Space missions are often accompanied by high costs and great risks. Therefore, the precise control of the ground simulation system is of great significance to the on-orbit state verification of the spacecraft. Taking the three-degree-of-freedom micro-low gravity air floating platform driven by solenoid valve as the research object, the theoretical model of solenoid valve is proposed from three aspects: structure, mathematics and energy loss. Then, according to the structural characteristics and parameters of the solenoid valve, a multi-voltage driving control strategy is proposed, and compared with the traditional driving mode. The results show that the multi-voltage drive control strategy can effectively improve the dynamic response characteristics of the solenoid valve and improve the frequency response capability of the solenoid valve. In addition, the lateral, rotational and planar motion control experiments are designed to verify that the solenoid valve based on the multi-voltage drive control strategy can control the air floating platform to obtain the ideal motion trajectory.

With the advancement of motorcycle electronic safety technology, stability control for emergency braking during cornering becomes a research focus. We address instability caused by steering torque from ground friction during curve braking. We propose a closed-loop wheel cylinder pressure control method that requires only a single pressure sensor. Firstly, a logic-threshold-based anti-lock braking system controller is designed. It employs a variable-slope pressure increase strategy and uses the pressure-volume characteristic curve of the wheel cylinder for precise pressure regulation. Secondly, to overcome the limitation of having only a front-axle pressure sensor, a master cylinder pressure estimation method based on wheel cylinder pressure feedback is introduced. A co-simulation platform is built using AMESim, Simulink, and BikeSim. Real-vehicle tests are conducted on typical road surfaces, including high-adhesion, low-adhesion and transitioning conditions. The results demonstrate that the proposed strategy enables fast and stable tracking of target wheel cylinder pressure. In experiments, the tracking error of the wheel cylinder pressure is consistently less than ±0.85 MPa. During braking tests on step-type road surfaces transitioning from low to high adhesion, the slip ratio is maintained within a stable range of -1.58% to 24.94%, and the braking process remained smooth. This provides an effective technical solution for enhancing the braking safety of motorcycles in cornering scenarios.

We investigate the high energy consumption caused by conventional pneumatic component selection methods. A nonlinear optimization design approach is proposed with the objective of minimizing system energy consumption. An experimental platform equipped with multiple sensors is established to validate the proposed method under several common industrial operating conditions. Comparative experiments and stability tests are conducted over ten operational cycles. The results show that the optimized pneumatic systems successfully complete all motion tasks with stable performance. Energy consumption is reduced by more than 30% per cylinder piston stroke. During multi-cycle reciprocating operation, the average energy-saving rate ranges from 31.6% to 33.1%. These findings confirm the engineering feasibility and energy-saving reliability of the proposed optimization method, providing strong experimental support for green design in pneumatic systems.

The hydraulic operating device of aircraft utilized in alpine areas typically operates within an ambient temperature range of -40 ℃ to 150 ℃. Under such extreme conditions, the radial clearances of the hydraulic slide valves may be altered, leading to sticking or a delayed response.To address the sticking problem of hydraulic slide valves under a wide temperature range, we establish a mathematical model of thermal deformation of clearance in the hydraulic slide valve and validate the finite element simulation model. The results show that the maximum relative error between the simulation model and the mathematical model does not exceed 0.3%, confirming the rationality and correctness of the thermal deformation model of clearance. Meanwhile, considering machining precision errors, hydraulic oil viscosity and other factors, we establish a mathematical model of sticking force incorporating the thermal deformation of hydraulic slide valve clearance. The study reveals the variation law of sticking force of hydraulic slide valves in different states. Through experimental research, the error between simulation and test results of the hydraulic slide valve is within 2% considering thermal deformation due to clearances, which verifies the accuracy of the sticking force model.

In view of the shortcomings of the research on leakage fault detection of civil aviation hydraulic system, we focuse on the monitoring parameters of fuel tank oil volume which are often neglected in the existing leakage analysis of hydraulic pipeline. An improved particle swarm optimization method for hydraulic system diagnosis is proposed. Firstly, a signal processing step is proposed, and a new physical information feature weighting layer is developed to enhance the sensitivity of the model to fault-related features. Secondly, aiming at the problem of complex calculation and slow convergence of traditional particle swarm optimization algorithm, we introduce the linear decreasing inertia weight, Latin hypercube initialization and local restart strategy to improve performance. Finally, the effectiveness of the proposed method is verified by experimental investigation. The research shows that the proposed method has higher robustness and accuracy than many classical fault diagnosis methods, and it does provide an effective method for detecting leakage fault diagnosis of aviation hydraulic systems.

The adjustment of hydraulic support posture and the straightening of scraper conveyors in underground coal mining require the operation of hydraulic cylinders through hydraulic valves. Currently, the commonly used switch valve groups often struggle to achieve precise adjustments. Additionally, the unique underground environment imposes strict requirements on the volume, pressure, flow rate, and working medium of hydraulic valves. To address these issues, a pilot-operated large-flow servo ball valve is proposed, and its simulation characteristics are analyzed and experimentally verified. The simulation results indicate that the ball valve can achieve multi-channel flow regulation and on/off control with a large flow rate. It also features a pilot control function, enabling follow-up control of the main valve and pilot valve. The main valve opening of the ball valve can be adjusted in three stages within the angle range of 5° to 37°, and the flow rate can be regulated in three stages, with flow rates of 102, 295, and 602 L/min, respectively. Furthermore, the ball valve can achieve driving control at a low power of 4 MPa, meeting the requirements of long-distance and large-flow liquid supply scenarios for mining hydraulic equipment.

To improve the friction performance of the valve plate pair in axial piston pumps under high-speed and high-pressure conditions, triangular, square, and cylindrical surface textures are constructed on the valve plate. A one-way fluid-structure interaction simulation model of the piston pump is establishedy using ANSYS. The effects of different rotational speeds and pressures on the oil film load-carrying capacity, friction coefficient, and structural deformation are analyzed and compared between textured and non-textured valve plates under full film lubrication. Results show that, compared to non-textured valve plate pair, the textured pair exhibits increases oil film load-carrying capacity and reduced friction coefficient as speed and pressure rise. However, solid domain deformation increases. Within a broad range of high-speeds and high pressures, the triangular texture demonstrates superior comprehensive performance compared to square, cylindrical, and non-textured surface. Under high-speed and high-pressure boundary conditions, the oil film load-bearing capacity of the valve plate pair with triangular texture is increased by 22.51% compared to that of the non-textured surface; the friction coefficient is reduced by 18.24%; and the maximum deformation of the cylinder block and the valve plate increases by only 10.9% and 1.6%, respectively, compared to those of the non-textured surface, demonstrating significant performance advantages.

To address the poor flow characteristics of the inlet throttle speed control circuit for throttle valve, it is proposed to use a pressure-compensating type relief throttle valve to replace the throttle valve and relief valve in the throttle speed control circuit. An AMESim simulation model of the speed control circuit is established, and experiments are built for verification. The performance of the speed control circuit under different loads and orifice opening degrees is analyzed. The results show that when the orifice opening is 80% and the load is 70 and 50 kN, the pressure difference at the orifice is between 0.35 and 1.1 MPa. The valving element of the relief valve automatically compensates for the pressure difference at the orifice to a certain fixed value under the change of load force, while the flow rate at the orifice remains constant, and the throttling rigidity is good. When the pressure difference at the orifice exceeds 1.1 MPa, the flow rate at the orifice increases linearly with the increase of the pressure difference, and the throttling rigidity is poor. When the load is 30 kN, the flow rate and pressure difference at the orifice are always in direct proportion, and the throttling rigidity is poor. When the orifice opening is 40%, regardless of the load size, the flow rate at the orifice increases proportionally with the increase of pressure difference. The flow characteristic ratio of the speed control circuit is worse when the opening is 80%. It is indicated that the throttling speed regulation circuit of the relief throttle valve has better flow characteristics when the load is large, the opening degree of the orifice is large and the pressure difference of the orifice is small.

For high-power hydrogen fuel cell systems, a large-flow hydrogen pressure-reducing valve with a reverse-unloading tapered valve core is designed. The structural design and working principle of the product are introduced. A static mathematical model is established, and its pressure and flow characteristics are studied using AMESim software. Analysis reveales that increasing the valving element angle, reducing spring stiffness and enlarging piston area can improve the output pressure accuracy of the pressure-reducing valve. A test platform for the pressure-reducing valve is built to evaluate its static characteristics under actual operating conditions. The results demonstrate that this valve exhibits stable output pressure accuracy which is ±8.1%. The adjustment accuracy is ±0.61%, and it has large output flow rate and minimal lock-up pressure, indicating excellent operational performance. Moreover, the theoretical calculations, simulation analyses, and experimental test results show close agreement.

The structure of the spring chamber oil discharge hole has a significant impact on the performance of the mechanical flow alarm valve. Rational design can enhance stability, sensitivity, and reliability, ensuring the normal operation of hydraulic systems. In this thesis, a combined method of simulation and experimentation is used to compare the effects of two spring chamber oil discharge hole structures (the oil discharge hole is directly opposite the inlet and the oil discharge hole is directly connected to the outlet) on the alarm flow threshold of the flow alarm valve. Computational fluid dynamics analysis shows that the oil discharge hole being directly opposite the inlet (model 1) causes the liquid in the spring chamber to interact with the incoming flow, increasing the pressure on the valve core to the right, raising the alarm threshold, and resulting in significant pressure loss and energy consumption. In contrast, connecting the oil discharge hole directly to the outlet (model 2) reduces the pressure inside the spring chamber, allowing the alarm to be triggered at a lower inlet flow rate, thus achieving higher flow sensitivity. Experimental results also confirm that, under identical conditions, the alarm flow threshold of model 1 (63.5 L/min) is much higher than that of model 2 (15.7 L/min), verifying the simulation analysis results.

Rope-hook recovery is a primary retrieval method for small fixed-wing unmanned aerial vehicles. To enhance its applicability, a dedicated recovery device is developed, incorporating a combined energy absorption mechanism of “recovery rope and elastic deformation”. The dynamic equations of the system are derived using the Lagrange method and an equivalent spring-damper model is established. Using the MATLAB platform, the response characteristics are solved. And key parameters of the recovery rope are prioritized based on static tensile tests. Furthermore, finite element analysis is carried out on all components of the device, and the method for calculating the overturning load is elaborated. The development process and key design aspects provide practical guidance for the engineering development of similar devices. Finally, recovery tests are conducted in ascending order of energy levels to validate the device's performance. The test results demonstrate that the device achieves a maximum recovery energy of 32.4 kJ (measured), exceeding the theoretical value of 28.9 kJ for certain RQ21 unmanned aerial vehicle system. The maximum recovery overload remains below 7.5 g.

To address the operational performance issues of swing cylinders in ultra-low temperature environments, this study focuses on the selection and matching of low-temperature materials. By simplifying the screw pair engagement into a planar model, fluid-structure interaction simulations are conducted on the oil film of the swing cylinder′s screw pair, analyzing the effects of different shaft speeds, circumferential clearances, and oil viscosities on oil film performance. A test bench is built to verify the operational performance of the prototype in ultra-low temperature environments, with comparisons of swing cylinder speed variations under different temperatures. The experimental results indicate that using low-temperature hydraulic oil can appropriately improve the transmission efficiency of swing cylinders in ultra-low temperature environments, laying a technical foundation for solving driving and control engineering challenges of related equipment in extreme environments.

Considering the issue of wear-induced failure in the piston/cylinder pair of hydraulic motors under field operation, we investigate the failure mechanisms of the piston/cylinder pair, the tribological wear mechanisms, the influence of piston/cylinder clearance on contact stress, and the contact stress characteristics of cylinder bores. The simulation results of cylinder bore wear are basically consistent with field failure observations, both exhibiting a pattern of less wear in the middle region and more severe wear at both ends. Furthermore, to address the failure issue caused by excessive initial clearance of the piston/cylinder pair, reproduction tests of the failure mechanism are conducted. Improvement measures for controlling piston/cylinder clearance are proposed and experimentally validated. The test results confirm that the proposed measures are effective.

The hydraulic Reservoir is a critical component of the aircraft hydraulic system, and its pulse fatigue performance is a key indicator for evaluating the durability of critical structures. During the development of the hydraulic Reservoir for the MA700 civil aircraft, 7075 aluminum alloy is firstly adopted as the main material for the high-pressure cylinder, a core part. However, the high-pressure cylinder cracks during pulse fatigue testing, causing external leakage of Hydraulic fluid. Penetrant testing, fracture analysis, and material microstructure and performance tests are conducted on the cracked area, clarifying the nature and characteristics of the cracking. The results show that the anodizing surface treatment process has a significant adverse effect on the fatigue life of aluminum alloy components, which is the root cause of the cracking.Corresponding solutions and improvements for the failure are proposed and validated through effectiveness tests. Furthermore, combined with the research results, the key design points for the high-pressure cylinder of hydraulic Reservoir in terms of pulse fatigue resistance were summarized.