The electro-hydraulic load-sensitive system based on feed-forward control is a volumetric throttling compound speed control system, which can open the valve port fully to reduce energy loss, but under overrunning conditions, the system speed characteristics can be affected by the reduced damping of the valve port, causing problems such as actuator overspeed drops and even safety accidents. To address this problem, a solution is proposed for electro-hydraulic load sensitive systems with post-valve pressure compensation: the load inlet cavity pressure is controlled to a constant value, and a corresponding pressure cascade controller is developed. The controller uses the speed feedback as the inner loop to improve the system's resistance to load disturbances and the PI controller with anti-windup compensation as the outer loop to control the working chamber pressure to a certain value. Test results based on different load conditions on a 2-ton excavator show that the working chamber pressure control can reduce the proportional valve orifice losses while maintaining the actuator speed control performance compared to the traditional direct control orifice by the handle.

The dynamic characteristics of micro high-speed axial piston pump affect the performance and life, vibration response and centroid trajectory of the shaft and cylinder can reflect the dynamic characteristics. Based on the simplified micro high-speed axial piston pump structure, the dynamic model is established under the operation condition. Vibration displacement spectrum, overturning angle spectrum and centroid trajectory of the shaft and cylinder are analyzed when working pressure is 21 MPa and rotating speeds are 18000, 20000, 23000 r/min respectively; vibration displacement spectrum, overturning angle spectrum and centroid trajectory of the shaft and cylinder are analyzed when rotating speed is 20000 r/min and pressures are 14, 21, 28 MPa respectively. The results show that the vibration displacement is more related with the even harmonics, the overturning angle is more related with the odd harmonics, and some harmonic responses of vibration increase with the pressure rises, the centroid trajectory of shaft and cylinder is in the shape of a fan blade.

Energy recovery device (ERD) is one of the core components of seawater reverse osmosis desalination system which can reduce energy consumption and save cost by recovering the pressure energy of high pressure brine, strengthening basic research on it and breaking technical bottleneck are strategic choices to alleviate the water resources crisis in China. According to the working principles, ERD can be divided into three types: hydraulic turbine type, positive displacement type and pump-motor type. Research situation of ERD at home and abroad is reviewed, and the development direction and key technologies of ERD in China are summarized and prospected. It shows that the hydraulic turbine type device has been gradually eliminated, and the positive displacement type device which dominate the market has technical drawbacks. At last, integrated designing and reducing energy consumption of the pump-motor type device are significance research direction in the future.

Pneumatic muscle actuators (PMAs) are widely used in industry and research fields because of light weight and good flexibility. However, the pneumatic equipment driving this actuator make the size of system relatively large. In order to solve this problem, this paper proposes a method of using the expansion work of fluorocarbon during gas-liquid phase change (GLPC) to drive the PMA, adopts metal ceramics heater (MCH) to heat the fluorocarbon, uses PI controller to control the internal pressure of the PMA, and manufactures antagonistic drive device to improve the dynamic characteristics of the force. The experimental results show that the pressure inside the PMA driven by GLPC can track the reference signal well. Compared with air driven method, the contraction rate of the PMA reduced almost by a same value when driven by GLPC. The antagonistic drive device can improve the dynamic characteristics during the force disappearing process.

In order to investigate the influence of the width of the valve orifice on the flow characteristics of the nozzle flap-type piezoelectric pneumatic microvalve. The flow characteristics of the valve orifice with different sealing widths were numerically simulated by using the SST k-ω turbulence model and CFD technology. It is found from the calculation results that the valve face sealing width has a significant effect on the flow characteristics of the piezoelectric microvalve port. The reasonable valve face sealing width can reduce the pressure loss of the valve port and improve the flow capacity of the pneumatic microvalve port. It is also found that the flow-pressure coefficient of the microvalve is not affected by the sealing width of the valve port end face. All the studies provide an important reference for valve port design.

Aiming at the current problems of the hydraulically actuated quadruped robot, such as chaotic structure, large energy loss and complex control strategy, the research status of quadruped robot is analyzed from the robot, hydraulic system and control strategy. Firstly, the robot of each team is introduced, and the technological gap between China and developed countries is pointed out. Then, the main two components of the hydraulic system are described from four aspects: power source, system types, hydraulic circuit and servo actuator, during which the energy saving system and highly integrated servo actuator are introduced in details. Then several mainstream control strategies are summarized, and their respective advantages and disadvantages are pointed out. Finally, the future trends of hydraulically actuated quadruped robot will concentrate on high speed, high pressure, lightweight, energy-saving system, noise reduction and advanced control algorithm, so as to realize the high dynamic performance and industrial application.

The spacesuit not only can provide the basic life guarantee for the spaceman but also should have a high movability. Due to the space suit vacuum protection caused by the high-pressure air, spacesuit joint inevitably has a considerable resistance moment, making a great impact on the movement of wearer. This paper develops a test platform which can eliminate the interference of gravity and traction trajectory error, and tests the resistance moment of the elbow joint, knee joint and hip joint of the spacesuit, and analyses the relationship between the resistance moment of the joint and the residual pressure of the spacesuit and the speed of the joint. Base on the data obtained through test, the mathematical model of spacesuit joint angle and joint resistance moment is established with the combination of the improved numerical implementation method of Preisach hysteresis model and linear interpolation method. The simulation and model prediction are carried out in MATLAB/Simulink software environment. Comparisons are drawn to verify the improved hysteresis model can accurately predict the resistance moment of spacesuit joint, which provides a theoretical reference for improving the movability of spacesuit joint.

In order to improve the position control performance of the pilot operated electro-hydraulic proportional valve, and solve the inconsistency problem caused by the mass production of the pilot operated electro-hydraulic proportional valve. Firstly, a non-linear mathematical model of the proportional valve is established. Secondly, for the problem of inconsistent and difficult detection of the proportional valve dead zone, an online dead zone detection method is proposed to collect the solenoid current value of the pilot valve when the main valve starts to move, the current that read online by the host computer for precise compensation is used to characterize the size of the dead zone. Then, aiming at the shortcomings of low control efficiency and accuracy caused by ordinary PID of fixed gain, a fuzzy PID adaptive position controller based on dead zone online detection is designed to dynamically adjust various parameters of the controller in real time. Finally, based on MATLAB software and proportional valve test platform, the effectiveness of the control method is verified. The research results lay a theoretical foundation for the mass production of pilot operated electro-hydraulic proportional valves.

Pump control systems have higher hardware integrations and faster responses as well as the high energy efficiency characteristic with the development of variable speed motor-pump direct-drive systems and the improvement of servo technology. In order to achieve the precise motion control of the pump-controlled hydraulic systems, this paper proposes a non-linear mapping method to obtain an accurate pump flow rate model. At the same time, the nonlinear adaptive robust backstepping strategy is used to achieve precise control of the hydraulic system with high-order dynamics and uncertain nonlinearities. Experiments show that the proposed control strategy can effectively handle flow deviation and achieve ideal trajectory tracking accuracy.

Fault features of axial piston pump are difficult to be extracted under variable speed conditions, a fault diagnosis approach is proposed using polynomial Chirplet transform and variational mode decomposition. First, polynomial Chirplet transform is applied to estimate the instantaneous frequency. Then the original signal in time domain is resampling to a stationary one in angular domain based on the estimated instantaneous frequency. Finally, the angular domain signal is decomposed by variational mode decomposition into a series of intrinsic mode functions, envelope order spectrum is applied to detect the bearing fault characteristic order and failure mode. The result of the experiment indicates that the new fault detection algorithm is efficient for the bearing of axial piston pump under varying speed conditions.

At present, multi-finger soft end-effector is difficult to hold different caliber vessels smoothly. Based on this situation, a new clamping method is proposed. Firstly, design the structure of the gas-braced soft end actuator, which consists of a soft actuator and a connecting device. Secondly, based on the yeoh model, virtual work principle and software driver structure to establish the nonlinear mathematical model of driving pressure and software driver expansion deformation. And then the abaqus software simulation and experiment of software end actuator expansion deformation are carried out, and the theoretical model and simulation and experimental results are compared. The results verify the correctness of the theoretical model. Finally, the clamping experiment of the gas brace soft end actuator is carried out. The experimental results show that the proposed gas brace end actuator can grasp the containers of different caliber well.

When the heavy load AGV turns at full load, the steering resistance increases obviously, which makes it difficult for the steering control system to control quickly and accurately. Therefore, a control method based on Fuzzy PID is proposed to modify the control parameters of steering system in real time and dynamically. According to the AGV steering system structure, the control model is established, the fuzzy PID controller is built, the membership function and fuzzy rules are formulated, and the parameters of the controller are updated according to the angle deviation and deviation change rate, so that the hydraulic adjustment can be dynamically modified according to the needs, so as to ensure the fast and accurate deflection of the wheel when the steering resistance is high. The simulation and experimental results show that the fuzzy adaptive PID algorithm can effectively reduce the overshoot and vibration amplitude of the system, accelerate the response speed of the system, and improve the control accuracy and response speed of the heavy load AGV hydraulic steering system.

The double-acting pneumatic hydraulic hammer uses the gravity of the ram and the nitrogen pressure at the top of the piston to achieve a quick strike to the pile and penetrate the pile into the soil. Based on the principles of impact dynamics and wave theory, the whole process from the impact of the hammer to the pile until the pile penetrates into the soil during the construction of the pile is analyzed, and the interaction model between the components of the pile driving system is established. The analytical solution of the hammering force during the pile driving process was derived by using Laplace transform method. From the theoretical aspect, the rationality of the “heavy hammer and light blow” in the actual construction process was verified. Finally, the dynamic equations of the hammer-pile-soil system were established for the two soil medium models.

In order to improve the precision of organic fertilizer and chemical fertilizer mixed fertilizer applicator, a kind of organic fertilizer chemical fertilizer ditching and fertilizing machine is designed with the fertilization requirements in Xinjiang orchard. The structure and working principle of the whole machine are described and the hydraulic system is analyzed theoretically and simulated. The torque of the fertilizer conveying motor is 363.21 N·m. The error is 0.27% compared with the theoretical calculation result of 364.2 N·m. The average velocity of the hydraulic cylinder is 30.59 mm/s, which meets the working requirements and verifies the accuracy of the theoretical calculation. In addition, the motor of organic fertilizer works stably under the theoretical calculation parameters, which verifies the rationality of parameter setting of AMESim simulation model.

The curriculum ideological and political education is an important method for colleges to carry out the fundamental task of fostering talents, and it is also a requirement of the development of the new era for the professional curriculum teaching on the goal of applied talents with both political integrity and ability. This study takes the “Fluid Mechanics and Hydraulic and Pneumatic Technology” as an example to explore the teaching mode of the hydraulic pneumatic technology, and promote the deep integration of professional course teaching and ideological and political education. In order to improve the training quality of hydraulic and pneumatic technical personnel, we put forward the “1+5” ideological and political construction practice method based on the attempt and experience in the ideological and political teaching reform.

Electrification of construction machinery is one of the most ideal driving methods for energy saving and emission reduction. The LUDV system used in traditional construction machinery is mainly used in the variable flow mode of variable displacement and fixed speed due to the limitation of the speed regulation characteristics of the diesel engine. When multiple actuators work at the same time, flow saturation is likely to occur. The motor has good speed regulation characteristics compared to the diesel engine. In order to further avoid the phenomenon of flow saturation, a dual variable power control method based on staged differential pressure control is proposed to explore the use of comparing the actual load pressure difference with the set pressure difference to improve maneuverability. The relationship between different target flow stages and the actual pressure difference of the load is analyzed to achieve a full range of flow matching. The variable displacement working range of the control variable pump is in a region of higher efficiency to avoid the occurrence of flow saturation. Simulation model is established in AMESim. Finally, a test prototype was built to test, and verified that the graded differential pressure control has a good flow follow-up, solves the problem of flow saturation at low speed and fixed speed of the traditional excavator, and improves energy saving by more than 19% at high speed.

Aiming at the characteristics of the existing magnetorheological brakes lacking power-off protection and relying on the power supply and the waste of excess rotational energy under the non-braking conditions of the brake shaft, a magnetic current with energy feedback function for traction elevators is designed. The variable brake can capture, collect and store the rotating energy of the shaft. The energy storage device can still act on the excitation coil together with the main power supply to compensate for braking under special circumstances. As far as possible, a circulating water cooling system is added to the brake in the design. This article first introduces the structure and working principle of the new magnetorheological brake, and then conducts theoretical analysis and modeling simulation. According to the design, the prototype of the new type of magnetorheological brake is manufactured and tested. The four aspects of its braking performance, energy recovery performance, temperature rise and noise are tested. The results show that this kind of energy feedback type magnetic current The maximum temperature under variable braking continuous braking conditions does not exceed 60 ℃, the system torque can reach 380 N·m, and the energy feedback efficiency can reach up to 50%.

The overturning phenomenon of cylinder block might occur in the actual working process of axial piston pump which affects the reliability and life time of axial piston pump. In order to identify the cause of the overturning of cylinder block, a 1D-3D co-simulation model is established for research. Firstly, analyzing the load conditions and dynamic equations with six degrees of freedom of the cylinder block. Secondly, a 1D hydraulic system model and a 3D multi-body dynamics model of the axial piston pump are built, and data interaction between the simulation models is realized through the interface to obtains a complete mechanical-hydraulic simulation model. Lastly, the dynamic movement of the cylinder block under different working conditions are simulated and analyzed. The research results show that the co-simulation model can simulate the load conditions of the cylinder block accurately, analyze the dynamic movement of cylinder block under different working conditions, and can be used as a powerful analysis tool for exploring the overturning phenomenon of the cylinder block.

In order to solve the problem of insufficient volumetric efficiency caused by the mismatch between the structural parameters of the check valve system of a new type of water hydraulic axial piston pump driven by a cross wobble plate and the pump speed and the diameter of the plunger, the ADAMS-AMESim solid-liquid coupling simulation model of the hydraulic pump is built. At the rated speed of the new pump, the influence of the check valve core mass, spring stiffness, spring preload and the spherical diameter of the valve core on the volumetric efficiency of the new pump is analyzed. And its check valve system is optimized. The results show that the volumetric efficiency of the new pump increases with the increase of the spring stiffness and preload of the check valve, and decreases with the increase of the mass and the spherical radius of the valve core. And, the influence of the structural parameters of the inlet valve on the volumetric efficiency is greater than that of the outlet valve. Therefore, in the design of the check valve system, the stiffness and preload of the spring of the check valve should be properly increased, the mass of the valve core and the spherical diameter of the valve core should be appropriately reduced, so as to improve the volumetric efficiency of the pump.

The rapid-erection device is widely used in the engineering machinery and military field, such as dump truck and missile launching vehicle respectively. The hydraulic drive system is the core of the quick erecting device, so it is of great significance to diagnose its faults accurately. With the increase of the number of fault types, the accuracy of fault diagnosis of traditional BP neural network drops sharply, which is difficult to meet the engineering requirements. A fault diagnosis method based on BP neural network and AdaBoost algorithm is proposed for the hydraulic drive system of quick erecting device. Through the combination of BP neural network and step-by-step superposition modeling algorithm, a multi classification BP AdaBoost fault diagnosis model is established. Design the experimental system and set up 8 typical working conditions. The results show that the BP AdaBoost algorithm used in this paper has better classification performance than the traditional BP neural network method.

In order to deeply understand the advantages of pilot control valves, as well as to effectively improve the performance, the recent developments of pilot control valves are summarized, divided into the drive components, spring components, valve core and damping hole; the different functions of pilot control valves controlled by the pilot structure are introduced from pressure control, flow control and direction control; the influence of different pilot structures on the performance of pilot control valves is analyzed from static and dynamic characteristics. The results show that, the valve core and the orifice position have great effects on the performance of valves, further innovations are needed in control strategies and principles for flow and direction control. There is a certain contradiction between the dynamic and static characteristics of pilot control valves. In future, novel special functional pilot control valve development, the quantitative analysis of pilot structure parameters effects on dynamic and static characteristics will be important research directions.

In order to meet the requirements of ultra-clean flow control in the fields of semiconductor and biomedicine, a new permanent magnet (PM) embedded ultra-clean valve is proposed. The control of ultra-clean liquid is realized by embedding the PM into the valve core, which is made by ultra-clean material (such as ultra-pure perfluororesin) and can be driven by moving of the PM outside the chest. The working principle of the propsed valve is presented firstly, and then its flow-pressure loss characteristics are analyzed by simulation. Besides, through calculating the fluid force and the magnetic force acting on the valve core under different spool positions, the feasibility of the idea is verified. Furthermore, to improve the opening and closing characteristics of the valve, the design of the driving magnetic field is optimized, which is proven to be effective by simulation.

Soft actuators possessed highly flexible, complex environment adaptability and safe human-interaction. Firstly, in order to solve the limitation of stiffness control poorly of traditional soft actuators, based on the antagonistic mechanism of extensor and contractor muscles, a novel variable-stiffness fluid-driven soft actuator is proposed in this paper. The actuator can realize the composite action of elongation/contraction, and realize stiffness control by cooperatively adjusting the elongation and contraction forces. Secondly, based on the flexible deformation mechanism of the stretched and contracted fabrics, the mechanical model of the soft actuator is established and simulated. Finally, the mechanical properties of the actuator were tested under different pressures and deformation displacements, and the variable-stiffness characteristics of the actuator were verified. This research has significance to the research of soft actuator with variable stiffness.

In view of the traditional engineering equipment manipulator problems such as gravitational potential energy waste and poor operation characteristics, a hydraulic-electric hybrid semi-active driving system is proposed. Hydraulic cylinders with high power-weight ratio assist low power electro-mechanical actuators to drive the manipulator. Electro-mechanical actuators actively control the manipulator to improve the operation characteristics. Hydraulic cylinders are connected with the accumulator to form energy storage balance system, recycling the gravitational potential energy. According to different combination modes of electro-mechanical actuators and hydraulic cylinders, three different driving schemes are proposed. Taking the excavator boom as specific application object, detailed parameter matching design and simulation analysis of the three driving schemes are carried out. Compared with the load sensitive controlling system of three-chamber hydraulic cylinder, the hydraulic-electric hybrid semi-active driving system can further reduce energy consumption by 51%~56%. The boom velocity overshoot and fluctuation are small. The research provides a new direction for driving system of lifting mechanism, can realize green driving and has broad application prospects.

In order to find the ultimate energy saving boundary and clarify the energy saving mechanism of the independent metering system (IMS), static efficiency models and static energy consumption models of the conventional valve-controlled system (CVS) and the IMS are established, and then simplified to non-dimensional form by normalization method. Two kinds of working conditions which can be compared with the CVS are selected, that is, the same pump pressure source conditions and the same orifices area conditions. The comparison is made when the IMS is in the ultimate energy saving condition (the meter-out orifice is full-opened). Finally, the static efficiency and static energy consumption of two systems under different working conditions are analyzed by simulation. The comparison of efficiency distributions under all working conditions is obtained by the efficiency mapping. The results show that under the same pump source pressure, the IMS can improve the efficiency by about 5.7% and reduce the energy consumption by about 22.7% at most. Under the same orifices area, the IMS can improve the efficiency by about 19.4% and reduce the energy consumption by about 53% at most. The IMS can reduce the throttling loss of the orifices, and thus reduce the energy consumption of the CVS.

In order to reduce the impact of the folded control surface of the missile when it is unfolded under severe wind load condition in hypersonic flight, it's necessary to design an active damping gas actuator and develop the principle prototype. Based on the introduction of actuator structure and working principle, the main parts of the actuator are designed, and analyed by finite element method. Then it gives the method of wind load simulation on the control surface, and also provides the ground simulation loading system. The mathematical model and simulation model of the working process of the actuator are established, and the main technical parameters of the actuator are obtained through the simulation analysis by MATLAB/Simulink. Finally, ground simulation loading experiment shows that under the condition of downwind load, the piston rod of the actuator firstly accelerates, then decelerates, and finally moves to the final position at a smaller speed, so the actuator has a good load adaptive ability. The result of the experiment is almost consistent with the result of the simulation analysis, so the result can be a reference for subsequent engineering application.

As a common fault type of the electro-hydraulic directional valve, the internal leakage vibration signal has the characteristics of non-stationary and non-linear, and it is easy to be submerged and corrupted by other signals. For the feature, an empirical mode decomposition (EMD) and one-dimensional densely connected convolutional networks (DenseNet) method is proposed to diagnose the internal leakage in the Electro-hydraulic Directional Valve. Firstly, a series of intrinsic mode functions (IMF) are obtained by decomposing the vibration signals with EMD, and the IMF components and the original vibration signals are stacked in parallel successively. Then, the parallel stacked signals are used as the input of one-dimensional densely connected convolution network for feature extraction and fault classification. Finally, compared with DenseNet and the traditional one-dimensional convolution neural network, it can be concluded that this method can accurately and effectively diagnose the internal leakage fault in the Electro-hydraulic Directional Valve.

The development trend of miniaturization and integration puts higher requirements for the design of the hydraulic valve block. It is difficult and complicated to process the internal flow channel of the valve block with traditional technology. And the flow characteristics need to be improved. The new manufacturing process, additive manufacturing shows great advantages to inflow channel processing. Based on additive manufacturing the transition region of the flow channel is optimized design. Simulation was carried out by Fluent to analyze the characteristics of the flow channel connected by three methods: A linear transition, a circular transition, and a B-spline curve. It is found that the pressure loss of the B-spline curve transitional flow reduces more than 55% compared with the straight line transitional flow channel. The circular arc transitional flow channel is reduced by 28%~56% differently. The results provide a theoretical basis for the necessity of flow channel design based on additive manufacturing.

Taking a semi-submersible floating wind turbine platform as the object, the anchor chain and polyester fiber rope are connected in sections to form a tension mooring system, and the mathematical model of environmental load and the dynamic equations of the platform and mooring system under the environmental load are established. By means of Simulink lumped parameter calculation and AQWA numerical simulation, the platform's response characteristics under wind load step input and wave load sinusoidal input are compared and analyzed. The results show that the Simulink lumped model calculation results are similar with the AQWA numerical simulation results, which shows the rationality of the lumped parameter modeling method to a certain extent. The study found that under the action of wind step input, the platform mainly shows the response of the three degrees of freedom of swaying, heaving, and rolling. The swaying stability time is short, but the offset is relatively large. The stability time of rolling is long and basically consistent. Under the action of wave sine input, the platform also mainly shows the response of the three degrees. The amplitude of the swaying is also larger than that of the heaving. The reason for the larger swaying displacement and amplitude is that the design of the semi-submersible platform with tensioned mooring is adopted. Further restricting this degree of freedom is the next research direction of the optimal design of the platform and mooring system.

Based on the Archard equation and fluid-thermal-solid coupling method, a friction and wear prediction model for the aircraft piston pump port pair under high-speed and high-pressure conditions is established. Considering the coupling effect between the pressure, temperature and solids of the port pair on wear, a fluid-thermal-solid coupling model of the port pair is established. The oil film pressure and temperature fields of port pair are obtained by the finite element method, which will be used as the boundary conditions of wear prediction model. Then through the relationship between leakage flow rate and oil film thickness, the wear failure life of port pair is predicted and analyzed. The results show that the wear failure life of port pair is more than 2000 h under the conditions of 10000 r/min speed and 28 MPa pressure of aircraft piston pump. However, with the increase of speed and pressure, the wear failure life of port pair is significantly shortened. When the speed is 15000 r/min and the pressure is 35 MPa, the wear life of port pair is only 450 h. Therefore, some methods to improve the wear life of port pair are proposed. The prediction model has a certain guiding significance for the design of port pair of the high-speed and high-pressure aircraft piston pump.