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RSS2016 Vol. 35, No. 7
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2016, 35(7): 985-991.
doi: 10.13433/j.cnki.1003-8728.2016.0701
PDF 888KB
Abstract:
The traditional hydrostatic bearing design and calculation method is based on the means of solving the model simplification that error exists among the calculation results. And some key physical parameters are difficult to get through the theoretical calculation. The introduction of computer numerical simulation technology made up for the inadequacy of the theory design method. In this paper, the flow field distribution and bearing characteristics of liquid hydrostatic guide-ways are studied through the method of combining the theoretical calculation and finite element simulation. First, based on the design parameters of liquid hydrostatic guide-ways, the theoretical value of load capacity and bearing stiffness are calculated. Then the flow field distribution and bearing characteristics of liquid hydrostatic guide-ways are simulated with ANSYS/Fluent software. The results indicate that the flow regime of the orifice is turbulent flow, the pressure in the oil chamber region is very uniform and it decreases linearly along oil seal surface, the dimensionless coefficients of load capacity and bearing stiffness of simulation results are consistent with theoretical results.
The traditional hydrostatic bearing design and calculation method is based on the means of solving the model simplification that error exists among the calculation results. And some key physical parameters are difficult to get through the theoretical calculation. The introduction of computer numerical simulation technology made up for the inadequacy of the theory design method. In this paper, the flow field distribution and bearing characteristics of liquid hydrostatic guide-ways are studied through the method of combining the theoretical calculation and finite element simulation. First, based on the design parameters of liquid hydrostatic guide-ways, the theoretical value of load capacity and bearing stiffness are calculated. Then the flow field distribution and bearing characteristics of liquid hydrostatic guide-ways are simulated with ANSYS/Fluent software. The results indicate that the flow regime of the orifice is turbulent flow, the pressure in the oil chamber region is very uniform and it decreases linearly along oil seal surface, the dimensionless coefficients of load capacity and bearing stiffness of simulation results are consistent with theoretical results.
2016, 35(7): 992-997.
doi: 10.13433/j.cnki.1003-8728.2016.0702
Abstract:
In order to achieve nanometer level precision positioning of objects, this paper presents a three driven foot precision positioning device using piezoelectric material as the driving element. T the design principles of precision positioning device based on inertial impact is described, and its specific work process is introduced Then the mathematical analysis of the working process of driven foot is carried out. Made A prototype and experimental system is built and a microscope objective lens is used to test the positioning precision. The results show that by changing the duty cycle of the driving voltage signal, the precision positioning device is capable of bi-directional linear movement of the clamping load with the sawtooth signal as the driving voltage .When the voltage is 80V and the voltage frequency is 80 Hz, the precision positioning device can achieve the minimum resolution of 100 nm, and it works smoothly with good performance, meeting the requirement of nanometer-scale positioning.
In order to achieve nanometer level precision positioning of objects, this paper presents a three driven foot precision positioning device using piezoelectric material as the driving element. T the design principles of precision positioning device based on inertial impact is described, and its specific work process is introduced Then the mathematical analysis of the working process of driven foot is carried out. Made A prototype and experimental system is built and a microscope objective lens is used to test the positioning precision. The results show that by changing the duty cycle of the driving voltage signal, the precision positioning device is capable of bi-directional linear movement of the clamping load with the sawtooth signal as the driving voltage .When the voltage is 80V and the voltage frequency is 80 Hz, the precision positioning device can achieve the minimum resolution of 100 nm, and it works smoothly with good performance, meeting the requirement of nanometer-scale positioning.
2016, 35(7): 998-1005.
doi: 10.13433/j.cnki.1003-8728.2016.0703
Abstract:
In order to study the dynamic responses of the shale shaker laminated flat-screen under the effect of vibration force from the motor, a multi-body simulation model of three-motor shale shaker was established and validated in RecurDyn. Based on the finite element multi-flexible-body dynamics (MFBD) technology, the rigid-flexible coupling multi-body dynamic simulation model was established on the basis of rigid model, which is between shale shaker and screen. Through the simulation, the vibration parameters, the dynamic stress of measured points and the stress nephogram of screen were got which is under the different vibration trajectories, different bolt preload, different support conditions. The results showed that: the rigid-flexible coupling model can reflect the throw index of shaker more exact; to increase the bolt preload within a certain range can reduce the dynamic stress of screen; to increase the number of supports makes the screen stress more evenly.
In order to study the dynamic responses of the shale shaker laminated flat-screen under the effect of vibration force from the motor, a multi-body simulation model of three-motor shale shaker was established and validated in RecurDyn. Based on the finite element multi-flexible-body dynamics (MFBD) technology, the rigid-flexible coupling multi-body dynamic simulation model was established on the basis of rigid model, which is between shale shaker and screen. Through the simulation, the vibration parameters, the dynamic stress of measured points and the stress nephogram of screen were got which is under the different vibration trajectories, different bolt preload, different support conditions. The results showed that: the rigid-flexible coupling model can reflect the throw index of shaker more exact; to increase the bolt preload within a certain range can reduce the dynamic stress of screen; to increase the number of supports makes the screen stress more evenly.
2016, 35(7): 1006-1010.
doi: 10.13433/j.cnki.1003-8728.2016.0704
Abstract:
To analyze the reliability of each part of the wind turbine pitch reducer under the case of other parts or subsystems failure and establish the accurate model for reliability, the reliability model of the planetary transmission system is established by using the theory of interference for stress-strength distribution, and base on Markov chain and pure death model, the formula of system reliability is deduced, and the reliability of the important parts of system is analyzed , and the result of the reliability of the wind turbine pitch reducer is then obtained. The example calculation and analysis results show that the reliability using pure death model is closer to the actual situation of parts and each system in actual situation. The proposed model is more objective than traditional model in reliability analysis. and it can intuitively analyze the weak links of parts and its causes from the view point of failure probability.
To analyze the reliability of each part of the wind turbine pitch reducer under the case of other parts or subsystems failure and establish the accurate model for reliability, the reliability model of the planetary transmission system is established by using the theory of interference for stress-strength distribution, and base on Markov chain and pure death model, the formula of system reliability is deduced, and the reliability of the important parts of system is analyzed , and the result of the reliability of the wind turbine pitch reducer is then obtained. The example calculation and analysis results show that the reliability using pure death model is closer to the actual situation of parts and each system in actual situation. The proposed model is more objective than traditional model in reliability analysis. and it can intuitively analyze the weak links of parts and its causes from the view point of failure probability.
2016, 35(7): 1011-1017.
doi: 10.13433/j.cnki.1003-8728.2016.0705
Abstract:
Kinematics of a kind of N degrees of freedom robot driven by 2N steel cables was studied in this paper. The kinematic analysis was accomplished by two steps, the first one is the derivation of kinematic models between the joint angle displacement and the end-effector of open-loop chain robots, and the second one is the kinematic model describing the relationship between the joint angular displacement and the motor-rotor angular displacement. Loop analysis method using loop matrix and equivalent radius matrix representation for kinematics of steel cable-driven robots were proposed on the basis of kinematic analysis. Loop matrix and equivalent radius matrix in motor-driven space was built and the mapping relationship models was got by observation method according to the schematic of steel cable transmission, which realized the motion decoupling of the existing joints of steel cable-driven robots. The full kinematic mapping models among motor actuator space, joint space, Cartesian space were accomplished, which speeds up and simplifies the kinematic modeling and analysis process of steel cable-driven robot. Finally, the kinematic analysis of the Utah/MIT finger and the end-effector trajectories analysis were performed by using Matlab and SolidWorks, which validates the correctness of loop analysis method.
Kinematics of a kind of N degrees of freedom robot driven by 2N steel cables was studied in this paper. The kinematic analysis was accomplished by two steps, the first one is the derivation of kinematic models between the joint angle displacement and the end-effector of open-loop chain robots, and the second one is the kinematic model describing the relationship between the joint angular displacement and the motor-rotor angular displacement. Loop analysis method using loop matrix and equivalent radius matrix representation for kinematics of steel cable-driven robots were proposed on the basis of kinematic analysis. Loop matrix and equivalent radius matrix in motor-driven space was built and the mapping relationship models was got by observation method according to the schematic of steel cable transmission, which realized the motion decoupling of the existing joints of steel cable-driven robots. The full kinematic mapping models among motor actuator space, joint space, Cartesian space were accomplished, which speeds up and simplifies the kinematic modeling and analysis process of steel cable-driven robot. Finally, the kinematic analysis of the Utah/MIT finger and the end-effector trajectories analysis were performed by using Matlab and SolidWorks, which validates the correctness of loop analysis method.
2016, 35(7): 1018-1022.
doi: 10.13433/j.cnki.1003-8728.2016.0706
Abstract:
The effect of the medium pressure, initial compression ratio on the deformation, contact stress, Von Mises stress and shear stress of the rubber D-ring was analyzed via ABAQUS software, and the comparison between the approximate size O-ring and the rubber D-ring was fulfilled. The results show that the Von Mises stress of D-ring is much more smaller and the contact area is much more bigger with that to the rubber O-ring. A better sealing performance will obtained under different medium pressure for rubber D-ring, but its lifetime at lower pressure is shorter than that for rubber O-ring. The rubber D-ring can get more efficient sealing performance under different compression ratio, and the higher lifetime can be also obtained under low compression ratio, but the material aging is more likely to be caused at a high compression ratio comparing with the rubber O-ring. A rounded boss was added to the rubber D-ring resulting in the decrease in Mises stress and shear stress, then a longer life was obtained.
The effect of the medium pressure, initial compression ratio on the deformation, contact stress, Von Mises stress and shear stress of the rubber D-ring was analyzed via ABAQUS software, and the comparison between the approximate size O-ring and the rubber D-ring was fulfilled. The results show that the Von Mises stress of D-ring is much more smaller and the contact area is much more bigger with that to the rubber O-ring. A better sealing performance will obtained under different medium pressure for rubber D-ring, but its lifetime at lower pressure is shorter than that for rubber O-ring. The rubber D-ring can get more efficient sealing performance under different compression ratio, and the higher lifetime can be also obtained under low compression ratio, but the material aging is more likely to be caused at a high compression ratio comparing with the rubber O-ring. A rounded boss was added to the rubber D-ring resulting in the decrease in Mises stress and shear stress, then a longer life was obtained.
2016, 35(7): 1023-1027.
doi: 10.13433/j.cnki.1003-8728.2016.0707
Abstract:
In order to meet young patients' needs of treating malignant bone tumor using limb salvage, the customized bipolar hemi-knee prosthesis is designed. With the design principle of "double gliding", the prosthesis can ease the wear of contralateral articular surface by transferring the major movement of the bipolar hemi-knee to the interior of the prosthesis. To verify the prosthesis' capability of easing the wear of articular surface, the contact mechanics performance in different typical states of the prosthesis is analyzed by using the finite element method and the natural knee and the customized hemi-knee prosthesis as contrast knees. The analysis results show that the maximum contact stress of the customized bipolar hemi-knee prosthesis is much smaller than that of the contrast knees in other typical states except in the standing state (the flection angle of the articular surface is 0 degree). Therefore, the prosthesis can not only achieve the movement function of a knee but also ease the wear of the articular surface.
In order to meet young patients' needs of treating malignant bone tumor using limb salvage, the customized bipolar hemi-knee prosthesis is designed. With the design principle of "double gliding", the prosthesis can ease the wear of contralateral articular surface by transferring the major movement of the bipolar hemi-knee to the interior of the prosthesis. To verify the prosthesis' capability of easing the wear of articular surface, the contact mechanics performance in different typical states of the prosthesis is analyzed by using the finite element method and the natural knee and the customized hemi-knee prosthesis as contrast knees. The analysis results show that the maximum contact stress of the customized bipolar hemi-knee prosthesis is much smaller than that of the contrast knees in other typical states except in the standing state (the flection angle of the articular surface is 0 degree). Therefore, the prosthesis can not only achieve the movement function of a knee but also ease the wear of the articular surface.
2016, 35(7): 1028-1034.
doi: 10.13433/j.cnki.1003-8728.2016.0708
Abstract:
For researching gas pipeline vibration, the vibration model and analysis methods for pipeline considering pressure pulsation and pipeline couplings are presented in this paper. According to the pipeline structure, the model of piston compressor of gas pipeline with different diameter pipes is established. Based on the models and combined with the structure parameters of pipeline, the calculation methods of gas column natural frequently, gas pressure pulsation and exciting force are established. Through these methods, the relationships between the gas column natural frequency and modal order, the gas pressure pulsation and modal order, and the exciting force and aspect ratio are acquired. Besides, the change relationship of vibration displacement and velocity of pipeline under the action of exciting force is obtained. Comparing the calculated results with the field test values, the calculated results are in agreement with the test values, and the correctness of the model and method is verified. The study results show that: in different diameter pipes, elbow, and collecting pipe, taking the pressure pulsating and pipe coupling effect account into the vibration analysis of pipeline, can truly reflect the vibration characteristics of pipeline and has important reference value for improving the service life and reducing the vibrations of the pipeline.
For researching gas pipeline vibration, the vibration model and analysis methods for pipeline considering pressure pulsation and pipeline couplings are presented in this paper. According to the pipeline structure, the model of piston compressor of gas pipeline with different diameter pipes is established. Based on the models and combined with the structure parameters of pipeline, the calculation methods of gas column natural frequently, gas pressure pulsation and exciting force are established. Through these methods, the relationships between the gas column natural frequency and modal order, the gas pressure pulsation and modal order, and the exciting force and aspect ratio are acquired. Besides, the change relationship of vibration displacement and velocity of pipeline under the action of exciting force is obtained. Comparing the calculated results with the field test values, the calculated results are in agreement with the test values, and the correctness of the model and method is verified. The study results show that: in different diameter pipes, elbow, and collecting pipe, taking the pressure pulsating and pipe coupling effect account into the vibration analysis of pipeline, can truly reflect the vibration characteristics of pipeline and has important reference value for improving the service life and reducing the vibrations of the pipeline.
2016, 35(7): 1035-1042.
doi: 10.13433/j.cnki.1003-8728.2016.0709
Abstract:
Through overall consideration of spool helical motion and feedback mechanism dynamics, by modifying the flow equations of valve ports, an integrated nonlinear state-space model was deduced based on LuGre friction model. Simulation results of the nonlinear dynamics were compared with those of other two existing models and experimental results, and the nonlinear state-space model was proved to be the most accurate one. Nonlinear analysis on dynamic responses of reverse motion was also carried out using the proposed nonlinear model. The results show that, nonlinear model can reflect the real system responses. The velocity flutter will be caused by coupling of imbalance impact and the friction Stribeck effect when reversing and it will also be affected by factors such as system pressure, dead zone, radial leakage, Stribeck velocity and feedback mechanism stiffness jointly, which means that the status of velocity flutter is mutable.
Through overall consideration of spool helical motion and feedback mechanism dynamics, by modifying the flow equations of valve ports, an integrated nonlinear state-space model was deduced based on LuGre friction model. Simulation results of the nonlinear dynamics were compared with those of other two existing models and experimental results, and the nonlinear state-space model was proved to be the most accurate one. Nonlinear analysis on dynamic responses of reverse motion was also carried out using the proposed nonlinear model. The results show that, nonlinear model can reflect the real system responses. The velocity flutter will be caused by coupling of imbalance impact and the friction Stribeck effect when reversing and it will also be affected by factors such as system pressure, dead zone, radial leakage, Stribeck velocity and feedback mechanism stiffness jointly, which means that the status of velocity flutter is mutable.
2016, 35(7): 1043-1047.
doi: 10.13433/j.cnki.1003-8728.2016.0710
Abstract:
The magnetic field of the worm inner-stator of toroidal electromechanical transmission experiment prototype was analyzed through calculation and finite element simulation. The distribution of worm inner-stator magnetic field was presented in this paper. According to the Biot-Savart law and the relationship between structural parameters, the magnetic field of worm inner-stator was calculated. Simulation of the magnetic field in the worm inner-stator was analyzed using the finite element software. The simulation results verified the validity of the calculation and the distribution of magnetic field. The results showed that the magnetic field of worm inner-stator has two pairs of magnetic poles, the rotating angle of magnetic field and the torsion angle of slot take the same value, and the air gap size should be controlled below 2 mm.
The magnetic field of the worm inner-stator of toroidal electromechanical transmission experiment prototype was analyzed through calculation and finite element simulation. The distribution of worm inner-stator magnetic field was presented in this paper. According to the Biot-Savart law and the relationship between structural parameters, the magnetic field of worm inner-stator was calculated. Simulation of the magnetic field in the worm inner-stator was analyzed using the finite element software. The simulation results verified the validity of the calculation and the distribution of magnetic field. The results showed that the magnetic field of worm inner-stator has two pairs of magnetic poles, the rotating angle of magnetic field and the torsion angle of slot take the same value, and the air gap size should be controlled below 2 mm.
2016, 35(7): 1048-1053.
doi: 10.13433/j.cnki.1003-8728.2016.0711
Abstract:
To prevent the trackslip of off-road vehicle, A new type of alterable torque differential with noncircular bevel gearing for off-road vehicles is put forward, in which the transmission ratio varies at a circle of the planetary gear, which has one half the number of the teeth of the half-axle gear. The variable range of ratio can go extreme as much as ±40%, which would be of great help to improve the passing capability of the vehicle. Based on Finite Element Method (FEM), the mechanical property of the gearing is analyzed and the mechanics model is built with a certain torque defined, the rotation displacement of the bevel gear is figured out by close nodes coupling on the contact surfaces. The stresses of all the gears are worked out by means of contact fiction model. The FEM simulation of the differential with improved gears as well as the former one is illustrated and compared in details, which shows the new one is reasonable and the the new design method is effective.
To prevent the trackslip of off-road vehicle, A new type of alterable torque differential with noncircular bevel gearing for off-road vehicles is put forward, in which the transmission ratio varies at a circle of the planetary gear, which has one half the number of the teeth of the half-axle gear. The variable range of ratio can go extreme as much as ±40%, which would be of great help to improve the passing capability of the vehicle. Based on Finite Element Method (FEM), the mechanical property of the gearing is analyzed and the mechanics model is built with a certain torque defined, the rotation displacement of the bevel gear is figured out by close nodes coupling on the contact surfaces. The stresses of all the gears are worked out by means of contact fiction model. The FEM simulation of the differential with improved gears as well as the former one is illustrated and compared in details, which shows the new one is reasonable and the the new design method is effective.
2016, 35(7): 1054-1058.
doi: 10.13433/j.cnki.1003-8728.2016.0712
Abstract:
In order to eliminate the influence of interference signal on constant pressure control performance of a variable speed hydraulic system and improve its control accuracy, pressure feedback signal is preprocessed and reconstructed by using multi-resolution analysis to decompose the signal and strip interference signal components. The constant pressure measurement and control of variable speed hydraulic system based on signal reconstruction is designed by adopting the LabVIEW and MATLAB hybrid programming method. The impact before and after adding control signal reconstruction device performance in a PID control system is analyzed through comparative experiments. Experimental results show that, in addition to keeping the system's response speed, the pressure feedback signal decomposition and reconstruction can reduce steady-state errors of the constant pressure system and pressure fluctuation, thus improving control accuracy.
In order to eliminate the influence of interference signal on constant pressure control performance of a variable speed hydraulic system and improve its control accuracy, pressure feedback signal is preprocessed and reconstructed by using multi-resolution analysis to decompose the signal and strip interference signal components. The constant pressure measurement and control of variable speed hydraulic system based on signal reconstruction is designed by adopting the LabVIEW and MATLAB hybrid programming method. The impact before and after adding control signal reconstruction device performance in a PID control system is analyzed through comparative experiments. Experimental results show that, in addition to keeping the system's response speed, the pressure feedback signal decomposition and reconstruction can reduce steady-state errors of the constant pressure system and pressure fluctuation, thus improving control accuracy.
2016, 35(7): 1059-1064.
doi: 10.13433/j.cnki.1003-8728.2016.0713
Abstract:
Contact is the core of the high-voltage circuit breaker, calculations of the contact pressure and analysis of the sliding friction change are the key points for the study of dynamic characteristics of high-voltage circuit breaker mechanism. In this paper, standardized dimensions of spring contact were listed based on structural features of screw spring contact. On the basis that one pitch of spring was considered as an equivalent cantilever, governing equations of radial deformation and pressure of spring contact were established and calculated by using Simpson numerical integration method. the changing rule of sliding friction was received by considering the effects of different type contact parameters on the rated laps of contact at the same time.
Contact is the core of the high-voltage circuit breaker, calculations of the contact pressure and analysis of the sliding friction change are the key points for the study of dynamic characteristics of high-voltage circuit breaker mechanism. In this paper, standardized dimensions of spring contact were listed based on structural features of screw spring contact. On the basis that one pitch of spring was considered as an equivalent cantilever, governing equations of radial deformation and pressure of spring contact were established and calculated by using Simpson numerical integration method. the changing rule of sliding friction was received by considering the effects of different type contact parameters on the rated laps of contact at the same time.
2016, 35(7): 1065-1072.
doi: 10.13433/j.cnki.1003-8728.2016.0714
Abstract:
As continuous working ability at complex pipe of the pipeline robot at home and abroad is not ideal, a kind of rigid flexible coupling robot is put forward, which the front part and the back part works together with the middle part that is composed of a spring letting the robot receive forward. Furthermore, under the influence of this way the robot can better adapt to the changes of the pipe. A new mode to pass through the pipeline is also presented, and a number of factors, including force analysis of robot, motion characteristics and force analysis of pipeline, are analyzed when the robot gets through the pipeline, and then a new robot can not only adapt to complex pipelines, but also detect the pipelines with different curvature radius. At last, the experiments are used to validate the robot.
As continuous working ability at complex pipe of the pipeline robot at home and abroad is not ideal, a kind of rigid flexible coupling robot is put forward, which the front part and the back part works together with the middle part that is composed of a spring letting the robot receive forward. Furthermore, under the influence of this way the robot can better adapt to the changes of the pipe. A new mode to pass through the pipeline is also presented, and a number of factors, including force analysis of robot, motion characteristics and force analysis of pipeline, are analyzed when the robot gets through the pipeline, and then a new robot can not only adapt to complex pipelines, but also detect the pipelines with different curvature radius. At last, the experiments are used to validate the robot.
2016, 35(7): 1073-1082.
doi: 10.13433/j.cnki.1003-8728.2016.0715
Abstract:
For the first time without circumferential oil groove back four cavity radial hydrostatic bearing for Progressive Mengen (PM) flow controller, the mathematical model for hydrostatic bearings is established and the effect of the bearing structure parameters on the static characteristics of aerostatic bearing is analyzed. The results show that the smaller the axial flow oil seal edge coefficient is, the bigger the circumfluence oil seal edge coefficient, the larger the bearing oil film stiffness and bearing capacity; the oil film stiffness decreases with the increasing of initial oil film clearance; the smaler the dynamic viscosity of lubricating oil large and initial oil film clearance is, the larger the oil film stiffness and bearing capacity; the smaller the liquid resistance ratio is, the larger the flow ratio and the oil film stiffness; the larger the oil pressure is, the larger the oil film stiffness, bearing force and flow. Based on the transfer function of hydrostatic bearing system, the dynamic characteristics of hydrostatic bearing system are studied in the time domain and frequency domain by using the Simulink Matlab. The results indicate that under the step load, with the increasing of oil pressure and flow ratio and shortening of transition time, the dynamic characteristics of hydrostatic bearing system become better; under sinusoidal load, with the increasing of supply pressure, the flow ratio will derease the steady-state amplitude of axial offset, the oil film dynamic stiffness increases, and the effect of the oil pressure on the frequency characteristics is more significant than the flow ratio.
For the first time without circumferential oil groove back four cavity radial hydrostatic bearing for Progressive Mengen (PM) flow controller, the mathematical model for hydrostatic bearings is established and the effect of the bearing structure parameters on the static characteristics of aerostatic bearing is analyzed. The results show that the smaller the axial flow oil seal edge coefficient is, the bigger the circumfluence oil seal edge coefficient, the larger the bearing oil film stiffness and bearing capacity; the oil film stiffness decreases with the increasing of initial oil film clearance; the smaler the dynamic viscosity of lubricating oil large and initial oil film clearance is, the larger the oil film stiffness and bearing capacity; the smaller the liquid resistance ratio is, the larger the flow ratio and the oil film stiffness; the larger the oil pressure is, the larger the oil film stiffness, bearing force and flow. Based on the transfer function of hydrostatic bearing system, the dynamic characteristics of hydrostatic bearing system are studied in the time domain and frequency domain by using the Simulink Matlab. The results indicate that under the step load, with the increasing of oil pressure and flow ratio and shortening of transition time, the dynamic characteristics of hydrostatic bearing system become better; under sinusoidal load, with the increasing of supply pressure, the flow ratio will derease the steady-state amplitude of axial offset, the oil film dynamic stiffness increases, and the effect of the oil pressure on the frequency characteristics is more significant than the flow ratio.
2016, 35(7): 1083-1088.
doi: 10.13433/j.cnki.1003-8728.2016.0716
Abstract:
The Aerostatic Spindle is widely used in the precision and ultra precision machinery, and the machining precision for key parts has a significant impact on the performance of the spindle. Taking the aerostatic thrust bearing designed by ourselves for an example, the effect which the typical manufacturing errors may have on the performance such as load capacity and stiffness of the bearing is analyzed. Based on the results of the error analysis, the design precision is defined. Considering the deformation of the static pushing plate caused by the vacuum suction with the requirement of submicron precision, a kind of error compensation cutting theory is put forward; in other words, the static thrust surface is machined to the opposite of the suction deformation error and the surface precision will be high when the vacuum suction is eliminated. An error compensation cutting experiment was carried out on the static push plate with the diameter of 188 mm and the error of the static thrust surface converged to 1μm below rapidly which meets the requirements of high machining precision for the static pushing plate.
The Aerostatic Spindle is widely used in the precision and ultra precision machinery, and the machining precision for key parts has a significant impact on the performance of the spindle. Taking the aerostatic thrust bearing designed by ourselves for an example, the effect which the typical manufacturing errors may have on the performance such as load capacity and stiffness of the bearing is analyzed. Based on the results of the error analysis, the design precision is defined. Considering the deformation of the static pushing plate caused by the vacuum suction with the requirement of submicron precision, a kind of error compensation cutting theory is put forward; in other words, the static thrust surface is machined to the opposite of the suction deformation error and the surface precision will be high when the vacuum suction is eliminated. An error compensation cutting experiment was carried out on the static push plate with the diameter of 188 mm and the error of the static thrust surface converged to 1μm below rapidly which meets the requirements of high machining precision for the static pushing plate.
2016, 35(7): 1089-1095.
doi: 10.13433/j.cnki.1003-8728.2016.0717
Abstract:
The dynamic characteristics of an axial piston pump with pressure control were studied. Its two key components were customized by AMESet. Its whole test model and load model based on the product sample of Rexroth were established in AMESim. The dynamic curves of variable displacement pump were obtained under load step conditions. The validity of the models was verified by comparing the simulation results with the dynamic operating curves of the product sample of Rexroth. The simulation results show that the variable displacement pump pressure pulsation is mainly affected by the spool diameter of the pressure control valve and the piston diameter of the piston stroke and that an appropriate increase in stroke cylinder preload improves the dynamic response time of variable displacement pump.
The dynamic characteristics of an axial piston pump with pressure control were studied. Its two key components were customized by AMESet. Its whole test model and load model based on the product sample of Rexroth were established in AMESim. The dynamic curves of variable displacement pump were obtained under load step conditions. The validity of the models was verified by comparing the simulation results with the dynamic operating curves of the product sample of Rexroth. The simulation results show that the variable displacement pump pressure pulsation is mainly affected by the spool diameter of the pressure control valve and the piston diameter of the piston stroke and that an appropriate increase in stroke cylinder preload improves the dynamic response time of variable displacement pump.
2016, 35(7): 1096-1101.
doi: 10.13433/j.cnki.1003-8728.2016.0718
Abstract:
A measuring model of attitude angle is established based on the measuring principle of the dual-axis tilt sensor. Then, considering the measuring model above, a solving model without error and one with error for attitude angle measurement are established. With the method of coordinate transforms, an solving model with the error term for the attitude angle is established; aiming to the error term in the model above, a calibration algorithm of dual-axis sensor for measuring attitude angle model is presented. Within the range of ±4°, this calibration algorithm is verified by experiments. The experimental results show that, the dual-axis tilt sensor's biaxial calibration accuracy is improved to 0.012 46° from 0.118° before amendment, which reflects that the calibration method can reduce the calibration error in aspect of an order of magnitude. The calibration algorithm is fast and simple, and also can meet the requirements of the accuracy 0.03° for the attitude angle measurement in many applications.
A measuring model of attitude angle is established based on the measuring principle of the dual-axis tilt sensor. Then, considering the measuring model above, a solving model without error and one with error for attitude angle measurement are established. With the method of coordinate transforms, an solving model with the error term for the attitude angle is established; aiming to the error term in the model above, a calibration algorithm of dual-axis sensor for measuring attitude angle model is presented. Within the range of ±4°, this calibration algorithm is verified by experiments. The experimental results show that, the dual-axis tilt sensor's biaxial calibration accuracy is improved to 0.012 46° from 0.118° before amendment, which reflects that the calibration method can reduce the calibration error in aspect of an order of magnitude. The calibration algorithm is fast and simple, and also can meet the requirements of the accuracy 0.03° for the attitude angle measurement in many applications.
2016, 35(7): 1102-1106.
doi: 10.13433/j.cnki.1003-8728.2016.0719
Abstract:
The kurtosis and negentropy, as two natural measures of independence for blind signals, can be utilized to capture the dynamic information characteristics of mechanical vibration signals. The dynamic information can be extracted as their fault features. The kurtosis and negentropy can explain the feature information of mechanical fault from two different viewpoints that the and their information contents are complementary mutually. If the kurtosis information and negentropy information were fused into one feature vector, it can definitely express the running states of machines more comprehensively and more profoundly. A feature extraction method based on ICA fusion for mechanical fault was proposed, which can fuse the kurtosis information and negentropy information as the final optimum feature information. The pattern recognition experiments of hydraulic gear pump indicate that this method can be applied to feature extraction of mechanical equipment.
The kurtosis and negentropy, as two natural measures of independence for blind signals, can be utilized to capture the dynamic information characteristics of mechanical vibration signals. The dynamic information can be extracted as their fault features. The kurtosis and negentropy can explain the feature information of mechanical fault from two different viewpoints that the and their information contents are complementary mutually. If the kurtosis information and negentropy information were fused into one feature vector, it can definitely express the running states of machines more comprehensively and more profoundly. A feature extraction method based on ICA fusion for mechanical fault was proposed, which can fuse the kurtosis information and negentropy information as the final optimum feature information. The pattern recognition experiments of hydraulic gear pump indicate that this method can be applied to feature extraction of mechanical equipment.
2016, 35(7): 1107-1111.
doi: 10.13433/j.cnki.1003-8728.2016.0720
Abstract:
Considering a tower crane hydraulic servo valve pocket, the cycle loads on which are handled by the rainflow-counting method and the safe S-N (Stress-Number of cycle) curve of the material used in valve pocket (440C) is obtained according to the classic processing method on the S-N curve firstly. Secondly, for each working condition in load spectrum, the maximum stress value is obtained during the finite element analysis on the MSC.PATRAN software platform. And then, consulting to the safe S-N curve, the fatigue damage value of each maximum stress value is obtained. Finally, the multiplying the fatigue damage value by cycle times, and the sum of which is the total fatigue damage value of the valve pocket. Comparing with the traditional fatigue test, the computational method on the fatigue damage proposed in this paper can not only save the analysis time and cost, but is also independent of the test specimen defects.
Considering a tower crane hydraulic servo valve pocket, the cycle loads on which are handled by the rainflow-counting method and the safe S-N (Stress-Number of cycle) curve of the material used in valve pocket (440C) is obtained according to the classic processing method on the S-N curve firstly. Secondly, for each working condition in load spectrum, the maximum stress value is obtained during the finite element analysis on the MSC.PATRAN software platform. And then, consulting to the safe S-N curve, the fatigue damage value of each maximum stress value is obtained. Finally, the multiplying the fatigue damage value by cycle times, and the sum of which is the total fatigue damage value of the valve pocket. Comparing with the traditional fatigue test, the computational method on the fatigue damage proposed in this paper can not only save the analysis time and cost, but is also independent of the test specimen defects.
2016, 35(7): 1112-1119.
doi: 10.13433/j.cnki.1003-8728.2016.0721
Abstract:
The paper uses the new unnatural equilibrium contour theory to perform the structural design of the contour of the radial tire 295/80R22.5. It redesigns the prototype tire with the new unnatural equilibrium contour. The tire radial stiffness, lateral stiffness and longitudinal stiffness are tested according to GB/T23663-2009. The finite element model of the radial tire 295/80R22.5 with the new unnatural equilibrium contour is built with ABAQUS, and the tire-ground pressure distribution, contour dimension, radial, lateral and longitudinal stiffness of the radial tire are numerically simulated. The experimental results show good agreement with the numerical simulation results. All the results show that the finite element model of the new unnatural equilibrium contour tire we built in this paper has high accuracy and can be used to analyze the overall performance of a radial tire.
The paper uses the new unnatural equilibrium contour theory to perform the structural design of the contour of the radial tire 295/80R22.5. It redesigns the prototype tire with the new unnatural equilibrium contour. The tire radial stiffness, lateral stiffness and longitudinal stiffness are tested according to GB/T23663-2009. The finite element model of the radial tire 295/80R22.5 with the new unnatural equilibrium contour is built with ABAQUS, and the tire-ground pressure distribution, contour dimension, radial, lateral and longitudinal stiffness of the radial tire are numerically simulated. The experimental results show good agreement with the numerical simulation results. All the results show that the finite element model of the new unnatural equilibrium contour tire we built in this paper has high accuracy and can be used to analyze the overall performance of a radial tire.
2016, 35(7): 1120-1124.
doi: 10.13433/j.cnki.1003-8728.2016.0722
Abstract:
The hydraulic engine mount (HEM) with decoupler is a typical switch system for the movement of a decoupler and has two dynamical states: continuous and discrete. The conventional methods for the dynamic characteristics analysis of HEM with decoupler were based on the lumped parameter model or the fluid-structure interaction model. With the hybrid trait of HEM considered, the dynamic characteristics model of the switch system was established, and the switching strategy between different modes was proposed by logical judgment. By using Simulink/Stateflow, the simulation model of a multi-mode switchsystem was designed. The simulation model is accurate and can represent the actual switch system completely. The dynamic characteristic tests of HEM with decoupler were carried out, and the effectiveness of the proposed switch system model was verified by experimental results.
The hydraulic engine mount (HEM) with decoupler is a typical switch system for the movement of a decoupler and has two dynamical states: continuous and discrete. The conventional methods for the dynamic characteristics analysis of HEM with decoupler were based on the lumped parameter model or the fluid-structure interaction model. With the hybrid trait of HEM considered, the dynamic characteristics model of the switch system was established, and the switching strategy between different modes was proposed by logical judgment. By using Simulink/Stateflow, the simulation model of a multi-mode switchsystem was designed. The simulation model is accurate and can represent the actual switch system completely. The dynamic characteristic tests of HEM with decoupler were carried out, and the effectiveness of the proposed switch system model was verified by experimental results.
2016, 35(7): 1125-1132.
doi: 10.13433/j.cnki.1003-8728.2016.0723
Abstract:
Both scratch test on TiN coating and finite element simulation are carried out in order to reveal the mechanism of surface crack of coating under frictionally sliding contact. The results of the scratch test show that arc-shaped cracks that have an average spacing of 5.12 μm come into being on the scratching surface. The three-dimensional finite element method is adopted to simulate the scratch process and the result indicates stress distributions in coating. Meanwhile the extended finite element method (XFEM) is applied to simulating cracks formation in the scratching process and the results show that surface cracks and interface cracks in coating results from the maximum tensile stress and those are mainly modelⅠcracks. Sub-surface cracks in coating are complex ones induced by both tensile stress and shear stress. Surface cracks are formed in following three ways. The first one is that microcracks at first emerge from the coating interface, and then surface cracks are formed with their propagating along coating thickness' direction to the surface. The second is that surface cracks are directly formed in the coating surface. The last is that microcracks at first are formed in the sub-surface of the coating,and then surface cracks come into being as their propagating along coating thickness' direction to the surface. In the process of simulation, it is found that the surface and the interface generate much more microcracks than the sub-surface does. With the propagation and fusion of cracks, the coating will spall.
Both scratch test on TiN coating and finite element simulation are carried out in order to reveal the mechanism of surface crack of coating under frictionally sliding contact. The results of the scratch test show that arc-shaped cracks that have an average spacing of 5.12 μm come into being on the scratching surface. The three-dimensional finite element method is adopted to simulate the scratch process and the result indicates stress distributions in coating. Meanwhile the extended finite element method (XFEM) is applied to simulating cracks formation in the scratching process and the results show that surface cracks and interface cracks in coating results from the maximum tensile stress and those are mainly modelⅠcracks. Sub-surface cracks in coating are complex ones induced by both tensile stress and shear stress. Surface cracks are formed in following three ways. The first one is that microcracks at first emerge from the coating interface, and then surface cracks are formed with their propagating along coating thickness' direction to the surface. The second is that surface cracks are directly formed in the coating surface. The last is that microcracks at first are formed in the sub-surface of the coating,and then surface cracks come into being as their propagating along coating thickness' direction to the surface. In the process of simulation, it is found that the surface and the interface generate much more microcracks than the sub-surface does. With the propagation and fusion of cracks, the coating will spall.
2016, 35(7): 1133-1138.
doi: 10.13433/j.cnki.1003-8728.2016.0724
Abstract:
Global warming increases probability of extreme weather, and an extreme temperature has great influence on working equipment. The composite material's initial failure under changing environment for 2MW wind turbine blade was been studied. Basing on the Xinjiang's climatic feature, the changing temperature and aerodynamic loading was combined via finite element method. The results shows that the change in temperature could varies the blade's properties, and reduces the servicing life at the same time by producing large load of blade, resulting in large equivalent stress, deformation and finally cracks on blades.
Global warming increases probability of extreme weather, and an extreme temperature has great influence on working equipment. The composite material's initial failure under changing environment for 2MW wind turbine blade was been studied. Basing on the Xinjiang's climatic feature, the changing temperature and aerodynamic loading was combined via finite element method. The results shows that the change in temperature could varies the blade's properties, and reduces the servicing life at the same time by producing large load of blade, resulting in large equivalent stress, deformation and finally cracks on blades.
2016, 35(7): 1139-1143.
doi: 10.13433/j.cnki.1003-8728.2016.0725
Abstract:
The Dempster-Shafer (D-S) theory was used to determine similarity factors of different similar products based on reliability information fusion, which makes full use of the information on similar products. Firstly, taking binominal products for example, by expressing the reliability information on multiple similar products as respective conjugate prior distribution, a mixture prior distribution as well as a mixture posterior distribution was built up. Then, considering the overlapping area of a prior distribution, the sample consistency for similar products was defined. Then combined with the D-S theory, the method for infusing reliability information on various similar products and determining similarity factors was proposed. Last but not least, a binominal example, given in the full paper, proves that the method is more effective than other methods.
The Dempster-Shafer (D-S) theory was used to determine similarity factors of different similar products based on reliability information fusion, which makes full use of the information on similar products. Firstly, taking binominal products for example, by expressing the reliability information on multiple similar products as respective conjugate prior distribution, a mixture prior distribution as well as a mixture posterior distribution was built up. Then, considering the overlapping area of a prior distribution, the sample consistency for similar products was defined. Then combined with the D-S theory, the method for infusing reliability information on various similar products and determining similarity factors was proposed. Last but not least, a binominal example, given in the full paper, proves that the method is more effective than other methods.
2016, 35(7): 1144-1148.
doi: 10.13433/j.cnki.1003-8728.2016.0726
Abstract:
The active vibration isolation system in the space station is the equipment to assure the efficiency of microgravity experiment. The disturbance to microgravity experiment in an isolated rack is primarily propagated via the umbilical cables for power and data transmission. To test the stiffness of the umbilical so as to optimize the design, a set of testing system was built. The paper illustrated the system hardware structure, software model and test program. The testing system mainly consists of a platform with six degrees of freedom, a controller, a sensor for measuring force and torque on six dimensions, and the LabVIEW software, etc. The controller drives the platform to move and rotate, and then the sensor gathers the force and moment data. Afterwards, the experimental data was collected using the LabVIEW software and sent to the Matlab software for processing. Finally, a 6×6 matrix representing the stiffness was generated to provide a theoretical support for the further design.
The active vibration isolation system in the space station is the equipment to assure the efficiency of microgravity experiment. The disturbance to microgravity experiment in an isolated rack is primarily propagated via the umbilical cables for power and data transmission. To test the stiffness of the umbilical so as to optimize the design, a set of testing system was built. The paper illustrated the system hardware structure, software model and test program. The testing system mainly consists of a platform with six degrees of freedom, a controller, a sensor for measuring force and torque on six dimensions, and the LabVIEW software, etc. The controller drives the platform to move and rotate, and then the sensor gathers the force and moment data. Afterwards, the experimental data was collected using the LabVIEW software and sent to the Matlab software for processing. Finally, a 6×6 matrix representing the stiffness was generated to provide a theoretical support for the further design.
