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RSS2020 Vol. 39, No. 9
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2020, 39(9): 1313-1322.
doi: 10.13433/j.cnki.1003-8728.20190293
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Abstract:
In the existing researches, the mechanism designs of elbow rehabilitation exercise almost use series mechanism as the body of the mechanism. There are many problems, such as low accuracy, large inertia, easy to cause injury to elbow muscles, and so on. In view of this, a (2-PRR-S)R-PRCR parallel robot mechanism is designed, which can realize 2 degrees of freedom rehabilitation movement of elbow joint, and verify the degree-of-freedom characteristics of the mechanism by using the screw theory. The inverse and forward position solutions of the mechanism are derived by using spatial geometric analysis method, and then the Jacobian matrix of the mechanism is given, and the singularity of the mechanism is analyzed by combining the Jacobian matrix. According to the constraints of the mechanism, the initial pose workspace of the mechanism is determined, and the goal of optimization is to maximize the pose workspace, and the mechanism is optimized by genetic algorithm. Based on the mechanism of human muscle movement, the training effect of elbow rehabilitation exercise is analyzed, and the applicability of the designed parallel mechanism is verified, which lays a foundation for the follow-up study of elbow rehabilitation training strategy.
In the existing researches, the mechanism designs of elbow rehabilitation exercise almost use series mechanism as the body of the mechanism. There are many problems, such as low accuracy, large inertia, easy to cause injury to elbow muscles, and so on. In view of this, a (2-PRR-S)R-PRCR parallel robot mechanism is designed, which can realize 2 degrees of freedom rehabilitation movement of elbow joint, and verify the degree-of-freedom characteristics of the mechanism by using the screw theory. The inverse and forward position solutions of the mechanism are derived by using spatial geometric analysis method, and then the Jacobian matrix of the mechanism is given, and the singularity of the mechanism is analyzed by combining the Jacobian matrix. According to the constraints of the mechanism, the initial pose workspace of the mechanism is determined, and the goal of optimization is to maximize the pose workspace, and the mechanism is optimized by genetic algorithm. Based on the mechanism of human muscle movement, the training effect of elbow rehabilitation exercise is analyzed, and the applicability of the designed parallel mechanism is verified, which lays a foundation for the follow-up study of elbow rehabilitation training strategy.
2020, 39(9): 1323-1328.
doi: 10.13433/j.cnki.1003-8728.20190276
Abstract:
In order to obtain the lowest cost reliability allocation scheme of the system under certain reliability level, an improved cost function is proposed based on the relationship between the system cost and the reliability and the general characteristics of the cost function. Combined with the actual situation of the reliability application in practice, a nonlinear programming model for reliability allocation via system cost as the objective function and system reliability as the design requirement is constructed. The model has the advantages of simple structure, easy access to parameters, etc., which is convenient for the reliability engineering personnel in practice. The obstacle function method is used to solve the model. The results show that the system reliability design scheme via lower total cost can be obtained under the condition that the system reliability requirements are met.
In order to obtain the lowest cost reliability allocation scheme of the system under certain reliability level, an improved cost function is proposed based on the relationship between the system cost and the reliability and the general characteristics of the cost function. Combined with the actual situation of the reliability application in practice, a nonlinear programming model for reliability allocation via system cost as the objective function and system reliability as the design requirement is constructed. The model has the advantages of simple structure, easy access to parameters, etc., which is convenient for the reliability engineering personnel in practice. The obstacle function method is used to solve the model. The results show that the system reliability design scheme via lower total cost can be obtained under the condition that the system reliability requirements are met.
2020, 39(9): 1329-1334.
doi: 10.13433/j.cnki.1003-8728.20190275
Abstract:
In order to improve the driving capability, the load-transferring property and the smooth performance of the yawing mechanism which is used in the wind tunnel experiment, sensitivity analysis and optimization of parameters to the yawing mechanism were carried out. Based on the factors which affect the performances of yawing mechanism, the judging indexes of dynamics optimization were proposed through solving kinematic and dynamic equations. Taking the Isight software as a platform, based on MATLAB, sensitivities of pressure angle of yawing mechanism, rotary inertia of the rotating part and acceleration of linear slider were analyzed. On this basis, the multiobjective optimization model was established; the influence factors above were optimized in Isight. The results show that the maximum pressure angle of yawing mechanism is reduced by 12.47%, the rotary inertia of the rotating part is lowered by 6.70% and the root mean square acceleration of linear slider is reduced by 43.72% after optimization.
In order to improve the driving capability, the load-transferring property and the smooth performance of the yawing mechanism which is used in the wind tunnel experiment, sensitivity analysis and optimization of parameters to the yawing mechanism were carried out. Based on the factors which affect the performances of yawing mechanism, the judging indexes of dynamics optimization were proposed through solving kinematic and dynamic equations. Taking the Isight software as a platform, based on MATLAB, sensitivities of pressure angle of yawing mechanism, rotary inertia of the rotating part and acceleration of linear slider were analyzed. On this basis, the multiobjective optimization model was established; the influence factors above were optimized in Isight. The results show that the maximum pressure angle of yawing mechanism is reduced by 12.47%, the rotary inertia of the rotating part is lowered by 6.70% and the root mean square acceleration of linear slider is reduced by 43.72% after optimization.
2020, 39(9): 1335-1345.
doi: 10.13433/j.cnki.1003-8728.20190278
Abstract:
For the uncertainty of test data in the identification process of multiple cracks in beams, the frequency characteristic equation of a cantilever cracked beam is deduced based on transfer matrix method, and the mapping relationship between damage parameters (damage location and depth) and dynamic characteristic parameters (frequency and mode) is constructed. Based on Bayesian inference theory, a Bayesian model for damage parameter identification is established. The uniform distribution is chosen as the prior distribution of damage parameters. The posterior probability distribution of damage parameters is established by taking the measured values of natural frequencies and modal modes of the cantilever cracked beam as sample information. The markov chain monte carlo simulation method is used to solve the problem of high dimensional integral in Bayesian equation. The effective detection of damage parameters of multiple cracks in beams is achieved through the analysis of simulation examples and experimental research.
For the uncertainty of test data in the identification process of multiple cracks in beams, the frequency characteristic equation of a cantilever cracked beam is deduced based on transfer matrix method, and the mapping relationship between damage parameters (damage location and depth) and dynamic characteristic parameters (frequency and mode) is constructed. Based on Bayesian inference theory, a Bayesian model for damage parameter identification is established. The uniform distribution is chosen as the prior distribution of damage parameters. The posterior probability distribution of damage parameters is established by taking the measured values of natural frequencies and modal modes of the cantilever cracked beam as sample information. The markov chain monte carlo simulation method is used to solve the problem of high dimensional integral in Bayesian equation. The effective detection of damage parameters of multiple cracks in beams is achieved through the analysis of simulation examples and experimental research.
2020, 39(9): 1346-1351.
doi: 10.13433/j.cnki.1003-8728.20190279
Abstract:
An electro-hydraulic position servo system is widely used in large inertia and heavy load systems. Due to its fast response speed, large power-to-volume ratio and strong interference suppression ability, in the case of large inertia operation, it is important to consider the influence of flexible connection on the stability and accuracy of the response of the electro-hydraulic position servo system. We simulate the frequency transfer and time domain of the transfer function model of the nonlinear dynamic system and then analyze the influence of elastic stiffness on the performance of the servo system at the flexible joint. The results show that its dynamic response is delayed when the flexible wire connection mechanism is considered but that the control accuracy and stability are improved after stabilization. The transfer function model of the nonlinear dynamic system with flexible connection is experimentally verified with the conventional PID control method and the controller of the cerebellar model articulation control (CMAC) algorithm. The experimental results show that the transfer function model that considers the elastic stiffness of the flexible connection is more in line with the actual conditions of the large inertia. The CMAC algorithm controller can optimize the parameters of the electro-hydraulic position servo system with flexible connection and improve the position tracking performance of the electro-hydraulic position servo system.
An electro-hydraulic position servo system is widely used in large inertia and heavy load systems. Due to its fast response speed, large power-to-volume ratio and strong interference suppression ability, in the case of large inertia operation, it is important to consider the influence of flexible connection on the stability and accuracy of the response of the electro-hydraulic position servo system. We simulate the frequency transfer and time domain of the transfer function model of the nonlinear dynamic system and then analyze the influence of elastic stiffness on the performance of the servo system at the flexible joint. The results show that its dynamic response is delayed when the flexible wire connection mechanism is considered but that the control accuracy and stability are improved after stabilization. The transfer function model of the nonlinear dynamic system with flexible connection is experimentally verified with the conventional PID control method and the controller of the cerebellar model articulation control (CMAC) algorithm. The experimental results show that the transfer function model that considers the elastic stiffness of the flexible connection is more in line with the actual conditions of the large inertia. The CMAC algorithm controller can optimize the parameters of the electro-hydraulic position servo system with flexible connection and improve the position tracking performance of the electro-hydraulic position servo system.
2020, 39(9): 1352-1357.
doi: 10.13433/j.cnki.1003-8728.20200110
Abstract:
In view of the change of the dynamic transmission error caused by the tooth surface wear of spiral bevel gear in service life, considering the wear degree and load of tooth surface, the influence law of load and wear amount on the dynamic response of transmission error under the single tooth and full tooth wear faults is studied based on the finite element method. It can be seen from the analysis results that the gear surface wear will increase the dynamic transmission error of the gear system. Under the single tooth wear fault, the relationship between the wear amount and the dynamic transmission error is approximately a sine function. When the load is fixed, and when the wear amount is large enough to cause the fault teeth not to participate in the meshing, the wear amount reaches the extreme value and no longer increases. When the wear amount is fixed, the extreme value of the dynamic transmission error amplitude is index Number function relationship with the load. In the case of full tooth wear fault, the fault tooth always takes part in the load, and the relationship between wear and dynamic transmission error is approximately linear.
In view of the change of the dynamic transmission error caused by the tooth surface wear of spiral bevel gear in service life, considering the wear degree and load of tooth surface, the influence law of load and wear amount on the dynamic response of transmission error under the single tooth and full tooth wear faults is studied based on the finite element method. It can be seen from the analysis results that the gear surface wear will increase the dynamic transmission error of the gear system. Under the single tooth wear fault, the relationship between the wear amount and the dynamic transmission error is approximately a sine function. When the load is fixed, and when the wear amount is large enough to cause the fault teeth not to participate in the meshing, the wear amount reaches the extreme value and no longer increases. When the wear amount is fixed, the extreme value of the dynamic transmission error amplitude is index Number function relationship with the load. In the case of full tooth wear fault, the fault tooth always takes part in the load, and the relationship between wear and dynamic transmission error is approximately linear.
2020, 39(9): 1358-1365.
doi: 10.13433/j.cnki.1003-8728.20190272
Abstract:
An approach based on adaptive local iterative filtering (ALIF), multivariate multiscale permutation entropy (MMPE) and directed acyclic graph support vector machine (DAG-SVM) is proposed in this paper for the problem of efficient fault feature extraction from the non-stationary vibration signals in the fault diagnosis of rolling bearings. ALIF could construct adaptive filtering functions to efficiently constrain noise and mode mixing, and a number of intrinsic mode functions (IMFs) are obtained with adaptive decomposition. The simulation result demonstrates that ALIF outperforms empirical mode decomposition (EMD). Then MMPE is employed to perform information infusion and feature extraction with the IMFs containing primary faulty information, and fault state feature sets are constructed with MMPE. After dimensionality reduction using principal component analysis (PCA), some of the new features are randomly selected to train the DAG-SVM, while the remaining ones are used as test samples for identification and fault diagnosis. Results of the experiment show that MMPE of ALIF is superior to the multiscale permutation entropy (MPE) of multiple IMFs and MMPE of EMD; the proposed method could efficiently identify different types of faults and severity levels of rolling bearings.
An approach based on adaptive local iterative filtering (ALIF), multivariate multiscale permutation entropy (MMPE) and directed acyclic graph support vector machine (DAG-SVM) is proposed in this paper for the problem of efficient fault feature extraction from the non-stationary vibration signals in the fault diagnosis of rolling bearings. ALIF could construct adaptive filtering functions to efficiently constrain noise and mode mixing, and a number of intrinsic mode functions (IMFs) are obtained with adaptive decomposition. The simulation result demonstrates that ALIF outperforms empirical mode decomposition (EMD). Then MMPE is employed to perform information infusion and feature extraction with the IMFs containing primary faulty information, and fault state feature sets are constructed with MMPE. After dimensionality reduction using principal component analysis (PCA), some of the new features are randomly selected to train the DAG-SVM, while the remaining ones are used as test samples for identification and fault diagnosis. Results of the experiment show that MMPE of ALIF is superior to the multiscale permutation entropy (MPE) of multiple IMFs and MMPE of EMD; the proposed method could efficiently identify different types of faults and severity levels of rolling bearings.
2020, 39(9): 1366-1372.
doi: 10.13433/j.cnki.1003-8728.20190292
Abstract:
An integrated analysis method is proposed to reduce the wear and vibration due to clearance joint of linkage mechanism by collaboratively calculating dimensional optimization and predicting wear. The clearance joint is defined contact force constraint and expressed by the nonlinear spring damping model combined with the modified Coulomb friction force. The wear prediction is performed by combing the Archard model and the finite element contact model. Wear and vibration are reduced by optimizing the link lengths of the linkage mechanism with the generalized reduced method. Detailed analysis and calculation of wear problem for exemplary four bar linkage mechanism are then presented. Results show that the angular acceleration peak can effectively characterize the vibration and wear of the mechanism. After optimization, the maximum absolute acceleration peak of the rocker is reduced by 71%, and the stability of the mechanism is greatly improved. The part of worn clearance joint experiencing low wear amount is obviously enlarged and the maximum wear depth is reduced by 36%, which proves the effectiveness of the algorithm for the tribological optimization problem for mechanism with clearance joint.
An integrated analysis method is proposed to reduce the wear and vibration due to clearance joint of linkage mechanism by collaboratively calculating dimensional optimization and predicting wear. The clearance joint is defined contact force constraint and expressed by the nonlinear spring damping model combined with the modified Coulomb friction force. The wear prediction is performed by combing the Archard model and the finite element contact model. Wear and vibration are reduced by optimizing the link lengths of the linkage mechanism with the generalized reduced method. Detailed analysis and calculation of wear problem for exemplary four bar linkage mechanism are then presented. Results show that the angular acceleration peak can effectively characterize the vibration and wear of the mechanism. After optimization, the maximum absolute acceleration peak of the rocker is reduced by 71%, and the stability of the mechanism is greatly improved. The part of worn clearance joint experiencing low wear amount is obviously enlarged and the maximum wear depth is reduced by 36%, which proves the effectiveness of the algorithm for the tribological optimization problem for mechanism with clearance joint.
2020, 39(9): 1373-1378.
doi: 10.13433/j.cnki.1003-8728.20190283
Abstract:
To upgrade a workshop from open to closed constant temperature and to be dust-free, a large heavy-duty bar material transportation manipulator is designed for highly accurate and stable transportation. Firstly, the computer simulation is conducted with SolidWorks and ADAMS software. Secondly, a rigid-flexible coupling model is established and simulated to confirm the validity of the model and obtain the stress and deformation cloud maps. Finally, the manipulator is optimized with a lightweight design to reduce its weight, making it more flexible and smooth. The simulation results show that the maximum deformation of the optimized manipulator decreases from 0.532 mm to 0.409 mm and that its maximum stress decreases from 480.33 MPa to 237.67 MPa, decreasing by 50.5%. The weight reduction of the optimized A-level manipulator is 7.6%.
To upgrade a workshop from open to closed constant temperature and to be dust-free, a large heavy-duty bar material transportation manipulator is designed for highly accurate and stable transportation. Firstly, the computer simulation is conducted with SolidWorks and ADAMS software. Secondly, a rigid-flexible coupling model is established and simulated to confirm the validity of the model and obtain the stress and deformation cloud maps. Finally, the manipulator is optimized with a lightweight design to reduce its weight, making it more flexible and smooth. The simulation results show that the maximum deformation of the optimized manipulator decreases from 0.532 mm to 0.409 mm and that its maximum stress decreases from 480.33 MPa to 237.67 MPa, decreasing by 50.5%. The weight reduction of the optimized A-level manipulator is 7.6%.
2020, 39(9): 1379-1384.
doi: 10.13433/j.cnki.1003-8728.20190287
Abstract:
In order to solve the problem of complex electrode modeling and non-interference motion path searching for electric discharge machining (EDM) with closed blisk, the processing scheme of EDM for closed blisk is studied, an electrode structure and its motion path design method is proposed. The principle of electrode separation is established, the ruled surface is constructed as the electrode parting surface. The search process of the electrode motion path is completed based on the stochastic direction method, and the optimal coordinates of the electrode upper surface central point at each node are obtained. The electrode motion path coordinates were fitting optimized based on the non-uniform rational B-splines (NURBS) curves. The experimental investigation of electrode motion path verification is carried out, and the result shows that the error of blade profile is ±0.08 mm, which meets the design requirements. The results show that the present design method of electrode structure and its motion path is reasonable and effective for the closed integral impeller of EDM, and can be used as a general solution for this kind of problem.
In order to solve the problem of complex electrode modeling and non-interference motion path searching for electric discharge machining (EDM) with closed blisk, the processing scheme of EDM for closed blisk is studied, an electrode structure and its motion path design method is proposed. The principle of electrode separation is established, the ruled surface is constructed as the electrode parting surface. The search process of the electrode motion path is completed based on the stochastic direction method, and the optimal coordinates of the electrode upper surface central point at each node are obtained. The electrode motion path coordinates were fitting optimized based on the non-uniform rational B-splines (NURBS) curves. The experimental investigation of electrode motion path verification is carried out, and the result shows that the error of blade profile is ±0.08 mm, which meets the design requirements. The results show that the present design method of electrode structure and its motion path is reasonable and effective for the closed integral impeller of EDM, and can be used as a general solution for this kind of problem.
2020, 39(9): 1385-1389.
doi: 10.13433/j.cnki.1003-8728.20190281
Abstract:
The contact R-test is a device for measuring the three-dimensional displacement of a precision measurement ball mounted on a machine tool spindle with respect to a table by using three contact displacement sensors. It can be used to measure the geometric error and linkage error of the rotary axis of a five-axis CNC machine tool. How to improve the calibration and spherical coordinates calculation accuracy of the measuring instrument is difficult in R-test development. Therefore, the structural model for the contact R-test measurement instrument and the construction method of the measurement coordinate system were studied. And the on-line calibration model for the measurement instrument is constructed by using the high-precision micro-movement of the machine tool linear axis in the measurement coordinate system, and the exact calculation model for the spherical coordinates is derived. Finally, the actual measurement is carried out by developing a prototype to verify the accuracy and feasibility of the present methods.
The contact R-test is a device for measuring the three-dimensional displacement of a precision measurement ball mounted on a machine tool spindle with respect to a table by using three contact displacement sensors. It can be used to measure the geometric error and linkage error of the rotary axis of a five-axis CNC machine tool. How to improve the calibration and spherical coordinates calculation accuracy of the measuring instrument is difficult in R-test development. Therefore, the structural model for the contact R-test measurement instrument and the construction method of the measurement coordinate system were studied. And the on-line calibration model for the measurement instrument is constructed by using the high-precision micro-movement of the machine tool linear axis in the measurement coordinate system, and the exact calculation model for the spherical coordinates is derived. Finally, the actual measurement is carried out by developing a prototype to verify the accuracy and feasibility of the present methods.
2020, 39(9): 1390-1394.
doi: 10.13433/j.cnki.1003-8728.20200158
Abstract:
In view of the existing detection methods of steel plate defect, which have the low efficiency of detection, limited scope of application, cumbersome operation steps and so on, a real-time detection method of defect based on an improved YOLOv3(You Only Look Once version 3) algorithm is proposed. The method divides the captured images into N×N grids, each grid is used to detect whether there is a center point of defect in the grid, and through multi-scale detection and residual layer fusion feature to locate the defects in the image, get the boundary boxes of multiple defects, and finally use the non maximum inhibition method to screen the highest score boundary boxes. In order to improve the detection effect, the histogram equalization image is used in the input, and the weight based loss function is used, which effectively improves the problem that the model mistakenly judges scratches as indentation. Experimental detection of indentations and scratches on steel plate surfaces with an improved YOLOv3 algorithm. The results show that the method can effectively detect the indentation and scratch on the steel surface, with the accuracy of 92% and 90% respectively.
In view of the existing detection methods of steel plate defect, which have the low efficiency of detection, limited scope of application, cumbersome operation steps and so on, a real-time detection method of defect based on an improved YOLOv3(You Only Look Once version 3) algorithm is proposed. The method divides the captured images into N×N grids, each grid is used to detect whether there is a center point of defect in the grid, and through multi-scale detection and residual layer fusion feature to locate the defects in the image, get the boundary boxes of multiple defects, and finally use the non maximum inhibition method to screen the highest score boundary boxes. In order to improve the detection effect, the histogram equalization image is used in the input, and the weight based loss function is used, which effectively improves the problem that the model mistakenly judges scratches as indentation. Experimental detection of indentations and scratches on steel plate surfaces with an improved YOLOv3 algorithm. The results show that the method can effectively detect the indentation and scratch on the steel surface, with the accuracy of 92% and 90% respectively.
2020, 39(9): 1395-1403.
doi: 10.13433/j.cnki.1003-8728.20200159
Abstract:
In order to realize the energy saving and emission reduction in the production process, a big data-driven real-time energy efficiency analysis method of discrete manufacturing workshops was proposed in this paper. Firstly, the manufacturing data models which include energy data and process data were constructed to realize their acquisition and storage. Then, through data clustering and data correlation analysis, a manufacturing big data analysis method was established to realize the feature extraction of energy consumption data and their association with process data. Finally, multi-level real-time energy efficiency analysis index of discrete manufacturing workshops was provided. This method combines big data processing with energy efficiency analysis of manufacturing workshop, and provides a decision basis for energy saving control of intelligent workshop by analyzing and visualizing energy consumption data.
In order to realize the energy saving and emission reduction in the production process, a big data-driven real-time energy efficiency analysis method of discrete manufacturing workshops was proposed in this paper. Firstly, the manufacturing data models which include energy data and process data were constructed to realize their acquisition and storage. Then, through data clustering and data correlation analysis, a manufacturing big data analysis method was established to realize the feature extraction of energy consumption data and their association with process data. Finally, multi-level real-time energy efficiency analysis index of discrete manufacturing workshops was provided. This method combines big data processing with energy efficiency analysis of manufacturing workshop, and provides a decision basis for energy saving control of intelligent workshop by analyzing and visualizing energy consumption data.
2020, 39(9): 1404-1411.
doi: 10.13433/j.cnki.1003-8728.20190319
Abstract:
Aiming at the problem that the separator film has a poor alignment in the manufacturing process of square lithium batteries using the laminated machine, a novel composite control algorithm is proposed by combining neural network approximate internal model and iterative learning control. Firstly, because the poor alignment is caused by many unknown factors in the manufacturing process of laminated lithium battery, it is impossible to describe the process using a physical mathematical model. A neural network is built to describe the process. Then, in order to enhance the robustness and avoid the non-affine nonlinearity, a neural approximate inverse control is applied to control the process, and the simulation results show that a good performance is obtained in the absence of periodic perturbations. However, the periodic changes of the separator film velocity and tension lead to bring about a periodic disturbance in the process. Finally, the iterative learning control is used to deal with periodic disturbances in the batch manufacturing process of lithium batteries. Experiments demonstrate the composite control algorithm can effectively improve the alignment in the manufacturing process of square lithium using the laminated machine.
Aiming at the problem that the separator film has a poor alignment in the manufacturing process of square lithium batteries using the laminated machine, a novel composite control algorithm is proposed by combining neural network approximate internal model and iterative learning control. Firstly, because the poor alignment is caused by many unknown factors in the manufacturing process of laminated lithium battery, it is impossible to describe the process using a physical mathematical model. A neural network is built to describe the process. Then, in order to enhance the robustness and avoid the non-affine nonlinearity, a neural approximate inverse control is applied to control the process, and the simulation results show that a good performance is obtained in the absence of periodic perturbations. However, the periodic changes of the separator film velocity and tension lead to bring about a periodic disturbance in the process. Finally, the iterative learning control is used to deal with periodic disturbances in the batch manufacturing process of lithium batteries. Experiments demonstrate the composite control algorithm can effectively improve the alignment in the manufacturing process of square lithium using the laminated machine.
2020, 39(9): 1412-1418.
doi: 10.13433/j.cnki.1003-8728.20190258
Abstract:
Based on the characteristics of layer-by-layer cladding, the quality of single bead forming has an important influence on multi-layer multi-pass stacking. In this paper, the influence of process parameters on weld bead height and width in TIG arc additive technology was studied by orthogonal test method, and the mathematical model of weld bead geometry was established. On this basis, single-pass multi-layer stacking and multi-pass lapping experiments were carried out to study the microstructure and microhardness.The results show that when the cooling time between the single-layer laps is sufficient, the overlapping area are obvious, the hardness of both sides of the bead is relatively larger than the incomplete recrystallization area.When the interlayer cooling is 5 s, the stratification of the deposit layers are not obvious, the top layer is lamellar structure, the middle and lower layers are roughly equiaxed crystal structures, and the hardness of the weld near the substrate is the largest.
Based on the characteristics of layer-by-layer cladding, the quality of single bead forming has an important influence on multi-layer multi-pass stacking. In this paper, the influence of process parameters on weld bead height and width in TIG arc additive technology was studied by orthogonal test method, and the mathematical model of weld bead geometry was established. On this basis, single-pass multi-layer stacking and multi-pass lapping experiments were carried out to study the microstructure and microhardness.The results show that when the cooling time between the single-layer laps is sufficient, the overlapping area are obvious, the hardness of both sides of the bead is relatively larger than the incomplete recrystallization area.When the interlayer cooling is 5 s, the stratification of the deposit layers are not obvious, the top layer is lamellar structure, the middle and lower layers are roughly equiaxed crystal structures, and the hardness of the weld near the substrate is the largest.
2020, 39(9): 1419-1425.
doi: 10.13433/j.cnki.1003-8728.20190244
Abstract:
When the image matching algorithm is applied to inspecting components, there are many factors which can increase the difficulty of extracting features and creating templates, such as complex background, non-uniform illumination, oil and iron filings on the surface of the component. These problems lead to unidentification and misidentification for existing image matching algorithms, which will make image matching algorithms more difficult to be applied in the industries. In order to solve those problems, an image matching algorithm was proposed based on the color image segmentation. Firstly, the different gray curve of each channel in the HSV color space is processed as square wave. Secondly, the threshold used in adaptive image segmentation and extraction is determined with the distribution of square curve. Finally, the edge character information is used for template matching. The experiment results show that the algorithm can eliminate the impact of illumination and background noise, accomplish object segmentation fast and accurate, and reduce the difficulty of feature selection and template creation. The algorithm eliminates the misidentification, and achieves the accuracy with less times consuming. The present algorithm has been applied to industrial production successfully.
When the image matching algorithm is applied to inspecting components, there are many factors which can increase the difficulty of extracting features and creating templates, such as complex background, non-uniform illumination, oil and iron filings on the surface of the component. These problems lead to unidentification and misidentification for existing image matching algorithms, which will make image matching algorithms more difficult to be applied in the industries. In order to solve those problems, an image matching algorithm was proposed based on the color image segmentation. Firstly, the different gray curve of each channel in the HSV color space is processed as square wave. Secondly, the threshold used in adaptive image segmentation and extraction is determined with the distribution of square curve. Finally, the edge character information is used for template matching. The experiment results show that the algorithm can eliminate the impact of illumination and background noise, accomplish object segmentation fast and accurate, and reduce the difficulty of feature selection and template creation. The algorithm eliminates the misidentification, and achieves the accuracy with less times consuming. The present algorithm has been applied to industrial production successfully.
2020, 39(9): 1426-1431.
doi: 10.13433/j.cnki.1003-8728.20190284
Abstract:
By studying structure and operating conditions of wind turbine pitch bearings, it is found that rolling elements and race ways take contacting alternately at two contact points of the four contact points as the impeller rotates, which leads to short duration of rolling elements continuous contacting with certain contact point. So it is proposed to collect vibration signals of pitch bearings when impeller is locked. In this case, the time of rolling elements continuous contacting with certain contact point is longer. Vibration signals of fault pitch bearings are analyzed. It shows that shock vibration caused by faults doesn't have strict periodicity. A shock-chain method which based on automatically detecting shock vibration and its approximate periodicity for detecting faults is proposed. Practical applications show that this fault detecting method can automatically detect local faults and hard debris in raceway.
By studying structure and operating conditions of wind turbine pitch bearings, it is found that rolling elements and race ways take contacting alternately at two contact points of the four contact points as the impeller rotates, which leads to short duration of rolling elements continuous contacting with certain contact point. So it is proposed to collect vibration signals of pitch bearings when impeller is locked. In this case, the time of rolling elements continuous contacting with certain contact point is longer. Vibration signals of fault pitch bearings are analyzed. It shows that shock vibration caused by faults doesn't have strict periodicity. A shock-chain method which based on automatically detecting shock vibration and its approximate periodicity for detecting faults is proposed. Practical applications show that this fault detecting method can automatically detect local faults and hard debris in raceway.
2020, 39(9): 1432-1438.
doi: 10.13433/j.cnki.1003-8728.20190277
Abstract:
In order to improve the uniformity of workpiece processing for supersonic equipment, a double-line rectangular supersonic nozzle is proposed. Based on the design theory of supersonic nozzle, the constrained and expanded sections of the double-line rectangular supersonic nozzle are separately designed to obtain their corresponding line equations. The flow-thermal coupling finite volume model of the double-line rectangular supersonic nozzle is established with the compressible ideal gas state equation. Then the influence on the inlet pressure of the double-line rectangular supersonic nozzle and the influence of the velocity of the outlet on the flow field are simulated. The influence of inlet pressure and outlet Mach number on the flow field are also simulated respectively. The simulation results show that at the velocity, the flow field of the double-line rectangular supersonic nozzle not only achieves the designed Mach number and the uniformity requirements but also possesses a rectangular cross section.
In order to improve the uniformity of workpiece processing for supersonic equipment, a double-line rectangular supersonic nozzle is proposed. Based on the design theory of supersonic nozzle, the constrained and expanded sections of the double-line rectangular supersonic nozzle are separately designed to obtain their corresponding line equations. The flow-thermal coupling finite volume model of the double-line rectangular supersonic nozzle is established with the compressible ideal gas state equation. Then the influence on the inlet pressure of the double-line rectangular supersonic nozzle and the influence of the velocity of the outlet on the flow field are simulated. The influence of inlet pressure and outlet Mach number on the flow field are also simulated respectively. The simulation results show that at the velocity, the flow field of the double-line rectangular supersonic nozzle not only achieves the designed Mach number and the uniformity requirements but also possesses a rectangular cross section.
2020, 39(9): 1439-1449.
doi: 10.13433/j.cnki.1003-8728.20190290
Abstract:
In view of the fact that the current lane detection and deviation warning method is not adaptable and the detection accuracy is not high, it can not meet the practical application requirements in a variety of road environments, and the different feature information of the image combined with the spatial positional relationship of the road image and related transcendental knowledge are being studied. In this paper, a lane line detection method that can adapt to various road scenes is proposed, and a corresponding lane deviation warning method is established to enhance the reliability and environmental adaptability of the whole lane line detection system.
In view of the fact that the current lane detection and deviation warning method is not adaptable and the detection accuracy is not high, it can not meet the practical application requirements in a variety of road environments, and the different feature information of the image combined with the spatial positional relationship of the road image and related transcendental knowledge are being studied. In this paper, a lane line detection method that can adapt to various road scenes is proposed, and a corresponding lane deviation warning method is established to enhance the reliability and environmental adaptability of the whole lane line detection system.
2020, 39(9): 1450-1456.
doi: 10.13433/j.cnki.1003-8728.20190291
Abstract:
In order to regulate the thermal stress and distortion in the laser solid forming (LSF) process, in-situ measurement platform is firstly used to monitor the temperature field and substrate distortion in LSF primary deposition and secondary deposition of single-wall. Then the finite element thermo-mechanical coupling model is verified by using the measurement results. Finally, a detailed analysis of the thermal and distortion evolution in LSF process is carried out. The results show that the simulation results are in a good agreement with the experimental. As the deposition layer increases, the area of the high temperature zone increases continuously and the temperature gradient at the front of the molten pool is significantly larger than that at the tail. Comparing with the primary deposition process, the molten pool temperature and the heating rate are significantly higher in the secondary deposition process. In addition, the high temperature gradient in the initial deposition phase and the high cooling rate in final cooling phase result in larger stress and distortion.
In order to regulate the thermal stress and distortion in the laser solid forming (LSF) process, in-situ measurement platform is firstly used to monitor the temperature field and substrate distortion in LSF primary deposition and secondary deposition of single-wall. Then the finite element thermo-mechanical coupling model is verified by using the measurement results. Finally, a detailed analysis of the thermal and distortion evolution in LSF process is carried out. The results show that the simulation results are in a good agreement with the experimental. As the deposition layer increases, the area of the high temperature zone increases continuously and the temperature gradient at the front of the molten pool is significantly larger than that at the tail. Comparing with the primary deposition process, the molten pool temperature and the heating rate are significantly higher in the secondary deposition process. In addition, the high temperature gradient in the initial deposition phase and the high cooling rate in final cooling phase result in larger stress and distortion.
2020, 39(9): 1457-1462.
doi: 10.13433/j.cnki.1003-8728.20190289
Abstract:
With the development of the wind energy industry, reduction of wind turbine noise becomes inevitable. The airfoil with trailing edge serrations is an effective means to reduce the self-noise of the blade. Over the years, domestic and foreign scholars have conducted much research on noise reduction of wind turbine serrated trailing edge in numerical simulations, wind tunnel experiments, and on-site measurements. The experiments are all carried out in NF-3 low speed wind tunnel of Northwestern Polytechnical University. The chosen sensors are selected by that it isn't located in the wake area, and using A-weighted and 1/8-octave band methods for noise spectrum analysis. The results show that the signal from chosen sensor could be used as data source for airfoil noise analysis. Installing trailing edge serrations on the wind turbine airfoil is feasible to reduce noise, and the frequency of noise reduction is the mid-high frequency range of the airfoil self-noise. Using A-weighted and 1/8-octave band methods can perform noise source analysis well.
With the development of the wind energy industry, reduction of wind turbine noise becomes inevitable. The airfoil with trailing edge serrations is an effective means to reduce the self-noise of the blade. Over the years, domestic and foreign scholars have conducted much research on noise reduction of wind turbine serrated trailing edge in numerical simulations, wind tunnel experiments, and on-site measurements. The experiments are all carried out in NF-3 low speed wind tunnel of Northwestern Polytechnical University. The chosen sensors are selected by that it isn't located in the wake area, and using A-weighted and 1/8-octave band methods for noise spectrum analysis. The results show that the signal from chosen sensor could be used as data source for airfoil noise analysis. Installing trailing edge serrations on the wind turbine airfoil is feasible to reduce noise, and the frequency of noise reduction is the mid-high frequency range of the airfoil self-noise. Using A-weighted and 1/8-octave band methods can perform noise source analysis well.
2020, 39(9): 1463-1470.
doi: 10.13433/j.cnki.1003-8728.20190285
Abstract:
In order to meet the requirement of the unlock and release for micro-nano satellite, a lock and release device by using the shape memory alloys tube is proposed, which the weight is below 0.95 kg, the unlock and release shock to the small satellite is below 16 g and the release is synchronized. The design methods of ejection-guide mechanism, reinforcement-preload mechanism and trigger-release mechanism are studied. Through the theoretical analysis and simulation, the main parameters of the cylindrical spring, torsion spring and grooved bolt of the lock and release device are determined. A function between the size of trigger-unlock and the reinforcement-preload mechanism installation position is established, and the value of the reinforcement-preload mechanism installation position is calculated. The mathematical models for the installation position are built, the relationship between the installation position and the fundamental frequency is achieved by using the neural network method. Tensor flow algorithm is used to optimize the installation position. The prototype test is used to verify the correctness of the parameters of the cylindrical spring, the parameters of the torsion spring and the design of the ejection-guide mechanism. In addition, the unlock shock and unlock time of the prototype are measured.
In order to meet the requirement of the unlock and release for micro-nano satellite, a lock and release device by using the shape memory alloys tube is proposed, which the weight is below 0.95 kg, the unlock and release shock to the small satellite is below 16 g and the release is synchronized. The design methods of ejection-guide mechanism, reinforcement-preload mechanism and trigger-release mechanism are studied. Through the theoretical analysis and simulation, the main parameters of the cylindrical spring, torsion spring and grooved bolt of the lock and release device are determined. A function between the size of trigger-unlock and the reinforcement-preload mechanism installation position is established, and the value of the reinforcement-preload mechanism installation position is calculated. The mathematical models for the installation position are built, the relationship between the installation position and the fundamental frequency is achieved by using the neural network method. Tensor flow algorithm is used to optimize the installation position. The prototype test is used to verify the correctness of the parameters of the cylindrical spring, the parameters of the torsion spring and the design of the ejection-guide mechanism. In addition, the unlock shock and unlock time of the prototype are measured.
2020, 39(9): 1471-1476.
doi: 10.13433/j.cnki.1003-8728.20190288
Abstract:
The precise attitude angle plays a very important role in the stable flight of the quadrotor. In order to realize the output of high-precision attitude data of small and low-cost quadrotor aircraft, an attitude detection system consisting of STM32F103, MPU6050 and barometer is built in this paper. Based on the quaternion differential equation, a design algorithm of PI-modified complementary filter attitude control is proposed. The algorithm performs high-pass filtering on gyroscope measurement data and low-pass filtering on accelerometer and magnetometer measurement data, which improves the accuracy of attitude control. Finally, the quadrotor attitude angles based on PI-modified complementary filtering algorithm and ordinary complementary filtering algorithm are compared and analyzed by the experimental platform. The experimental results show that the dynamic error of the attitude angle of the PI-modified complementary filtering algorithm solver is smaller, its performance is more stable, and it can meet the small and low-cost quadrotor flight requirements.
The precise attitude angle plays a very important role in the stable flight of the quadrotor. In order to realize the output of high-precision attitude data of small and low-cost quadrotor aircraft, an attitude detection system consisting of STM32F103, MPU6050 and barometer is built in this paper. Based on the quaternion differential equation, a design algorithm of PI-modified complementary filter attitude control is proposed. The algorithm performs high-pass filtering on gyroscope measurement data and low-pass filtering on accelerometer and magnetometer measurement data, which improves the accuracy of attitude control. Finally, the quadrotor attitude angles based on PI-modified complementary filtering algorithm and ordinary complementary filtering algorithm are compared and analyzed by the experimental platform. The experimental results show that the dynamic error of the attitude angle of the PI-modified complementary filtering algorithm solver is smaller, its performance is more stable, and it can meet the small and low-cost quadrotor flight requirements.
