Hydraulic cylinder is a primary component of the hydraulic valve systems.The numerical study of hydraulic cylinder to evaluate the stress analysis,the life assessment and the performance of operation characteristics i...Hydraulic cylinder is a primary component of the hydraulic valve systems.The numerical study of hydraulic cylinder to evaluate the stress analysis,the life assessment and the performance of operation characteristics in hydraulic cylinder were described.The calculation of safety factor,fatigue life,piston chamber pressure,rod chamber pressure and the change of velocity of piston with flow time after the beginning of hydraulic cylinder were incorporated.Numerical analysis was performed using the commercial CFD code,ANSYS with unsteady,dynamic mesh model,two-way FSI(fluid-structure interaction)method and k-εturbulent model.The internal pressure in hydraulic cylinder through stress analysis show higher than those of the yield strength.展开更多
Cylinder-crown integrated hydraulic press( CCIHP) is a new press structure. The hemispherical hydraulic cylinder also functions as a main portion of crown,which has lower weight and higher section modulus compared wit...Cylinder-crown integrated hydraulic press( CCIHP) is a new press structure. The hemispherical hydraulic cylinder also functions as a main portion of crown,which has lower weight and higher section modulus compared with the conventional hydraulic cylinder and press crown. In order to design cylinder-crown integrated hydraulic press with large capacity, the theoretical design of hemispherical hydraulic cylinder was first proposed,and the structural parameters of 150 MN CCIHP were listed. Then the simulation was carried out to analyze the stress and deformation of CCIHP,and weight comparison was conducted between CCIHP and conventional press. It is shown that the weight reduction for hydraulic cylinder and press crown is about 20% compared with that for conventional press,and the stress and deformation are both within the range of constraints including strength and stiffness conditions. It is possible to manufacture cylinder-crown integrated hydraulic press with large capacity.展开更多
As a typical bionic walking robot, hydraulic quadruped robot has attracted much attention because of its high mobility, strong load capacity and steady motion. The electro-hydraulic servo cylinder, as its power actuat...As a typical bionic walking robot, hydraulic quadruped robot has attracted much attention because of its high mobility, strong load capacity and steady motion. The electro-hydraulic servo cylinder, as its power actuator, requires low friction, good lateral load resistance and high speed motion. The electro-hydraulic servo cylinder hydrostatic bearing seal guide sleeve is taken as the research object in this paper. By using Fluent software to analyze and contrast the film characteristics of rectangular and I-shaped oil chamber of hydrostatic bearing seal guide sleeve, the relationship between piston rod moving speed, eccentricity, oil film carrying capacity, friction force and leakage volume, as well as the relationship between oil feed flow and oil film bearing capacity, friction force, inlet pressure and leakage volume were analyzed. This study provides a theoretical basis for optimizing the static pressure bearing seal parameters.展开更多
A kind of four degree-of-freedom (DOF) electrohydraulic lift system is studied in this pa- per, after analyzing the motion characteristics and the mathematic model of the hydraulic cylinders, a cross-coupled synchro...A kind of four degree-of-freedom (DOF) electrohydraulic lift system is studied in this pa- per, after analyzing the motion characteristics and the mathematic model of the hydraulic cylinders, a cross-coupled synchronization method with load force and synchronization error feedback had been proposed to solve the synchronization problem encountered when realizing the needed roll and pitch attitude of the lift system. In this paper, mathematic model of asymmetric hydraulic cylinder was es- tablished and the lift system had been simplified to a dual-cylinder system. By incorporating the load force and the displacement of each cylinder, a cross-coupled synchronized control method was pro- posed to fit each cylinder' s tracking performance and multi-cylinder' s trajectory synchronization property. The proposed method not only solved the synchronization problem when multi-cylinder had a same trajectory, but also could fit the coordinated synchronization need when different trajectories of multi-cylinder were desired. Simulations and experiments on a four DOF electrohydraulic lift sys- tem with load of 100 tons verified the effectiveness of the proposed method.展开更多
Although conventional model reference adaptive control (MRAC) achieves good tracking performance for cylinder control, the controller structure is much more complicated and has less robustness to disturbance in real...Although conventional model reference adaptive control (MRAC) achieves good tracking performance for cylinder control, the controller structure is much more complicated and has less robustness to disturbance in real applications. This paper discusses the use of simple adaptive control (SAC) for positioning a water hydraulic servo cylinder system. Compared with MRAC, SAC has a simpler and lower order structure, i.e., higher feasibility. The control performance of SAC is examined and evaluated on a water hydraulic servo cylinder system. With the recent increased concerns over global environmental problems, the water hydraulic technique using pure tap water as a pressure medium has become a new drive source comparable to electric, oil hydraulic, and pneumatic drive systems. This technique is also preferred because of its high power density, high safety against fire hazards in production plants, and easy availability. However, the main problems for precise control in a water hydraulic system are steady state errors and overshoot due to its large friction torque and considerable leakage flow. MRAC has been already applied to compensate for these effects, and better control performances have been obtained. However, there have been no reports on the application of SAC for water hydraulics. To make clear the merits of SAC, the tracking control performance and robustness are discussed based on experimental results. SAC is confirmed to give better tracking performance compared with PI control, and a control precision comparable to MRAC (within 10 μm of the reference position) and higher robustness to parameter change, despite the simple controller. The research results ensure a wider application of simple adaptive control in real mechanical systems.展开更多
The dynamic characteristics of hydraulic self servo swing cylinder were analyzed according to the hydraulic system natural frequency formula. Based on that,a method of the hydraulic self servo swing cylinder structure...The dynamic characteristics of hydraulic self servo swing cylinder were analyzed according to the hydraulic system natural frequency formula. Based on that,a method of the hydraulic self servo swing cylinder structure optimization based on genetic algorithm was proposed in this paper. By analyzing the four parameters that affect the dynamic characteristics, we had to optimize the structure to obtain as larger the Dm( displacement) as possible under the condition with the purpose of improving the dynamic characteristics of hydraulic self servo swing cylinder. So three state equations were established in this paper. The paper analyzed the effect of the four parameters in hydraulic self servo swing cylinder natural frequency equation and used the genetic algorithm to obtain the optimal solution of structure parameters. The model was simulated by substituting the parameters and initial value to the simulink model. Simulation results show that: using self servo hydraulic swing cylinder natural frequency equation to study its dynamic response characteristics is very effective.Compared with no optimization,the overall system dynamic response speed is significantly improved.展开更多
The mold filling process of titanium alloy in a thin-walled cylinder cavity under vertical centrifugal casting process was studied by means of the hydraulic simulation experiments. Results show that the filling mode o...The mold filling process of titanium alloy in a thin-walled cylinder cavity under vertical centrifugal casting process was studied by means of the hydraulic simulation experiments. Results show that the filling mode of the melt in the cylinder cavity varies with casting wall-thickness. When the casting wall-thickness is less than or equal to the thickness of the first layer during the filling process, the melts fill the cavity from the bottom to the top.When the casting wall-thickness is greater than the thickness of the first layer during the filling process, the melts first fill the largest radius parts of the cavity with a certain thickness of the first layer from the bottom to the top of the cavity, and then they fill the cavity from the larger radius part to the smaller radius part. The melt filling ability increases with the increment of the mold rotational speed and the pouring temperature. In another aspect, the melt filling ability rises with the decrement of the melt viscosity, and the melt with the better filling ability is prone to fill the cylinder cavity layer by layer.展开更多
An inside-cushion structure with sidestep and taper-shaped plungers is studied to address the problems of high impact and vibration in high-speed hydraulic cylinders.First,the three stages of cushion processes are dis...An inside-cushion structure with sidestep and taper-shaped plungers is studied to address the problems of high impact and vibration in high-speed hydraulic cylinders.First,the three stages of cushion processes are discussed according to the varying flow area as the piston moves.Then,to establish a precise mathematical model,the states of the flow field are estimated in terms of the Reynolds number.Accordingly,the simulation model parameterized against measured data is developed and verified by experiment.Last,the average velocity,peak cushion pressure,and terminal velocity are defined to evaluate cushion performance.According to these optimized objectives,the non-linear programming by quadratic Lagrange(NLPQL)algorithm is applied to optimize the structure parameters.The optimization results indicate that the peak cushion pressure is reduced by 28%and terminal velocity is reduced by 21%without reduction of average velocity.展开更多
In this paper a model of a high pressure hydraulic system was developed to simulate the effect of increased internal leakages inside the hydraulic cylinder and the 4/2 way directional control valve and to calculate th...In this paper a model of a high pressure hydraulic system was developed to simulate the effect of increased internal leakages inside the hydraulic cylinder and the 4/2 way directional control valve and to calculate the main parameters of the hydraulic system under various loads through the use of leakage-simulating throttle valves. After the completion of modeling, the throttle valves that simulate the internal leakages were calibrated and a number of test runs were performed for the cases of normal operation and the operation with increased internal leakages. The theoretical predictions were compared against the experimental results from an actual hydraulic test platform installed in the laboratory. In all cases, modeling and experimental data curves correlate very well in form, magnitude and response times for all the system’s main parameters. This proves that the present modeling can be used to accurately predict various faults in hydraulic systems, and can thus be used for proactive fault finding in many cases, especially when the defective component is not easily detected and obvious at first sight.展开更多
This research proposes a component to restrict dust from entering an oil hydraulic system through the rod-seal clearance of an oil hydraulic cylinder.The oil hydraulic cylinder as one of main parts of the hydraulic sy...This research proposes a component to restrict dust from entering an oil hydraulic system through the rod-seal clearance of an oil hydraulic cylinder.The oil hydraulic cylinder as one of main parts of the hydraulic system,controls position of load by reciprocation.For example,on construction machines such as excavators and graders,the cylinder controls position of folk lift,crane and bucket.However,during operation,dust enters the cylinder,wears seals,causes fluid degradation and affects lubrication of valves,pumps and other parts of hydraulic system.This increases breakdown rate of cylinder and entire system.Thus,it seems necessary to reduce on intrusion of dust into the system via the hydraulic cylinder.In this research,we made an experimental apparatus to simulate intrusion of the dust into system.Results proved that the apparatus is a suitable simulator to realize the intrusion.The proposed component to restrict dust from entering cylinder was fabricated and its performance tested when inserted with various elastic rings.The component gave tremendous results when inserted with O-ring seal and a plastic nylon washer,and can be retrofitted on new and old hydraulic cylinders.It is an appropriate technology especially in developing countries where dust is still a major concern.展开更多
The electro-hydraulic servo drive hydraulic cylinder has many unique advantages, such as fast response, high load stiffness, high control power, strong anti-eccentric load ability and so on, so it has been widely used...The electro-hydraulic servo drive hydraulic cylinder has many unique advantages, such as fast response, high load stiffness, high control power, strong anti-eccentric load ability and so on, so it has been widely used in industrial control. Based on the guide sleeve of hydrostatic seal of hydraulic cylinder, the reasonable number of oil chamber of guide sleeve is studied in this paper. ICEM CFD software and FLUENT simulation software are used to calculate and analyze the number of different oil chambers of guide sleeve of hydrostatic seal. The temperature field of piston rod with different moving speed, different initial pressure of oil chamber and oil film under different number of oil chambers is analyzed. The relationship between the pressure field and temperature field provides a better basis for optimizing the design of hydrostatic guide sleeve and helps to improve the servo drive cylinder.展开更多
基金supported by the International Cooperation on Technology Development Program of the Korea Institute for Advancement of Technology ( KIAT),Republic of Korea ( N0000902)
文摘Hydraulic cylinder is a primary component of the hydraulic valve systems.The numerical study of hydraulic cylinder to evaluate the stress analysis,the life assessment and the performance of operation characteristics in hydraulic cylinder were described.The calculation of safety factor,fatigue life,piston chamber pressure,rod chamber pressure and the change of velocity of piston with flow time after the beginning of hydraulic cylinder were incorporated.Numerical analysis was performed using the commercial CFD code,ANSYS with unsteady,dynamic mesh model,two-way FSI(fluid-structure interaction)method and k-εturbulent model.The internal pressure in hydraulic cylinder through stress analysis show higher than those of the yield strength.
基金Sponsored by the High-end CNC Machine Tools and Basic Manufacturing Equipment Technology Major Project(Grant No.2011ZX04001-011)
文摘Cylinder-crown integrated hydraulic press( CCIHP) is a new press structure. The hemispherical hydraulic cylinder also functions as a main portion of crown,which has lower weight and higher section modulus compared with the conventional hydraulic cylinder and press crown. In order to design cylinder-crown integrated hydraulic press with large capacity, the theoretical design of hemispherical hydraulic cylinder was first proposed,and the structural parameters of 150 MN CCIHP were listed. Then the simulation was carried out to analyze the stress and deformation of CCIHP,and weight comparison was conducted between CCIHP and conventional press. It is shown that the weight reduction for hydraulic cylinder and press crown is about 20% compared with that for conventional press,and the stress and deformation are both within the range of constraints including strength and stiffness conditions. It is possible to manufacture cylinder-crown integrated hydraulic press with large capacity.
基金supported by the National 863 Project(2011AA040701)
文摘As a typical bionic walking robot, hydraulic quadruped robot has attracted much attention because of its high mobility, strong load capacity and steady motion. The electro-hydraulic servo cylinder, as its power actuator, requires low friction, good lateral load resistance and high speed motion. The electro-hydraulic servo cylinder hydrostatic bearing seal guide sleeve is taken as the research object in this paper. By using Fluent software to analyze and contrast the film characteristics of rectangular and I-shaped oil chamber of hydrostatic bearing seal guide sleeve, the relationship between piston rod moving speed, eccentricity, oil film carrying capacity, friction force and leakage volume, as well as the relationship between oil feed flow and oil film bearing capacity, friction force, inlet pressure and leakage volume were analyzed. This study provides a theoretical basis for optimizing the static pressure bearing seal parameters.
文摘A kind of four degree-of-freedom (DOF) electrohydraulic lift system is studied in this pa- per, after analyzing the motion characteristics and the mathematic model of the hydraulic cylinders, a cross-coupled synchronization method with load force and synchronization error feedback had been proposed to solve the synchronization problem encountered when realizing the needed roll and pitch attitude of the lift system. In this paper, mathematic model of asymmetric hydraulic cylinder was es- tablished and the lift system had been simplified to a dual-cylinder system. By incorporating the load force and the displacement of each cylinder, a cross-coupled synchronized control method was pro- posed to fit each cylinder' s tracking performance and multi-cylinder' s trajectory synchronization property. The proposed method not only solved the synchronization problem when multi-cylinder had a same trajectory, but also could fit the coordinated synchronization need when different trajectories of multi-cylinder were desired. Simulations and experiments on a four DOF electrohydraulic lift sys- tem with load of 100 tons verified the effectiveness of the proposed method.
文摘Although conventional model reference adaptive control (MRAC) achieves good tracking performance for cylinder control, the controller structure is much more complicated and has less robustness to disturbance in real applications. This paper discusses the use of simple adaptive control (SAC) for positioning a water hydraulic servo cylinder system. Compared with MRAC, SAC has a simpler and lower order structure, i.e., higher feasibility. The control performance of SAC is examined and evaluated on a water hydraulic servo cylinder system. With the recent increased concerns over global environmental problems, the water hydraulic technique using pure tap water as a pressure medium has become a new drive source comparable to electric, oil hydraulic, and pneumatic drive systems. This technique is also preferred because of its high power density, high safety against fire hazards in production plants, and easy availability. However, the main problems for precise control in a water hydraulic system are steady state errors and overshoot due to its large friction torque and considerable leakage flow. MRAC has been already applied to compensate for these effects, and better control performances have been obtained. However, there have been no reports on the application of SAC for water hydraulics. To make clear the merits of SAC, the tracking control performance and robustness are discussed based on experimental results. SAC is confirmed to give better tracking performance compared with PI control, and a control precision comparable to MRAC (within 10 μm of the reference position) and higher robustness to parameter change, despite the simple controller. The research results ensure a wider application of simple adaptive control in real mechanical systems.
基金Sponsored by the National Natural Science Foundation of China(Grant No.61105086)Self-Planned Task of State Key Laboratory of Robotics and System(HIT)(Grant No.SKLRS-2010-MS-12)Hubei Province Natural Science Foundation(Grant No.2010CDB0 3405)
文摘The dynamic characteristics of hydraulic self servo swing cylinder were analyzed according to the hydraulic system natural frequency formula. Based on that,a method of the hydraulic self servo swing cylinder structure optimization based on genetic algorithm was proposed in this paper. By analyzing the four parameters that affect the dynamic characteristics, we had to optimize the structure to obtain as larger the Dm( displacement) as possible under the condition with the purpose of improving the dynamic characteristics of hydraulic self servo swing cylinder. So three state equations were established in this paper. The paper analyzed the effect of the four parameters in hydraulic self servo swing cylinder natural frequency equation and used the genetic algorithm to obtain the optimal solution of structure parameters. The model was simulated by substituting the parameters and initial value to the simulink model. Simulation results show that: using self servo hydraulic swing cylinder natural frequency equation to study its dynamic response characteristics is very effective.Compared with no optimization,the overall system dynamic response speed is significantly improved.
基金financially supported by the National Natural Science Foundation of China(Grant No.51475120)the Project of Science and Technology of Henan Province of China(2018QNJH25,182102110096)
文摘The mold filling process of titanium alloy in a thin-walled cylinder cavity under vertical centrifugal casting process was studied by means of the hydraulic simulation experiments. Results show that the filling mode of the melt in the cylinder cavity varies with casting wall-thickness. When the casting wall-thickness is less than or equal to the thickness of the first layer during the filling process, the melts fill the cavity from the bottom to the top.When the casting wall-thickness is greater than the thickness of the first layer during the filling process, the melts first fill the largest radius parts of the cavity with a certain thickness of the first layer from the bottom to the top of the cavity, and then they fill the cavity from the larger radius part to the smaller radius part. The melt filling ability increases with the increment of the mold rotational speed and the pouring temperature. In another aspect, the melt filling ability rises with the decrement of the melt viscosity, and the melt with the better filling ability is prone to fill the cylinder cavity layer by layer.
基金National Natural Science Foundation of China(51705152)Jiangxi Provincial Natural Science Foundation(20161BAB206150+2 种基金20161BAB216133)Jiangxi Provincial Key R&D Program(20171BBG70040)Innovation Fund Designated for Graduate Students of Jiangxi Province(YC2018-S246)。
文摘An inside-cushion structure with sidestep and taper-shaped plungers is studied to address the problems of high impact and vibration in high-speed hydraulic cylinders.First,the three stages of cushion processes are discussed according to the varying flow area as the piston moves.Then,to establish a precise mathematical model,the states of the flow field are estimated in terms of the Reynolds number.Accordingly,the simulation model parameterized against measured data is developed and verified by experiment.Last,the average velocity,peak cushion pressure,and terminal velocity are defined to evaluate cushion performance.According to these optimized objectives,the non-linear programming by quadratic Lagrange(NLPQL)algorithm is applied to optimize the structure parameters.The optimization results indicate that the peak cushion pressure is reduced by 28%and terminal velocity is reduced by 21%without reduction of average velocity.
文摘In this paper a model of a high pressure hydraulic system was developed to simulate the effect of increased internal leakages inside the hydraulic cylinder and the 4/2 way directional control valve and to calculate the main parameters of the hydraulic system under various loads through the use of leakage-simulating throttle valves. After the completion of modeling, the throttle valves that simulate the internal leakages were calibrated and a number of test runs were performed for the cases of normal operation and the operation with increased internal leakages. The theoretical predictions were compared against the experimental results from an actual hydraulic test platform installed in the laboratory. In all cases, modeling and experimental data curves correlate very well in form, magnitude and response times for all the system’s main parameters. This proves that the present modeling can be used to accurately predict various faults in hydraulic systems, and can thus be used for proactive fault finding in many cases, especially when the defective component is not easily detected and obvious at first sight.
文摘This research proposes a component to restrict dust from entering an oil hydraulic system through the rod-seal clearance of an oil hydraulic cylinder.The oil hydraulic cylinder as one of main parts of the hydraulic system,controls position of load by reciprocation.For example,on construction machines such as excavators and graders,the cylinder controls position of folk lift,crane and bucket.However,during operation,dust enters the cylinder,wears seals,causes fluid degradation and affects lubrication of valves,pumps and other parts of hydraulic system.This increases breakdown rate of cylinder and entire system.Thus,it seems necessary to reduce on intrusion of dust into the system via the hydraulic cylinder.In this research,we made an experimental apparatus to simulate intrusion of the dust into system.Results proved that the apparatus is a suitable simulator to realize the intrusion.The proposed component to restrict dust from entering cylinder was fabricated and its performance tested when inserted with various elastic rings.The component gave tremendous results when inserted with O-ring seal and a plastic nylon washer,and can be retrofitted on new and old hydraulic cylinders.It is an appropriate technology especially in developing countries where dust is still a major concern.
基金supported by the National 863 Project(2011AA040701)
文摘The electro-hydraulic servo drive hydraulic cylinder has many unique advantages, such as fast response, high load stiffness, high control power, strong anti-eccentric load ability and so on, so it has been widely used in industrial control. Based on the guide sleeve of hydrostatic seal of hydraulic cylinder, the reasonable number of oil chamber of guide sleeve is studied in this paper. ICEM CFD software and FLUENT simulation software are used to calculate and analyze the number of different oil chambers of guide sleeve of hydrostatic seal. The temperature field of piston rod with different moving speed, different initial pressure of oil chamber and oil film under different number of oil chambers is analyzed. The relationship between the pressure field and temperature field provides a better basis for optimizing the design of hydrostatic guide sleeve and helps to improve the servo drive cylinder.