Deflector jet servo valve fault signals are limited and easily affected by noise under complex conditions, resulting in difficult feature extraction. This paper presents a fault diagnosis method combining starfish optimization algorithm-based variational mode decomposition, temporal convolutional network, and a self-attention bidirectional gated recurrent unit network. The starfish optimization algorithm selects variational mode decomposition parameters to improve decomposition accuracy and robustness. Main features are extracted from key intrinsic mode functions based on minimum envelope entropy. These features are entered into a temporal convolutional network and a self-attention-based bidirectional gated recurrent unit network to enhance fault classification. A fault simulation platform and dataset are built, with experiments under typical fault conditions. Results show that the fault recognition accuracy of the method achieves 97.33%, demonstrating strong robustness and high diagnostic performance.

The noise generated during the operation of hydraulic pumps seriously affects the physical and mental health of operators. To study the influence of different rotational speed conditions on the sound quality of their radiated noise, a composite evaluation index for the sound quality of hydraulic pumps suitable for constant-speed and variable-speed conditions is constructed, which is based on four psychoacoustic parameters:loudness, sharpness, roughness and articulation index. Using the hemispherical measurement method, constant-speed and variable-speed noise tests are conducted on the hydraulic pump in a semi-anechoic chamber. The variation laws of psychoacoustic parameters and sound quality indicators under different conditions are analyzed and compared. The experimental results show that as the rotational speed increases, the composite evaluation index shows a fluctuating deterioration trend. The change rate of variable-speed has a relatively small impact on the psychoacoustic parameters. In the high-speed range, the loudness, sharpness and total sound energy under constant-speed conditions are all lower than those under variable-speed conditions at the same rotational speed. At the same time, the composite evaluation index of the sound quality for hydraulic pumps shows stronger fluctuations in the high-speed range, and the fluctuation amplitude intensifies with the increase of rotational speed. The above research results provide theoretical support and evaluation basis for the optimization of hydraulic pump operating conditions and noise control strategies.

Slipper wear is a common failure in piston pumps. Aimed at the failures of the flow rate decrease and excessive vibration of the pump caused by slipper wear in the fuel piston pump of a certain type of aero-engine, a comprehensive failure diagnosis method is proposed within the framework of multiple disciplines including dynamics, tribology, fluid lubrication, and structural strength. The calculation and simulation of the oil film thickness, structural strength, and pv value of the slipper of this type of fuel piston pump under multiple operating conditions are carried out, and the associated mechanism between each operating condition and the wear failure is analyzed. The research results show that the structural strength of the slipper of the fuel piston pump meets the requirements within the full operating condition range, and the oil film characteristics are favorable when the rotational speed is below 4500 r/min. However, when the rotational speed of the fuel piston pump gradually increases, the proportion of the axial inertial force and centrifugal force acting on the slipper pair in the contribution to the pressing force gradually increases. When the rotational speed increases to 5000 r/min, the supporting force cannot effectively compensate for the external pressing force, resulting in the rupture of the hydrostatic oil film of the slipper pair. The slipper and the swash plate change from the fluid lubrication state to the boundary lubrication state or the direct contact state. Moreover, the pv value of the material of the slipper pair is in an over-limit state under the high rotational speed operating condition, which ultimately leads to wear failure.

The disc spring hydraulic mechanism is a key equipment in the power system, and its performance directly impacts the reliability of the system. Dynamic characteristic analysis of its key components aims to enhance operational stability. The mechanism's structural composition and operational principles are analysed firstly. Subsequently, Fluent-based simulations investigate the pressure variation characteristics in both rodless and rod cavities of the working cylinder piston. These simulations reveal the intrinsic correlation between piston velocity and pressure fluctuations. Further research focuses on gas pressure dynamics in the arc-extinguishing chamber during circuit-breaking operations, employing pressure cloud diagrams to analyse the spatial-temporal pressure distribution patterns in both the disc spring hydraulic mechanism and the arc-extinguishing chamber. Experimental validation confirms the accuracy of this dynamic analyses, establishes a theoretical foundation for optimizing mechanism design and improving operational stability.

By designing different anti-friction lubricating structures and comparing the oil film characteristics, the influence of different anti-friction lubricating structures on the servo hydraulic cylinder to overcome the radial load and reduce the friction is studied, the best shape structure of anti-friction lubricating structure is obtained, and tests are verified. Based on the rectangular structure of anti-friction lubricating, I-shaped structure and trapezoidal structure are proposed. The pressure distribution and bearing capacity characteristic curves of different anti-friction lubricating structures are obtained by theoretical analysis and flow field simulation. The anti-friction lubricating structure of trapezoidal structure can provide more bearing capacity, and the temperature rise of oil film is smaller. The anti-friction lubricating structure can effectively overcome the radial load on the piston rod and reduce the friction of the servo hydraulic cylinder. The results show that the oil film characteristics of different anti-friction lubricating structures are different, which can effectively overcome the partial load, greatly reduce the friction of the servo hydraulic cylinder, and improve the control precision and service life of the servo hydraulic cylinder.

Hydraulic axial piston pumps are core power components in hydraulic systems, so effectively diagnosing faults in axial piston pumps is crucial for ensuring the safe and reliable operation of hydraulic equipment. This paper proposes an improved fault diagnosis method that combines an auxiliary classification generative adversarial network and a model migration strategy. A fault diagnosis framework and adopts a pre-training-fine-tuning strategy to improve the model's generalisation ability in the target domain task is proposed. This method solves the problem of traditional deep learning diagnostic methods having a poor effect, or even failing, in the actual operation process of normal and fault data due to data imbalance and insufficient quantity. Experimental results show that this method increases the structural similarity value by 20.4% and the peak signal noise ratio value by 5.4% when samples are imbalanced. The three datasets achieve F1 scores of 96.3%, 94.4% and 92.5%, respectively, effectively improving the quality of production samples and the fault recognition rate of axial piston pumps.

To address the issue of insufficient adjustability of low-frequency dynamic characteristics in heavy-duty special vehicle mount systems, this study proposes a magnetorheological fluid mount with controllable multi-inertial channel combined squeezing mode. A multi-channel magnetorheological fluid damper is developed, and experimental methods are employed to validate the switching effect of controllable flow channels. An aggregate parameter model for the magnetorheological fluid mount with controllable multi-inertial channel combined squeezing mode and a model of magnetorheological fluid mount system for 1/4 heavy-duty special vehicle are established. Finally, dynamic characteristics and vibration isolation performance are investigated based on these models. The results demonstrate that by the application of large current on different inertial channels, the peaks and peak frequencies of dynamic stiffness and hysteresis angle in the magnetorheological fluid mount become adjustable within 0~50 Hz. Additionally, under squeezing mode operation, the mount exhibits high-stiffness and high-damping characteristics at low frequencies.

Designing airfoils with biomimetic leading-edge structures offers an effective approach to concurrently improve aerodynamic and noise reduction performance. Five biomimetic airfoils with wavy leading-edge characterized by different combinations of amplitude and wavelength are designed using the NACA0012 airfoil as a baseline. Numerical simulations employing the SST k-ω and large eddy simulation methods are performed to analyze their aerodynamic performance and flow noise. The results indicate that increasing the wavelength significantly improves aerodynamic performance, with the lift-drag ratio enhanced by up to 21.8%. Increasing the amplitude strengthens flow control at the leading edge, resulting in a more uniform pressure distribution and delayed flow separation. The biomimetic structure reduces the angle of attack corresponding to the maximum lift-drag ratio and improves aerodynamic performance at high angles of attack. The biomimetic airfoils demonstrate notable noise reduction in the mid-to-high frequency range. Under small angles of attack, both tonal and broadband noises are suppressed. A reduction in sound pressure level is observed across all studied angles, peaking at 14 dB at an angle of attack of 3°.

Aiming at the fault diagnosis of data-driven external gear pump (hereinafter referred to as gear pump), there are the problems of easy noise interference in actual operation, redundant fault features and cumbersome fault feature selection and classifier parameter optimization, so we propose a wear fault diagnosis method for gear pump based on the simultaneous optimal feature selection with sand cat swarm optimization-variational mode decomposition and dung beetle optimization algorithm. Firstly, the original fault data are obtained by building a gear pump fault experimental bench, and the vibration signals of four types of gear pump wear faults are reconstructed by noise reduction using the method of sand cat swarm optimization-variational mode decomposition. Then, a total of 26 statistical features are extracted from the four reconstructed signals in the time domain, the frequency domain, and the time-frequency domain, and the feature layers are composed. Finally, the feature selection of the fault feature set based on the dung beetle optimization algorithm and the optimization of parameters of classifier for support vector machine are carried out simultaneously, achieving wear fault type recognition of gear pumps. The results show that the accuracy rate of the fault diagnosis method for gear pump is as high as 99.6%, and the consumed time is only 49.8 s, which demonstrates the high diagnostic accuracy and computational efficiency of the proposed method.

To meet the posture adjustment requirements of the wind proof and sand fixation transverse grass grid laying machine when operating on uneven desert surfaces, we design an electro-hydraulic control posture adjustable suspension system for connecting the wind proof and sand fixation transverse grass grid laying machine to the tractor. The mechanical structure of the posture adjustable suspension is analyzed, and a kinematic model is established; a hydraulic system for posture adjustment is designed, and a valve-controlled cylinder hydraulic power element model is established; and an electro-hydraulic control system scheme is designed. A simulation model of the posture adjustable suspension of the transverse grass grid laying machine is established using AMESim software. The simulation results indicate that the electro-hydraulic control system design is feasible; the posture adjustable suspension design for the transverse grass grid laying machine is feasible.

To address the insufficient control precision and load oscillation of crane hoisting systems under micro-flow conditions, a solution of coordinated pump-valve electro-hydraulic hybrid-driven system is proposed. A volumetric efficiency test platform for pumps/motors is constructed to establish pressure-flow leakage compensation curves, forming a dual-mode control strategy: the valve spool is fully opened with flow regulated by the hydraulic pump based on leakage compensation curves under the rapid motion mode, and real-time spool opening adjustment is implemented according to valve pressure difference for precision control under the micro-motion mode. A synchronously designed motor-motor hoisting mechanism effectively suppresses the impact of load disturbances on system pressure difference. The AMESim simulations verifies that under abrupt load changes at four flow levels (120, 60, 20 and 10 L/min), the motor rotational speed is decreased by 2.92%, 5.17%, 17.02% and 42.92%, respectively, only by using the leakage compensation strategy. With the introduction of the motor-motor mechanism, speed fluctuations are essentially eliminated, with motor operating pressure stabilized within 4.3~3.8 MPa across all flow conditions and leakage maintained at steady levels. The study demonstrates that this coordinated control architecture significantly enhances the control precision under micro-flow condition and effectively suppresses system oscillations induced by load disturbances through dynamic pressure stabilization mechanisms.

The hydraulic manipulators provide high thrust/torque, making it suitable for handling heavy-payload objects. However, compared with electric drives, the hydraulic systems equip with more complex structures and respond more slowly. The hydraulic systems exhibit nonlinear characteristics, such as flow/pressure variations in servo valves and friction. Nevertheless, PID control remains the most widely used method in engineering practice. But PID performances negatively under system nonlinearities and heavy load disturbances, this study focused on the pipe-gripping manipulator and took the hydraulic nonlinearities, friction, and load disturbances into consideration. A dynamic model using the Lagrange method to describe the system response and designed two nonlinear controllers is established. A fuzzy PID controller and a fuzzy sliding-mode controller based on backstepping are designed. The simulation results showed that the latter could effectively handle system nonlinearities and heavy-load disturbances, limiting the manipulator's position error to within 1%. Additionally, the thesis adopts a saturation integral function and fuzzy sliding-mode control to mitigate the chattering problem common in sliding-mode control.