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RSS2019 Vol. 38, No. 11
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2019, 38(11): 1641-1646.
doi: 10.13433/j.cnki.1003-8728.20190034
PDF 1181KB
Abstract:
The design of spray lubrication has an important influence on the oil film distribution of teeth surface, and the study on spraying oil and oil film spreading is also significant for designing the spray lubrication. A numerical model is developed based on the Computational Fluid Dynamics method to calculate the spreading characteristics of oil film on teeth surface. The results indicated that the region of characteristic tooth under the spray nozzle has more oil. The oil reduces when the oil stream between the spray nozzle and the characteristic tooth surface is blocked. The distribution of oil film in characteristic tooth surface is obviously different when the meshing angle is changed. Two nozzles spray the oil on the same tooth surface when meshing angle is 1.5°.
The design of spray lubrication has an important influence on the oil film distribution of teeth surface, and the study on spraying oil and oil film spreading is also significant for designing the spray lubrication. A numerical model is developed based on the Computational Fluid Dynamics method to calculate the spreading characteristics of oil film on teeth surface. The results indicated that the region of characteristic tooth under the spray nozzle has more oil. The oil reduces when the oil stream between the spray nozzle and the characteristic tooth surface is blocked. The distribution of oil film in characteristic tooth surface is obviously different when the meshing angle is changed. Two nozzles spray the oil on the same tooth surface when meshing angle is 1.5°.
2019, 38(11): 1647-1653.
doi: 10.13433/j.cnki.1003-8728.20190187
Abstract:
In order to study the influence of joint stiffness and inertance on damping performance of damper and the train suspension, the unified equivalent ″Mass-Spring-Damper″ (MSD) model and vertical dynamic model with joint stiffness and inertance were established for the first time, based on the equivalent principle and forced vibration theory. The numerical analysis shows that the equivalent damping is proportional to the original damping, and the proportional factor is a function of stiffness ratio, mass ratio, damping ratio and frequency ratio. The characteristics of the equivalent MSD model are consistent with the theoretical results without considering the joint stiffness, but their amplification factors are larger. However, the effects of joint stiffness and inertance on damping performance of damper and the train suspension are just opposite; the rational design of suspension structure can be obtained with organic combination of joint stiffness and inertance. The derived formulas provide a new way and method for the structural optimization design of train suspension system.
In order to study the influence of joint stiffness and inertance on damping performance of damper and the train suspension, the unified equivalent ″Mass-Spring-Damper″ (MSD) model and vertical dynamic model with joint stiffness and inertance were established for the first time, based on the equivalent principle and forced vibration theory. The numerical analysis shows that the equivalent damping is proportional to the original damping, and the proportional factor is a function of stiffness ratio, mass ratio, damping ratio and frequency ratio. The characteristics of the equivalent MSD model are consistent with the theoretical results without considering the joint stiffness, but their amplification factors are larger. However, the effects of joint stiffness and inertance on damping performance of damper and the train suspension are just opposite; the rational design of suspension structure can be obtained with organic combination of joint stiffness and inertance. The derived formulas provide a new way and method for the structural optimization design of train suspension system.
2019, 38(11): 1654-1662.
doi: 10.13433/j.cnki.1003-8728.20190067
Abstract:
Knowledge push in the product design field devoted to recommend suitable knowledge to the right person at the right time. The problems of inaccurate timing, low quality and lagging behind of pushing content were mostly due to inaccurate description of the design context. Referring to the principle of context awareness, a method of identifying design context comprehensively, modeling and reasoning was proposed. The classification method was used to extract design context elements, and ontology was used to construct design context model. Then, the low-level design context data was comprehensively perceived based on the ontology model, and filtered and fused to trigger design context reasoning rules and obtain high-level design context information. Finally, a case study on an aircraft wing was demonstrated to verify the feasibility and validity of the model and method, which could provide support for accurate, timely and efficient design knowledge push.
Knowledge push in the product design field devoted to recommend suitable knowledge to the right person at the right time. The problems of inaccurate timing, low quality and lagging behind of pushing content were mostly due to inaccurate description of the design context. Referring to the principle of context awareness, a method of identifying design context comprehensively, modeling and reasoning was proposed. The classification method was used to extract design context elements, and ontology was used to construct design context model. Then, the low-level design context data was comprehensively perceived based on the ontology model, and filtered and fused to trigger design context reasoning rules and obtain high-level design context information. Finally, a case study on an aircraft wing was demonstrated to verify the feasibility and validity of the model and method, which could provide support for accurate, timely and efficient design knowledge push.
2019, 38(11): 1663-1668.
doi: 10.13433/j.cnki.1003-8728.20190048
Abstract:
A method of robot lightweight combining global finite element analysis and local topology optimization is proposed and applied to the design of a six-degree-of-freedom cooperative robot to solve the lightweight and dynamic characteristics. The method obtains the load and boundary conditions of the component to be optimized with finite element analysis on the whole, and then optimizes the topology based on the above conditions to obtain an optimal structure. The optimization results show that the optimal structure loses 4.83 kg compared with the initial structure. The simulation results show that the end displacement is reduced to 2.57 mm and the measured value is 2.88 mm, all of which can meet the target requirements. At the same time, the sixth-order natural frequency of the whole machine increased by about 11.30%, which is higher than the 1.69% improvement of the current literature. Finally, the effectiveness of this method was demonstrated by the anterior cruciate ligament positioning experiment.
A method of robot lightweight combining global finite element analysis and local topology optimization is proposed and applied to the design of a six-degree-of-freedom cooperative robot to solve the lightweight and dynamic characteristics. The method obtains the load and boundary conditions of the component to be optimized with finite element analysis on the whole, and then optimizes the topology based on the above conditions to obtain an optimal structure. The optimization results show that the optimal structure loses 4.83 kg compared with the initial structure. The simulation results show that the end displacement is reduced to 2.57 mm and the measured value is 2.88 mm, all of which can meet the target requirements. At the same time, the sixth-order natural frequency of the whole machine increased by about 11.30%, which is higher than the 1.69% improvement of the current literature. Finally, the effectiveness of this method was demonstrated by the anterior cruciate ligament positioning experiment.
2019, 38(11): 1669-1675.
doi: 10.13433/j.cnki.1003-8728.20190038
Abstract:
A triangle decoupled 1T2R parallel mechanism was synthesized by analyzing the characteristics of the Jacobian matrices of a triangle decoupled mechanism. The decoupling relationship between the active pair of branch chains and the freedom of a moving platform was obtained. The freedom of a branched chain was obtained by combining the implicated motion and the conditions of rotational freedom. Then the type synthesis was carried out based on the screw theory, and the structural analysis of the PU+PRU+PUS mechanism was conducted. The degree of freedom of the mechanism, the positive and negative solutions of its position, the velocity and acceleration were analyzed. Meanwhile, the Jacobian matrix was obtained; the ADAMS software was used for modeling and simulation to verify the correctness of the kinematics of the mechanism. Finally, its working space was solved.
A triangle decoupled 1T2R parallel mechanism was synthesized by analyzing the characteristics of the Jacobian matrices of a triangle decoupled mechanism. The decoupling relationship between the active pair of branch chains and the freedom of a moving platform was obtained. The freedom of a branched chain was obtained by combining the implicated motion and the conditions of rotational freedom. Then the type synthesis was carried out based on the screw theory, and the structural analysis of the PU+PRU+PUS mechanism was conducted. The degree of freedom of the mechanism, the positive and negative solutions of its position, the velocity and acceleration were analyzed. Meanwhile, the Jacobian matrix was obtained; the ADAMS software was used for modeling and simulation to verify the correctness of the kinematics of the mechanism. Finally, its working space was solved.
2019, 38(11): 1676-1681.
doi: 10.13433/j.cnki.1003-8728.20190043
Abstract:
It is proposed to use the prime number to describe the motion pair between the components of the mechanism and obtain the matrix of prime weights of the kinematic chain. Based on this, the improved Floyd algorithm is used to obtain the minimum weight continuous product matrix with the least number of steps between any two vertices, and sorted according to certain rules. The mapping relationship reflects the mutual relationship of the unique institutional kinematic chain, and gives the necessary and sufficient conditions for the isomorphism of the two institutions' kinematic chains. A new method for the isomorphism identification of kinematic chains is established. This method is also applicable to the isomorphic discrimination of general undirected graphs. Finally, the discriminated examples show that the method is accurate, simple and easy to implement in computer. The solution of isomorphic discrimination lays the foundation for institutional synthesis and analysis.
It is proposed to use the prime number to describe the motion pair between the components of the mechanism and obtain the matrix of prime weights of the kinematic chain. Based on this, the improved Floyd algorithm is used to obtain the minimum weight continuous product matrix with the least number of steps between any two vertices, and sorted according to certain rules. The mapping relationship reflects the mutual relationship of the unique institutional kinematic chain, and gives the necessary and sufficient conditions for the isomorphism of the two institutions' kinematic chains. A new method for the isomorphism identification of kinematic chains is established. This method is also applicable to the isomorphic discrimination of general undirected graphs. Finally, the discriminated examples show that the method is accurate, simple and easy to implement in computer. The solution of isomorphic discrimination lays the foundation for institutional synthesis and analysis.
2019, 38(11): 1682-1688.
doi: 10.13433/j.cnki.1003-8728.20190221
Abstract:
Aiming at the low efficiency in the working process of piston air compressor driven by internal combustion engine, a principle design scheme for three-cylinder internal combustion air compressor was proposed, which can output gas pressure energy and drive the auxiliary system of the internal combustion engine, but also can provide additional power to drive other working loads outside the machine. Based on the method of theoretical analysis and simulation calculation, the variation of the output power of air compressor under different throttle opening and different output air pressure was systematically studied. Based on the virtual prototype technique, the dynamic simulation model of the main part of the internal combustion air compressor was established, the dynamic simulation analysis was completed. The data of the motion characteristics and stress distribution of the simulation model under the specific working conditions were obtained, and the error of the simulation results and the calculation results was analyzed.
Aiming at the low efficiency in the working process of piston air compressor driven by internal combustion engine, a principle design scheme for three-cylinder internal combustion air compressor was proposed, which can output gas pressure energy and drive the auxiliary system of the internal combustion engine, but also can provide additional power to drive other working loads outside the machine. Based on the method of theoretical analysis and simulation calculation, the variation of the output power of air compressor under different throttle opening and different output air pressure was systematically studied. Based on the virtual prototype technique, the dynamic simulation model of the main part of the internal combustion air compressor was established, the dynamic simulation analysis was completed. The data of the motion characteristics and stress distribution of the simulation model under the specific working conditions were obtained, and the error of the simulation results and the calculation results was analyzed.
2019, 38(11): 1689-1694.
doi: 10.13433/j.cnki.1003-8728.20190220
Abstract:
Aiming at the application requirements of climbing on rough walls and ceilings, based on the gripping mechanism of caterpillar preleg crochets, a bio-inspired tracked wall-climbing robot with spiny grippers is developed. The robot's tread consists of dozens of spiny grippers connected by chain structure, and constitutes a cam mechanism with the robot body, which is used to mimic the gripping and releasing movements of the crochets of the ctaterpillar preleg in climbing. The robot can climb steadily on rough walls and ceilings. The gripping mechanism model for the caterpillar preleg crochets is established, the bio-inspired tracked wall-climbing robot is designed, and the gripping and releasing movements of the foot in the climbing process are analyzed, and several climbing experiments of a robot prototype are carried out on a variety of rough walls and ceilings.
Aiming at the application requirements of climbing on rough walls and ceilings, based on the gripping mechanism of caterpillar preleg crochets, a bio-inspired tracked wall-climbing robot with spiny grippers is developed. The robot's tread consists of dozens of spiny grippers connected by chain structure, and constitutes a cam mechanism with the robot body, which is used to mimic the gripping and releasing movements of the crochets of the ctaterpillar preleg in climbing. The robot can climb steadily on rough walls and ceilings. The gripping mechanism model for the caterpillar preleg crochets is established, the bio-inspired tracked wall-climbing robot is designed, and the gripping and releasing movements of the foot in the climbing process are analyzed, and several climbing experiments of a robot prototype are carried out on a variety of rough walls and ceilings.
2019, 38(11): 1695-1701.
doi: 10.13433/j.cnki.1003-8728.20190027
Abstract:
In order to improve the shift performance of the Hydraulic Mechanical Continuously Variable Transmission (HMCVT), the relationship between clutch oil filling flow, pressure and shift performance was studied by the simulation and experiment in this paper. The variation law of clutch driven-end speed and clutch transmission torque in sliding phase was analyzed. At the same time, the transmission model was established with SimulationX, and the model was tested and verified under specific conditions. The influence of clutch oil filling flow rate and oil filling pressure on the quality of shift performance was simulated and analyzed with the model. Objective function of the shift performance was established, and the weight value of each evaluation index in the function was determined by the AHP. According to simulation test results:increasing the oil filling flow and pressure of the clutch can reduce the speed changing, maximum sliding friction power and sliding friction work, and improve the quality of shift performance. However, increasing the clutch oil filling flow has no effect on the dynamic load factor, and increasing the oil filling pressure will increase the dynamic load factor. The best shift performance can be obtained when the clutch oil filling flow and pressure combination is 6 L/min and 5 MPa, respectively.
In order to improve the shift performance of the Hydraulic Mechanical Continuously Variable Transmission (HMCVT), the relationship between clutch oil filling flow, pressure and shift performance was studied by the simulation and experiment in this paper. The variation law of clutch driven-end speed and clutch transmission torque in sliding phase was analyzed. At the same time, the transmission model was established with SimulationX, and the model was tested and verified under specific conditions. The influence of clutch oil filling flow rate and oil filling pressure on the quality of shift performance was simulated and analyzed with the model. Objective function of the shift performance was established, and the weight value of each evaluation index in the function was determined by the AHP. According to simulation test results:increasing the oil filling flow and pressure of the clutch can reduce the speed changing, maximum sliding friction power and sliding friction work, and improve the quality of shift performance. However, increasing the clutch oil filling flow has no effect on the dynamic load factor, and increasing the oil filling pressure will increase the dynamic load factor. The best shift performance can be obtained when the clutch oil filling flow and pressure combination is 6 L/min and 5 MPa, respectively.
2019, 38(11): 1702-1711.
doi: 10.13433/j.cnki.1003-8728.20190047
Abstract:
When the workpiece of cemented carbide surface is grinded and polished, there are many influencing factors and coupling, and the grinding and polishing efficiency is low and the quality is unstable. In order to achieve high-efficiency grinding and polishing on the surface of the workpiece and reduce the wear of the abrasive tool, the characteristics of the contact area between M300 steel and the elastic abrasive tool was analyzed in order to establish the removal function model for the surface grinding and polishing material; the reliability of the model was also verified by the experimental results. The effects of the grinding tool rotation speed, penetration depth, feed rate and abrasive particle size on the material removal rate, abrasive wear and workpiece surface roughness were studied by the single factor experiment, in which the orthogonal experiment and sensitivity analysis method were used to determine the optimal parameter combination and the multi-objective optimization parameter interval of each evaluation target. The experimental results showed that the surface quality of the workpiece was improved and the wear of the abrasive tool was reduced by using the optimized parameter interval.
When the workpiece of cemented carbide surface is grinded and polished, there are many influencing factors and coupling, and the grinding and polishing efficiency is low and the quality is unstable. In order to achieve high-efficiency grinding and polishing on the surface of the workpiece and reduce the wear of the abrasive tool, the characteristics of the contact area between M300 steel and the elastic abrasive tool was analyzed in order to establish the removal function model for the surface grinding and polishing material; the reliability of the model was also verified by the experimental results. The effects of the grinding tool rotation speed, penetration depth, feed rate and abrasive particle size on the material removal rate, abrasive wear and workpiece surface roughness were studied by the single factor experiment, in which the orthogonal experiment and sensitivity analysis method were used to determine the optimal parameter combination and the multi-objective optimization parameter interval of each evaluation target. The experimental results showed that the surface quality of the workpiece was improved and the wear of the abrasive tool was reduced by using the optimized parameter interval.
2019, 38(11): 1712-1719.
doi: 10.13433/j.cnki.1003-8728.20190053
Abstract:
In order to improve the mining efficiency of gangue coal rock, theoretical calculation and discrete element numerical simulation are used to design and study powerful screw drum of thin coal seam shearer. The coal wall discrete element simulation model was established by use of PRO/E and EDEM, the 3D model of the screw drum is introduced to simulate cutting and crushing complicated coal and rock processes. The orthogonal test method was used to study the influence trend of solidity coefficient of gangue, spiral angle of drum, arrangement of cutting teeth on the load of the shearer's screw drum by MATLAB, and then a simulation according to actual working condition was carried out. The research results indicate that:the order of influence on the force on the screw drum is obtained as follows:the solidity coefficient of gangue, arrangement of cutting teeth, spiral angle of drum. The order of influence on the load fluctuation of screw drum is as follows:arrangement of cutting teeth, the solidity coefficient of gangue, spiral angle of drum. The optimum structural parameters of screw drum under different coal seam occurrence conditions are obtained through the analysis of simulation results. When the solidity coefficient of gangue is over 6.8, the load fluctuation of the sequential screw drum decreases by 39.2% compared with that of cross drum. The designed strong drum is used to simulate the typical working conditions and verify the reliability of drum design.
In order to improve the mining efficiency of gangue coal rock, theoretical calculation and discrete element numerical simulation are used to design and study powerful screw drum of thin coal seam shearer. The coal wall discrete element simulation model was established by use of PRO/E and EDEM, the 3D model of the screw drum is introduced to simulate cutting and crushing complicated coal and rock processes. The orthogonal test method was used to study the influence trend of solidity coefficient of gangue, spiral angle of drum, arrangement of cutting teeth on the load of the shearer's screw drum by MATLAB, and then a simulation according to actual working condition was carried out. The research results indicate that:the order of influence on the force on the screw drum is obtained as follows:the solidity coefficient of gangue, arrangement of cutting teeth, spiral angle of drum. The order of influence on the load fluctuation of screw drum is as follows:arrangement of cutting teeth, the solidity coefficient of gangue, spiral angle of drum. The optimum structural parameters of screw drum under different coal seam occurrence conditions are obtained through the analysis of simulation results. When the solidity coefficient of gangue is over 6.8, the load fluctuation of the sequential screw drum decreases by 39.2% compared with that of cross drum. The designed strong drum is used to simulate the typical working conditions and verify the reliability of drum design.
2019, 38(11): 1720-1725.
doi: 10.13433/j.cnki.1003-8728.20190033
Abstract:
The model of driving cab was built with finite element method, sound insulation property of plates were obtained by solving control equations which describe the coupling of structural vibration and acoustic field. Then sound insulation property was tested in semi-anechoic room to verify the simulation results. Finally the sound insulation property was optimized using appropriate acoustic pad. The results indicated:theory method and simulation model are validated after comparing the numerical solutions with experimental results, and can be used to predict sound insulation property of driving cab. Using this simulation model, the weak plate can be identified, optimal design can be chosen. The simulation based on acoustic-structural coupling method can be used to predict the sound insulation property of driving cab at the design stage, and then the low-noise design of cab will be realized.
The model of driving cab was built with finite element method, sound insulation property of plates were obtained by solving control equations which describe the coupling of structural vibration and acoustic field. Then sound insulation property was tested in semi-anechoic room to verify the simulation results. Finally the sound insulation property was optimized using appropriate acoustic pad. The results indicated:theory method and simulation model are validated after comparing the numerical solutions with experimental results, and can be used to predict sound insulation property of driving cab. Using this simulation model, the weak plate can be identified, optimal design can be chosen. The simulation based on acoustic-structural coupling method can be used to predict the sound insulation property of driving cab at the design stage, and then the low-noise design of cab will be realized.
2019, 38(11): 1726-1731.
doi: 10.13433/j.cnki.1003-8728.20190040
Abstract:
As how to improve the accuracy and algorithm efficiency of roll bearing fault diagnosis, a new method of bearing fault diagnosis based on deep belief network (DBN) and the particle swarm optimization support vector machine (PSO-SVM) with the time-frequency characteristic statistic is proposed. Firstly, time-frequency characteristic statistic of the bearing vibration signal is calculated. And then the DBN is used to extract features of time-frequency feature extraction. Finally, the extracted parameters are input to the PSO-SVM to be classified. The experimental results show that this method not only has higher accuracy, but also greatly shorten the training time, and the accuracy and efficiency of fault diagnosis is improved as a result.
As how to improve the accuracy and algorithm efficiency of roll bearing fault diagnosis, a new method of bearing fault diagnosis based on deep belief network (DBN) and the particle swarm optimization support vector machine (PSO-SVM) with the time-frequency characteristic statistic is proposed. Firstly, time-frequency characteristic statistic of the bearing vibration signal is calculated. And then the DBN is used to extract features of time-frequency feature extraction. Finally, the extracted parameters are input to the PSO-SVM to be classified. The experimental results show that this method not only has higher accuracy, but also greatly shorten the training time, and the accuracy and efficiency of fault diagnosis is improved as a result.
2019, 38(11): 1732-1737.
doi: 10.13433/j.cnki.1003-8728.20190035
Abstract:
In this paper, Electrolytic In-process Dressing(ELID) grinding technology is used to carry out high-efficiency and precision processing experiments of Inconel625 nickel alloy. The experimental method combining orthogonal test design and grey system theory was used to analyze the influence of the surface roughness as the evaluation index on the processing parameters and the optimal parameter combination was obtained. The surface quality with a surface roughness of 48 nm was processed. The experimental results show that ELID grinding technology in the processing of Inconel625 nickel alloy can effectively solve the processing problems such as blunt edge grinding and cracking of the Inconel625 nickel alloy. This experiment achieved the efficient and precision processing of Inconel 625 nickel alloy.
In this paper, Electrolytic In-process Dressing(ELID) grinding technology is used to carry out high-efficiency and precision processing experiments of Inconel625 nickel alloy. The experimental method combining orthogonal test design and grey system theory was used to analyze the influence of the surface roughness as the evaluation index on the processing parameters and the optimal parameter combination was obtained. The surface quality with a surface roughness of 48 nm was processed. The experimental results show that ELID grinding technology in the processing of Inconel625 nickel alloy can effectively solve the processing problems such as blunt edge grinding and cracking of the Inconel625 nickel alloy. This experiment achieved the efficient and precision processing of Inconel 625 nickel alloy.
2019, 38(11): 1738-1744.
doi: 10.13433/j.cnki.1003-8728.20190044
Abstract:
A topological optimization method combines the differential Jacobian matrix of the parallel prototype mechanism with the solid isotropic material with penalization. Taking the minimum structural compliance and the maximum modal frequency as multi-objective, we establish the planar 3 degree-of-freedom (DOF) compliant mechanism's topological optimization model. Using the topological optimization model's boundary as the shape optimization design variable, the stress and moving platform displacement constraints were optimized twice. The twice optimization model was established with the 3D printing method, and the moving platform displacement data were measured and collected by using the Renishaw dual-frequency laser interferometer. Experimental results and finite element simulation results show that:the planar 3-DOF compliant mechanism designed by combining multi-objective topological optimization with shape optimization and using twice optimization has a low-order modal frequency to realize vibration fitting, thus satisfying the requirements of the planar compliant mechanism with good overall stiffness and realizing micro/nano-scale displacement movement.
A topological optimization method combines the differential Jacobian matrix of the parallel prototype mechanism with the solid isotropic material with penalization. Taking the minimum structural compliance and the maximum modal frequency as multi-objective, we establish the planar 3 degree-of-freedom (DOF) compliant mechanism's topological optimization model. Using the topological optimization model's boundary as the shape optimization design variable, the stress and moving platform displacement constraints were optimized twice. The twice optimization model was established with the 3D printing method, and the moving platform displacement data were measured and collected by using the Renishaw dual-frequency laser interferometer. Experimental results and finite element simulation results show that:the planar 3-DOF compliant mechanism designed by combining multi-objective topological optimization with shape optimization and using twice optimization has a low-order modal frequency to realize vibration fitting, thus satisfying the requirements of the planar compliant mechanism with good overall stiffness and realizing micro/nano-scale displacement movement.
2019, 38(11): 1745-1751.
doi: 10.13433/j.cnki.1003-8728.20190030
Abstract:
Because the spiral bevel gear tooth surface detection method can not reflect the structural characteristics, large amount of measurement data and high cost of measurement equipment, and because the complex measurement path and the measuring point layout do not consider the influence of manufacturing quality characteristics, an adaptive measurement point distribution algorithm for the spiral bevel gear tooth surface was presented. The cloud models of geometric features and manufacturing quality characteristics of the spiral bevel gear tooth surface were established respectively. The spiral bevel gear tooth surface measurement point distribution algorithm was studied. A numerical example of pinion was given and validated. The results indicate that the spiral bevel gear tooth surface measurement point distribution algorithm reflects the tooth surface geometry and manufacturing quality characteristics, needs relatively few measurement points and distributes them as expected.
Because the spiral bevel gear tooth surface detection method can not reflect the structural characteristics, large amount of measurement data and high cost of measurement equipment, and because the complex measurement path and the measuring point layout do not consider the influence of manufacturing quality characteristics, an adaptive measurement point distribution algorithm for the spiral bevel gear tooth surface was presented. The cloud models of geometric features and manufacturing quality characteristics of the spiral bevel gear tooth surface were established respectively. The spiral bevel gear tooth surface measurement point distribution algorithm was studied. A numerical example of pinion was given and validated. The results indicate that the spiral bevel gear tooth surface measurement point distribution algorithm reflects the tooth surface geometry and manufacturing quality characteristics, needs relatively few measurement points and distributes them as expected.
2019, 38(11): 1752-1759.
doi: 10.13433/j.cnki.1003-8728.20190050
Abstract:
Aiming at the large surface volume, large machining allowance and long processing time of large marine propeller casting blank with free-form surface, an adaptive machining method of the propeller allowance based on 3D scanning is proposed by combining the five-axis milling and the grinding compound machine tool. Firstly, a 3D scanner is used to obtain propeller scanning data, and the algorithm is used to compare the model with the scanning data. Then, the machining allowance is extracted after model matching. And the propeller machining trajectory is planned based on the machining allowance distribution, which is also applied to the algorithm of propeller milling and grinding compound machining. Finally, the propeller machining experiment is carried out based on the machining theory.
Aiming at the large surface volume, large machining allowance and long processing time of large marine propeller casting blank with free-form surface, an adaptive machining method of the propeller allowance based on 3D scanning is proposed by combining the five-axis milling and the grinding compound machine tool. Firstly, a 3D scanner is used to obtain propeller scanning data, and the algorithm is used to compare the model with the scanning data. Then, the machining allowance is extracted after model matching. And the propeller machining trajectory is planned based on the machining allowance distribution, which is also applied to the algorithm of propeller milling and grinding compound machining. Finally, the propeller machining experiment is carried out based on the machining theory.
2019, 38(11): 1760-1765.
doi: 10.13433/j.cnki.1003-8728.20190171
Abstract:
In order to find an efficient micro-machining method of NdFeB, the experiment of fiber laser etching of NdFeB with a thinness of 1.5 mm is investigated. The effects of the various process parameters on the etching depth, groove surface morphology and heat affected zone are analyzed. The results show that the etching depth increases with the increasing of laser power. When the laser power is 12 W, the depth increases to 120.1 μm, and then the growth ratio decreases gradually. At lower laser frequencies, a larger etch trench depth can be obtained, up to 149.3 μm, but the trench edge topography is degraded. Suitable low-speed etching can not only obtain deep trenches, but also ensure the material's etching amount while obtaining better edge morphology and smaller heat affected zone. When the number of scans increases to 6 times, the laser depth increases to 139.5 μm. At this time, the trench groove wall has the least slag and the edge morphology is the best.
In order to find an efficient micro-machining method of NdFeB, the experiment of fiber laser etching of NdFeB with a thinness of 1.5 mm is investigated. The effects of the various process parameters on the etching depth, groove surface morphology and heat affected zone are analyzed. The results show that the etching depth increases with the increasing of laser power. When the laser power is 12 W, the depth increases to 120.1 μm, and then the growth ratio decreases gradually. At lower laser frequencies, a larger etch trench depth can be obtained, up to 149.3 μm, but the trench edge topography is degraded. Suitable low-speed etching can not only obtain deep trenches, but also ensure the material's etching amount while obtaining better edge morphology and smaller heat affected zone. When the number of scans increases to 6 times, the laser depth increases to 139.5 μm. At this time, the trench groove wall has the least slag and the edge morphology is the best.
2019, 38(11): 1766-1770.
doi: 10.13433/j.cnki.1003-8728.20190037
Abstract:
In order to reveal the wear mechanism and breakage mechanism of the end milling cutter, a self-developed embedded temperature monitoring tool holder is adopted. The temperature measurement experiments of the difficult to machine AISI 304 stainless steel with different cooling methods, cutting speeds and cutter diameters were carried out. The results show that the maximum temperature decreases 246℃, from dry milling to cool milling at 10 000 r/min. At the same milling cutter and borehole ratio (1:1.5) and 6 000 r/min, the maximum temperature is higher 500℃ with Ø12 mm milling cutter than that with Ø20 mm milling cutter. The advantages of the cool milling include the higher quality of the machined borehole surface and the cylindricity is less than 0.02 mm. The advantage of internal cool milling is more obvious in deep-hole milling. The results provide a reference for promoting and applying the high speed internal cooling method.
In order to reveal the wear mechanism and breakage mechanism of the end milling cutter, a self-developed embedded temperature monitoring tool holder is adopted. The temperature measurement experiments of the difficult to machine AISI 304 stainless steel with different cooling methods, cutting speeds and cutter diameters were carried out. The results show that the maximum temperature decreases 246℃, from dry milling to cool milling at 10 000 r/min. At the same milling cutter and borehole ratio (1:1.5) and 6 000 r/min, the maximum temperature is higher 500℃ with Ø12 mm milling cutter than that with Ø20 mm milling cutter. The advantages of the cool milling include the higher quality of the machined borehole surface and the cylindricity is less than 0.02 mm. The advantage of internal cool milling is more obvious in deep-hole milling. The results provide a reference for promoting and applying the high speed internal cooling method.
2019, 38(11): 1771-1777.
doi: 10.13433/j.cnki.1003-8728.20190041
Abstract:
To improve the general genetic algorithm for solving the assembly sequence planning (ASP) problem that it has slow search speed and massive repeated solutions, an ASP method based on the memetic algorithm (MA) was proposed. The strategy of dynamically updating the number of population by combining global search with local search is introduced. The assembly sequence planning model that adopts the constraint matrix and the interference matrix was constructed, and the fitness function for calculating the sum of similarity between assembly units was established. The assembly sequence planning is globally searched in the non-interference solution space. In order to traverse binary trees, the sorting algorithm is adopted to transform an optimal assembly sequence planning solution into a feasible solution. The optimal solution is locally searched in the feasible solution space through crossover and mutation operations. The assembly sequence planning process of a typical plunger pump is used as an example to prove the feasibility of the proposed ASP method. Compared with the genetic algorithm, the algorithm proposed in the paper is more effective.
To improve the general genetic algorithm for solving the assembly sequence planning (ASP) problem that it has slow search speed and massive repeated solutions, an ASP method based on the memetic algorithm (MA) was proposed. The strategy of dynamically updating the number of population by combining global search with local search is introduced. The assembly sequence planning model that adopts the constraint matrix and the interference matrix was constructed, and the fitness function for calculating the sum of similarity between assembly units was established. The assembly sequence planning is globally searched in the non-interference solution space. In order to traverse binary trees, the sorting algorithm is adopted to transform an optimal assembly sequence planning solution into a feasible solution. The optimal solution is locally searched in the feasible solution space through crossover and mutation operations. The assembly sequence planning process of a typical plunger pump is used as an example to prove the feasibility of the proposed ASP method. Compared with the genetic algorithm, the algorithm proposed in the paper is more effective.
Study on Multi-reservoir Echo State Network Modeling of Control Handing Comfort for Standing Posture
2019, 38(11): 1778-1783.
doi: 10.13433/j.cnki.1003-8728.20190046
Abstract:
Control handing comfort is one of the most important study items of the man-machine system. Aiming at the uncertainty and fuzziness of control handing comfort evaluation, the aim of this study is to show the feasibility with a multi-reservoir echo state network (ESN) based on Bayesian regression to model comfort evaluation model for standing posture. The data for model training and testing were random selected. Fifteen adults participated in the experiment, they were asked to reach 100 different targets. Joint angle, foot pressure distribution, human characteristics, target position, and subjective comfort rating were collected during the experiment. The multi-reservoir ESN based on Bayesian regression was tested based on the 10% experimental data, the result showed that, the T-S FNN model has smaller root mean square error than BP neural network. In order to verify this model, 10 groups of different tasks were randomly selected, the results showed that the correlation coefficient between this method and the actual value was 0.97 (p < 0.05), with the rapid upper limb assessment (RULA) was 0.66(p < 0.05). It shows that this method can reflect the real results.
Control handing comfort is one of the most important study items of the man-machine system. Aiming at the uncertainty and fuzziness of control handing comfort evaluation, the aim of this study is to show the feasibility with a multi-reservoir echo state network (ESN) based on Bayesian regression to model comfort evaluation model for standing posture. The data for model training and testing were random selected. Fifteen adults participated in the experiment, they were asked to reach 100 different targets. Joint angle, foot pressure distribution, human characteristics, target position, and subjective comfort rating were collected during the experiment. The multi-reservoir ESN based on Bayesian regression was tested based on the 10% experimental data, the result showed that, the T-S FNN model has smaller root mean square error than BP neural network. In order to verify this model, 10 groups of different tasks were randomly selected, the results showed that the correlation coefficient between this method and the actual value was 0.97 (p < 0.05), with the rapid upper limb assessment (RULA) was 0.66(p < 0.05). It shows that this method can reflect the real results.
2019, 38(11): 1784-1789.
doi: 10.13433/j.cnki.1003-8728.20190039
Abstract:
The imaging distortion caused by applying the principle of visual measurement to high temperature gradient environment is discussed. In this paper, we study the abstraction of light as light ray, and discuss the imaging of optical systems by discussing the propagation of light. And this method was used to correct the image distortion and compared with the actual error obtained by the corner detection method. The experimental results show that the method of image correction caused by interference of heat source with ray tracing algorithm is feasible, and the error compensation of image distortion is realized, and the corrected image can be obtained accurately.
The imaging distortion caused by applying the principle of visual measurement to high temperature gradient environment is discussed. In this paper, we study the abstraction of light as light ray, and discuss the imaging of optical systems by discussing the propagation of light. And this method was used to correct the image distortion and compared with the actual error obtained by the corner detection method. The experimental results show that the method of image correction caused by interference of heat source with ray tracing algorithm is feasible, and the error compensation of image distortion is realized, and the corrected image can be obtained accurately.
2019, 38(11): 1790-1796.
doi: 10.13433/j.cnki.1003-8728.20190036
Abstract:
Based on standard κ-ε double equation turbulence model and Lagrange discrete phase model, the value of computational domain's length in front of the train under heavy rainfall conditions is studied in this paper. On this basis, aerodynamic characteristics of high-speed trains under different speed and rainfall intensity are analyzed, and the simulation results are compared with those under no rain conditions. The results show that the length of the computational domain in the front of the train should reach 1.5 times of the horizontal distance of raindrop movement. With rainfall intensity increasing, raindrop concentration around the train increases overall. The closer the raindrops get to the tail train, the higher the concentration is. The greater the speed is, the greater the splash and the distance are. Under heavy rainfall conditions, the drag force of the whole train, the head train and the middle train increases gradually with the growth of rainfall intensity and speed. The drag force of the tail train decreases with the growth of rainfall intensity, whereas, it increases with the growth of speed. The percentage change of the drag force increases with the increase of rainfall intensity and decreases with the increase of speed.
Based on standard κ-ε double equation turbulence model and Lagrange discrete phase model, the value of computational domain's length in front of the train under heavy rainfall conditions is studied in this paper. On this basis, aerodynamic characteristics of high-speed trains under different speed and rainfall intensity are analyzed, and the simulation results are compared with those under no rain conditions. The results show that the length of the computational domain in the front of the train should reach 1.5 times of the horizontal distance of raindrop movement. With rainfall intensity increasing, raindrop concentration around the train increases overall. The closer the raindrops get to the tail train, the higher the concentration is. The greater the speed is, the greater the splash and the distance are. Under heavy rainfall conditions, the drag force of the whole train, the head train and the middle train increases gradually with the growth of rainfall intensity and speed. The drag force of the tail train decreases with the growth of rainfall intensity, whereas, it increases with the growth of speed. The percentage change of the drag force increases with the increase of rainfall intensity and decreases with the increase of speed.
2019, 38(11): 1797-1804.
doi: 10.13433/j.cnki.1003-8728.20190028
Abstract:
The development of aviation and aerospace technologies increases the demand of low-porosity composites. Localized pores in composites will lead to performance degradation. Method for detecting localized pores in those composites is proposed in this paper. Firstly, the propagation of ultrasonic wave in composite is investigated. The available model given in frequency domain is extended to the time-frequency domain. The existence of resonant structural noise is validated; the frequency diversity between resonant structural noise and flaw echoes are investigated. Secondly, the variation mode decomposition (VMD) is used to separate random noise and resonant structural noise from low-frequency component. The low-frequency component, which contains the flaw echoes, is used for localized pores detection. Thirdly, the concepts of energy function and instant gain are put forward to solve the shadowing problem. The experimental results have shown that the established method based on VMD and instant gain is able to suppress noise interference and alleviate the shadowing effect, and validated the effectiveness in localized pores detection.
The development of aviation and aerospace technologies increases the demand of low-porosity composites. Localized pores in composites will lead to performance degradation. Method for detecting localized pores in those composites is proposed in this paper. Firstly, the propagation of ultrasonic wave in composite is investigated. The available model given in frequency domain is extended to the time-frequency domain. The existence of resonant structural noise is validated; the frequency diversity between resonant structural noise and flaw echoes are investigated. Secondly, the variation mode decomposition (VMD) is used to separate random noise and resonant structural noise from low-frequency component. The low-frequency component, which contains the flaw echoes, is used for localized pores detection. Thirdly, the concepts of energy function and instant gain are put forward to solve the shadowing problem. The experimental results have shown that the established method based on VMD and instant gain is able to suppress noise interference and alleviate the shadowing effect, and validated the effectiveness in localized pores detection.
