and the task priority is adjusted by the weight matrix. The robot task is decomposed under the position constraint to solve the conflict between the interactive force control and the optimal control based on the dynamic model, to realize the coordinated motion and force control of the robot end. Finally, the effectiveness of the proposed control strategy is verified by simulation and experiment, which shows that the hydraulic quadruped robot can perform large load operation during interactive operation and can control the appropriate contact force.

As electro-hydrostatic actuator (EHA) with high order nonlinear and strong coupling characteristics, the parameters of its position sliding mode controller are difficult to adjust. Conventional swarm intelligence algorithms often fall into local optimal solutions and have poor computational efficiency. Therefore, piranha foraging optimization algorithm (PFOA) is proposed to adjust and optimize the parameters of the sliding mode controller. Therefore, on the basis of analyzing the composition principle of EHA, a mathematical model is established, and PFOA algorithm is used to adjust and optimize the sliding mode surface and approach rate parameters in the sliding mode controller. Simulation and verification work are carried out on the MATLAB/Simulink and AMESim joint platform. The simulation results show that, compared with the sliding mode PID optimized by other swarm intelligence algorithms, the sliding mode PID control optimized by PFOA algorithm has smaller steady-state error and tracking error, better robustness, and higher computational efficiency, which provides an important research idea for ensuring better control performance of EHA position sliding mode controller.

A novel nonlinear integral sliding mode control method is developed to resolve the constant speed regulation challenge in closed-circuit hydraulic traction machine systems for power transmission cable deployment equipment. Firstly, a comprehensive mathematical model of the traction machine's constant speed control system is formulated through rigorous dynamic analysis. Moreover, to simplify controller complexity and facilitate engineering implementation, the model's order is systematically reduced following singular perturbation theory principles. Subsequently, a nonlinear integral sliding mode control scheme is developed through the strategic incorporation of nonlinear compensation terms, with its enhanced convergence properties and tracking accuracy being theoretically verified using Lyapunov stability analysis. Additionally, an uncertainty observer is developed to improve system robustness by observing and compensating for multiple uncertainties, including parametric variations and external disturbances. Finally, a high-fidelity multi-physics simulation platform is established using Simscape modeling toolbox for the traction machine's speed control system. Comparative simulations with traditional integral sliding mode control and proportional-integral control are conducted, and the results not only validate the effectiveness of the reduced-order model-based controller design, but also demonstrate that the designed uncertainty observer achieves accurate estimation under both step-type and sinusoidal time-varying loads. The traction machine's speed step response exhibits no overshoot, with a settling time reduced to 1.2 seconds. Under a 100 N·m static load, the speed drop is merely 0.0127 m/s. For a 100sin(πt) N·m dynamic load, the maximum speed steady-state error is 0.012 m/s. Even under the combined operating condition of simultaneous positive/negative parameter perturbations and a 100sin(πt) N·m time-varying load, the maximum speed steady-state error remains as low as 0.016 m/s. Consequently, the constant speed control performance of the traction machine is significantly enhanced by the proposed control method.