最新刊期
期 5 ， 2021
- 摘要：In order to further understand the relationship between the errors and the load sharing performance of the split torque transmission system， the static model and equation of the system are established for the single input double output gear split torque transmission system. The influence of the interaction between errors on the statics load sharing coefficient of the system is studied， and the orthogonal experiment parameter matching analysis based on the interaction is carried out. The results show that there is interaction between partial backlash and between any two center distance errors， and the optimal combination mode can be obtained to improve the load sharing performance of the system through the parameter matching analysis based on interaction.关键词：Gear;Split torque transmission;Error;Interaction;Orthogonal experiment;Load sharing coefficient
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发布时间：2022-11-10 - 摘要：Rolling-sliding motion is a special motion form which leads to the failure of rolling bearings. In order to study the wear characteristics of rolling bearings under rolling-sliding motion， the method of combining simulation with experiment is adopted. Firstly， Abaqus finite element software is used to establish the finite element simulation model of rolling bearing under rolling-sliding state， the dynamic response of friction force is obtained. Then， the friction data of the bearing in the process of motion are obtained through the rolling wear test bed. By using the Gray Correlation Analysis method，it is concluded that the correlation between the simulation data and the experiment data reached more than 0.8. Therefore，the friction obtained by simulation could be used as the basis to judge the changes of bearing wear state. In the bearing wear experiments， the particle size in the oil is detected and the surface topography of inner ring is recorded. The results show that the change of friction force obtained by simulation affects the change of oil particle size and surface morphology. The increase of particle number in oil and the wear mark on the inner ring surface are the wear results caused by the change of friction force. The positive feedback to the friction force makes its amplitude increase continuously， which further aggravates the wear of the bearing. The method of combining simulation with experiments provides the basis for the analysis and research of the bearing wear characteristics at each point under rolling-sliding state.关键词：Rolling-sliding motion;Rolling bearing;Finite element analysis;Particle size;Surface topography
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发布时间：2022-11-10 - 摘要：To improve the stability of the vehicle in the starting process and prolong the service life of the clutch， a dynamics model of the engagement process is established according to the motion state of the active and driven discs of the clutch. The NSGA-Ⅱ algorithm is introduced to solve the multi-objective optimization problem， and the crossover operator of normal distribution and adaptive mutation operator are adopted to improve it，which keeps the diversity of population and effectively prevents falling into local optimum. Finally，the engagement speed and time of clutch are taken as the design variable，and the impact degree and sliding friction work are taken as the optimization objective function， and the simulation experiment is carried out. The simulation results show that the improved NSGA-Ⅱ algorithm has better Pareto front and faster convergence speed， and distribution is more uniform， obviously superior to the other two comparison algorithms， and the smaller impact degree and sliding friction work can be obtained by smoothly controlling the engagement speed of clutch in the condition of the same joint time，which provides technical support for the design of clutch engagement control strategy.关键词：Clutch engagement control;Dynamics model;NSGA-Ⅱ algorithm;Impact degree;Sliding friction work;Normal distribution crossover;Adaptive variation;Stability and durability
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发布时间：2022-11-10 - 摘要：The economic performance of single pedal matched regenerative braking system for pure electric vehicle under CLTC condition is studied. Firstly， the differences between the two working conditions of CLTC and NEDC are compared， and a virtual simulation model is built on AVL_CURISE platform based on a certain vehicle， a pure electric vehicle model equipped with a single pedal braking energy recovery control system is established. The economic performance differences between the single pedal system and the original parallel braking regenerative system are compared under different working conditions. The simulation results show that， the single pedal braking system is better than the former parallel braking system， the replacement of NEDC with CLTC have limited impact on driving range.关键词：CLTC working condition;NEDC working condition;Single pedal brake recovery system;Pure electric vehicle;AVL_CRUISE;Economic performance
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发布时间：2022-11-10 - 摘要：In order to study the microstructure evolution of the formed parts in the axial vibration cold extrusion process， the microstructure evolution process of the blank in the axial cold extrusion process is simulated by using the cellular automata method. It is found that the average grain size of internal spline processed by cold extrusion with auxiliary vibration is significantly smaller than that without auxiliary vibration. The effects of vibration frequency，vibration amplitude and extrusion speed on the microstructure of the formed parts are analyzed by orthogonal test. The results of variance analysis show that the vibration amplitude has the most significant influence on the average grain size at the tooth root，and the most significant influence on the grain size at the pitch circle and the top of the tooth is the vibration frequency and extrusion speed， the vibration frequency has the most significant influence on the average grain uniformity at the root and pitch circle of the formed part， and the extrusion speed has the most significant influence on the grain uniformity of the tooth top. The mechanism of the effect of auxiliary vibration parameters on grain refinement is summarized.关键词：Cold extrusion;Auxiliary vibration;Cellular automata;Grain size;Grain uniformity
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发布时间：2022-11-10 - 摘要：Face gear is a new gear transmission form in which involute cylindrical gear and approximate bevel gear mesh with each other. The curved tooth face gear uses the involute arc tooth cylindrical gear as the face gear formed by the imaginary tool envelope. The working tooth surface equation of the face gear is derived， and the fillet modification design of the tooth tip of the cylindrical gear is carried out. Cross-section fillet equation， fillet surface equation， and modified curved tooth surface transition surface equation are deduced， and the mathematical model of the two kinds of tooth tip cylindrical gears is established by Matlab. It is found that the tooth thickness of the face gear generated by the top fillet envelope is larger than that of the face gear generated by the top fillet envelope at the root of the inside diameter. The research results show that rounding the tool tooth tip can not only avoid the contact of the face gear and the cylindrical gear edge causing the face gear tooth surface wear，but also increase the thickness of the tooth root of the inner diameter of the face gear. This type of face gear modification also provides a theoretical basis for other tooth profile face gears.关键词：Curved tooth face gear;Filleting of cylindrical gear tooth tip;Modification;Transition surface
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发布时间：2022-11-10
Theory·Reserach
- 摘要：At present， parallelogram traction steering mechanism is mostly adopted in traction vehicles used in warehousing cargo loading and transfer. Because the steering mechanism does not conform to Ackermann's principle， the sliding friction force is large when steering， which will lead to traction and steering operation laborious. A trapezoidal traction steering mechanism based on Ackerman principle is designed， and uses the sequential quadratic programming genetic algorithm in multivariate nonlinear programming to optimize the specific dimensions of the trapezoidal traction steering mechanism， the size parameters which more satisfy the Ackerman principle are obtained. A prototype is made based on the optimized parameters. By using the Adams dynamics simulation software， the simulation and comparative experiment of the trapezoidal steering mechanism with the optimized parallelogram mechanism from three dimensions of steering trajectory， steering start torque， and energy conversion efficiency are carried out. The analysis results show that the optimized mechanism has a smoother steering trajectory， smaller steering starting torque and higher energy conversion efficiency.关键词：Trapezoidal traction steering mechanism;Ackerman steering principle;Optimization operation;Dynamics analysis;Trajectory analysis
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发布时间：2022-11-10 - 摘要：Aiming at the problems of the single flight mode and inflexible flight attitude，a variable amplitude flapping wing aircraft is designed. By adjusting the flapping amplitude， the flapping wing motion attitude and flight mode can be switched. The kinematics model of flapping wing mechanism with variable amplitude is established to analyze the kinematic characteristics of flapping wing mechanism based on the joint simulation of Adams and Matlab. The aerodynamic model of flapping wing with multiple flight modes is established to analyze the aerodynamic characteristics of flapping wing mechanism with variable amplitude by XFLR5 software. According to set relevant parameters， various flight modes such as take-off， fast flight and slow cruise have been realized and the flexibility of flapping wing aircraft is improved， which provides a research basis for the further development of flapping wing aircraft in the future.关键词：Flapping wing aircraft;Variable amplitude;Kinematic analysis;Multiple flight modes
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发布时间：2022-11-10 - 摘要：Based on the design theory of position and orientation characteristic set， a kind of parallel robot mechanism is proposed， whose moving platform can realize three translations and one rotation. According to the orientation characteristic equation， the topological structure of the mechanism is analyzed， and the kinematics equation model is established by the constraint condition of the length of the rod， and the forward and inverse solution analysis is completed. The motion conditions of singular configuration are determined according to the Jacobian matrix. The operation space shape and rotation flexibility of the moving platform of the mechanism are further studied. At the same time， according to the single variable method， the influence of structural parameters on the operation space is analyzed. The optimization model of operation space maximization is established， the scale optimization is carried out by using beetle antennae search algorithm with fast search speed and strong global search ability. The results show that the mechanism has large， regular shape workspace and strong rotation ability， and the optimized size parameters provides a theoretical basis for the application design of the manipulator.关键词：Position and orientation characteristic set;Parallel mechanism;Workspace;Parameter optimum;Beetle antennae search algorithm
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发布时间：2022-11-10 - 摘要：In view of the limitations of walking robots such as complex driving and inability to adapt to different walking environments， a new type of single-degree-of-freedom walking robot with two leg origami configurations based on the origami mechanism is designed， by folding Miura origami crease angle theory is combined with leg equivalent kinematics model， the kinematics solution is simplified and a new driving mode is designed. The theory of single-vertex origami is extended to the multi-vertex origami configuration， and the definite relationship between the crease corners of different units is obtained. A gait plan that matches the folding state of origami is proposed. The simulation results show that the origami configuration of the robot legs can achieve a long-span and long-span walking gait. Due to the large-span motion at the end of the foot， it does not slide relative to the ground， can achieve smooth walking on roads of different complexity.关键词：Walking robot;Miura origami;Origami mechanism;Kinematics
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发布时间：2022-11-10 - 摘要：A variety of dual-motor dynamic coupling structure schemes based on planetary gear mechanism are designed， and the quantitative relations of various dynamic coupling devices are obtained by using lever analysis method. Then，the transmission characteristics of each scheme are compared and analyzed， and two better schemes are selected for power matching and parameter calculation. Based on Simulation X，the simulation model of the dual motor dynamic coupling device is built，the kinematics simulation analysis is carried out，and the final transmission scheme is optimized. The results show that the proposed method can effectively reduce the number of coupling transmission schemes， and the selected dynamic coupling transmission scheme has excellent speed and torque performance， which can meet the operating requirements of electric tractor under multi-working conditions of electric tractors. This research has important theoretical significance to the development of planetary gear train and automobile transmission.关键词：Electric tractor;Double motor coupling;Planetary gear mechanism;Transmission characteristic
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发布时间：2022-11-10 - 摘要：In order to meet the nursing needs of the elderly and disabled patients with mobility difficulties， a standing and lying nursing wheelchair that can assist standing and assisting lying is designed. The design scheme and working principle of the wheelchair mechanism are expounded. Based on the principle of ergonomics， three-dimensional gait analysis and motion system are used to analyze the movement trajectory of normal joints during the process of standing up and lying down. The geometric relationship between wheelchair mechanisms is established， and the kinematics analysis of the mechanism carried out. Combining the anthropometric data， the parameters of each component are determined and a virtual prototype is established. By using the Adams software， the motion simulation of the mechanism is carried out， the mechanism runs smoothly in the simulation. The simulation results show that the sitting， standing and lying nursing wheelchair assists the human body to sit， stand， and lie down in accordance with the laws of healthy human movement， which verifies the rationality of the mechanism design.关键词：Nursing wheelchair;Mechanism design;Kinematic analysis;Adams simulation
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发布时间：2022-11-10
Design· Calculation
- 摘要：In order to study the influence of lubrication conditions on the scuffing damage of gear under low speed and heavy load， the meshing of gear teeth is simulated by a pair of ring specimens in rolling and sliding contact， and the scuffing tests of 18CrNiMo7-6 carburized steel gear material under different lubrication conditions are carried out on MJP-30A rolling wear testing machine. The variation of friction coefficient among different tests and the surface morphology of the specimens after tests are analyzed. The results show that the contact stress of scuffing damage is 1 927 MPa under the dry friction condition， and the friction coefficient decreases with the increase of contact stress before scuffing damage occurs. Under the good lubrication， no scuffing occurs even when the contact stress is increased as high as 3 047 MPa， and the friction coefficient decreases with the increase of contact stress during the test. Under the condition of oil scarcity， the friction coefficient increases obviously with the increase of oil scarcity， and the scuffing damage occurs only when the friction coefficient almost increases to the level of dry friction coefficient. Therefore， in order to avoid the scuffing damage of the gear tooth surfaces in the operation under low speed and heavy load， the lubrication status should be taken as an important monitoring index of preventing the serious starvation of lubrication or dry friction contact from occurring in the meshing of tooth surfaces.关键词：Lubrication condition;Gear;Scuffing;Low speed and heavy load
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发布时间：2022-11-10 - 摘要：The rail traffic gearbox is a key part of the transmission system in the train. It plays a vital role in the operation of the train. Heat balance analysis of rail traffic gearbox has great influence on the operation of the gearbox. Based on subway gear transmission system， the heat balance equations of the transmission based on thermal network method is established， and the calculation models of heat source，thermal resistance and convective transfer coefficient are given，the temperature of each node is solved by the heat balance equations. The research shows that the efficiency of the rail transit gearbox decreases with the increase of the speed， and the temperature of each node increases with the increase of the speed，and the temperature of the gear meshing point is the highest.关键词：Gearbox;Thermal balance;Thermal network method;Transmission efficiency
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发布时间：2022-11-10 - 摘要：In order to improve the accuracy and stability of the robot in the process of high-speed motion， the method of modeling the dynamic equation of the 4-DOF Delta high-speed parallel robot is studied. The geometrical method is used to solve the inverse kinematics equation of the robot， and the Kane method of screw theory is combined to establish the dynamic equation of the robot. Matlab programming is used to solve the kinematics and dynamics models， and the displacement， velocity， acceleration and torque curves of the driving arm are drawn. The dynamics control system of the Delta robot is established in Simscape， and the displacement curve of the driving arm is obtained with torque as input. Comparing the calculation and simulation results， the correctness of the dynamic equation is verified.关键词：Delta robot;Screw theory;Kane equation;Simscape simulation
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发布时间：2022-11-10 - 摘要：The bending torsion coupling model of elliptical gear pair is established， including the factors of tooth surface friction， time-varying stiffness， damping， backlash and so on. Different parameters are selected and solved by 4~5-step Runge-Kutta numerical method to analyze the nonlinear dynamic characteristics of elliptic gear pair. It can be seen from the analysis that， under certain conditions， when the speed is low， the elliptical gear system is in the stable and regular single period motion stage. The quasi periodic motion， appear with the unstable chaotic motion alternatively under the circumstance of the increasing of the rotational speed. The system motion can be more stable under the circumstance of increasing of friction coefficient and damping ratio， while the system motion can be more unstable under the circumstance of increasing of stiffness coefficient and eccentricity ratio.关键词：Elliptic gear;Bending torsion coupling;Tooth surface friction;Nonlinear;Dynamic characteristic
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发布时间：2022-11-10 - 摘要：Knock noise is a kind of transmission noise. It is very important to study the knocking noise of transmission because it has the characteristics of jumping noise level and wide frequency band， which is different from other noises. A two speed automatic mechanical transmission of a pure electric vehicle is taken as the research object， and the multi-body dynamics model of the transmission gear transmission system is established. The meshing force and angular acceleration of the transmission gear and the loose gear in the running process are analyzed. The gear with the largest knocking noise is theoretically calculated. Taking this as an example， combined with the simulation results of the bearing dynamic load， the accuracy of the gear dynamic model is indirectly verified by theoretical calculation of the vibration response of the transmission structure， and the influence of the retarding torque on the knocking noise is studied.关键词：Automatic transmissison;Knocking noise;Multibody dynamics;Retarding torque
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发布时间：2022-11-10 - 摘要：Polymer gears are light and corrosion resistant， which can reduce noise and improve economic benefits. Correspondingly， polymer gear teeth are weaker than metal ones， so asymmetric design is adopted to improve the strength of polymer gear. In order to investigate the elastohydrodynamic characteristics of asymmetric polymer gears， analysis of transient elastohydrodynamic lubrication of asymmetric polymer gears is carried out under water lubrication by using the multi-grid method. The water film pressure and thickness of asymmetric gear are compared with that of traditional symmetric gear. The influence of changing gear operating condition and considering gear tooth surface roughness on gear elastohydrodynamic lubrication analysis is studied. The results show that the elastohydrodynamic performance of gears can be effectively improved by asymmetric design. The pressure and film thickness of the lubrication film are greatly affected by rotational velocity and load. The roughness has a negative effect on elastohydrodynamic lubrication of asymmetric polymer gears and the tooth surface quality should be guaranteed in applications.关键词：Asymmetric gear;Elastohydrodynamic lubrication;Multi-grid method;Polymer gear
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发布时间：2022-11-10 - 摘要：Based on the tilting pad bearing rotor system， the influence of bearing span，shaft diameter and bearing related parameters on the critical speed of bearing-rotor system is analyzed through simulation calculation， which provides the basis for the optimal design of high-speed gearbox bearing-rotor system. The influence of the span is closely related to the speed， when the shaft diameter exceeds 54 mm， the influence is negligible， the clearance ratio， pivot offset and preload coefficient have basically the same influence on the first and second order critical speeds. The relationship curves are linear，logarithmic and exponential. According to the analysis results，the gearbox of 60 000 r/min is designed，the bearing-rotor system passed the no-load test，and the overall performance of the gearbox met the requirements.关键词：Bearing-rotor;Critical rotation speed;Bearing span;Bearing parameter;Gearbox
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发布时间：2022-11-10 - 摘要：Aiming at the problem of matching and optimization of the power transmission system of two-speed electric vehicles， according to the design parameters and target requirements of the whole vehicle， the power matching of the core components such as the drive motor， power battery， and transmission of the pure electric vehicle is carried out through theoretical calculations， and by using the Cruise simulation software， the vehicle model of the target vehicle is established， and the matching result is simulated and verified. On the premise that the dynamic performance meets the design requirements， in order to further improve the economy， a joint simulation model of Cruise and Isight is built， and an improved non-dominated sorting genetic algorithm （NSGA-Ⅱ） is adopted to optimize the transmission ratio of the transmission system with multiple objectives to achieve the best solution for power and economy. The optimization results show that the power consumption under the optimized NEDC （New european driving cycle） cycle is reduced by 0.38 kWh/100 km， and the economy is increased by 2.4%. The acceleration time of 0~100 km/h is reduced by 0.95 s compared with that before the optimization， and the power performance increased by 7.5%.关键词：Co-simulation;Speed ratio optimization;Isight software;NSGA-Ⅱ
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发布时间：2022-11-10
Test·Analysis
- 摘要：In order to solve the problem of measuring the assembly error of gear shafting in engineering， a method of measuring the assembly error of gear shafting based on stereo vision is proposed. In this method， the circular mark points arranged on the feature to be measured are used as the medium to obtain the spatial pose of the corresponding features through 3D reconstruction and mathematical fitting， and then the assembly error is calculated. Taking a bevel gearbox as an example， the complete technical process of the proposed method is given， and the influence of the number of States and the installation angle of the target plate on the fitting accuracy is systematically studied. A complete hardware and software system is developed， and the effectiveness and efficiency of the measurement method are verified by experiments.关键词：Gear shafting;Stereo vision;Assembly error;Pose fitting
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发布时间：2022-11-10 - 摘要：Aiming at the problem that the measured signal of gear system can’t accurately reflect the fault characteristics due to noise interference， a fault identification method combining adaptive local iterative filtering and fuzzy entropy is proposed. By using adaptive local iterative filtering， the nonstationary signals of gears can be decomposed into finite stationary intrinsic mode functions. Since the adaptive local iterative filtering can effectively separate the rotating frequency signals of gear system， the fuzzy entropy of the first several intrinsic mode functions is calculated based on the intrinsic mode functions corresponding to the rotating frequency signals. Finally， grey relevance degree of the vibration signal’s fuzzy entropy under different working conditions is calculated to identify different fault types of gear system. The results show that the method can be effectively applied to the fault diagnosis of gear system.关键词：Fault analysis;Gear;Signal processing;Adaptive local iterative filtering;Fuzzy entropy
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发布时间：2022-11-10 - 摘要：Based on the analysis of the characteristics of the existing bevel gear measurement technology， a non-contact measurement method of the bevel gear is proposed based on the laser displacement sensor and the algorithm of the tooth distance deviation， the tooth phase deviation and the tooth ring pulsation deviation of the Gleason system spiral bevel gear. The comprehensive measuring device of spiral bevel gear and its principle are introduced. By using the least square method and coordinate transformation knowledge on the sampled data of the measured tooth profile， the ideal model of tooth surface and tooth profile of spiral bevel gear is established. The comparison and analysis of the smooth curve and the collection point， the tooth pitch deviation and tooth profile relative deviation are obtained. The measuring process of spiral bevel gear can be simplified and the measuring efficiency and precision are improved by this method.关键词：Spiral bevel gear;Spacing tolerance;Relative deviation of tooth profile;Coordinate transformation
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发布时间：2022-11-10 - 摘要：The fan-driven gearbox is characterized by complex structure and difficult system dynamics analysis. The accuracy of the component level model is verified through the modal analysis and the percussion modal test of the gearbox component. Then the rationality of the subsystem structure analysis is verified through the comparative analysis of the dynamic response analysis and performance test of the external meshing subsystem. Finally， through the mode synthesis method， each subsystem is unified into the internal meshing system for dynamic response calculation， and it is analyzed and verified with the test data. The key points of analysis and verification of each part are clarified and iterated step by step. A set of system-level analysis methods for theoretical analysis and test verification from component level to subsystem level and then to system level are established， so as to provide guidance and help for the parametric sensitivity analysis and modal identification of complex systems in the future.关键词：Fan-driven gearbox;Dynamic response analysis;Mode synthesis method;System-level analysis method
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发布时间：2022-11-10 - 摘要：The vehicle gearbox has a bad working environment and the fault mode is difficult to identify. On the basis of existing methods， a method based on two-layer-mode decomposition （TMD） and singular value decomposition （SVD） is proposed， combined with particle swarm （POS）-BP neural network for fault diagnosis. Firstly， the vibration signals under four typical conditions of normal transmission， rolling failure， outer ring crack and gear wear are collected on a self-built experimental platform. Then， the first 5 IMFs components of the signal is decomposed by EMD， since the spectrum of IMF1 is still complicated， the wavelet packet is used to continue the 2-layer decomposition. Finally， the eight sub-sequences are obtained by TMD， and the signal component matrix is constructed. Then， the singular value （SVD） of the component matrix is extracted as the eigenvalue， the eigenvalues are entered into the constructed POS-BP neural network diagnostic model， and the gearbox fault type is identified based on the output. The analysis results show that the method can be effectively applied to the fault diagnosis of special vehicle gearboxes， and the diagnostic accuracy rate reaches 92%， which provides an effective reference for gearbox state recognition under complex conditions.关键词：Two-layer-mode decomposition（TMD）;Singular value decomposition（SVD）;POS-BP neural network;Fault diagnosis
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发布时间：2022-11-10
Development·Application
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