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.

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.

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.

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.

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.

Due to the fact that electro-hydraulic servo systems are often affected by internal and external disturbances, and internal parameters change due to mechanical structure wear, the traditional control strategies are no longer sufficient to meet the control performance requirements. Therefore, a filter-based adaptive asymptotic tracking control method with guaranteed performance is proposed. Firstly, a mathematical model of the electro-hydraulic servo system is established, which is transformed into a strict feedback form space state expression by defining state variables. Then, the controller design and stability analysis are carried out. A novel error transformation is designed and combined with a barrier function to achieve the prescribe performance constraints on the tracking error. In the controller design, a single-parameter adaptive method is adopted to estimate the unknown parameters. Meanwhile, to avoid the continuous differentiation of the virtual controller, a nonlinear filter is introduced. Finally, by using the Lyapunov stability theorem and Barbalat's lemma, it is proved that the system can achieve asymptotic tracking, and the tracking error is limited within the prescribe performance function range. All signals of the closed-loop system are semi-globally uniformly bounded. The effectiveness of the control strategy is verified through simulation and compared with traditional PID and backstepping control strategies. The research results show that the rise time is increased by 82.8% and 80.3% respectively, the adjustment time is decreased by 88.9% and 91.4% respectively, and there is no obvious overshoot with a relatively small tracking error.

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.

Addressing the issues of inadequate resistance to eccentric loads, low synchronization accuracy, limited control points and complex operation in derrick rectification equipment, an electro-hydraulic rectification system for mega-derricks is designed. This system employs a centralized control and multi-point drive architecture, utilizing a servo motor to power a radial piston pump as the oil source, using high-speed on/off valves for control and 12 high-pressure hydraulic cylinders are employed to synchronously lift the derrick legs. A dynamic master-slave multi-point synchronous control method with selection capability is proposed, which replaces closed-loop control with switch control, enabling high-precision synchronous control under heavy eccentric load conditions, regardless of the number of control points. We develop an electro-hydraulic rectification equipment for mega-derricks and conduct bench tests and field operations. The synchronous position error among multiple hydraulic cylinders is less than 0.3 mm, facilitating one-click alignment and significantly enhancing the efficiency, safety and automation level of large-scale derrick alignment tasks.

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.

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.

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.

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.

We design a purely soft-structured gripper and analyze the bending performance of its finger section. The gripper features a series of gas-driven elliptical cavities. A stepped cavity structure incorporates three parallel air channels for the fingertip, middle finger segment and finger root, respectively. The palm adopts an arc-triangle shape. The gripper is made of hyperelastic material Ecoflex 00-30 silicone rubber and polydimethylsiloxane, and its model uses the Yeoh constitutive model derived from uniaxial tensile theory. Building on this, we develop models for a single airbag, a single cavity group's bending and the bending deformation prediction of the entire multi-channel fully flexible gripper. Inputting the finger's structural parameters into the mathematical model yields the geometric relationship of its bending curve. The comparison of these analytical results with simulation data verifies the model's accuracy and practicality. Finally, analyzing the finger's bending performance allows us to determine optimal gripper performance parameters. Key factors include cavity structure type/number, finger width, cavity gap length and the bottom strain-limiting layer. This provides valuable research data and a reference for soft actuator development.

To diagnose internal leakage in hydraulic cylinders, a method based on a two-set-valued identification algorithm is proposed. This method detects faults by analyzing pressure signal variations under both normal and leakage conditions. Fifteen time-domain features are extracted from pressure signals in the rod chamber and piston chamber. Principal component analysis is applied to reduce these features to three principal components per chamber. A mathematical model integrating the six principal components from both chambers is established. The two-set-valued identification algorithm is employed to estimate model parameters for establishing internal leakage diagnosis algorithm. Experimental validation using AMESim simulation data confirms the method's feasibility and accuracy in diagnosing internal leakage, providing a theoretical basis for hydraulic cylinder fault detection.

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.

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.

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.

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.

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.

Traditional passive hydro-pneumatic suspensions, limited by their ride comfort and handling stability, becomes a performance bottleneck for mining trucks. A semi-active hydro-pneumatic suspension model predictive control strategy based on whale algorithm optimization is proposed, aiming to achieve rapid convergence and optimize control system performance. A system model including a double-chamber hydro-pneumatic suspension model, a 7-degree-of-freedom dynamic model and a model predictive controller is established, and the stiffness and damping are equivalent. The whale algorithm optimizes the controller weight matrix under various road excitations. It then builds the optimization algorithm model predictive controller. The semi-active hydro-pneumatic suspension based on whale algorithm optimization is compared and analyzed with passive hydro-pneumatic suspension and traditional model predictive control semi-active hydro-pneumatic suspension on different roads. The simulation results demonstrate that the proposed model predictive control strategy optimized by the whale algorithm significantly enhances the ride comfort and handling stability of mining trucks. It also effectively reduces the dynamic load impact on road surfaces, offering considerable engineering significance for efficient mining area operations.

The application of traditional pneumatic mesh actuators is limited due to insufficient output force, with their structural design being a key constraining factor. To address this issue, we propose a stepped structure with non-uniform chamber heights, which enhances the terminal output force by suppressing radial expansion. A mathematical model of the actuator is established based on the principle of virtual work, revealing the correlation between structural parameters and bending performance. Combined with Hertzian contact theory, the contact force of the chamber wall is analyzed, and the theoretical relationship between the bending angle and contact pressure is established. To maximize the output force under the maximum input pressure 50 kPa, a three-factor and four-level orthogonal experimental design is adopted to optimize the parameter combination. The accuracy of the theoretical and finite element models is verified through bending performance analysis and experiments. Finally, the output forces of the stepped actuator and the traditional equal-height actuator are compared. The experimental results show that the stepped structure effectively suppresses radial expansion, with an output force of 3.5 N at 50 kPa, which is a 40% improvement compared to that of the traditional structure.

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.

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.

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.

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 adual-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.

The problem of energy efficiency and thermal stability of underground coal mine explosion-proof vehicles under long-distance and large slope conditions has seriously restricted its unmanned development. Based on the chassis by-wire architecture, this thesis explores the thermal management strategy of unmanned development explosion-proof vehicles. A transient thermodynamic modeling method of multi physical field coupling is proposed, and the series hydraulic hybrid power system architecture based on closed loop is constructed. The architecture integrates the accumulator cooperative control and bidirectional energy conversion mechanism to improve the braking energy recovery efficiency and peak power output capacity. At the same time, a dynamic temperature boundary model based on oil flow direction identification is established to effectively overcome the time lag problem of the traditional model in transient response. Through the hardware in the loop experiment, the nonlinear relationship between the hydraulic oil temperature rise process and the system efficiency is revealed. The final test results show that the temperature prediction error of all key components such as hydraulic pump, motor and accumulator does not exceed ±3.5 ℃, and the model shows high accuracy in the prediction of system temperature level and change trend. This thesis provides a theoretical model and solution for the thermal management optimization of underground trackless auxiliary transportation equipment.

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.

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 address the issues of low efficiency in calculating unbalanced forces on pneumatic control valving element and the difficulty in accurately predicting dynamic characteristics. Applying a physics-informed neural network to calculations of valving element unbalanced force is proposed. By analyzing the working principle of pneumatic control valves and the generating mechanism of valving element unbalanced forces, the neural network model integrating fundamental fluid mechanics equations and simulation data is constructed. This enables efficient prediction of valving element unbalanced forces, with the method's validity ultimately verified through CFD simulations. Research findings demonstrate that the physics-informed neural network predictions closely match CFD simulations, with computation time reduced to under 10 seconds. The maximum error (<8%) occurs at the valve's critical closing point. This approach overcomes the high computational costs of traditional methods, enabling real-time, precise prediction of dynamic unbalanced forces. It provides a novel technical pathway for intelligent design and dynamic characteristic optimization of pneumatic control valves.

High-precision control of excavator electro-hydraulic servo systems is significantly hindered by difficulties in accurately identifying parameters for nonlinear friction models. To address this, a hybrid optimization algorithm is developed by integrating genetic algorithm selection and crossover operations into a particle swarm optimization framework, enhanced with adaptive strategies for inertia weight and learning coefficients. This proposed algorithm demonstrates superior performance in identifying parameters for the LuGre friction model, achieving a maximum friction force error of only 1.70 kN—a 40.68% improvement in solution quality over a standard genetic algorithm. Subsequently, an adaptive friction compensation controller is designed based on the identified model. The experimental validation on a 23 t excavator shows that the proposed controller achieves a maximum trajectory tracking error of 11.56 mm for a sinusoidal input, significantly outperforming traditional PID and feedforward compensation controllers. The proposed controller effectively compensates for friction and disturbances, eliminating stick-slip phenomena and improving system robustness and tracking accuracy.

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.

The flap system's rapid response is prone to speed loop overshoot, which degrades system stability and shortens equipment life. To address this, a composite control method featuring “speed loop adaptive control and position loop smooth planning” is proposed. Firstly, a dynamic model of the flap system is constructed through an in-depth analysis of its components' working principles. Secondly, a theoretical mathematical model of the system under a loading environment is established to accurately characterize its dynamic behavior under actual operating conditions. Finally, to ensure stability and reduce start-up overshoot, the dynamic performance of the composite method is compared with traditional PID control in the speed loop. Based on the system performance specifications, the position loop performance of the composite control method is comprehensively verified under both no-load and load conditions. Simulation results demonstrate that, compared to the traditional PID control, the proposed method effectively reduces start-up overshoot, suppresses oscillation, and enhances system stability while meeting the system's rapidity requirements.

A hierarchical control strategy with adaptive neuro fuzzy inference system compensation is proposed for heavy-duty automatic guided vehicle on unstructured roads. It improves posture control performance under severe nonlinear conditions. The strategy addresses hydro-pneumatic suspension nonlinearity and electromagnetic valve force inaccuracies. The upper layer uses linear quadratic regulator for optimal vertical body control. A fuzzy PID controller suppresses roll motion. Desired active suspension forces are generated. The lower layer applies adaptive neuro fuzzy inference system for force tracking error compensation. It maps force errors to electromagnetic valve control signals. High-precision force tracking is achieved. Simulation results validate the proposed strategy. Under class C road excitation, root mean square vertical and roll accelerations decrease by 30.4% and 38.9%. Under single-side step excitation, peak roll angle decreases by 44%. The strategy shows strong robustness under complex conditions.

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.

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.

As an important part of the thrust reverser system, the hydraulic thrust reverser actuation system is used to control the deployment and stowage of the thrust reverser device, and the thrust reverser force is generated during the plane to reduce the speed of aircraft. In order to investigate the movement characteristics of system, the experimental method is adopted to conduct experimental measurement research on the development of the hydraulic thrust reverser actuation system at different operating conditions, and the performance changes of different external forces and environmental temperatures. Based on the experimental boundary conditions, the hydraulic thrust reverser actuation system is carried out numerical simulation research, including simulation tool selection, model establishment, parameter settings, etc. The results of the study show that at the design conditions, the hydraulic thrust reverser actuation system can be deployed within 2 s and stowed within 3 s. At the end of the movement, the fierce impact effect of the operator can be weakened, and the speed is reduced to less than 150 mm/s. Different external forces seriously affect the synchronization exercise accuracy of deployment and stowage. The greater the external force, the worse the synchronous exercise accuracy. When the oil pressure and temperature are changed, the system movement performance deviates from the design point. And increasing pressure and temperature can effectively shorten the running time. In addition, except for different external forces (greater than 1500 N), the simulation and experiment have a good consistency, and this simulated model can be used as an effective tool for system operation evaluation.

The use of aluminum honeycomb as the energy-absorbing medium in automotive sideimpact simulation devices has inevitabledrawbacks, 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.

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.

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.

In the full authority digital control system of aero-engines, the hydraulic servo actuator serves as the core executive mechanism for thrust vector control. It is dedicated to regulating the direction, magnitude, and dynamic characteristics of thrust. To enhance the mission reliability of the engine, an innovative integrated high-speed solenoid valve is adopted to construct a pulse width modulation balanced duty cycle control architecture. This architecture not only improves the system compatibility and anti-contamination capability but also achieves the design goal of low cost. However, the stability of the system is compromised due to the nonlinear output control of the high-speed solenoid valve. To address this issue, an in-depth investigation into the pulse width modulation balanced duty cycle control strategy of the high-speed solenoid valve is conducted to enhance system compatibility and mitigate the influence of hydraulic characteristic variations on the system. Utilizing the AMESim modeling and simulation platform, a double closed-loop hydraulic actuation system model based on high-speed solenoid valve control is developed. Based on this system model, simulations and analysis of system stability are performed under the 50%±5% pulse width modulation balanced duty cycle signal condition. The simulation results indicate that increasing hydraulic damping can effectively reduce the fluctuations in the system caused by nonlinear outputs; appropriately setting throttling can lessen flow regulation gain, thereby diminishing the impact of external factor variations on the system. These research findings provide significant theoretical foundations and technical support for product development and prototype creation.