Author Center
Editor Work
Peer Review
Editorial Entry
Email Alert
RSS2022 Vol. 41, No. 2
Display Method:
2022, 41(2): 165-171.
doi: 10.13433/j.cnki.1003-8728.20200322
PDF 4768KB
Abstract:
Periodic vibration and shock signal will be generated when rolling bearing has local spalling, pitting and other faults. Usually, the severity and location of the fault can be diagnosed by analyzing the signal. However, the equipment operation is often accompanied by large noise, so the shock signal, especially the vibration shock signal of early fault, is easy to be submerged by noise. In order to solve this problem, this paper proposes a constant Q transform binary energy weight (CQTBEW) algorithm based on constant Q transform and binary energy weight. Firstly, the vibration shock signal is analyzed by constant Q transform to obtain the time-frequency spectrum matrix. Secondly, the matrix is processed by frequency segmentation. The sliding window is set in the time axis, and the local extreme value is filtered and binarized. The energy time domain signal is obtained by superimposing the time domain signal, and the characteristic frequency is obtained by spectrum analysis diagnosis. Finally, the simulation signal and experimental signal are analyzed and verified, the results show that the CQTBEW method is feasible.
Periodic vibration and shock signal will be generated when rolling bearing has local spalling, pitting and other faults. Usually, the severity and location of the fault can be diagnosed by analyzing the signal. However, the equipment operation is often accompanied by large noise, so the shock signal, especially the vibration shock signal of early fault, is easy to be submerged by noise. In order to solve this problem, this paper proposes a constant Q transform binary energy weight (CQTBEW) algorithm based on constant Q transform and binary energy weight. Firstly, the vibration shock signal is analyzed by constant Q transform to obtain the time-frequency spectrum matrix. Secondly, the matrix is processed by frequency segmentation. The sliding window is set in the time axis, and the local extreme value is filtered and binarized. The energy time domain signal is obtained by superimposing the time domain signal, and the characteristic frequency is obtained by spectrum analysis diagnosis. Finally, the simulation signal and experimental signal are analyzed and verified, the results show that the CQTBEW method is feasible.
2022, 41(2): 172-177.
doi: 10.13433/j.cnki.1003-8728.20200339
Abstract:
In view of the present situation that the volumetric small-capacity expander currently used in the organic Rankine cycle has a complicated structure and is difficult to apply and promote, a novel spherical rolling rotor expander is proposed, which combines some features and advantages of the rolling rotor expander and the reciprocating piston expander. It has the features of simple construction, few components, convenient manufacturing and good balance of movement. By introducing the working principle and running process of spherical ball expander and the design of some main parts, an optimization scheme is designed which is different from the conventional intake structure. The intake valve is cancelled, the flow loss and valve vibration noise is reduced. Finally, the size of the expander was designed for a certain working condition, and the lubrication design, leakage analysis and volumetric efficiency estimation were carried out for this expander.
In view of the present situation that the volumetric small-capacity expander currently used in the organic Rankine cycle has a complicated structure and is difficult to apply and promote, a novel spherical rolling rotor expander is proposed, which combines some features and advantages of the rolling rotor expander and the reciprocating piston expander. It has the features of simple construction, few components, convenient manufacturing and good balance of movement. By introducing the working principle and running process of spherical ball expander and the design of some main parts, an optimization scheme is designed which is different from the conventional intake structure. The intake valve is cancelled, the flow loss and valve vibration noise is reduced. Finally, the size of the expander was designed for a certain working condition, and the lubrication design, leakage analysis and volumetric efficiency estimation were carried out for this expander.
2022, 41(2): 178-185.
doi: 10.13433/j.cnki.1003-8728.20200318
Abstract:
To improve the efficiency and accuracy for exploring a multi-robot environment, this paper proposes a path planning method based on the partially observable Markov decision process (POMDP) to control multiple robots equipped with sensors and to realize the coordinated exploration of the environment. Taken information entropy as the return function, the multi-robot environment exploration system based on the POMDP is established to move the robots with the largest information gain in the direction. The robot′s belief in the environment uses a non-parametric, sample-based representation, and the Bayesian filtering is used to update the robot′s belief in the environment. With our simulation software, the CO concentration of the two environments was precepted. The exploration results are in a good agreement with the predesigned environment. Compared with the traditional full coverage path planning method, the system proposed in this paper has advantages in both efficiency and accuracy.
To improve the efficiency and accuracy for exploring a multi-robot environment, this paper proposes a path planning method based on the partially observable Markov decision process (POMDP) to control multiple robots equipped with sensors and to realize the coordinated exploration of the environment. Taken information entropy as the return function, the multi-robot environment exploration system based on the POMDP is established to move the robots with the largest information gain in the direction. The robot′s belief in the environment uses a non-parametric, sample-based representation, and the Bayesian filtering is used to update the robot′s belief in the environment. With our simulation software, the CO concentration of the two environments was precepted. The exploration results are in a good agreement with the predesigned environment. Compared with the traditional full coverage path planning method, the system proposed in this paper has advantages in both efficiency and accuracy.
2022, 41(2): 186-191.
doi: 10.13433/j.cnki.1003-8728.20200323
Abstract:
In order to alleviate the inherent contradiction between tire grip and wear performance, a radial tire of a certain type of 205/55R16 passenger car was taken as the research object, and the tire crown was bionic designed in this paper. The dynamic grounding characteristics of cat′s paw were obtained by WALKWAY pressure test system, and the reverse topology was carried out with 3D laser scanner. Polynomial fitting is carried out on the cross-sectional point cloud of cat paw pad, and bionic design of tire crown is carried out with similarity principle. The finite element models of bionic tire and sample tire were built in ABAQUS and used to compare the ground contact area and pressure distribution between bionic tire and sample tire under static load, braking and cornering conditions. The results show that the bionic tire design can effectively increase the ground contact area, reduce the peak ground contact pressure, improve the tire eccentric wear phenomenon, and thus realize the synergistic improvement of tire grip and wear performance.
In order to alleviate the inherent contradiction between tire grip and wear performance, a radial tire of a certain type of 205/55R16 passenger car was taken as the research object, and the tire crown was bionic designed in this paper. The dynamic grounding characteristics of cat′s paw were obtained by WALKWAY pressure test system, and the reverse topology was carried out with 3D laser scanner. Polynomial fitting is carried out on the cross-sectional point cloud of cat paw pad, and bionic design of tire crown is carried out with similarity principle. The finite element models of bionic tire and sample tire were built in ABAQUS and used to compare the ground contact area and pressure distribution between bionic tire and sample tire under static load, braking and cornering conditions. The results show that the bionic tire design can effectively increase the ground contact area, reduce the peak ground contact pressure, improve the tire eccentric wear phenomenon, and thus realize the synergistic improvement of tire grip and wear performance.
2022, 41(2): 192-198.
doi: 10.13433/j.cnki.1003-8728.20200325
Abstract:
The performance optimization of the traditional machine tool structure for cast iron or steel is close to the extreme value, but the high speed and high precision machining requires the machine tool performance to be further improved. In recent years, the application of resin concrete in the foundation parts of machine tools has been widely concerned. The CK5116 Computer Numerical Control (CNC) machine tool is take as an example according to the equivalent cross section, its resin concrete column model is designed, combining with the finite element software on the static analysis, modal analysis and harmonic response analysis, and comparing with the traditional cast iron material of machine tool column. Comparing the results of the analysis, it demonstrated that the machine tool column is lightweight and the static rigidity is improved, and has better dynamic and static characteristic. The maximum response amplitude is decreased by 55.18%, 77.27% and 20.88% respectively comparing with the maximum response amplitude of cast iron in X-axis, Y-axis and Z-axis. The results show that the resin concrete machine tool column has better anti-vibration performance.
The performance optimization of the traditional machine tool structure for cast iron or steel is close to the extreme value, but the high speed and high precision machining requires the machine tool performance to be further improved. In recent years, the application of resin concrete in the foundation parts of machine tools has been widely concerned. The CK5116 Computer Numerical Control (CNC) machine tool is take as an example according to the equivalent cross section, its resin concrete column model is designed, combining with the finite element software on the static analysis, modal analysis and harmonic response analysis, and comparing with the traditional cast iron material of machine tool column. Comparing the results of the analysis, it demonstrated that the machine tool column is lightweight and the static rigidity is improved, and has better dynamic and static characteristic. The maximum response amplitude is decreased by 55.18%, 77.27% and 20.88% respectively comparing with the maximum response amplitude of cast iron in X-axis, Y-axis and Z-axis. The results show that the resin concrete machine tool column has better anti-vibration performance.
2022, 41(2): 199-206.
doi: 10.13433/j.cnki.1003-8728.20200340
Abstract:
The common cable-driven snake-arm robot is prone to loosening when the distal end is subjected to external lateral force, which may lead to an uncontrollable configuration. This phenomenon is referred to as passive compliance. To avoid the phenomenon, the joint configurations in cable-driven snake-arm robots and the structural characteristics of typical cable-driven snake-arm robots were firstly summarized and analyzed in this paper. Then, the passive compliance was discussed with the example of the snake-arm robot with pivot-based joints. Furthermore, a passive compliance index was proposed to analyze the influence of the joint parameters on passive compliance. As a result, the joint parameter design requirements which can avoid passive compliance are obtained. Finally, three different cable-driven snake-arm robots without passive compliance are established.
The common cable-driven snake-arm robot is prone to loosening when the distal end is subjected to external lateral force, which may lead to an uncontrollable configuration. This phenomenon is referred to as passive compliance. To avoid the phenomenon, the joint configurations in cable-driven snake-arm robots and the structural characteristics of typical cable-driven snake-arm robots were firstly summarized and analyzed in this paper. Then, the passive compliance was discussed with the example of the snake-arm robot with pivot-based joints. Furthermore, a passive compliance index was proposed to analyze the influence of the joint parameters on passive compliance. As a result, the joint parameter design requirements which can avoid passive compliance are obtained. Finally, three different cable-driven snake-arm robots without passive compliance are established.
2022, 41(2): 207-212.
doi: 10.13433/j.cnki.1003-8728.20200315
Abstract:
A kind of soft actuator structure similar to human finger is designed, which contains three ″joints″. It is made of thermoplastic elastomer (TPE) with a shore hardness of 83A. Due to the influence of the forming temperature and other factors on the structural parameters of the material, the stress-strain curve was obtained via tension test, on Mooney Rivlin model, the material parameters C10 and C01 are calculated via tension test, and the bending performance is analyzed with the finite element software. To compare and analyze the finite element simulation results, the bending performance experiment is carried out. The experimental platform was built to grasp the experimental objects in the range of 0-100 g.
A kind of soft actuator structure similar to human finger is designed, which contains three ″joints″. It is made of thermoplastic elastomer (TPE) with a shore hardness of 83A. Due to the influence of the forming temperature and other factors on the structural parameters of the material, the stress-strain curve was obtained via tension test, on Mooney Rivlin model, the material parameters C10 and C01 are calculated via tension test, and the bending performance is analyzed with the finite element software. To compare and analyze the finite element simulation results, the bending performance experiment is carried out. The experimental platform was built to grasp the experimental objects in the range of 0-100 g.
2022, 41(2): 213-219.
doi: 10.13433/j.cnki.1003-8728.20200316
Abstract:
In order to study the influence of rotor systems with different shaft diameter ratios on the power-to-weight ratio of aviation plunger pumps, a rotor system consisting of three parts of the eleven-plunger aviation hydraulic pump cylinder block, drive shaft and support bearing is modeled in this paper. First, a calculation model for pump displacement, flow and power is established. Based on the principle of constant displacement, sixteen groups of aviation plunger pump rotor systems with different shaft diameter ratios are designed, and the cylinder strength is theoretically checked. Then, the power-to-weight ratio calculation model of the rotor system is established. Finally, through the finite element simulation of the cylinder block strength and the theoretical calculation of the power-to-weight ratio, it is concluded that the rebuilt cylinder blocks with different shaft diameter ratios can meet the strength requirements and requirements of the rotor system. The influence law of the rotor system with different shaft diameter ratios on power to weight ratio is obtained, which provides theoretical support for subsequent analysis of unbalanced response of aviation hydraulic pumps and optimization design of cylinder structure.
In order to study the influence of rotor systems with different shaft diameter ratios on the power-to-weight ratio of aviation plunger pumps, a rotor system consisting of three parts of the eleven-plunger aviation hydraulic pump cylinder block, drive shaft and support bearing is modeled in this paper. First, a calculation model for pump displacement, flow and power is established. Based on the principle of constant displacement, sixteen groups of aviation plunger pump rotor systems with different shaft diameter ratios are designed, and the cylinder strength is theoretically checked. Then, the power-to-weight ratio calculation model of the rotor system is established. Finally, through the finite element simulation of the cylinder block strength and the theoretical calculation of the power-to-weight ratio, it is concluded that the rebuilt cylinder blocks with different shaft diameter ratios can meet the strength requirements and requirements of the rotor system. The influence law of the rotor system with different shaft diameter ratios on power to weight ratio is obtained, which provides theoretical support for subsequent analysis of unbalanced response of aviation hydraulic pumps and optimization design of cylinder structure.
2022, 41(2): 220-226.
doi: 10.13433/j.cnki.1003-8728.20200338
Abstract:
Elliptic texture with the major semi-axis is 600 μm, the depth 20 μm remains unchanged, and the minor semi-axis is 200-500 μm was corroded with the nanosecond laser marking machine on the surface of Pin-disk element specimens. The influence of the surface texture on the friction properties of bit sliding bearing when machined on shaft diameter and sleeve surface respectively were investigated under the simulated condition with the test force is 435 N and the speed is 0.29 m/s with the MDW-1 type testing machine. The experimental results show that the lubrication and wear reduction performance is optimal when the texture is staggered on the surface of the pin and the disc sample, while the lubrication effect is the worst when the texture is parallel distributed on the surface of the pin and the disk sample.
Elliptic texture with the major semi-axis is 600 μm, the depth 20 μm remains unchanged, and the minor semi-axis is 200-500 μm was corroded with the nanosecond laser marking machine on the surface of Pin-disk element specimens. The influence of the surface texture on the friction properties of bit sliding bearing when machined on shaft diameter and sleeve surface respectively were investigated under the simulated condition with the test force is 435 N and the speed is 0.29 m/s with the MDW-1 type testing machine. The experimental results show that the lubrication and wear reduction performance is optimal when the texture is staggered on the surface of the pin and the disc sample, while the lubrication effect is the worst when the texture is parallel distributed on the surface of the pin and the disk sample.
2022, 41(2): 227-234.
doi: 10.13433/j.cnki.1003-8728.20200408
Abstract:
Aiming at the product design improvement, a collection and analysis method of user experience information in online product reviews was proposed. Firstly, an user experience element model was constructed. Then, according to the element model, the user emotion, product feature and usage context in a single review sentence were extracted step by step. Finally, the user experience elements extracted from a single review sentence were classified and integrated, and through quantitative analysis of the review data, the product features and use contexts that have a greater impact on user experience were identified. The method was verified by taking the online reviews of a smart phone on Jingdong Mall as the example. The experimental results show that the method can effectively extract the user experience elements from online product reviews, identify the product features and use contexts that have a great impact on the user experience, and assist designers to improve the product design.
Aiming at the product design improvement, a collection and analysis method of user experience information in online product reviews was proposed. Firstly, an user experience element model was constructed. Then, according to the element model, the user emotion, product feature and usage context in a single review sentence were extracted step by step. Finally, the user experience elements extracted from a single review sentence were classified and integrated, and through quantitative analysis of the review data, the product features and use contexts that have a greater impact on user experience were identified. The method was verified by taking the online reviews of a smart phone on Jingdong Mall as the example. The experimental results show that the method can effectively extract the user experience elements from online product reviews, identify the product features and use contexts that have a great impact on the user experience, and assist designers to improve the product design.
2022, 41(2): 235-238.
doi: 10.13433/j.cnki.1003-8728.20200345
Abstract:
The warp of bismuth telluride-based thermoelectric material wafers, which is must be controlled in the multi-wire slicing process, has an important influence on the quality of thermoelectric cooling sheets. In order to reflect the wafer warp by the node displacement of sliced wafer surface, a finite element model for sequential coupled thermal strain analysis in the multi-wire slicing process was established. Firstly, a three-dimensional finite element model for the temperature field was established to simulate the temperature distribution in the slicing process. And then the temperature field was used as a boundary condition to establish a thermal strain analysis model. The model with different combinations of tension, feed speed and wire speed was also simulated and the corresponding warping degree value was calculated. Finally, the results demonstrated that the warp increases with the increasing of feed and wire speeds, and the warp decreases with the increasing of tension force.
The warp of bismuth telluride-based thermoelectric material wafers, which is must be controlled in the multi-wire slicing process, has an important influence on the quality of thermoelectric cooling sheets. In order to reflect the wafer warp by the node displacement of sliced wafer surface, a finite element model for sequential coupled thermal strain analysis in the multi-wire slicing process was established. Firstly, a three-dimensional finite element model for the temperature field was established to simulate the temperature distribution in the slicing process. And then the temperature field was used as a boundary condition to establish a thermal strain analysis model. The model with different combinations of tension, feed speed and wire speed was also simulated and the corresponding warping degree value was calculated. Finally, the results demonstrated that the warp increases with the increasing of feed and wire speeds, and the warp decreases with the increasing of tension force.
2022, 41(2): 239-245.
doi: 10.13433/j.cnki.1003-8728.20200317
Abstract:
There are some problems in small diameter internal thread tapping, such as large torque, easy to break tap and poor thread quality. In this paper, the effect mechanism of reciprocating advance and retreat of manual tapping on tapping torque is analyzed, and a torque model of tapping process considering cutting, extrusion friction and chip resistance is established. The effect of ironing times and chip rolling breaking on friction torque and chip resistance torque is studied by experiments and analysis. The results show that the extrusion friction torque and the number of reciprocating ironing times decrease exponentially, and the chip resistance torque increases linearly with the continuous tapping time. The established tapping torque formula can accurately predict the changing trend of the tapping torque, which provides a basis for the realization of automatic humanoid tapping motion strategy.
There are some problems in small diameter internal thread tapping, such as large torque, easy to break tap and poor thread quality. In this paper, the effect mechanism of reciprocating advance and retreat of manual tapping on tapping torque is analyzed, and a torque model of tapping process considering cutting, extrusion friction and chip resistance is established. The effect of ironing times and chip rolling breaking on friction torque and chip resistance torque is studied by experiments and analysis. The results show that the extrusion friction torque and the number of reciprocating ironing times decrease exponentially, and the chip resistance torque increases linearly with the continuous tapping time. The established tapping torque formula can accurately predict the changing trend of the tapping torque, which provides a basis for the realization of automatic humanoid tapping motion strategy.
2022, 41(2): 246-252.
doi: 10.13433/j.cnki.1003-8728.20200627
Abstract:
Aiming at the problem of low accuracy of wear state recognition due to complex working conditions of turning tools in actual machining, a combined classification algorithm of variational mode decomposition (VMD) based on the maximum envelope kurtosis combined with long and short-term memory (LSTM) networks is proposed in this paper. First, the maximum envelope kurtosis method is used to determine the optimal decomposition mode number of VMD, the signal-to-noise ratio is calculated to reduce the noise and reconstruct the high-frequency signal, and then the original signal and the decomposed signal are feature extraction and cleaning. Then, aiming at the unbalanced data sample for the problem, the SMOTE algorithm is introduced to synthesize a minority of samples, combined with feature changes and the wear division data set during tool processing, and the LSTM model is used to classify the wear status of the turning tool under multiple working conditions. Finally, the effectiveness of the proposed model and method is verified through experiments. The experimental results show that this model has higher classification accuracy and better generalization than other classification models.
Aiming at the problem of low accuracy of wear state recognition due to complex working conditions of turning tools in actual machining, a combined classification algorithm of variational mode decomposition (VMD) based on the maximum envelope kurtosis combined with long and short-term memory (LSTM) networks is proposed in this paper. First, the maximum envelope kurtosis method is used to determine the optimal decomposition mode number of VMD, the signal-to-noise ratio is calculated to reduce the noise and reconstruct the high-frequency signal, and then the original signal and the decomposed signal are feature extraction and cleaning. Then, aiming at the unbalanced data sample for the problem, the SMOTE algorithm is introduced to synthesize a minority of samples, combined with feature changes and the wear division data set during tool processing, and the LSTM model is used to classify the wear status of the turning tool under multiple working conditions. Finally, the effectiveness of the proposed model and method is verified through experiments. The experimental results show that this model has higher classification accuracy and better generalization than other classification models.
2022, 41(2): 253-262.
doi: 10.13433/j.cnki.1003-8728.20200577
Abstract:
In numerical control system, interpolation is often used to realize complex curve machining, which will introduce some chord errors. The commonly used Osculating Circle(OC) method and single-direction Hausdorff distance method can obtain estimated chord errors, then make subsequent compensations, but they both introduce other errors in the estimation process. For this problem, based on the both-direction Hausdorff distance definition of the chord error, an iterative evaluation algorithm is proposed in this paper. This algorithm can improve the estimation precision of chord error without considering the flexibility of curves, and obtain the maximum interpolation step length that satisfies the error limitation, thereby further generating the accurate feed rate constraints to prevent the reduction of both machining accuracy and efficiency due to the introduction of other errors. Finally, it is simulated by '∞'-shaped and petal-shaped NURBS curves, the simulation results verify the performance and the effectiveness of the proposed algorithm.
In numerical control system, interpolation is often used to realize complex curve machining, which will introduce some chord errors. The commonly used Osculating Circle(OC) method and single-direction Hausdorff distance method can obtain estimated chord errors, then make subsequent compensations, but they both introduce other errors in the estimation process. For this problem, based on the both-direction Hausdorff distance definition of the chord error, an iterative evaluation algorithm is proposed in this paper. This algorithm can improve the estimation precision of chord error without considering the flexibility of curves, and obtain the maximum interpolation step length that satisfies the error limitation, thereby further generating the accurate feed rate constraints to prevent the reduction of both machining accuracy and efficiency due to the introduction of other errors. Finally, it is simulated by '∞'-shaped and petal-shaped NURBS curves, the simulation results verify the performance and the effectiveness of the proposed algorithm.
2022, 41(2): 263-269.
doi: 10.13433/j.cnki.1003-8728.20200319
Abstract:
Due to the poor rigidity of thin-walled work-piece, it is inevitable that there are the various disturbances in the milling process, which is prone to chatter and seriously affects the accuracy and surface quality of work-piece. Considering the different sizes of the same material and the different natural frequencies of the different materials, to solve this problem, a method with the variable frequency magneto rheological elastomer (MRE) absorber in the machining process is proposed. In this paper, the design process of MRE absorber is introduced in detail, and the frequency of the absorber under different current is tested, and the performance of MRE absorber in milling process is analyzed. The stability lobe diagram and anti-interference ability of milling system are compared and analyzed. The results show that the designed variable frequency MRE absorber is correct and feasible to prevent cutting chatter, and it can be applied to different materials and different sizes of work-pieces by changing the current.
Due to the poor rigidity of thin-walled work-piece, it is inevitable that there are the various disturbances in the milling process, which is prone to chatter and seriously affects the accuracy and surface quality of work-piece. Considering the different sizes of the same material and the different natural frequencies of the different materials, to solve this problem, a method with the variable frequency magneto rheological elastomer (MRE) absorber in the machining process is proposed. In this paper, the design process of MRE absorber is introduced in detail, and the frequency of the absorber under different current is tested, and the performance of MRE absorber in milling process is analyzed. The stability lobe diagram and anti-interference ability of milling system are compared and analyzed. The results show that the designed variable frequency MRE absorber is correct and feasible to prevent cutting chatter, and it can be applied to different materials and different sizes of work-pieces by changing the current.
2022, 41(2): 270-277.
doi: 10.13433/j.cnki.1003-8728.20200353
Abstract:
As a new and effective machining technology, ultrasonic vibration assisted machining (UVAM) can effectively improve the machining performance of workpieces, which has been widely used in the field of titanium alloy machining. A thermo-mechanical coupled model is established to simulate the transient cutting process of titanium alloy Ti6Al4V in ultrasonic vibration assisted machining. The influence of different vibration amplitudes on the serrated chips of titanium alloy is studied. The simulation results show that the coupling effect of ultrasonic vibration and cutting speed leads to large plastic deformation, and high temperature is the main reason for the formation of serrated chips. The bending radius, serration pitch and serration coefficient of chip all increase with the increase of amplitude. The conclusion can provide a guidance for the research of serrated chips formation mechanism of titanium alloy in ultrasonic vibration assisted machining.
As a new and effective machining technology, ultrasonic vibration assisted machining (UVAM) can effectively improve the machining performance of workpieces, which has been widely used in the field of titanium alloy machining. A thermo-mechanical coupled model is established to simulate the transient cutting process of titanium alloy Ti6Al4V in ultrasonic vibration assisted machining. The influence of different vibration amplitudes on the serrated chips of titanium alloy is studied. The simulation results show that the coupling effect of ultrasonic vibration and cutting speed leads to large plastic deformation, and high temperature is the main reason for the formation of serrated chips. The bending radius, serration pitch and serration coefficient of chip all increase with the increase of amplitude. The conclusion can provide a guidance for the research of serrated chips formation mechanism of titanium alloy in ultrasonic vibration assisted machining.
2022, 41(2): 278-287.
doi: 10.13433/j.cnki.1003-8728.20200343
Abstract:
This paper presents a machine learning based fault prediction integration method for rolling linear guideway. Firstly, through the life test, the vibration signals collected by the triaxial acceleration sensor have been decomposed by wavelet packet, and the partial energy has been extracted as the signal feature. Secondly, the SOM (self organizing map) neural network has been trained by the extracted feature, and the trained SOM has been applied to identify the health status of the railway. Finally, the minimum quantization error and EWMA (exponential weighted moving average control chart) have been used to realize dynamic fault early warning. This method combines SOM with wavelet packet decomposition, selects the minimum quantization error to build EWMA control chart, solves the problems of visual monitoring and numerical evaluation of fatigue degree, and the effectiveness of the integrated method for fault prediction of linear guideway was verified.
This paper presents a machine learning based fault prediction integration method for rolling linear guideway. Firstly, through the life test, the vibration signals collected by the triaxial acceleration sensor have been decomposed by wavelet packet, and the partial energy has been extracted as the signal feature. Secondly, the SOM (self organizing map) neural network has been trained by the extracted feature, and the trained SOM has been applied to identify the health status of the railway. Finally, the minimum quantization error and EWMA (exponential weighted moving average control chart) have been used to realize dynamic fault early warning. This method combines SOM with wavelet packet decomposition, selects the minimum quantization error to build EWMA control chart, solves the problems of visual monitoring and numerical evaluation of fatigue degree, and the effectiveness of the integrated method for fault prediction of linear guideway was verified.
2022, 41(2): 288-294.
doi: 10.13433/j.cnki.1003-8728.20200324
Abstract:
This paper mainly researches the method of pattern recognition of car body solder joint size, with COMSOL as a simulation tool to establish a model for eddy current sensor testing solder joints, the influence of the solder joints on the detection voltage is studied, and the simulation results are verified via experiments. The conclusion is as follows: the greater the excitation frequency, the smaller the eddy current skin depth, the greater the detection sensitivity. The lift-off increases, the eddy current density decreases, the detection sensitivity decreases, and the solder joints are more difficult to measure. The edge of the solder joint will cause the voltage in a convex state and cause a wave signal. The larger size of the solder joint, the greater output voltage amplitude. In this paper, the time-domain integral of the voltage curve and the wavelength width of the voltage amplitude gradient are used as the characteristic value and the solder joint size to perform regression analysis to identify the solder size information. The frequency response of the solder joint phase trajectory at different depths is used to identify the solder joint In-depth information.
This paper mainly researches the method of pattern recognition of car body solder joint size, with COMSOL as a simulation tool to establish a model for eddy current sensor testing solder joints, the influence of the solder joints on the detection voltage is studied, and the simulation results are verified via experiments. The conclusion is as follows: the greater the excitation frequency, the smaller the eddy current skin depth, the greater the detection sensitivity. The lift-off increases, the eddy current density decreases, the detection sensitivity decreases, and the solder joints are more difficult to measure. The edge of the solder joint will cause the voltage in a convex state and cause a wave signal. The larger size of the solder joint, the greater output voltage amplitude. In this paper, the time-domain integral of the voltage curve and the wavelength width of the voltage amplitude gradient are used as the characteristic value and the solder joint size to perform regression analysis to identify the solder size information. The frequency response of the solder joint phase trajectory at different depths is used to identify the solder joint In-depth information.
2022, 41(2): 295-299.
doi: 10.13433/j.cnki.1003-8728.20200341
Abstract:
Taking the airbag ignition time as the object of study, deriving the formula for calculating optimal ignition time of an airbag in a frontal collision based on the conservation of occupant crash energy and the T5in-30 ms principle, crash test parameters of small electric vehicles were used to calculate the ignition time of airbags. A finite element model of the driver restraint system was developed and the effect trend of airbag ignition time on occupant injury was discussed. Finally, the lowest range of the occupant-weighted injury guideline WIC stability was used to determine the optimal airbag ignition time. The results show that the airbag ignition time calculated by the formula is consistent with the best ignition time obtained from the simulation results, and the occupant damage value meets relative regulations, which verifies the accuracy of the airbag ignition moment formula.
Taking the airbag ignition time as the object of study, deriving the formula for calculating optimal ignition time of an airbag in a frontal collision based on the conservation of occupant crash energy and the T5in-30 ms principle, crash test parameters of small electric vehicles were used to calculate the ignition time of airbags. A finite element model of the driver restraint system was developed and the effect trend of airbag ignition time on occupant injury was discussed. Finally, the lowest range of the occupant-weighted injury guideline WIC stability was used to determine the optimal airbag ignition time. The results show that the airbag ignition time calculated by the formula is consistent with the best ignition time obtained from the simulation results, and the occupant damage value meets relative regulations, which verifies the accuracy of the airbag ignition moment formula.
2022, 41(2): 300-305.
doi: 10.13433/j.cnki.1003-8728.20200320
Abstract:
For the research of the influence of the milling parameters on the mechanical performance of the components, a full factors experiment was carried out with two variables of spindle speed and feed rate per rotation, and statistics the tensile properties and compressive properties. The results of the experiments show that the tensile property of the composite does not relate to the milling parameters, while the compression property will decrease with the increasing of spindle speed, and does not relate to the feed rate. Meanwhile, the fracture morphology of the tensile tests and compressive tests under different cutting conditions shows that the excessive spindle speed will cause the matrix's thermal damage in the machining area, and the analysis suggests that the thermal damage causes the decreasing of the compressive properties.
For the research of the influence of the milling parameters on the mechanical performance of the components, a full factors experiment was carried out with two variables of spindle speed and feed rate per rotation, and statistics the tensile properties and compressive properties. The results of the experiments show that the tensile property of the composite does not relate to the milling parameters, while the compression property will decrease with the increasing of spindle speed, and does not relate to the feed rate. Meanwhile, the fracture morphology of the tensile tests and compressive tests under different cutting conditions shows that the excessive spindle speed will cause the matrix's thermal damage in the machining area, and the analysis suggests that the thermal damage causes the decreasing of the compressive properties.
2022, 41(2): 306-310.
doi: 10.13433/j.cnki.1003-8728.20200344
Abstract:
K6509 cobalt-based alloy samples were cryogenically cooled in liquid nitrogen at -196 ℃ for 4-44 hours. The microstructure and hardness analysis were used to investigate the changes in microstructure and mechanical properties after cryogenic treatment, and friction coefficient and wear rate via linear reciprocating friction and wear experiment. The experimental results show that the hardness basically increased gradually with the increasing of cryogenic time. The hardness increased by 23.6% reaching the highest after 44 h. The friction coefficient curve of the cobalt-based alloy sample becomes relatively stable, and the average friction coefficient is significantly reduced after deep cooling, and the friction coefficient curve of DCT36 sample was the most stable with the lowest average friction coefficient. The wear rate increased firstly and then decreased with the increasing of cryogenic time. The wear rate of DCT28 sample reached the highest, and the wear rate increased by 57.91%, 44.29%, 27%.
K6509 cobalt-based alloy samples were cryogenically cooled in liquid nitrogen at -196 ℃ for 4-44 hours. The microstructure and hardness analysis were used to investigate the changes in microstructure and mechanical properties after cryogenic treatment, and friction coefficient and wear rate via linear reciprocating friction and wear experiment. The experimental results show that the hardness basically increased gradually with the increasing of cryogenic time. The hardness increased by 23.6% reaching the highest after 44 h. The friction coefficient curve of the cobalt-based alloy sample becomes relatively stable, and the average friction coefficient is significantly reduced after deep cooling, and the friction coefficient curve of DCT36 sample was the most stable with the lowest average friction coefficient. The wear rate increased firstly and then decreased with the increasing of cryogenic time. The wear rate of DCT28 sample reached the highest, and the wear rate increased by 57.91%, 44.29%, 27%.
2022, 41(2): 311-315.
doi: 10.13433/j.cnki.1003-8728.20200326
Abstract:
For augmented reality assembly, high-precision manual work can only be done by experienced workers because they can represent accurate information into a series of manual operation rules. Because these rules are not formed in brain, a novice's operation precision is not high and his operation efficiency is low. In order to describe these rules, this paper first defines the AR visualization oriented to operational accuracy and then clarifies the differences and relations between AR visualization and traditional AR visualization to guide manual operations. Secondly, an augmented reality instruction (micro-AR) for manual operation rules is proposed. The traditional AR and micro-AR instruction-assisted micro-assembly process is designed respectively. The assembly time and operation experience of the two interfaces are verified by an example. The results show that, compared with the traditional AR instruction, the micro-AR instruction can improve its user's assembly efficiency and deepen his cognition of the assembly task.
For augmented reality assembly, high-precision manual work can only be done by experienced workers because they can represent accurate information into a series of manual operation rules. Because these rules are not formed in brain, a novice's operation precision is not high and his operation efficiency is low. In order to describe these rules, this paper first defines the AR visualization oriented to operational accuracy and then clarifies the differences and relations between AR visualization and traditional AR visualization to guide manual operations. Secondly, an augmented reality instruction (micro-AR) for manual operation rules is proposed. The traditional AR and micro-AR instruction-assisted micro-assembly process is designed respectively. The assembly time and operation experience of the two interfaces are verified by an example. The results show that, compared with the traditional AR instruction, the micro-AR instruction can improve its user's assembly efficiency and deepen his cognition of the assembly task.
2022, 41(2): 316-321.
doi: 10.13433/j.cnki.1003-8728.20200342
Abstract:
To satisfy speed limit requirements and high dynamic response requirements for an EMA (electro-mechanical actuator) servo system, a robust PTOC (approximate time optimal control) position control strategy based on the first-order linear active disturbance rejection control speed controller is proposed. By combining speed loop dynamics with position loop control laws, the switching between speed control law and position control law in the general PTOC servo system is avoided. The effect of the speed controller on the PTOC control law under different working conditions is analyzed, and the PTOC control law under the saturated and unsaturated working conditions of the speed loop is proposed respectively. To solve the problem of conservative parameter selection with the typical PTOC control law, an improved method based on variable switching region and linear region is proposed. The stability proof is given. The simulation results show that the proposed control strategy can enhance the dynamic performance of the EMA position servo and its disturbance rejection ability.
To satisfy speed limit requirements and high dynamic response requirements for an EMA (electro-mechanical actuator) servo system, a robust PTOC (approximate time optimal control) position control strategy based on the first-order linear active disturbance rejection control speed controller is proposed. By combining speed loop dynamics with position loop control laws, the switching between speed control law and position control law in the general PTOC servo system is avoided. The effect of the speed controller on the PTOC control law under different working conditions is analyzed, and the PTOC control law under the saturated and unsaturated working conditions of the speed loop is proposed respectively. To solve the problem of conservative parameter selection with the typical PTOC control law, an improved method based on variable switching region and linear region is proposed. The stability proof is given. The simulation results show that the proposed control strategy can enhance the dynamic performance of the EMA position servo and its disturbance rejection ability.
2022, 41(2): 322-328.
doi: 10.13433/j.cnki.1003-8728.20200604
Abstract:
As the main bearing component of the aircraft structure, the strength check of the stiffened panel structure has always been one of the key concerns of designers. In order to reduce the complexity and repeatability of this work, on the basis of the domestic CAE software platform HAJIF, the strength check software for the metal stiffened panel structure was developed, which realized the process and automation of the strength check work. The software adopted the idea of a unified layered architecture, and successively developed independent front-end interface, strength calculation, work stress extraction, result post-processing and other core modules, and organically integrated with the front and rear interface of the HAJIF software to achieve unified dispatching between modules. The verification example shows that the software can meet the check requirements of the typical analysis situation of aircraft stiffened panels, conform to the strength check process and usage habits, and significantly improve the work efficiency of strength design and analysts.
As the main bearing component of the aircraft structure, the strength check of the stiffened panel structure has always been one of the key concerns of designers. In order to reduce the complexity and repeatability of this work, on the basis of the domestic CAE software platform HAJIF, the strength check software for the metal stiffened panel structure was developed, which realized the process and automation of the strength check work. The software adopted the idea of a unified layered architecture, and successively developed independent front-end interface, strength calculation, work stress extraction, result post-processing and other core modules, and organically integrated with the front and rear interface of the HAJIF software to achieve unified dispatching between modules. The verification example shows that the software can meet the check requirements of the typical analysis situation of aircraft stiffened panels, conform to the strength check process and usage habits, and significantly improve the work efficiency of strength design and analysts.
