最新刊期
卷 47 ， 期 2 ， 2023
- 摘要：Based on the potential energy method, the full tooth profile of the gear teeth is divided into the involute part and the transition curve part, and an improved calculation method for the time-varying meshing stiffness of spur gears is proposed. Using this method, the parametric equation of the tooth root transition curve is considered, and based on the relative size relationship between the radius of the involute starting point, the radius of the base circle and the radius of the root circle, the tooth model with different numbers of teeth is established. A part of the integral upper limit has been corrected to make the gear tooth model more accurate. The time-varying meshing stiffness of gear teeth under different numbers of teeth is calculated, and the calculation results with this method before and after the improvement are compared. The results show that the calculation error caused by the non-coincidence of the starting point radius and the base circle radius of the involute tooth profile will increase with the increase of the number of teeth; when calculating the time-varying meshing stiffness of the teeth with a large difference in the number of teeth, the meshing stiffness calculation should be carried out according to the size of the teeth. There might be a large calculation error when the uniform gear model is used for calculation. Referring to the calculation results of the finite element method, the causes of errors are analyzed, and the effectiveness of the method proposed is verified.关键词：Improved potential energy method;Spur gear;Time-varying meshing stiffness;Different gear models
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发布时间：2023-02-25 - 摘要：In order to solve the problems of eccentric load of planetary gear train and large impact of gear teeth meshing caused by torsional deformation of double planetary gear shafts under load, a topological modification method considering torsional deformation of double planetary gear shaft is proposed. The causes of torsional deformation of the double planetary gear shaft and its influence on the load sharing performance of the gear train are analyzed. Based on the multi body gear bearing contact analysis (PLTCA) and the gear bearing contact analysis (LTCA), the bearing transmission error and the tooth surface load distribution coefficient under the deformation are solved; the optimization intelligent algorithm is used to solve the optimal solution of the modification parameters under the condition of the maximum modification amount of the tooth surface; the simulation results show that the proposed method can effectively reduce the unit length load of the tooth surface and the amplitude of the transmission error. The unit length load of the first and second planetary tooth surfaces is reduced by 33.58% and 21.35% respectively, and the amplitude of the transmission error is reduced by 77.74%; the experimental verification is carried out on the reducer load test-bed, and the experimental results are consistent with the simulation results. The wear condition of the planetary gear surface is greatly improved, the problem of eccentric load of NGWN planetary gear train is better solved, and the transmission accuracy and service life of the equipment are improved.关键词：Double planetary gear;Torsional deformation;Transmission error;3D topography;PLTCA
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发布时间：2023-02-25 - 摘要：Due to the coupling effect of gears, the vibration of each rotor in the gear rotor bearing system is coupled and affected by each other. The study of the dynamics of the gear rotor bearing system must be analyzed based on a systematic and holistic concept. Therefore, the dynamic modeling and model reduction of the gear rotor bearing coupling system have always been a common concern. Based on the basic principle of gear meshing, this study establishes the geometric coupling model (or called kinematic coupling model) of the spur gear pair, helical gear pair, spur bevel gear pair and spiral bevel gear pair; and by using the transformation matrix of the coupling model, a unified, convenient and normative modeling method for the dynamic study of arbitrary complex gear-rotor-bearing coupled system including the above four kinds of gear pairs is given, which provides convenience for the dynamic study of complex gear shafting.关键词：Complex gear coupled rotor-bearing system;Dynamics modeling;Normative modeling method;Geometry coupling model;Transformation matrix of the coupling model
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发布时间：2023-02-25 - 摘要：Aiming at the existence of multiple complex vibration transmission paths in the multistage transmission gearbox, a mathematical model of the multistage transmission vibration transmission path of the gearbox is established, and the frequency spectrum structure of the vibration model is deduced by the Fourier series analysis method. Vibration source, time-varying transmission path and multistage transmission gear vibration frequency characteristics are considered comprehensively, an equivalent time-varying transmission path function from the meshing point to the accelerometer mounted on the ring tooth is proposed and the time-varying transmission path is modeled as having different periodic function of decay amplitude. Taking the multistage transmission gearbox as an example, the validity of the proposed mathematical model is verified by simulation and experiment. The model can provide reference for the condition monitoring and fault diagnosis of the multistage gearbox.关键词：Multistage transmission gearbox;Vibration signal;Transmission path;Frequency characteristics
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发布时间：2023-02-25 - 摘要：The rotating arm bearing is a key component of RV reducers, and its dynamic parameters directly affect the overall performance of RV reducers. Thus, taking the rotating arm bearing of RV reducers as the research object and considering the geometric parameters of the rotating arm bearing and the change of physical parameters under the working condition, a dynamic calculation model of the rotating arm bearing is established. The relationship between the bearing clearance, oil film thickness, temperature rise and the synthetic clearance of the rotating arm bearing is analyzed. The influence of the bearing clearance on the time-varying support stiffness of the rotating arm bearing under different working conditions is obtained by numerical calculation. With the decrease of the synthetic clearance, the radial support stiffness of the bearing tends to be stable. The results show that when considering the synthetic clearance of the rotating arm bearing, the radial support stiffness decreases by 9.7%, so the influence of the synthetic clearance of the rotating arm bearing on the dynamic performance of the system cannot be ignored.关键词：RV reducer;Rotating arm bearing;Synthetic clearance;Dynamic parameter
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发布时间：2023-02-25 - 摘要：Due to the large scale of AT planetary gear trains (PGTs) schemes with 4-5 degrees of freedom, the optimization time is too long. In order to be qualified for large-scale AT structural schemes synthesis, a link synthesis and isomorphism identification method based on string encoding is proposed. The characters of the links are defined according to each link type of the PGT, and the AT structure is converted into a string. By analyzing the characteristics of the brake links and interconnection links in the planetary gear set string, and using the combination principle to design a reasonable string synthesis algorithm, the isomorphism identification of the PGTs and the AT structures are realized respectively. During the synthesis of the AT structures, the PGT strings and AT structure strings that do not satisfy the link constraints are eliminated separately. The correctness and efficiency of the method are verified by five examples.关键词：Planetary gear trains;Multi degree of freedom (Multi-DOF);Structural synthesis;Isomorphism identification;String encoding
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发布时间：2023-02-25
Theory·Research
- 摘要：The aircraft cabin door is a passage channel of the cabin. The center line of the fuselage guide groove shall coincide with the movement track of the guide wheel at the end of the lifting mechanism, ensuring the reliable opening/locking of the cabin door. Based on the ordered single open chain method, the trajectory synthesis kinematic equations of two single open chain units of the lifting mechanism are established; the variables of the equations are grouped into homogeneous groups and the Bezout number is only 320, which reduce the homotopy tracking path; by constructing the initial equations and solving the homotopy equations, six sets of non-negative real number configuration solutions of rod length are obtained, and the corresponding configuration of single open chain element combination is drawn. Based on the motion space of the mechanism and the force transmission efficiency of the lifting mechanism, the door lifting mechanism to realize the movement of the aircraft door according to the desired trajectory is obtained.关键词：Aircraft cabin door;Lifting mechanism;Trajectory synthesis;Homotopy equations;Mechanism configuration
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发布时间：2023-02-25 - 摘要：Aiming at the weak stiffness of the series support mechanism of the partial-face boring machine, poor adaptability of the non-circular TBM section, and difficulties in dealing with the blind area of excavation, a partial-face TBM propulsion mechanism based on the 6-SPS parallel mechanism is designed, and a stiffness prediction model establishment method considering the local flexibility of the platform is proposed. Firstly, the geological conditions is selected, the propulsion reaction force is calculated according to the total thrust prediction model, and the propulsion mechanism is designed. On the basis of inverse kinematics; the rectangular coordinate boundary search method is used to calculate the position workspace of the mechanism. Then, by deriving the micro-displacement mapping between branch chain and the platform, the branch chain is considered, the gravity of the moving platform is regarded as an external load, and the finite element software is used to identify the flexibility coefficient at the contact point between the platform and the branch chain; a semi-analytical static stiffness model of the propulsion mechanism is established, which is verified by the finite element software. Finally, the influence of the local flexibility of the platform on the stiffness performance is compared and analyzed, and the results show that the stiffness model considering the local flexibility of the platform is more accurate. This study provides a theoretical basis for the design and development of the partial-face TBM propulsion mechanism.关键词：Partial-face TBM;Parallel mechanism;Workspace;Stiffness performance
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发布时间：2023-02-25 - 摘要：The ideal tooth surface in the meshing process of helical gears is an involute helical surface, but in the actual service process, there is a certain deviation between the actual tooth surface and the ideal tooth surface due to the influence of gear load, thermal deformation and support deformation. The tooth surface modification method is usually used to reduce the tooth surface eccentric load and vibration caused by position deviation. The existing modification methods often use the formula method considering the size of the load to calculate the modification amount. Although it can improve the transmission performance to a certain extent, there is still the problem of low design accuracy. Thus, a topological modification tooth surface design method based on the time-varying meshing process of gears is proposed to improve the meshing performance of gear pair transmission. Firstly, Ishikawa formula is improved by dividing the tooth surface along the contact trace of helical gears, and the time-varying stiffness model of helical gear pair tooth surface is established; then, the six-degree-of-freedom dynamic equation is established according to the actual meshing process of the gear pair; finally, according to the comprehensive deformation of the tooth surface calculated by the dynamic equation, the topological modification of the compensated tooth surface is designed, and the dynamic simulation is carried out. Through the simulation comparison with the modified gear designed by the traditional formula method, the effectiveness of the proposed method is verified.关键词：Time-varying meshing stiffness;Topological modification;Gear dynamics
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发布时间：2023-02-25 - 摘要：The rope rail conveyor has certain advantages over the belt conveyor in long-distance transportation, but the antiskid problem of its driving system has not been paid attention to. Combined with the structure of the driving wheel and transmission mode, an antiskid meshing pair is designed. Based on kinematics and high degree meshing contact theory, the load-bearing curve of a second-order contact antiskid meshing pair meeting the conditions of non-interference and strength, and the overall structure are designed. The second-order contact antiskid meshing pair and line contact antiskid meshing pair are modeled and simulated, and the sliding condition of the second-order contact antiskid meshing pair is tested by a single factor. The results show that the stress of the second-order contact antiskid meshing pair is more uniform than that of the line contact antiskid meshing pair; the curvature radius and height of antiskid bump of the antiskid meshing pair shall be smaller, and the width shall be larger.关键词：Rope rail conveyor;Antiskid meshing pair;Geometric design;High degree meshing contact theory;Simulation analysis
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发布时间：2023-02-25 - 摘要：Aiming at the problems of high labor intensity and low efficiency in manually collecting camellia pollen, a camellia pollen picking robot is designed based on the growth characteristics of camellia flower. Taking the camellia oleifera pollen picking manipulator as the research object, the D-H method is used to model and analyze its forward and inverse kinematics. In the Matlab software environment, the Monte Carlo method is used to solve the workspace of the end claw, and the point cloud image of the manipulator end workspace is obtained. The simulation data shows that the designed manipulator can well meet the requirements of camellia oleifera pollen picking. Due to the low efficiency and unstable operation of traditional robot trajectory planning, an improved particle swarm optimization (IPSO) algorithm is proposed to optimize the trajectory of camellia pollen picking manipulator. This method takes time as the fitness function and effectively combines 5-5-5 polynomial interpolation function with IPSO algorithm. The comparison between traditional genetic algorithm (SGA) and traditional particle swarm optimization (SPSO) shows that the IPSO algorithm can be better applied to the time optimal trajectory planning of camellia oleifera pollen picking manipulators.关键词：Camellia oleifera pollen picking robot;D-H method;Particle swarm optimization algorithm;5-5-5 polynomial;Trajectory planning
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发布时间：2023-02-25 - 摘要：The trajectory planning and control of the manipulator are based on forward kinematics analysis. At present, the analytical method mainly used is the D-H parameter method. This study proposes a screw theory method which is faster and simpler in terms of calculation than the D-H method. The kinematics modeling and forward kinematics equation of dual-arm operating system are established by product of exponentials formula. Simpack software is used to simulate and analyze the dual-arm operating system. The correctness of the forward kinematics model established by screw theory is verified by comparing the simulation results with the results obtained by the forward kinematics equation. Matlab software is used to analyze the workspace, and the workspace of the dual-arm operating system is obtained by comparing the workspace cloud map.关键词：Dual-arm operating system;Screw theory;Product of exponentials formula;Forward kinematics;Workspace
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发布时间：2023-02-25 - 摘要：In order to realize the variable clearance characteristic, the gear sector on the pitman arm shaft in recirculating ball steering gears is usually set with eccentricity. This eccentric gear sector is also an important component to realize the variable ratio of steering gears. Because of the eccentricity of the gear sector, the output ratio curve of steering gears will be affected, especially the variable ratio curve, and variation will occur. The coordinate system is established based on the geometric center point of the gear sector and the axis point of the pitman arm shaft respectively to calculate and analyze the instantaneous change of the ratio caused by the eccentric gear sector at each corner point. It is proposed to use the expected ratio of the steering gear to subtract the instantaneous change for correction. According to the instantaneous corrected ratio, the tooth profile surface of the eccentric gear sector is designed, which can enable the steering gear to output the expected ratio curve. At the same time, a simplified method for the ration correction ratio is proposed, and the error with the expected value can be controlled within 0.3%.关键词：Recirculating ball steering gear;Eccentric gear sector;Variable ratio of steering gear;Variable clearance characteristic;Ratio of designing correction;Expecting variable ratio curve
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发布时间：2023-02-25
Design· Calculation
- 摘要：A kind of clearance elimination and vibration reduction structure of cylindrical gear slot holes is proposed. The vibration acceleration of slotted and backlash gears with different sizes is simulated using the dynamics software Adams. The vibration acceleration spectrum and power spectrum are obtained by Fourier transform and correlation power spectrum estimation method. A three-factor and three-level orthogonal test table is designed. Taking the amplitude of angular acceleration of meshing frequency as the evaluation index of orthogonal tests, the relatively optimal parameter design scheme is obtained. The effectiveness of the proposed damping structure design is verified by vibration tests. The slot structure can reduce the gear vibration acceleration by about 20%-33%, and the test results are similar to the simulation results. Under the constraint of slot relaxation, the negative backlash has an obvious inhibitory effect on the vibration.关键词：Clearance elimination damping structure;Dynamics simulation;Power spectrum;Orthogonal test;Experimental study
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发布时间：2023-02-25 - 摘要：The flow field distribution in the star herringbone gearbox lubricated by oil injection is very complex, and there are many difficulties in the flow simulation analysis. Based on the smooth particle hydrodynamics (SPH) method, the particle simulation model of the flow field in the star herringbone gearbox with oil injection lubrication is established, and the oil-gas two-phase distribution characteristics at different cross-section positions in the gearbox are obtained. The oil-liquid distribution and velocity distribution of flow field under different gear speeds and oil injection speeds are compared and analyzed. The results show that the oil flow field distribution is obviously different at different cross-section positions in the gear shaft direction, the oil flow in the middle cross-section position of the gearbox is the largest, and the local eddy current phenomenon occurs in the area between the solar wheel, planetary wheel and oil injection port. The gear speed and oil injection speed have great influence on the oil distribution in the gearbox.关键词：Star herringbone gearbox;Oil injection lubrication;Smooth particle hydrodynamics;Flow field analysis
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发布时间：2023-02-25 - 摘要：This study analyzes the transmission principle and structural characteristics of a high-speed-ratio compound gear with small tooth difference. On this basis, the finite element meshing characteristic analysis model of the above gear transmission device is established. The model considers the coupling deformation of 3-stage transmission, the specific structure of the cycloid gear, the output disc, the planet carrier and the case. The stress of each key component and the transmission error of the whole machine are simulated and analyzed, and the dynamic process of the multi-tooth meshing of the pin-cycloid transmission is discussed in detail. The results show that during the operation of the reducer, the stress fluctuation range of each component is small, and they are all far below the yield limit of their materials. The two cycloidal gears always bear the load through a rigid zone and a flexible zone simultaneously. The teeth of the rigid zone are the main bearing zone, and the teeth of the flexible zone are less stressed. The total number of meshing gear teeth of the two cycloidal gears is 9-11. The transmission error curve is stable and periodic, without noticeable long waves, and the peak-to-peak value of the transmission error of the whole machine is 46.719 5″. This research provides a theoretical basis for the optimal design of dynamic characteristics and meshing characteristics of the high-speed-ratio compound gear with small tooth difference.关键词：Small tooth difference;Pin-cycloid transmission;Meshing characteristics;Transmission error;Finite element method
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发布时间：2023-02-25 - 摘要：The multi-body contact model and dynamics model for flexible bearings are established based on the Ansys Workbench software, and the stress and deformation of flexible bearings are analyzed under the conditions of assembly stress and external load. The fatigue life of the inner and outer rings of flexible bearings is analyzed based on the nCode-Designlife software. In addition, orthogonal experiments are designed to explore the relationship between mechanical characteristics and three design parameters of flexible bearings. The results show that the fatigue weak area of the inner ring is located at the outer face of the long shaft, while the outer ring is located at the contact area between the ball and the channel at the long shaft; the maximum radial deformation has a significant effect on the stress of the inner and outer rings. Reducing radial deformation in a certain range and controlling the number of balls are helpful to reduce stress and improve life, which provides reference for the design of flexible bearings.关键词：Flexible bearing;Multi-body contact model;Fatigue life;Mechanical characteristics;Orthogonal experimental design
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发布时间：2023-02-25 - 摘要：In the process of large module gear hobbing of high-order modification tooth profile, the cutting edge curve is different according to the variation of rake angle, which has a great influence on tooth profile accuracy. Thus the 2-degree envelope method is applied to the gear hobbing process to obtain the hobbing contact trace between the tooth surface and the base worm of the hobbing cutter. The cutting edge curve is calculated based on the different rake angles of the hobbing cutter. The shape and the slope of the cutting edge are analyzed, which provides the reference for the design and measurement of hobbing cutter edge. In the end, a modified gear profile is hobbed and measured to verify the above design method.关键词：Large module;Profile modification;Hob cutter rake angle;Envelope;Cutting edge curve
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发布时间：2023-02-25
Test·Analysis
- 摘要：As the core components of metro vehicles, the reliability of metro gearboxes determines the reliability of the whole train. The operation process of subway includes start-up, continuity, high-speed and short circuit conditions. In short circuit conditions, the box body has the maximum stress and the lowest reliability. According to the test requirements of national standard “Railway applications—Rolling stock equipment—Shock and vibration tests”, the reliability analysis of metro gearboxes in abnormal condition (condition 1) and short circuit condition (condition 2) occurring in actual operation is carried out. Thus, the influence of casting tolerance, material parameters and input torque uncertainties on the maximum equivalent stress and maximum deformation of the box body are considered. The CCD experimental design method is used to calculate the sample and fit the response surface, and the static reliability is obtained combined with Monte Carlo sampling. On this basis, combined with the order statistic theory, the reliability of the box with the number of loads is obtained. The results show that the reliability of the box body is still very high and meets the design requirements after 100 thousand loads under the two working conditions. According to the time-dependent reliability diagram, although the mean value of stress in working condition 2 is smaller than that in working condition 1, the variance is larger than that in working condition 1, which leads to the reliability decline rate of working condition 2 is greater than that in working condition 1. Therefore, the dispersion of stress should be reduced to increase the reliability during operation.关键词：Monte carlo;Response surface;Order statistic;Time-dependent reliability
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发布时间：2023-02-25 - 摘要：Aiming at the problem that the conventional oil-immersed lubrication condition cannot truly reflect the operating environment of gear oil-injection lubrication, referring to the FZG A/8.3/90 gear scuffing load capacity test method and using oil injection lubrication gear fatigue test bench, the scuffing load capacity test of 18CrNiMo7-6 carburized gears is carried out based on oil injection lubrication condition with 4106 aviation lubricant. Based on the two-parameter Weibull distribution theory, the gear scuffing performance is evaluated under different reliabilities. Furthermore, based on Python language and database SQLite, a gear scuffing test data management system is developed to realize the effective management and efficient utilization of scuffing test data. The results show that under the same working and process condition, the gear scuffing failure FZG load level has 2-3 degree dispersity. Based on GB/Z 6413.1—2003 flash temperature method, it is found that under the condition of 4106 aviation lubricant injection lubrication, for 50%, 90% and 99% reliability, the gear scuffing temperature of shot peening process is 212.55 ℃, 183.22 ℃ and 152.24 ℃ respectively, improving by 1.51%, 7.31%, 14.99% respectively compared with the grinding process state. The developed data management system realizes scuffing test data flow management. Through the fitting function of two-parameter Weibull distribution, the gear scuffing temperature under different reliability can be obtained, which provides an efficient tool for the evaluation of gear scuffing load capacity.关键词：Carburized gear;Aviation lubricant;Scuffing test;Weibull distribution;Data management system
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发布时间：2023-02-25 - 摘要：The characteristics of non-smoothness and uncertainty of gearbox fault vibration signal lead to the low accuracy of gearbox fault diagnosis. To address this problem, a gearbox fault diagnosis method based on local mean decomposition (LMD) cloud model feature extraction combined with particle swarm optimization (PSO) kernel extreme learning machine (KELM) is proposed. Firstly, the fault vibration signal is decomposed by LMD to obtain several PF components, and the PF components with higher correlation are screened out using the correlation coefficient principle. Secondly, the screened PF components are input into the cloud model, and the feature vectors are extracted using the inverse cloud generator and input into PSO-KELM for fault diagnosis. Finally, the performance of the method is analyzed using the measured data of the QPZZ-Ⅱ test-bed gearbox. The results show that the recognition accuracy of the method is 97.65%, and compared with various methods this method has the best recognition performance.关键词：Gearbox;Fault diagnosis;Local mean decomposition;Cloud model;Particle swarm optimization kernel extreme learning machine
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发布时间：2023-02-25 - 摘要：In order to solve the problems in the existing gear pump with another trapped oil buffer groove, an external gear pump with axial stepped-gear structure for realizing two different contact ratios is proposed; the trapped-oil load flow from the gear section with a contact ratio greater than 1 is balanced by the trapped-oil relief flow from the gear section with a contact ratio equal to 1, and the trapped-oil phenomenon will be fully alleviated; then the relief gap from the gear section with a contact ratio equal to 1 is calculated by 3D feature method, and the trapped-oil pressure formula is derived by making the trapped-oil load flow equal to the trapped-oil relief flow; finally, an example is demonstrated and validated by PumpLinx software. The results show that the flexible adjustment of the two section gear width ratio makes up for the shortage of the non-adjustable buffer capacity of the existing buffer groove, and has strong applicability to working conditions; the trapped oil pressure formula considering cavitation pressure corrects the negative pressure when the trapped oil expands, which is applicable to the trapped oil pressure calculation under any structure. It is concluded that the pump can effectively alleviate the trapped-oil phenomenon, doesn't need another buffer groove, has simple structure and is convenient for processing.关键词：Gear pump;Trapped-oil phenomenon;Width-ratio of stepped-gear;Trapped-oil load flow;Trapped-oil relief flow;Trapped-oil pressure
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发布时间：2023-02-25 - 摘要：Tooth break is a common fault which always occurs in the planetary gearboxes, and when it occurs, due to the influence of transmission path, the vibration signal collected by the sensor becomes complicated, which brings difficulties to fault diagnosis. Thus, in order to study the influence of transmission path on spectrum structure of planetary gearboxes with tooth break fault, the rigid-flexible coupling models with no fault, sun gear tooth break fault, planet gear tooth break fault and ring gear tooth break fault of planetary gearboxes are established on Adams, and the vibration signals of the box body are extracted and analyzed by simulation. The simulation results show that: in the time-domain, the change of the path will have an obvious amplitude modulation on the vibration signal which is measured at a fixed point of the box. What's more, in the spectrum diagram, the two sides of the meshing frequency will also produce side bands composed of different frequencies.This study can provide basis and reference for fault diagnosis of planetary gearboxes in the future.关键词：Planetary gearbox;Transmission path;Rigid-flexible coupling model;Tooth break fault;Simulation analysis
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发布时间：2023-02-25
Development·Application
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