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RSS2020 Vol. 39, No. 3
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2020, 39(3): 329-335.
doi: 10.13433/j.cnki.1003-8728.20190131
PDF 1112KB
Abstract:
The wear prediction of tool is of great significance for improving the safety and reliability of equipment operation. In order to improve the accuracy of wear prediction of tool, a method based on distributed convolutional neural network is proposed. This method takes the original high-frequency signal sample as input and divides it into several sub-sequences in the model with distributed convolution pooling layer as local feature extractors. Features are adaptively extracted from subsequences and batch normalization is performed. Finally, the wear of tool is predicted with nonlinear mapping. Comparing with BPNN model, the present model reduces the mean square error by 51.3% and it has a higher tool wear prediction accuracy.
The wear prediction of tool is of great significance for improving the safety and reliability of equipment operation. In order to improve the accuracy of wear prediction of tool, a method based on distributed convolutional neural network is proposed. This method takes the original high-frequency signal sample as input and divides it into several sub-sequences in the model with distributed convolution pooling layer as local feature extractors. Features are adaptively extracted from subsequences and batch normalization is performed. Finally, the wear of tool is predicted with nonlinear mapping. Comparing with BPNN model, the present model reduces the mean square error by 51.3% and it has a higher tool wear prediction accuracy.
2020, 39(3): 336-343.
doi: 10.13433/j.cnki.1003-8728.20190134
Abstract:
Based on the practical design requirements regarding to the parallelism of steel disc during the development of wet clutch, a three-dimensional model of friction pairs on a wet clutch was developed with nonlinear finite element method (FEM) software ABAQUS to study the effect of parallelism of steel discs on its thermal characteristic, providing a theoretical basis for the design requirements of parallelism. The FEM simulation result shows that parallelism of steel disc can change the distribution of contact pressure on friction pairs, improving the radial temperature gradient and stress gradient and making the local high temperature appearing. Improving the parallelism will increase the maximum temperature and stress of steel disc. When the parallelism is 0.1 mm, the maximum equivalent stress of steel disc exceeds its yield strength resulting in plastic deformation.
Based on the practical design requirements regarding to the parallelism of steel disc during the development of wet clutch, a three-dimensional model of friction pairs on a wet clutch was developed with nonlinear finite element method (FEM) software ABAQUS to study the effect of parallelism of steel discs on its thermal characteristic, providing a theoretical basis for the design requirements of parallelism. The FEM simulation result shows that parallelism of steel disc can change the distribution of contact pressure on friction pairs, improving the radial temperature gradient and stress gradient and making the local high temperature appearing. Improving the parallelism will increase the maximum temperature and stress of steel disc. When the parallelism is 0.1 mm, the maximum equivalent stress of steel disc exceeds its yield strength resulting in plastic deformation.
2020, 39(3): 344-349.
doi: 10.13433/j.cnki.1003-8728.20190133
Abstract:
Aiming at the problem that the acceleration signal generated by the low-speed broken gear under speed variations contains the impact resonance, and the energy of quasi-stationary component is lower, a new fault diagnosis method for varying speeds gears is presented. The time of the single impulse component peaks emerged within each rotation of the fault gear shaft, is determined directly with searching extreme value. It makes the cost reduction of calculation, as the parameters estimation of modal (natural frequencies and damping ratio) are calculated according to the shorter time series on the right side of the peaks time based on correlation filtering. The time domain impulse response component is extracted by matching pursuit algorithm via the impact dictionary. After removing the impact component from original vibration, residual signal is converted into the angular domain. The steady-type fault feature of the system is extracted from angular residual signal by utilizing the quasi-steady modulation dictionary. Simulation and experimental results show that the impulse component in time domain and steady-type fault components of angular domain are reconstructed well. Feature extraction of vibration and fault diagnosis of the gearbox are implemented with order tracking.
Aiming at the problem that the acceleration signal generated by the low-speed broken gear under speed variations contains the impact resonance, and the energy of quasi-stationary component is lower, a new fault diagnosis method for varying speeds gears is presented. The time of the single impulse component peaks emerged within each rotation of the fault gear shaft, is determined directly with searching extreme value. It makes the cost reduction of calculation, as the parameters estimation of modal (natural frequencies and damping ratio) are calculated according to the shorter time series on the right side of the peaks time based on correlation filtering. The time domain impulse response component is extracted by matching pursuit algorithm via the impact dictionary. After removing the impact component from original vibration, residual signal is converted into the angular domain. The steady-type fault feature of the system is extracted from angular residual signal by utilizing the quasi-steady modulation dictionary. Simulation and experimental results show that the impulse component in time domain and steady-type fault components of angular domain are reconstructed well. Feature extraction of vibration and fault diagnosis of the gearbox are implemented with order tracking.
2020, 39(3): 350-355.
doi: 10.13433/j.cnki.1003-8728.20190132
Abstract:
The raceway of rolling bearing is subject to the large contact stress in working process, and contact fatigue is the main kind of bearing failure. In order to investigate the contact fatigue of the bearing and the internal crack induced by the contact fatigue, the present method can accurately simulate the topological randomness of bearing materials and the material fatigue damage process by combining the damage mechanics with the Voronoi finite element method. The contact fatigue crack propagation model for bearing is established, and the process of crack initiation, growth, intersection and propagation to the surface of the raceway is simulated effectively, the life of crack on bearing and the path of crack propagation are obtained. The energy released during crack propagation is calculated. The results can provide new ideas and tools for the study of contact fatigue damage of bearings.
The raceway of rolling bearing is subject to the large contact stress in working process, and contact fatigue is the main kind of bearing failure. In order to investigate the contact fatigue of the bearing and the internal crack induced by the contact fatigue, the present method can accurately simulate the topological randomness of bearing materials and the material fatigue damage process by combining the damage mechanics with the Voronoi finite element method. The contact fatigue crack propagation model for bearing is established, and the process of crack initiation, growth, intersection and propagation to the surface of the raceway is simulated effectively, the life of crack on bearing and the path of crack propagation are obtained. The energy released during crack propagation is calculated. The results can provide new ideas and tools for the study of contact fatigue damage of bearings.
2020, 39(3): 356-360.
doi: 10.13433/j.cnki.1003-8728.20190151
Abstract:
The elliptical control theory is introduced into bearing fault detection and a new bearing detection method is proposed in this paper. First the bearing data under the normal working state are segmented, with paragraphs data extraction to the AR model coefficient vector as the original features; then the AR model coefficient and its residual error of the vibration acceleration data, in turn, are joined to the original characteristics and its order in the first two principal components is calculated; finally according to the order of the first two principal components, the ellipse control chart is established, and from the distribution of the test data in the oval control chart to judge whether the bearing failure. The experimental results show that this method can effectively identify the failure of bearings.
The elliptical control theory is introduced into bearing fault detection and a new bearing detection method is proposed in this paper. First the bearing data under the normal working state are segmented, with paragraphs data extraction to the AR model coefficient vector as the original features; then the AR model coefficient and its residual error of the vibration acceleration data, in turn, are joined to the original characteristics and its order in the first two principal components is calculated; finally according to the order of the first two principal components, the ellipse control chart is established, and from the distribution of the test data in the oval control chart to judge whether the bearing failure. The experimental results show that this method can effectively identify the failure of bearings.
2020, 39(3): 361-366.
doi: 10.13433/j.cnki.1003-8728.20190149
Abstract:
The wind turbine and converter often operate under the condition of variable speed, the traditional FFT analysis of rolling bearings which is one of the important parts of the equipment causes frequency aliasing during the variable speed operation, and it is difficult to extract the effective fault feature information. Therefore, a new failure diagnosis method of rolling bearings which combines order tracking and dual-tree complex wavelet is proposed in this paper. First, the order tracking is used to transform the non-stationary time domain vibration signal into a stationary angular domain signal, and then the dual-tree complex wavelet transforms is used to reduce the noise-signal ratio of the angular domain signal. Finally, the order spectrum analysis is carried out to recognize the fault feature of the rolling bearing in the unstable operation. The feasibility and effectiveness of the method are verified by simulation and experimental data analysis.
The wind turbine and converter often operate under the condition of variable speed, the traditional FFT analysis of rolling bearings which is one of the important parts of the equipment causes frequency aliasing during the variable speed operation, and it is difficult to extract the effective fault feature information. Therefore, a new failure diagnosis method of rolling bearings which combines order tracking and dual-tree complex wavelet is proposed in this paper. First, the order tracking is used to transform the non-stationary time domain vibration signal into a stationary angular domain signal, and then the dual-tree complex wavelet transforms is used to reduce the noise-signal ratio of the angular domain signal. Finally, the order spectrum analysis is carried out to recognize the fault feature of the rolling bearing in the unstable operation. The feasibility and effectiveness of the method are verified by simulation and experimental data analysis.
Lateral Tire Forces and Cornering Stiffness Estimation of 4WID-EVs Considering Lateral Load Transfer
2020, 39(3): 367-373.
doi: 10.13433/j.cnki.1003-8728.20190147
Abstract:
For the problem that the lateral tire forces and cornering stiffness of four-wheel-independent-drive electric vehicles (4WID-EVs) are difficult to be measured, a dual Kalman filter observer are designed to estimate lateral tire forces and tire lateral stiffness respectively, considering the lateral mass transfer of vehicle combining with the advantages of unscented Kalman filter (UKF) and extended Kalman filter (EKF). Firstly, a 7-DOF vehicle model is built in this paper, and the UKF observer is designed to estimate the lateral tire forces based on the UKF algorithm. Secondly, the EKF observer is designed to estimate the cornering stiffness based on the estimated lateral tire forces. Finally, the simulation analysis is carried out in MATLAB/Simulink. The results show that the lateral tire forces and cornering stiffness could be estimated by the UKF observer and EKF observer respectively, and the estimated results have high estimation accuracy.
For the problem that the lateral tire forces and cornering stiffness of four-wheel-independent-drive electric vehicles (4WID-EVs) are difficult to be measured, a dual Kalman filter observer are designed to estimate lateral tire forces and tire lateral stiffness respectively, considering the lateral mass transfer of vehicle combining with the advantages of unscented Kalman filter (UKF) and extended Kalman filter (EKF). Firstly, a 7-DOF vehicle model is built in this paper, and the UKF observer is designed to estimate the lateral tire forces based on the UKF algorithm. Secondly, the EKF observer is designed to estimate the cornering stiffness based on the estimated lateral tire forces. Finally, the simulation analysis is carried out in MATLAB/Simulink. The results show that the lateral tire forces and cornering stiffness could be estimated by the UKF observer and EKF observer respectively, and the estimated results have high estimation accuracy.
2020, 39(3): 374-378.
doi: 10.13433/j.cnki.1003-8728.20190153
Abstract:
Three local methods, critical distance method, stress averaging approach and the approach of equivalent stress intensity factor were used to assess the fatigue performance of Al6082-T6 aluminum tubular friction stir welded joints. The results show that the three kinds of fatigue assessment methods can make a reasonable fatigue assessment of the friction stir welded joints of aluminum alloy. The critical distance parameter L is calculated by Peterson's revised formula when using the critical distance method. It turns out that the method can predict the fatigue limit (prediction error only 4%) and weak location for Al6082-T6 FS welded tubular joint. The results of the stress averaging approach are conservative. The prediction result is 7.46% lower than the testing result, which indicates the way of regarding the welded toe as the sharp notch has its engineering application value. The approach of equivalent stress intensity factor was used to calculate the equivalent stress intensity factor range of the welded joint by modelling the joint as if it being a crack of standard geometry and determine whether the joint fatigue failure or not by comparing with the crack propagation threshold. The results show that the method can make a reasonable fatigue evaluation of Al6082-T6 friction stir welded joint.
Three local methods, critical distance method, stress averaging approach and the approach of equivalent stress intensity factor were used to assess the fatigue performance of Al6082-T6 aluminum tubular friction stir welded joints. The results show that the three kinds of fatigue assessment methods can make a reasonable fatigue assessment of the friction stir welded joints of aluminum alloy. The critical distance parameter L is calculated by Peterson's revised formula when using the critical distance method. It turns out that the method can predict the fatigue limit (prediction error only 4%) and weak location for Al6082-T6 FS welded tubular joint. The results of the stress averaging approach are conservative. The prediction result is 7.46% lower than the testing result, which indicates the way of regarding the welded toe as the sharp notch has its engineering application value. The approach of equivalent stress intensity factor was used to calculate the equivalent stress intensity factor range of the welded joint by modelling the joint as if it being a crack of standard geometry and determine whether the joint fatigue failure or not by comparing with the crack propagation threshold. The results show that the method can make a reasonable fatigue evaluation of Al6082-T6 friction stir welded joint.
2020, 39(3): 379-384.
doi: 10.13433/j.cnki.1003-8728.20190137
Abstract:
The model for calculating the stress concentration factor surface micro topography in the grinding was studied. Notched model is used to calculate the stress concentration factor of surface micro topography in grinding of workpiece by observing the characteristics of gully in the feed direction; a method to calculate the characteristic parameters of the notch based on the 2D profile data is proposed, and notched model for infinite plane is established, which is modified by iteration method, and finite element method is used to verify the present method. The quantitative relationship between the stress concentration factor of surface micro topography in grinding and the characteristic parameters of notch model-width, depth and valley root radius was studied by obtaining empirical formula. The results supply a quantitative calculation method for studying the relationship between the grinding surface micro topography and the stress concentration factor, it has basic function in the analysis of fatigue performance of surface micro topography in the grinding of workpiece.
The model for calculating the stress concentration factor surface micro topography in the grinding was studied. Notched model is used to calculate the stress concentration factor of surface micro topography in grinding of workpiece by observing the characteristics of gully in the feed direction; a method to calculate the characteristic parameters of the notch based on the 2D profile data is proposed, and notched model for infinite plane is established, which is modified by iteration method, and finite element method is used to verify the present method. The quantitative relationship between the stress concentration factor of surface micro topography in grinding and the characteristic parameters of notch model-width, depth and valley root radius was studied by obtaining empirical formula. The results supply a quantitative calculation method for studying the relationship between the grinding surface micro topography and the stress concentration factor, it has basic function in the analysis of fatigue performance of surface micro topography in the grinding of workpiece.
2020, 39(3): 385-390.
doi: 10.13433/j.cnki.1003-8728.20190130
Abstract:
The producing mechanism of nonlinear error during the machining process of 5-axis Computer Numerical Control (CNC) machine tool is analyzed through solving the kinematics of the machine tool in this article. The mathematical model of the nonlinear error is also established taking the A-C cutter-tilting type of five-axis CNC machine tool as the object of study. The homogeneous coordinate transformation method is used to deduce the forward and reverse mathematical calculation formulas of the actual tool-tip point position in the machining process. A reverse compensation method of interpolation points is proposed for the nonlinear error caused by rotation of the axes of the five-axis CNC machine tool. The method of reducing nonlinear error is considered from the perspective of position interpolation algorithm for rotation center of five-axis CNC machining and the method's objective is to control the more actual tool-tip points being located on the theoretical interpolation tool path. The MATLAB software is used as simulation verification platform of the actual data. The simulation results show that the proposed method can effectively control the nonlinear error within the allowable range, and significantly improve the trajectory controlling accuracy of the five-axis CNC system. Consequently, the proposed method in this article has better feasible and the value of practical application.
The producing mechanism of nonlinear error during the machining process of 5-axis Computer Numerical Control (CNC) machine tool is analyzed through solving the kinematics of the machine tool in this article. The mathematical model of the nonlinear error is also established taking the A-C cutter-tilting type of five-axis CNC machine tool as the object of study. The homogeneous coordinate transformation method is used to deduce the forward and reverse mathematical calculation formulas of the actual tool-tip point position in the machining process. A reverse compensation method of interpolation points is proposed for the nonlinear error caused by rotation of the axes of the five-axis CNC machine tool. The method of reducing nonlinear error is considered from the perspective of position interpolation algorithm for rotation center of five-axis CNC machining and the method's objective is to control the more actual tool-tip points being located on the theoretical interpolation tool path. The MATLAB software is used as simulation verification platform of the actual data. The simulation results show that the proposed method can effectively control the nonlinear error within the allowable range, and significantly improve the trajectory controlling accuracy of the five-axis CNC system. Consequently, the proposed method in this article has better feasible and the value of practical application.
2020, 39(3): 391-399.
doi: 10.13433/j.cnki.1003-8728.20190142
Abstract:
The roundness error of a permanent magnet carbon fiber sheath affects the rotor surface air-friction loss, the motor temperature field and the safety of the motor operation, it also irreversibly demagnetizes the permanent magnet. Therefore, this paper established a three-dimensional incompressible steady-state turbulent mathematical model of the air gap of the permanent magnet synchronous high-speed and high-power motor to reduce the carbon fiber sheath roundness error and then solved the model based on CFD (computational fluid dynamics). The effects of roundness error, cooling parameters, rotating speed and temperature boundary of the permanent magnet sheath on the rotor surface air-friction loss were studied, and the special case was verified by comparing the calculation results on the empirical formula. The results show that, with the increase of the roundness error amplitude, the rotor surface air-friction loss increases continuously and that the heat dissipation of the inner surface of the stator and the outer surface of the rotor also increases.
The roundness error of a permanent magnet carbon fiber sheath affects the rotor surface air-friction loss, the motor temperature field and the safety of the motor operation, it also irreversibly demagnetizes the permanent magnet. Therefore, this paper established a three-dimensional incompressible steady-state turbulent mathematical model of the air gap of the permanent magnet synchronous high-speed and high-power motor to reduce the carbon fiber sheath roundness error and then solved the model based on CFD (computational fluid dynamics). The effects of roundness error, cooling parameters, rotating speed and temperature boundary of the permanent magnet sheath on the rotor surface air-friction loss were studied, and the special case was verified by comparing the calculation results on the empirical formula. The results show that, with the increase of the roundness error amplitude, the rotor surface air-friction loss increases continuously and that the heat dissipation of the inner surface of the stator and the outer surface of the rotor also increases.
2020, 39(3): 400-410.
doi: 10.13433/j.cnki.1003-8728.20190126
Abstract:
Aiming at the complex engineering project products job shop scheduling problem (CEPP-JSP), by considering the characteristics of complete production process, parallelism, decentralization and high flexibility, a multi-objective optimization model for CEPP-JSP basic production task allocation and job center production scheduling is constructed. The improved non-dominated sorting genetic algorithm (NSGA-Ⅱ) is proposed to solve the optimization model and the comprehensive optimal solution of CEPP-JSP is obtained. Finally, the feasibility and validity of the model and algorithm are verified by using an example of workshop scheduling in a hydraulic turbine.
Aiming at the complex engineering project products job shop scheduling problem (CEPP-JSP), by considering the characteristics of complete production process, parallelism, decentralization and high flexibility, a multi-objective optimization model for CEPP-JSP basic production task allocation and job center production scheduling is constructed. The improved non-dominated sorting genetic algorithm (NSGA-Ⅱ) is proposed to solve the optimization model and the comprehensive optimal solution of CEPP-JSP is obtained. Finally, the feasibility and validity of the model and algorithm are verified by using an example of workshop scheduling in a hydraulic turbine.
2020, 39(3): 411-418.
doi: 10.13433/j.cnki.1003-8728.20190150
Abstract:
To electrochemically machine (ECM) a high-aspect-ratio micro-hole with the diameter of 100~200 μm and to reduce the easy fracture or falling off of the sidewall-insulating film on hollow electrode, a novel method of hollow-electrode sidewall-insulating preparation of micro-hole using the acrylic epoxy resin electrophoresis method was proposed. The process parameters were optimized; the machining experiments were carried out; the size and morphology of the machined hole and the machined electrode surface were compared. The results show that the sidewall-insulating film prepared with the acrylic epoxy resin electrophoresis method is highly compact and has uniformity, durability and consistency. Finally, the hollow-electrode sidewall-insulating film was prepared with the above-mentioned method. A high-aspect-ratio micro-hole array was machined on a stainless 304 steel plate with the thickness of 500 μm. The diameters of a typical micro-hole at its inlet and outlet are 180.6 μm and 173.8 μm, respectively, and the taper of the micro-hole is about 70% lower than that of the hollow-electrode non-sidewall-insulating film. Moreover, the micro-holes are basically straight.
To electrochemically machine (ECM) a high-aspect-ratio micro-hole with the diameter of 100~200 μm and to reduce the easy fracture or falling off of the sidewall-insulating film on hollow electrode, a novel method of hollow-electrode sidewall-insulating preparation of micro-hole using the acrylic epoxy resin electrophoresis method was proposed. The process parameters were optimized; the machining experiments were carried out; the size and morphology of the machined hole and the machined electrode surface were compared. The results show that the sidewall-insulating film prepared with the acrylic epoxy resin electrophoresis method is highly compact and has uniformity, durability and consistency. Finally, the hollow-electrode sidewall-insulating film was prepared with the above-mentioned method. A high-aspect-ratio micro-hole array was machined on a stainless 304 steel plate with the thickness of 500 μm. The diameters of a typical micro-hole at its inlet and outlet are 180.6 μm and 173.8 μm, respectively, and the taper of the micro-hole is about 70% lower than that of the hollow-electrode non-sidewall-insulating film. Moreover, the micro-holes are basically straight.
2020, 39(3): 419-424.
doi: 10.13433/j.cnki.1003-8728.20190135
Abstract:
The new requirement for the self-diagnosis ability of CNC machine tools has been put forward in order to improve the manufacturing automation level, and the development of artificial intelligence has opened aiming at this purpose. In order to evaluate the tool wear state more efficiently and comprehensively, the force and acceleration signals in the end milling are collected. The eigenvalues of the time domain, frequency domain and wavelet energy of the signals are extracted. And a model for evaluating the tool wear state via Random Forest algorithm is established. In the comparative verification of the experimental data, the accuracy of the tool wear state of the 107 sets of test samples by using the random forest model is of 99.1%, and the time for establishing the model is below 1 s. The result shows that the random forest algorithm has the characteristics of high efficiency and high accuracy, which lays a foundation for establishing the online monitoring system for tool wear state.
The new requirement for the self-diagnosis ability of CNC machine tools has been put forward in order to improve the manufacturing automation level, and the development of artificial intelligence has opened aiming at this purpose. In order to evaluate the tool wear state more efficiently and comprehensively, the force and acceleration signals in the end milling are collected. The eigenvalues of the time domain, frequency domain and wavelet energy of the signals are extracted. And a model for evaluating the tool wear state via Random Forest algorithm is established. In the comparative verification of the experimental data, the accuracy of the tool wear state of the 107 sets of test samples by using the random forest model is of 99.1%, and the time for establishing the model is below 1 s. The result shows that the random forest algorithm has the characteristics of high efficiency and high accuracy, which lays a foundation for establishing the online monitoring system for tool wear state.
2020, 39(3): 425-432.
doi: 10.13433/j.cnki.1003-8728.20190127
Abstract:
The damping characteristics of magnetorheological damper used for the seat suspension system were tested, and the parameters of hyperbolic tangent model were identified with least square method. The 3-DOF model of semi-active seat suspension system was established by combining with the dynamic characteristic of seat suspension. Aiming at the problem of low precision of traditional fuzzy control, a variable universe fuzzy control based on the fuzzy reasoning was proposed. Taking the random road response and impulse road response as input excitations, the simulation analysis of the control effects of passive suspension system, traditional fuzzy control semi-active suspension system and variable universe fuzzy control semi-active suspension system were carried out, respectively. The results show that the parameters and the model identified with least square method can satisfy the subsequent calculation. And the vibration reduction effects of the variable universe fuzzy control strategy are obviously better than that of traditional fuzzy control, which can effectively isolate the impacts interference of the road surface and improve the comprehensive performance of the seat suspension system.
The damping characteristics of magnetorheological damper used for the seat suspension system were tested, and the parameters of hyperbolic tangent model were identified with least square method. The 3-DOF model of semi-active seat suspension system was established by combining with the dynamic characteristic of seat suspension. Aiming at the problem of low precision of traditional fuzzy control, a variable universe fuzzy control based on the fuzzy reasoning was proposed. Taking the random road response and impulse road response as input excitations, the simulation analysis of the control effects of passive suspension system, traditional fuzzy control semi-active suspension system and variable universe fuzzy control semi-active suspension system were carried out, respectively. The results show that the parameters and the model identified with least square method can satisfy the subsequent calculation. And the vibration reduction effects of the variable universe fuzzy control strategy are obviously better than that of traditional fuzzy control, which can effectively isolate the impacts interference of the road surface and improve the comprehensive performance of the seat suspension system.
2020, 39(3): 433-437.
doi: 10.13433/j.cnki.1003-8728.20190124
Abstract:
Aiming at the low efficiency of large blade finishing, a collaborative method of multi-manipulator for machining large blade was proposed, and the method of multi-task collaborative modeling and assignment for manipulator is studied in depth and elaborated in detail. Firstly, a multi-task allocation model for the collaborative processing of large-scale blade using multi-manipulator is constructed. According to the curvature cloud of blade, the blade is divided into several processing tasks. Then, in order to decrease the shortest processing time, a multi-task allocation method based on the greedy algorithm for collaborative processing is proposed, and the flow chart and specific steps are given. Finally, an example is given to verify the effectiveness and feasibility of this method.
Aiming at the low efficiency of large blade finishing, a collaborative method of multi-manipulator for machining large blade was proposed, and the method of multi-task collaborative modeling and assignment for manipulator is studied in depth and elaborated in detail. Firstly, a multi-task allocation model for the collaborative processing of large-scale blade using multi-manipulator is constructed. According to the curvature cloud of blade, the blade is divided into several processing tasks. Then, in order to decrease the shortest processing time, a multi-task allocation method based on the greedy algorithm for collaborative processing is proposed, and the flow chart and specific steps are given. Finally, an example is given to verify the effectiveness and feasibility of this method.
2020, 39(3): 438-445.
doi: 10.13433/j.cnki.1003-8728.20190139
Abstract:
Based on the classical heat conduction equation and thermoplastic mechanics, the two-dimensional heat transfer model and thermal stress model for the grinding process of High Velocity Oxygen Fuel (HVOF) WC-10Co4Cr coating under the action of moving heat source were established. On considering the temperature dependent material properties, the transient temperature field and thermal stress field were simulated via finite element method. As the thermal conductivity and specific heat capacity of WC-10Co4Cr are larger than 300 M, the temperature rise mainly stays in the coating. The grinding temperature is discontinuous along the depth direction of the workpiece, and the temperature gradient of the coating/substrate junction surface is the largest. Due to the large difference in thermal expansion coefficient between the coating and the substrate, the great thermal stress is generated at the bonding surface. The grinding temperature and thermal stress of the coating/substrate junction surface increase with the decreasing of coating thickness. The grinding temperature experiments were carried out, the surface grinding temperature with different coating thicknesses was measured and the simulation results were compared with those experimental. A good agreement was found between the FEM results and the experimental.
Based on the classical heat conduction equation and thermoplastic mechanics, the two-dimensional heat transfer model and thermal stress model for the grinding process of High Velocity Oxygen Fuel (HVOF) WC-10Co4Cr coating under the action of moving heat source were established. On considering the temperature dependent material properties, the transient temperature field and thermal stress field were simulated via finite element method. As the thermal conductivity and specific heat capacity of WC-10Co4Cr are larger than 300 M, the temperature rise mainly stays in the coating. The grinding temperature is discontinuous along the depth direction of the workpiece, and the temperature gradient of the coating/substrate junction surface is the largest. Due to the large difference in thermal expansion coefficient between the coating and the substrate, the great thermal stress is generated at the bonding surface. The grinding temperature and thermal stress of the coating/substrate junction surface increase with the decreasing of coating thickness. The grinding temperature experiments were carried out, the surface grinding temperature with different coating thicknesses was measured and the simulation results were compared with those experimental. A good agreement was found between the FEM results and the experimental.
2020, 39(3): 446-455.
doi: 10.13433/j.cnki.1003-8728.20190141
Abstract:
To carry out the low-carbon scheduling of a discrete manufacturing workshop, considering the real-time status of manufacturing resources, a real-time data-driven status monitoring framework was constructed and the optimization model of the real-time status of manufacturing resources driven by the low-carbon scheduling of the discrete manufacturing workshop was established, considering the make-span and energy consumption of machine tool, tool wear and cutting fluid loss as carbon emission sources. An improved multi-objective Jaya optimization algorithm with the Tent chaotic map was proposed. Firstly, the algorithm initialized the population with the Tent chaotic sequence and executed the local search with the neighborhood search and simulated annealing algorithm. Then it preserved the solution with the strict external archival set. Finally, the example data of the filling equipment production workshop is used to verify the validity of the algorithm and the model. The results show that the algorithm and model proposed in the paper can effectively reduce carbon emissions and the impact of abnormal conditions on production plans.
To carry out the low-carbon scheduling of a discrete manufacturing workshop, considering the real-time status of manufacturing resources, a real-time data-driven status monitoring framework was constructed and the optimization model of the real-time status of manufacturing resources driven by the low-carbon scheduling of the discrete manufacturing workshop was established, considering the make-span and energy consumption of machine tool, tool wear and cutting fluid loss as carbon emission sources. An improved multi-objective Jaya optimization algorithm with the Tent chaotic map was proposed. Firstly, the algorithm initialized the population with the Tent chaotic sequence and executed the local search with the neighborhood search and simulated annealing algorithm. Then it preserved the solution with the strict external archival set. Finally, the example data of the filling equipment production workshop is used to verify the validity of the algorithm and the model. The results show that the algorithm and model proposed in the paper can effectively reduce carbon emissions and the impact of abnormal conditions on production plans.
2020, 39(3): 456-460.
doi: 10.13433/j.cnki.1003-8728.20190138
Abstract:
In order to obtain the preferable mould temperature and sheet temperature in the nonisothermal stamping of magnesium alloy, Quantum genetic algorithm (QGA) and support vector regression machine (SVR) were adopted to optimize temperature. The SVR surrogate model was estabilished between the parts of temperature and the target area thickness of forming part via finite element model. The surrogate model is optimized with the quantum genetic algorithm to obtain the optimal temperature parameters in the nonisothermal stamping of AZ31B magnesium alloy. Taking NUMISHEET2011 cross-shaped cup part for an example, the optimal temperature was adopted for simulation. Comparing the results with test data, the optimal temperature can effectively improve the thickness uniformity.
In order to obtain the preferable mould temperature and sheet temperature in the nonisothermal stamping of magnesium alloy, Quantum genetic algorithm (QGA) and support vector regression machine (SVR) were adopted to optimize temperature. The SVR surrogate model was estabilished between the parts of temperature and the target area thickness of forming part via finite element model. The surrogate model is optimized with the quantum genetic algorithm to obtain the optimal temperature parameters in the nonisothermal stamping of AZ31B magnesium alloy. Taking NUMISHEET2011 cross-shaped cup part for an example, the optimal temperature was adopted for simulation. Comparing the results with test data, the optimal temperature can effectively improve the thickness uniformity.
2020, 39(3): 461-467.
doi: 10.13433/j.cnki.1003-8728.20190146
Abstract:
In order to overcome the drawbacks of the effective information loss or redundancy caused by subjectively selecting sensor measuring points in planetary gearbox fault detection. In this paper, an optimization method of vibration measuring points based on virtual simulation technology and locally linear embedding algorithm was studied. The planetary gearbox rigid-flexible coupling dynamics model was firstly established in ADAMS software, and the vibration signals under different gear states were simulated. Then, considering the actual situation of the gearbox and the operability of the measuring points, these points were preselected and characteristic parameters of signals were calculated. Finally, the high-dimensional feature matrix formed by the characteristic parameters is reduced by locally linear embedding, and the sensitivity of measuring points in different states is obtained to determine the optimal measuring points. The results show that four measuring points have high sensitivity under the sun gear broken teeth, planetary gear broken teeth and normal conditions, which can effectively collect vibration signals to reflect the gear state and lay good foundation for actual test.
In order to overcome the drawbacks of the effective information loss or redundancy caused by subjectively selecting sensor measuring points in planetary gearbox fault detection. In this paper, an optimization method of vibration measuring points based on virtual simulation technology and locally linear embedding algorithm was studied. The planetary gearbox rigid-flexible coupling dynamics model was firstly established in ADAMS software, and the vibration signals under different gear states were simulated. Then, considering the actual situation of the gearbox and the operability of the measuring points, these points were preselected and characteristic parameters of signals were calculated. Finally, the high-dimensional feature matrix formed by the characteristic parameters is reduced by locally linear embedding, and the sensitivity of measuring points in different states is obtained to determine the optimal measuring points. The results show that four measuring points have high sensitivity under the sun gear broken teeth, planetary gear broken teeth and normal conditions, which can effectively collect vibration signals to reflect the gear state and lay good foundation for actual test.
2020, 39(3): 468-476.
doi: 10.13433/j.cnki.1003-8728.20190143
Abstract:
Aiming at the influence on the vehicle stability control during the parallel hybrid electric vehicle (HEV) energy recovery process, this paper analyzes the energy recovery system structure with the semi-active suspension system (SAS) and anti-lock braking system (ABS), and proposes an integrated control strategy to distribute the electromotor - hydraulic braking torque and coordinate the SAS and ABS system, in order to maximum compatible with parallel HEV energy recovery efficiency and vehicle stability. A model of the parallel HEV energy recovery system was built on the CarSim-Simulink software platform, and simulation analysis was carried out on the integrated control strategy, and compared with the independent control strategy, the results show that the integrated control strategy is better able to maintain stability, allocate energy recovery ratio more reasonable, and improve fuel economy of vehicles.
Aiming at the influence on the vehicle stability control during the parallel hybrid electric vehicle (HEV) energy recovery process, this paper analyzes the energy recovery system structure with the semi-active suspension system (SAS) and anti-lock braking system (ABS), and proposes an integrated control strategy to distribute the electromotor - hydraulic braking torque and coordinate the SAS and ABS system, in order to maximum compatible with parallel HEV energy recovery efficiency and vehicle stability. A model of the parallel HEV energy recovery system was built on the CarSim-Simulink software platform, and simulation analysis was carried out on the integrated control strategy, and compared with the independent control strategy, the results show that the integrated control strategy is better able to maintain stability, allocate energy recovery ratio more reasonable, and improve fuel economy of vehicles.
2020, 39(3): 477-483.
doi: 10.13433/j.cnki.1003-8728.20190140
Abstract:
In order to prevent the stress relaxation of the spring contact fingers in power connector, a uniaxial stress relaxation model based on the Norton creep theory is established to prevent the stress relaxation behavior of beryllium bronze C17500. And a model improvement is carried out in combination with the Arrhenius theory. The modified stress relaxation constitutive equation is fitted through the stress relaxation test of the metal bronze under different loads and different temperatures. The predicted curves of the model parameters at different loads and different temperatures are obtained. The stress relaxation characteristic analysis on different stress levels at a specific temperature is realized according to the prediction curve.
In order to prevent the stress relaxation of the spring contact fingers in power connector, a uniaxial stress relaxation model based on the Norton creep theory is established to prevent the stress relaxation behavior of beryllium bronze C17500. And a model improvement is carried out in combination with the Arrhenius theory. The modified stress relaxation constitutive equation is fitted through the stress relaxation test of the metal bronze under different loads and different temperatures. The predicted curves of the model parameters at different loads and different temperatures are obtained. The stress relaxation characteristic analysis on different stress levels at a specific temperature is realized according to the prediction curve.
2020, 39(3): 484-492.
doi: 10.13433/j.cnki.1003-8728.20190145
Abstract:
This paper proposes a finite element (FE) method for the orthogonal cutting simulation, and ultrasonic drilling experiments with hand-held ultrasonic vibration drilling system is carried out so as to study the mechanism of material removal in machining of composite materials. Firstly, based on the orthogonal to oblique cutting transformation, a thermo-mechanical FE model was established to simulate the conventional drilling (CD) and ultrasonic vibration drilling (UVD) processes. Drilling-induced damage such as fiber fracture, matrix cracking and fiber-matrix interfacial debonding were predicted. The effect of the vibration amplitude and frequency on the cutting forces was studied. Then, based on the FE simulation results at four specific fiber orientations, energy balance analysis is carried out to quantify the dominating energy dissipating mechanisms during CD and UVD, respectively. Combining with the comparison of chip formation, the reason which ultrasonic vibration technology can reduce drilling forces and improve surface quality is analyzed. Finally, experiments with various process parameters were performed, and the drilling thrust forces and sub-surface damage were compared. Results show that the optimized vibration parameters obtained by the FE approach can contribute to reducing drilling forces and improving machining quality in the practical machining processes.
This paper proposes a finite element (FE) method for the orthogonal cutting simulation, and ultrasonic drilling experiments with hand-held ultrasonic vibration drilling system is carried out so as to study the mechanism of material removal in machining of composite materials. Firstly, based on the orthogonal to oblique cutting transformation, a thermo-mechanical FE model was established to simulate the conventional drilling (CD) and ultrasonic vibration drilling (UVD) processes. Drilling-induced damage such as fiber fracture, matrix cracking and fiber-matrix interfacial debonding were predicted. The effect of the vibration amplitude and frequency on the cutting forces was studied. Then, based on the FE simulation results at four specific fiber orientations, energy balance analysis is carried out to quantify the dominating energy dissipating mechanisms during CD and UVD, respectively. Combining with the comparison of chip formation, the reason which ultrasonic vibration technology can reduce drilling forces and improve surface quality is analyzed. Finally, experiments with various process parameters were performed, and the drilling thrust forces and sub-surface damage were compared. Results show that the optimized vibration parameters obtained by the FE approach can contribute to reducing drilling forces and improving machining quality in the practical machining processes.
