Aiming at the problems of the existing isothermal discharge method, such as big measurement error and poor repeatability, a deep research on the measurement errors of the isothermal discharge method has been conduced. The influences of the pressure gradient, the temperture gradient and the measurement noise on the results of the isothermal discharge method have been discussed, the research products are helpful for improving the performance of the isothermal chamber and reduce the measurement error of the isothermal discharge method for testing the flowrate characteristics of the pneumatic components.

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.

In order to imitate the working environment of plunger pump in profiling buoy under sea and provide stable pressure, a new test platform is designed after the scheme of reliability test platform is analyzed. The composition, principle and characteristics of the mechanism are analyzed. The hydraulic cylinder and pulley block are designed. The mounting plate is optimized via the strength analysis using finite element analysis software. The results indicate that the mechanism is reliable, which output pressure for different size of plunger pump is adjustable.

The Chinese and foreign research on torque converter are summarized from three aspects including design, analysis of flow field and optimization. The development trend in future is also investigated primarily including flat design, design platform development and details research of flow field characteristics. Based on the current research achievements, it is noted that design, analysis and optimization are always researched synthetically. Finally, the new development trend on the integration of the three aspects is put forward and the key technologies are discussed.

This paper introduces the basic principle of high-pressure water jet technology, analysis the principle and characteristics of continuous jet and pulse jet, and summarizes the high pressure pure water jet and abrasive water jet with different characteristics, summarizes the principle and characteristics of two kinds of mixed mode of abrasive, and the high pressure water jet cutting technology as emerging applications in the field of rust and the.

Hydraulic simulation technology has become an important tool for the design and analysis of hydraulic system. As one of the hydraulic simulation softwares, the AMESim software with its own advantages has been accepted and applied in the construction machinery and the hydraulic industry. Combined with the actual cases, the applications of AMESim software in system optimization design, component series development, dynamic power flow simulation analysis, cosimulation and so on are exampled in this paper.

The aircraft piston pump is the key power component of the aircraft hydraulic system, whose power density can be improved by increasing its speed and working pressure. The characteristics and classification of the aircraft piston pump are described in the paper, the critical research challenges and achievements of the high speed piston pump at home and abroad are also analyzed and summarized. Furthermore the dynamic characteristics of the rotary assembly, suction and discharge, and power loss of the high speed aircraft piston pump are given, some improvement measurements are also put forward.

In some engineering applications, accumulators are used for supplying oil for electro-hydraulic position control systems. Different from the traditional electro-hydraulic control systems, the supply pressure of the accumulators will decline over time, and the variable supply pressure will influence the control performance of systems. Aimed at the control problem of electro-hydraulic position systems based on the variable pressure oil source, an experiment platform is set up, and the mathematical model of the system is also built. In order to implement the dynamic compensation of this kind of electro-hydraulic position control system, the relationship between the supply pressure and the output flow rate of the accumulator, and the friction model based on the LuGre model are obtained by experimental methods. A compound compensation controller, which consists of one conventional PID controller, one feed-forward compensator (FFC), and one fuzzy controller (FC), is developed in this paper, and the trajectory tracking performance of the controller in the period intermittently operating electro-hydraulic systems is validated via comparative experimental results.

 编者按：  2019年9月22日，在奉化举行的“中国流体传动与控制青年科学家论坛”上，中国工程院院士、浙江大学机械工程学院院长、浙江大学流体动力与机电系统国家重点实验室主任杨华勇院士受邀发表了一场精彩的报告，题为《智能制造与智能液压件的一些探索》。杨院士的报告，从理论到实践，包括5个实例，深入解读了智能制造在实际的工业应用中到底用在哪里，怎么来用，也指明了智能液压件下一个研究方向，以及青年学者、高校的研究团队下一步要努力的方向。本文是根据杨华勇院士演讲录音整理。

In this paper, the three-dimensional geometric model of hydraulic retarder is built based on an enterprise production as reference prototype, On CFD platform, based on the three-dimensional entity model of the hydraulic retarder, the internal flow field at full-filling condition is simulated and the braking performance is calculated. The simulation results show that there were some problems such as vast vortexes and wall flow separations which added braking torque losses. In order to improve the braking torque, this paper built some schemes with different vane degrees, after calculating and simulating, got the best optimization scheme. The simulation results show that, compared with the optimization schemes and the prototype, the braking performance of hydraulic retarder is obviously improved.

In order to reduce the pollution of external air to the oil, we design a closed tank using an external energy accumulator to adjust the internal pressure of the closed tank. The closed tank and working principle are described, and the related parameters are calculated and a number of tests are verified. The experimental results show that the function of the closed tank is reasonable and the parameters are calculated accurately.

The stateoftheart of pneumatic vacuum technology in material handling is introduced in this paper. First, research on the performance improving and energy saving of the vacuum ejector is presented. Then, the research and developing advance on vacuum pads and the novel integrated vacuum pads such as coanda ejector, cyclone pad and Bernoulli pad are introduced. Moreover, the new advance on the vacuum confirming and isolating technology is also described. Thus, some trends on the development of the pneumatic vacuum technology in material handling are summarized.

As one of the important means to ensure the quality and safety of the product, the air tightness of industrial equipment is required to be higher and higher. For the three aspects of leakage detection, leakage judgment, leak localization and leakage ratedetermination, this paper describes the history and development of domestic and international gas leak detection methods, and explains the technology of ultrasonic and infrared detections which rise in recent years in detail.

环境压力补偿是目前深海水下液压系统最常用的结构。本文介绍它的结构与工作原理,分析了影响其长时间工作可靠性的两大核心风险——旋转轴动密封和运动软管老化问题。在此基础上,介绍了远程液压源、深海静压源两种目前国外回避上述风险的方法,分析了各自的优缺点和适用条件。最后指出,廉价的、长寿命的海水液压系统,仍然是彻底解决深海水下液压系统的高风险问题的最佳途径,但尚有一段路要走。

Compared with the oil hydraulic, the water hydraulic has many advantages such as safety and environment protection, resource saving and being easy to use, and becomes one of the research hotspots on the field of fluid power transmission and control. However, hydraulic components have some common problems such as cavitation, abrasion, corrosion and leakage, which seriously restrict the further development of water hydraulic. The emulsion hydraulic has both advantages of mineral oil and pure water medium because of the use of high water-based emulsion as its transmission medium, which makes it widely used in underground coal mines. In this paper, firstly, the application of emulsion hydraulic technology on the support equipment underground coal mines and the existing problems such as pollution, lubrication and abrasion, are described; then, the surface texture technology of core of three-function valve for support equipments of coal mine are introduced especially; finally, the development prospect of the water hydraulic in coal mines is summarized and presented.

Unloading eggs machine is one of the main equipment in clean egg production line. It replaces manual unloading eggs and greatly improves the production rate.This article mainly introduces the institutions of machine , pneumatic system, vacuum system. Vacuum suction cups and vacuum generator are calculated and selected. Practice shows that it can be used with existing clean egg production line.

In order to improve the adaptability and reliability of the prestressed tensioning device, a tension control system is designed, which based on variable frequency motor driving quantitative pump, and the mathematical model is established. After that, considering the nonlinearity and time-variant parameters of the variable frequency hydraulic control system, the adaptive fuzzy PID control algorithm is proposed to solve the adaptability problem of the regular PID control. And the fuzzy set, the fuzzy tuning rules are given based on the expert experience, and the reasonable PID parameters are selected. Finally, the control system simulation is simulated by using MATLAB/Simulink, and the experiments are used to verify the control effect of the algorithm. The results of simulation and experiments show that the adaptive fuzzy PID control can reduce the overshoot of tension, shorten the adjusting time, and can effectively improved the dynamic response and steady state performance of the variable frequency pump-control system.

Accelerated Lifetime Test (ALT) on virtual test is an efficient aid to conduct experiments. A general scheme of virtual test and fatigue analysis for aircraft hydraulic pumps is described. In addition, four key technologies: the multi-domain modeling, the data flow management, the analysis flow of fatigue lifetime, and the verification and validation, are presented. An application of an aircraft hydraulic pump is given to show the results by the presented method under two working conditions. Finally, the advantages and limitations, and combination method of virtual lifetime test and regular lifetime test are summarized.

To improve the signal tracking accuracy and suppression of surplus torque of electric load simulator system,the structure and principle of electric load simulator were analyzed,on the basis of which a complete mathematical model of the system was established. A compound control method based on the combination of feed-forward compensation and PID control based on wavelet neural network was proposed to solve the torque tracking of the electric loading system.The improved feed-forward compensation method was used to restrain the surplus torque.The PID controller based on wavelet neural network was used to adjust the PID parameters on-line and to improve the dynamic performance of the system.Simulation results demonstrate that the compound controller has a good inhibitory effect on the surplus torque and the tracking accuracy meets the requirements. The system robustness is improved significantly comparing with the traditional PID control.

The hydraulic system principle of suspension for girder machine TLMEL900 is expounded. Great vibration and noise are created during the downward moving period of the girder machine. To solve the noise problem, the theory analysis and simulation are done and a new scheme using a hydraulically pilot operated check valve with external pilot oil drain is proposed. Simulation analysis and tests have been carried out and the results show that the improved suspension system is stable and no noise.

Oil temperature rise in hydraulic system depends on the rates of heat generation and heat transfer. Convective heat transfer coefficient is the key to accurate computation of heat transfer and one of the difficulties of thermoanalysis in hydraulic system. In this paper, the development of measurement and computation methods of convective heat transfer coefficient is presented first, and then a summary of the methods applied in engineering is given, which includes the analysis ofcharacteristics, applicability and prospects of these methods, to provide reference for accurate measurement and computation of hydraulic system.

During offshore operations in harsh sea conditions, the active heave compensation (AHC) system used on the ship-mounted crane can improve the vessel’s safety and efficiency. Also the variation of the cable forces resulting from the vertical motion of the vessel can be effectively reduced due to the application of the AHC system. Hence, the crane’s winch driving system is constructed based on the secondary regulated hydrostatic drive technology. And the full mathematic model of the heave compensation system is presented. Then a triple closed-loop control structure, which includes the position closed-loop of the stroke cylinder fixed in the secondary unit, the speed closed-loop of the secondary regulated hydraulic motor and the position closed-loop of the secondary regulated hydraulic motor, is developed. Afterwards, the vertical motion of the vessel is adopted as the measurable disturbance and the feedforward compensator is introduced by the structure-invariable principle. After that, an observer is designed to estimate the position of the crane’s cargo by the cable tension. Lastly, a design example for the active heave compensation is provided and the effectiveness of the controller design method is demonstrated by numerical simulations.

 By the softwar the internal jet velocity contours, the pressure contours, the velocity and pressure distribution characteristics of jet flow field of deflector jet valve with different ratios of nozzle width to the minimum width of flow guide window are obtained by the geometric model and flow field simulation of deflector jet valve. The influence law that ratio for oil flow rate, jet flow rate and jet flow efficiency are obtained by the simulation data. The study shows that part of the oil from the nozzle can reverse movement along the Vtype guide slope due to the effect of Vtype guide slope, so that the effective jet flow of the oil flow is reduced. Meanwhile the whirlpool and the energy loss appears on both sides of the entrance of deflection plate; the oil flow rate approximately linearly increases, and the jet flow rate increases firstly and then decreases with ratio increasing; When the ratio is 1, the jet flow rate will achieve the maximum value of 12.5 kg/s, The corresponding efficiency of jet flow is 77.6% maximum. The research results provide theoretical basis and reference for the improvement of the efficiency and the structure optimization design of the deflector jet servo valve.

The piston rod of the adjustable stroke of the hydraulic cylinder is taken as the object of study.For its structural characteristics affect the performance of the hydraulic cylinder as a whole, the finite element model is established based on structural features taking advantage of ANSYS. Through the analysis of the working condition of hydraulic cylinder with adjustable stroke, predict the position of the largest stress condition.Static analysis and fatigue analysis of the piston rod were conducted in this position. The yield strength of the piston rod is checked.The stress, deformation and life distribution of the piston rod are obtained. And the deformation is found to be larger which directly affects the sealing performance of the hydraulic cylinder. Based on this analysis, the optimization design to the piston rod is carried out. The structure size of sealing ring is changed. The appropriate transition chamfer of piston rod is increased and the model again conducted. The results show that the optimum can significantly increase the characteristic of piston rod.

To ensure the stability and security of self-handing trailers’ lifting mechanism during operation, a design method of synchronous hydraulic system is put forward. The new control method based on electro-hydraulic proportional technology is adopted. Design and calculation of its synchronous hydraulic system and selection of relevant hydraulic components are completed. Reference is provided for the hydraulic system simulation and practical application in the future.

Electro-hydrostatic actuator with high power/weight ratio is compact and efficient. In order to obtain an accurate linear model of the actuator, genetic algorithm is adopted to identify the parameters of the model. A group of parameters can be seen as the genetic code of a chromosome. We use the real frequency response data of the system to evaluate the quality of the chromosome and establish a fitness function. By the selection method based on sequence, the arithmetical crossover operator and the Gauss mutation operator in the iterative calculation, the population of chromosomes gradually evolves to search for the optimal solution. Finally, the identification result is presented to prove the efficacy of this method.

For single-stage expander inefficiencies and other defects, two-stage expansion device is proposed by the thermodynamic and kinetic analysis method, and a mathematical modelis built. According to two-stage system model computer simulation results show that: two-stage expansion in the high pressure conditions, high-pressure gas is expanded more fully in accordance with the high-torque, low-speed performance requirements. In addition, a number of control parameters are selected to study their impact on aerodynamic efficiency and pneumatic power. Under the same design speed, adopting different intake stroke ratio and the transmission ratio, the aerodynamic efficiency of the system is basically the same and the low load rate will improve the efficiency of the system; the second cylinder size has little effect on the aerodynamic efficiency of the system, but it has influence on pneumatic power, the appropriate size should be selected.

Adding an electro-hydraulic power steering system to the rear axles of tradition multi-axils vehicle can make it become an all-wheel steering vehicle and enhance the steering performance d. However, the additional system causes some problems. The first is whether the front axles steering mechanism need to be redesigned to meet Ackerman steering. The second is how to keep rear wheels in straight line when these do not need to steer or the EPS (electrical power steering) is failure. The third is how to ensure mode switching smoothly if the controller has multi-steering-modes. An effective solution of those problems will determine vehicle's performance. So, in this paper, those problems have been analyzed mainly from mechanical, hydraulic and electronic controlling based on four axles vehicle.

In order to test the control performance and energy saving effect of semi-active heave compensation drawworks, the principle prototype and experimental system of compensation drawworks are designed on the basis of similitude theory. The experimental system includes heave simulation hydraulic system, load simulation hydraulic system and the 1∶5 reduced scale principle prototype of compensation drawworks , respectively achieve experimental functions of wave making, loading, heave compensation and automatic bit-feeding motion. The electric control system is developed. Heave compensation control employs hook displacement closed loop, automatic bit-feeding control employs load pressure closed loop and motor control employs vector control mode with velocity feedback. The principle prototype of compensation drawworks is tested. Heave compensation process, automatic bit-feeding process and the linkage of the two processes are simulated through experiment. Meanwhile, the control performance of compensation drawworks and energy saving effect of hydraulic accumulator are tested. The experimental results indicate that the control effect of compensation drawworks is good, the energy saving effect of semi-active compensation system with respect to active compensation system is obvious.

A new type of 4/2 directional control valves applied to Large flow systems is proposed and experimented in this study. The opening and closing of the four cartridge unit are controlled by pilot control cavity pressure of the 3/2 pilot ball valve. The performance of the water hydraulic valve was tested on the testing platform after its processing and assembly. By experiment of the impact of the pilot damping, springs, and other factors on the valve dynamic performance, the testing results reveal that 1) the plug-in 4/2 valve achieved a good performance under static condition; 2) valve core was without buffer head and the pilot orifice diameter equals 3 mm, the dynamic performance of system could perform better; 3) while under the condition that normally closed valve cores were with spring, the response time of the entire valve would sped up, and the dynamic performance of system would effectively improved.