最新刊期
期 7 ， 2022
- 摘要：The computational fluid dynamic （CFD） method is used to study the two injection modes of the non-symmetrical helical gear injection，namely，the injection mode of the entry side and the injection mode of the exit side. The thermal boundary conditions of the injection lubrication simulation model are obtained based on the finite element method. The simulation calculation of the injection lubrication of the asymmetric helical gear is carried out in the CFX fluid simulation software，and the influence rules of the injection parameters on the flow heat transfer coefficient of the tooth face under different injection methods are obtained. Under the method of oil injection lubrication on the meshing entry side，the average convective heat transfer coefficient of tooth surface decreases with the increase of lubricating oil viscosity，but the decreasing trend is slow. Under the method of oil injection lubrication on the meshing exit side， the average convective heat transfer coefficient of the tooth surface will gradually decrease as the viscosity of the lubricating oil increases，but the decreasing degree gets slower gradually. It shows that the average convective heat transfer coefficient of the tooth surface is less and less affected by the viscosity of the lubricating oil. The tooth-to-surface flow heat transfer coefficients of the two oil injection methods，the meshing entry side oil injection method and the meshing exit side oil injection method，both increase with the increase of the fuel injection speed，and the linear change is obvious. The effect of oil injection velocity on the average convective heat transfer coefficient of tooth surface is obvious. Under the conditions of the same lubricating oil viscosity and the same oil injection speed，the meshing entry side oil injection lubrication method and the meshing exit side oil injection lubrication method have a larger tooth flow heat transfer coefficient during the meshing entry side oil injection method.关键词：Asymmetric helical gears;Oil injection lubrication;Computed fluid dynamics;Convective heat transfer coefficient
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发布时间：2022-09-24 - 摘要：For the vibration response of gear-rotor-bearing system with compound faults，after the gear pair model and ball bearing model are combined，a coupling vibration model of gear-rotor-bearing system with 36 degrees of freedom based on the Lagrange equation is built，and the spalling defect on the driving gear and surface damage compound faults of bearings are set to study the vibration response of gear pair under compound faults. The results show that the vibration amplitude of the healthy gearing-rotor-bearing system is relatively uniform on time domain，and the vibration spectrum mainly consists of the characteristic frequencies of the bearing outer raceway，as well as the meshing frequencies of the gear pair. When there is a spalling single fault on the gear pair，the sidebands generated by the frequency modulation of the rotating shaft and meshing frequencies can be found. When compound faults of the gear-rotor-bearing system occurs，the amplitude of system vibration on the time domain increase and the vibration are becoming more complicated. The modulation phenomenon is serious on frequency domain， and the amptitude of the signal generated by modulation increases. However，the fault frequencies and harmonic frequencies can be found in the vibration frequency domain，which can determine fault types of system.关键词：Gear-rotor-bearing system;Compound faults;Tooth surface spalling;Bearing damage;Vibration response
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发布时间：2022-09-24 - 摘要：Aiming at the application requirements on a variety of complex roads and based on the biological metamorphosis mechanism，a wheel-tracked reconfigurable robot is proposed. The robot includes two motion modes，namely wheel mode and crawler mode. By switching between the two modes，the adaptability of the robot on multiple ground features can be significantly improved. The study of switching mechanism and transmission principle is carried out. The changing trend of the contact width is analyzed to obtain a maximum value of 230.36 mm in crawler mode. The robot's ability to overcome obstacles in wheel and crawler modes is calculated separately，and the trend of the robot's center of gravity position during obstacle-crossing is analyzed through simulation software. Finally，a prototype of the robot is developed by integrating the power system. Wooden boards and hollow bricks with different heights as experimental platforms are used to test the robot's mode-switch and obstacle crossing ability in groups. The experimental results show the maximum obstacle crossing heights in wheel and crawler modes are 98.5 mm and 290 mm which are consistent with the theoretical value. In addition，the robot can flexibly switch between wheel mode and crawler modes，which has the ability to adapt to a variety of complex roads.关键词：Wheel-tracked reconfigurable robots;Switching mechanism;Contact width;Obstacle
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发布时间：2022-09-24 - 摘要：In order to simplify the solution method of inverse kinematics of the manipulator， improve the accuracy of the solution， and enhance the universality of the method， the intelligent optimization algorithms are used to turn the inverse kinematic solution into an optimization problem. Firstly， the objective function of the end pose error according to the positive kinematic equation is established， and the best flexibility and energy consumption constraints to construct the fitness function are combined so that the manipulator has the best flexibility and lower energy consumption when meeting the requirements of the pose error； In order to unify the accuracy of position and attitude convergence and control the evolution direction， the pose balance coefficient and the pose error adjustment coefficient are introduced； Then， the individual optimization of the beetle search with excellent performance in group optimization is integrated with the differential evolution algorithm， so as to improve the convergence accuracy and speed of the algorithm； Finally， inverse solution experiments are conducted on the 6R manipulator and the redundant manipulator. The results show that the proposed algorithm has high convergence accuracy， a fast speed and a good versatility.关键词：Redundant manipulator;Inverse kinematic solution;Differential evolution algorithm;Beetle antennae search;Optimal compliance criterion
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发布时间：2022-09-24 - 摘要：The influence of non-uniform wear on the modal characteristics of gears under quasi-static condition is studied. Based on Hertz contact theory and Archard formula， a quasi-static wear model is established to simulate the wear of gear tooth surfaces. The calculation results show that the wear at the top and root of the driving and driven gears is larger， the wear at the top is smaller than that at the root， the wear at the root of the driving gears is the largest. The pure rolling of the gear at the node does not cause wear， and the wear at the alternation of single tooth and double tooth meshing zones has a mutation. Based on the numerical analysis results， the tooth surface wear fault is applied and imported into Abaqus for simulation， and the modal characteristics of the gear before and after wear are further analyzed. The simulation results show that the gear has a variety of vibration modes， the effect of wear on the vibration modes is not obvious， the natural frequency increases significantly， the increase amplitude of the high natural frequency of the seventh order to the tenth order is higher than that of the low order natural frequency.关键词：Spur gears;Gear surface wear;Archard model;Modal analysis
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发布时间：2022-09-24 - 摘要：To improve the contact performance of curvilinear cylindrical gears，a forming method for adjusting the contact area of tooth surfaces is proposed. Firstly，a basic scheme is established for adjusting the contact area of tooth surfaces，which means the large gear is formed by a double-edged face-milling cutter，and the concave and convex surfaces of the pinion are formed by the outer-edge and inner-edge face-milling cutters，respectively. Secondly，mathematical models of the gear pair are educed based on meshing theory. Then，under assembly errors，mathematical models of contacting and transmission errors are established based on tooth contact analysis （TCA）. Finally，the feasibility of the proposed scheme is verified through 8 sets of examples. The research results show that the proposed forming method is feasible. Adjusting the curvature radius of the cutter can form gear pairs with any length of contact area. A larger tooth surface contact area can improve the mechanical properties of the gear. If tooth surface contact area is too large，it will increase the sensitivity of transmission errors.关键词：Curvilinear cylindrical gears;Adjustable contact area;Forming method;Mathematical model;TCA;Finite element method
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发布时间：2022-09-24
Theory·Reserach
- 摘要：The nut threadless area of the circulating planetary roller screw mechanism design method is proposed based on the specific structural characteristics of its nut， and related formulas are derived for the structural parameters of the nut threadless area. On this basis， a cross-section design method for rollers， screws， and nuts is developed in accordance with the actual meshing situation of the components. By adjusting the clearance between the two oblique edges and the arc， oblique edges， the meshing accuracy of the screw and roller threads， roller and nut threads can be improved. The relationship between the distance from the center of the rollers to the end of the cam ring is provided to ensure the meshing between the rollers and the screw， the rollers and the nut. Finally， according to the working principle and structural characteristics of the circulating planetary roller screw mechanism， a three-dimensional model is established using its relevant structural parameters， and the relevant assembly is carried out. The design and virtual assembly method of the nut threadless area proposed can serve as a model and guide for the design and analysis of the circulating planetary roller screw mechanism.关键词：Circulating planetary roller screw mechanism;Nut threadless area;Matching design;Virtual assembly method
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发布时间：2022-09-24 - 摘要：In order to give full play to the mechanical properties of stamping machine，a multi-bar mechanism is used to replace a manual production to solve a series of problems when stamping sponge blank. A mechanism model is constructed and a kinematic analysis is carried out； A mathematical model for optimizing the geometric parameters of multi-bar light-load stamping machine is established，which takes the maximum effective stamping angle of crank and the minimum fluctuation of acceleration of main slider in the effective stamping stroke as evaluation criteria； The optimization model of the mechanism is constructed by step search method with Matlab，and then a simulation analysis is carried out with Adams. The optimization results show that within the range of effective stamping stroke，the effective stamping time increases by 22.03% and the effective stamping angle increases by 25.43%. The increase of effective stamping time and effective stamping angle can prolong the deformation time of the workpiece，which is beneficial to the full deformation of the workpiece and improve the machining quality of the blank. The fluctuation of acceleration of the main slider in the effective stamping stroke is reduced by 10.63%，which means that the inertia force of the whole mechanism is reduced and the stamping accuracy is increased to a certain extent.关键词：Light load stamping machine;Optimization design;Matlab;Kinematic analysis
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发布时间：2022-09-24 - 摘要：A double cycloid permanent magnetic gear （DCPMG） based on Halbach magnetizing array is designed. The operation mechanism of DCPMG and the design and calculation method of preliminary parameters are given，the calculation model of transmission ratio is established by space electromagnetic harmonic method.The expressions of electromagnetic torque of inner and outer air gap are given by equivalent current method and Maxwell tensor method.Based on Ansoft Maxwell 2D，a finite element model of DCPMG is established，and the correctness of the primary model is verified.The air gap length，eccentricity，yoke thickness and permanent magnet thickness of DCPMG are simulated and optimized by control variable method. The results show that the torque density of the optimized DCPMG can reach 353 kN
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发布时间：2022-09-24 - 摘要：Taking a certain type of dual-power drive gearbox transmission system as the research object，through static simulation，the transmission error and tooth surface load of the gear pair at the input end of the power source A are analyzed. According to the gear pair modification method， the Romax software is used to carry out the research on the influence law of the modification parameters in the transmission error and tooth surface load. Based on this，through genetic algorithm， the gear comprehensive modification optimization design combining tooth profile modification and helical modification is carried out， and the gear pair before and after modification is compared and analyzed. The results show that the gear transmission error is obviously reduced after the modification， and the tooth surface load distribution is more uniform.关键词：Gears;Modification;Transmission errors;Tooth surface load
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发布时间：2022-09-24 - 摘要：The failures of diaphragm couplings in application are mostly originated from fatigue failures of the diaphragm. To improve the fatigue performance of the diaphragm coupling，a optimization design method for the diaphragm profile parameters based on the Kriging model is proposed to maximize the high-cycle fatigue safety factor of the diaphragm design. After analyzing the structure of the diaphragm profile and the feature of the high-cycle fatigue stress for the diaphragm under various loads，the sample data of the high-cycle fatigue safety factors for groups of diaphragm profile parameters （including outside/inside radius ratio，profile index and minimum thickness） are obtained，and an initial Kriging model is then constructed on the basis of these sample data. Finally，the initial Kriging model is updated with MP （minimizing the predicted objective function） infill-sampling criterion and genetic algorithm，and the optimal design is obtained via the final Kriging model. The proposed method is then utilized to optimize the profile design of a diaphragm in a helicopter transmission system，and the results show that the static stress and dynamic stress of the critical point for the optimized diaphragm are decreased by 18.7% and 40.7% respectively compared with the original diaphragm design，and thus the high-cycle fatigue safety factor of the optimized diaphragm is increased by 52.8%. The proposed method can be used to improve the fatigue performance of the diaphragm，which provides a reference for the design of the diaphragm profile.关键词：Diaphragm coupling;Kriging model;Optimization design;MP infilling-sampling criterion;High-cycle fatigue
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发布时间：2022-09-24 - 摘要：In order to study the variation law of kinematic parameters in the process of multi intersection and replacement in the process of human-machine carrying exoskeleton walking，a kinematic model of exoskeleton is established based on D-H coordinate system，and the kinematic expression in the process of walking is calculated by Newton Euler recursive formula. In order to realize the carrying movement between exoskeleton and human body，the parameters of joints in the process of human walking are measured and analyzed by displacement attitude sensor. Based on the exoskeleton carried by the third generation human-machine of Southwest Jiaotong University as research object，a virtual prototype is established in Adams environment，and a kinematic simulation of exoskeleton driven by human motion parameters is carried out. Taking the process of multi leg replacement as the starting point，the simulation results are analyzed. The results can provide a reliable basis for the measurement and control system driven by human-machine exoskeleton.关键词：Lower extremity exoskeleton;Alternating multiphase;Kinematic simulation;Human-machine carrying
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发布时间：2022-09-24 - 摘要：A mathematical model for tooth profile curve of cylinder gear with high-order modification gear surface is established. Applying two-parameter envelope theory to determine the meshing relationship between worm grinding wheel and helical gears，the transverse tooth profile is calculated. The grinding wheel dressing and gear grinding experiments are conducted on worm grinding wheel gear grinding machine. According to the results of tooth profile deviation measurement，the tooth surface modification curve is coincided with the requirements. The experiment results verify the correctness of calculation and effectiveness of dressing for worm grinding wheel profile curve.关键词：High-order modification;Worm grinding wheel;Two-parameter envelope;Dressing
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发布时间：2022-09-24
Design· Calculation
- 摘要：Based on the roll deformation theory，a roll model through Deform-3D finite element simulation software is established，the roll forming process of the face gear is analyzed and the metal flow conditions of the active and passive faces of the face gear tooth profile is analyzed according to the finite element simulation results； the influence trend of process parameters on the maximum load of the rolling wheel and the distribution law of equivalent strain and equivalent residual stress on the tooth profile are analyzed. The results show that， the metal fluidity of the passive surface of the tooth profile of the face gear is greater than that of the active surface，and “lugs” are easily formed on the tooth top of the passive surface； the maximum load of the rolling wheel decreases with the increase of the speed，and the feed speed increases. The maximum load of the rolling wheel increases； the change trend of the equivalent strain of the tooth profile and the maximum residual stress is the same，which increases with the increase of the speed，and decreases with the increase of the feed speed. These results provide certain reference significance for further experiments.关键词：Roll forming;Numerical simulation;Metal flow;Equivalent strain;Residual stress
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发布时间：2022-09-24 - 摘要：Belt drive has been widely used in front end auxiliary system of vehicle internal combustion engine. The vibration and noise of belt have drawn more and more attention，which directly affects the safe and comfortable driving experience of market customers. In order to solve the belt noise problem，the abnormal noise of the engine bay during the acceleration of a compact SUV model is taken as an example to systematically carry out the identification and investigation of the belt noise. The potential mechanism of the belt transverse vibration and noise is expounded. By optimizing the dynamic characteristics of the crankshaft damper TVD，the torsional vibration excitation of the accessory belt train is reduced. Then，the belt abnormal noise is eliminated and the dynamic sound quality of the vehicle is improved. The paper provides a new engineering development idea for solving similar belt noise problems.关键词：Torsion vibration damper （TVD）;Belt transmission;Belt transverse vibration noise;FEAD （Front end auxiliary drive）
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发布时间：2022-09-24 - 摘要：Taking a herringbone gear transmission system with star gear train as the research object and based on the finite node method，a system-level dynamics model considering shaft-bearing-rigid rotor and the meshing of gears is established. The dynamic characteristics of the system are analyzed based on the RMS of vibration velocity at the bearings with the rotation speeds. Then the theoretical analysis results are compared with the experimental data to verify the reliability of the proposed model. After that，based on the analysis of vibration characteristics and modal characteristics of the gear system，resonance localization and resonance cause analysis are carried out. The results show that the theoretical analysis is in good agreement with experimental results. This study provides a valuable reference method for resonance prediction and resonance cause analysis of herringbone gear transmission system of star gear train.关键词：Star gear train;Herringbone gears;Finite node method;Vibration characteristics;Modal characteristics
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发布时间：2022-09-24 - 摘要：Energy saving and emission reduction is an important trend in the development of automotive industry. As the core component of transmission system，transmission needs to be further optimized to improve its transmission efficiency. The bearing of a domestic 5-speed manual transmission is studied. The influence of bearing accuracy，bearing clearance and bearing sealing structure on transmission efficiency under different working conditions is considered. The results show that the improvement of bearing accuracy can improve the transmission efficiency in low gear，but has little effect on the transmission efficiency in high gear； compared with the original bearing clearance （C3 group），both Cm group and C5 group can improve the transmission efficiency，but the working condition improved by Cm group clearance is closer to the real working condition； the friction torque generated by the bearing seal accounts for more than 85% of the total friction torque of the bearing. The optimization scheme of transmission bearing is formulated. Through the vehicle WLTC （World-wide harmonized light duty test cycle） fuel consumption，it is found that the use of Cm group bearing clearance and non-contact sealing structure can reduce the vehicle WLTC fuel consumption by 0.97%.关键词：Transmission;Bearings;Transmission efficiency;Fuel consumption
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发布时间：2022-09-24 - 摘要：Based on the principle of double-degree-of-freedom meshing with interleaved axes in space， the material removal process is complicated，and the cutting force and temperature change dynamically during the cutting process. Thus，a finite element simulation analysis model of the gear skiving process is established，and the constitutive model and fracture criterion of the workpiece material suitable for the simulation analysis of the gear skiving process are determined through comparison and analysis，so as to realize the accurate prediction of the dynamic change process of the cutting force and the cutting temperature. On this basis， the influence of different tool speeds and axial feed rates on the three-direction cutting force and cutting temperature is analyzed. The research results can provide method support for the analysis and optimization of the gear skiving technology.关键词：Gear skiving technology;Finite element;Cutting force;Cutting temperature
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发布时间：2022-09-24 - 摘要：A classification of silent chains in chain drives is introduced； the simulations of different oil pump silent chains with Adams simulation analysis software are compared； the stability of different silent chains in the gearbox oil pump system is analyzed； its wear，noise and other characteristics are finally verified through experiments to select the best tooth profile. It provides ideas and methods for the design and selection of the gear shape of the automobile transmission oil pump chain.关键词：Gearbox;Silent chain;Wear;Noise;Simulation analysis;Experimental study
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发布时间：2022-09-24 - 摘要：Based on the mechanism of human cervical traction rehabilitation and the characteristics of the cervical spine area that is precise and easily damaged， a 2-UPR/RPS three-degree-of-freedom cervical traction rehabilitation mechanism is proposed； the error analysis and compensation of this mechanism are carried out to avoid secondary damage to the cervical spine. Firstly， the error modeling is based on the closed vector method， and 11 important errors are identified according to the global error sensitivity； then， based on the given error range， global pose errors and local errors of the moving platform when z=600 mm and z=650 mm are analyzed； finally， based on the particle swarm algorithm， the optimal solutions for the four sets of error compensation are derived， and the joint experimental simulation analysis is carried out by Matlab and Adams software. The results show that the global pose error and the local error of vertical traction are reduced by 59.14% and 89.47% respectively， which effectively ensure the safety of the patient's cervical spine.关键词：Cervical traction rehabilitation mechanisms;Error modeling;Pose errors;Error compensation
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发布时间：2022-09-24
Test·Analysis
- 摘要：In order to realize the generating machining of worm gears， the worm gear hob is used on the NC transformed ordinary milling machine. The proportional relationship between the rotation of one turn of the worm gear hob and the rotation of one tooth of the worm gear workpiece is realized by extending the function of thread instruction and taper thread instruction. By distributing the allowable cumulative error of worm gear pitch evenly on several arcs of worm gear pitch circle， the accuracy of worm gear pitch and transmission is greatly improved， and thus the transmission stability is improved. The practice shows that this method not only achieves high machining accuracy of worm gears， but also expands the application range of NC transformation.关键词：Numerical control transformation;Generating machining of worm gears;Expanding the function of thread instruction
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发布时间：2022-09-24 - 摘要：Aiming at the problems of insufficient samples of gear fault signals collected in practical engineering，insufficient training，low fault recognition rate and easy pattern collapse of generative adversarial networks when using common deep learning network for pattern recognition under noise interference. An intelligent diagnosis method of gear faults based on MGAN （Mixture Generative Adversarial Nets） and CNN （Convolutional Neural Networks） is proposed. The real gear signals are transformed into time-frequency signals by time-frequency transformation technology after morphological filtering，and new samples are synthesized by MGAN to obtain a balanced data set，which overcomes the problem of insufficient samples. At the same time，the influence law of main parameters of MGAN on the quality of synthesized samples is analyzed. The balanced data set is used to train CNN for fault diagnosis，which effectively improves the fault diagnosis rate. Through the comparative test and bench test，the effectiveness and advantages of this method in accurately identifying faults and overcoming the collapse of neural network mode under the condition of insufficient samples are verified，which provides a new research idea for typical fault extraction and intelligent identification of gearboxes.关键词：Generative adversarial network;Model collapse;Insufficient samples;Fault diagnosis
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发布时间：2022-09-24 - 摘要：Due to properties of reducing impact，improving uneven load，and lowering noise in the meshing process，the technology of tooth surface modified are very common in the wind power gear. As the last process of machining gear，form grinding determines the accuracy of gear directly. Therefore，solving geometry error of form grinding becomes vital for optimize grinding tool path and enhancing the machining precision. Thus，this paper builds a model of geometrical error. In order to solve the geometry error of form grinding， firstly， tooth surface model of gears combining the profile and axial modification （including drum and helix modification） is constructed. Then，based on the tooth surface parameter，the length of common perpendicular between axes of the gear and the wheel，the contacting curve between the gear and the wheel is solved. The form grinding tooth surface is constructed. Finally，the geometrical error of tooth surfuce form grinding is defined by using the theoretical tooth surface and form grinding tooth surface， the geometric error model of tooth surface form grinding is established， some suggestions are given to reduce the geometry error of form grinding.关键词：Form grinding;Wind power gear;Large modulus;Geometry error
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发布时间：2022-09-24 - 摘要：Aiming at the problem that feature extraction in bearing fault diagnosis needs to rely heavily on manual experience and expert knowledge，a bearing fault diagnosis method based on Gramian angle field（GAF） transformation and adaptive depth network is proposed. Firstly，the collected signals are analyzed by empirical mode decomposition method， and the Intrinsic mode functions（IMFs） are effectively determined by Mahalanobis distance measurement method. It can not only select the similar modal components of the noisy signal and the original signal to improve the signal-to-noise ratio of the noisy signal，but also eliminate the similar modal components of different types of signals to highlight the signal characteristics； then，the signal is reconstructed by using the selected IMFs，and the reconstructed signal is visualized based on GAF transform； finally，the depth adaptive network is used for feature learning and state recognition. The results show that the accuracy of the proposed method is 94.97%，which is better than the common vibration signal fault diagnosis methods，and the proposed method can also suppress the noise and has good robustness，which provides a reasonable idea for the intelligent and accurate diagnosis of bearings.关键词：Bearings;Gramian angle transformation;Deep adaptive network;Fault diagnosis
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发布时间：2022-09-24
Development·Application
- 摘要：An image acquisition method based on machine vision and its application in many fields are expounded； an image processing technology is introduced，and a schematic diagram of the processing results of each method is given by taking the gear tooth surface as an example； the characteristics of various classification and recognition technologies are summarized； finally，the application and development trend of machine vision recognition technology in the field of mechanical transmission，such as gear tooth surface damage recognition direction，are prospected.关键词：Machine vision;Image recognition;Transmission parts;Development trend
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发布时间：2022-09-24
Review
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