最新刊期
期 9 ， 2022
- 摘要：Pure electric vehicle two-gear dry dual clutch automatic transmission completes the shift through the control of two clutches engagement and separation. Since the friction coefficient of clutch changes with temperature， the parameter adaptive method is used to estimate the friction coefficient online in real time. According to the shifting dynamics model， a backstepping controller based on the extended state observer is designed， and the shifting process is transformed into speed tracking problem by giving the target speed of the motor and the first gear clutch disk. Simulation and hardware-in-the-loop verify that the controller can effectively ensure the shift quality of automatic transmission under the condition of external interference， and has good robustness.关键词：Dual clutch transmission;Extended state observer;Robust control;Shift quality
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发布时间：2022-09-26 - 摘要：The transmission efficiency of the reducer is the main factor affecting the efficiency of the whole transmission system. Establishing the transmission efficiency model and analyzing the influencing factors on transmission efficiency are of great significance to improve the transmission efficiency of electric vehicles. According to the characteristics of electric vehicle reducer， four transmission efficiency loss factors including gear meshing loss， bearing loss， oil stirring wind resistance loss and oil seal loss are analyzed and the transmission efficiency calculation model is established. The lubricant， speed and torque are developed. The effects of oil， speed and torque on the transmission efficiency of single gear two-stage reducer for electric vehicles are studied theoretically. A high-speed three-axis comprehensive performance test bench is built and the orthogonal experimental research on the precision of an established model and the influencing factors of transmission efficiency are performed. The theoretical and experimental research results show that： the maximum relative error of the established model is -0.59%， which is less than that of ISO/TR 14179—1：2001 （-1.75%）； as the speed increases， the transmission efficiency gradually decreases； the speed has the greatest influence on transmission efficiency； as the torque increases， the transmission efficiency gradually increases； the lower the lubricating oil temperature is， the lower the transmission efficiency becomes； the influence of the lubricating oil grade on the transmission efficiency is not obvious； the lower the lubricating oil viscosity is， the higher the transmission efficiency becomes and the oil has the least influence on transmission efficiency.关键词：Electric vehicle;Reducer;Transmission efficiency;Orthogonal test
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发布时间：2022-09-26 -
Study on Electromechanical Coupling Dynamic Characteristics of Robot Joint Servo Transmission System
摘要：At present， the robot joint servo is developing towards miniaturization and integration. In view of the high operation accuracy requirements of intelligent robots， it is very necessary to study the dynamic characteristics of the typical motor driven gear electromechanical coupling system of robot joint servo under different working conditions. According to the time-varying meshing characteristics of multistage gear system and the dynamic characteristics of brushless motor， a dynamic model of multistage gear system and brushless motor is established， and an electromechanical coupling dynamic model of robot joint servo transmission system is established. Based on this model， the free torsional vibration characteristics and modal energy of the system are analyzed， and the dynamic response characteristics of the robot joint servo transmission system under steady-state and impact load conditions are further studied. The results show that there is an electromechanical coupling effect between the multistage gear system and the motor. After the system is impacted， the meshing force of the gear pair and the torsional vibration of the gear become violent and then tend to become stable.关键词：Robot joint;Micro servo;Transmission system;Electromechanical coupling;Dynamic characteristics- 3
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发布时间：2022-09-26 - 摘要：The discharging work of fermented grains is a necessary process in the production of wine， the difficulties in automating the work with mechanical arms include the long and narrow working space and the loose form of fermented wine which tends to fall. The working space is long and narrow， and the end of the grab needs to be grabbed multiple times. Being easy to spill， it is necessary to ensure the tightness of the grasping end and the controllability of the posture of the grasping end during the movement after grasping， etc. Aiming at the problem that multiple grabbing is required for the discharging work， a joint division strategy is proposed. According to the importance of the joints， the joint types are divided and the appropriate number of trajectory planning algorithms is selected. On the premise of satisfying the operating performance of the manipulator， the computational difficulty of each grasping planning is reduced. For the tightness requirements of the grab end， a grasping end is designed to ensure that the bottom is closed. Aiming at the requirement of attitude controllability during operation， an attitude adjustment model is established and the controllability of the end posture of the manipulator in joint space based motion planning is improved.关键词：Fermented grains fetching;Trajectory planning;Joint space;Attitude adjustment
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发布时间：2022-09-26 - 摘要：Based on the meshing principle of the roller enveloped end face worm drive pair， the influence of the center distance， the roller radius， the throat coefficient， and the worm gear diameter are considered comprehensively. According to the elastohydrodynamic lubrication theory， the Newton iteration method is used in Matlab. The Newton-Raphson method is used to solve its numerical calculation， the conjugate teeth of the new transmission pair are studied， and the analysis of the line contact between the conjugate teeth is completed. The schematic diagram of lubricating oil film pressure and oil film thickness under the change of geometric parameters and roughness amplitude of the conjugate tooth surface of the transmission pair is given， and the analysis is completed. The results show that the performance of the transmission pair is good. The important parameters affecting the lubrication are the roller radius and the meshing position， while the throat coefficient and the worm gear diameter have little effect on the lubrication characteristics. Full-film lubrication can be generated between the conjugated tooth surfaces to avoid direct contact， reduce wear and oil temperature， and improve transmission efficiency and anti-glue ability at the same time. Therefore， the necessary theory and application value are given for the development of the new transmission pair.关键词：Roller;Roughness;Elastohydrodynamic lubrication;Oil film pressure;Oil film thickness
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发布时间：2022-09-26 - 摘要：In order to improve the gear machining accuracy， a modeling method of mapping relationship between machine tool errors and gear errors is proposed. According to the gear meshing principle and spatial envelope milling theory， a homogeneous coordinate transformation matrix including machine tool error is established， and the corresponding gear end profile is solved. Through the error sensitivity analysis， it is found that the tooth profile and tooth direction error are in positive proportion to the rotation angle errors of Y-axis and Z-axis， and meet the superposition principle. According to the error detection results of the workpiece， the error compensation components of each axis are calculated. The experimental results show that the tooth profile error is improved from grade 7 accuracy （ISO 1328-1:2013） to grade 4 accuracy， and the tooth direction error is improved from grade 7 to grade 6.关键词：Envelope milling tooth;Machining error;Tooth deviation
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发布时间：2022-09-26 - 摘要：A novel plane symmetric 2RUPaR-2RRU parallel mechanism with two translational and two rotational degrees of freedom is proposed， and it is can be used as the main body structure of a vibrating screen. The screw theory is applied to analyze its degrees of freedom and to identify the motion characteristics. The displacement analysis model is established to obtain the analytical expressions of inverse displacement solutions to this mechanism. This study analyzes the velocity of the mechanism by means of the vector method and derives the input and output Jacobian matrices. On this basis， the possible singular configurations of the mechanism are investigated. The input and output transmission indices are used to evaluate the motion and force transmission performances of the mechanism. Furthermore， the definition， the numerical calculation method of the effective transmission orientation workspace and the effective transmission positional workspace （ETPW） are introduced. A constrained optimization model is constructed to formulate the design problem of dimensional parameters on the maximizing ETPW， and the differential evolutionary algorithm is employed to solve this problem. A case of dimensional optimization design of the mechanism is given to show that the presented model and algorithm are feasible and effective. The ETPW of the mechanism obtained by optimization design is better than that obtained by the experience design.关键词：Parallel mechanism;Displacement analysis;Singular configuration;Performance index;Dimensional parameters optimization
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发布时间：2022-09-26
Theory·Reserach
- 摘要：In order to accurately analyze the influence of the kinematic pair clearance on the mechanism dynamic characteristics， a nonlinear stiffness coefficient is introduced based on the Gonthier contact force model， and an improved Gonthier model is obtained， which can more accurately describe the elastic force in the kinematic pair. The system dynamic equation of planar four-bar linkage with two-state clearance is established using Newton Euler equation， and the correctness of the clearance model is verified by Adams. The influence of different clearance， rotation speed and friction coefficient on the acceleration of the rocker is analyzed， and the contact and free states of the inner shaft of the kinematic pair are studied. The results show that the shaft has three states of collision， contact and freedom under certain conditions. After the system becomes stable， the shaft is always in contact with the kinematic pair， which indicates that the motion of the shaft in the kinematic pair is not random collision. The driving force of the mechanism is mainly transmitted by the contact force generated by the deformation of the contact point， rather than the collision force between the shaft and the bearing. The results can predict the position of the clearance， and have important theoretical value for restraining the vibration and wear of the mechanism caused by the clearance.关键词：Contact force model;Clearance of kinematic pair;Collision;Dynamics
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发布时间：2022-09-26 - 摘要：In order to meet the needs of better completing tasks in a variety of terrains， a quadruped multi-mode mobile robot with walking mode， obstacle crossing mode and semi folding mode is designed， which can change the motion mode according to different terrains. When the robot is in walking mode， it can walk on ordinary flat road； when in obstacle crossing mode， you can climb over obstacles by raising the height of your legs； when in the semi folding mode， the wheelbase can be shortened through the folding of the platform for narrow road conditions. The freedom of the platform and leg of the mechanism is analyzed using the screw theory； the forward kinematic equation of the quadruped robot is solved by D-H parameter method； three modes of the robot are simulated by Adams simulation software. The results show that the robot can complete the tasks of walking， obstacle crossing and the half folding platform can pass through a certain width channel， which realize the multi motion mode of the robot.关键词：Multi-mode;Degree of freedom;Mobile robot;Simulation
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发布时间：2022-09-26 - 摘要：In the inner box forming station of the high-end carton， an eight-bar mechanism for bending rectangular cardboard strips is designed， and a theoretical analysis and a simulation are carried out to verify whether it can achieve double-sided bending during the carton forming process. Based on the kinematic and dynamic principles of the plane linkage mechanism， the mechanism is analyzed， and the kinematic model and dynamic model in the mechanism are obtained； combined with the actual working conditions， the mechanism is simulated by Adams software. The displacement， velocity and acceleration equations of the key components and the dynamic statics equations of the components， as well as the displacement， velocity， acceleration and the force curves of the key components in the ideal state and under the condition of a rotation pair with clearance are obtained. The curve analysis conclusions obtained by the simulation meet the design requirements and provide a certain reference， thus verifying the certainty of the eight-bar bending mechanism.关键词：Eight-bar mechanism;Kinematics;Dynamics;Adams
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发布时间：2022-09-26 - 摘要：In order to improve the flexibility of cooperative robots to avoid real-time obstacles in target space， a comprehensive optimization index is proposed， and the size of its key members is optimized. Firstly， the kinematics of the optimized cooperative robot is analyzed， the mathematical model is established， and the reachable workspace is solved； then the target space is selected with the robot's task path as the reference， the flexibility comprehensive evaluation index is defined as the optimization goal， and the particle swarm algorithm is used to optimize the key size parameters； finally， the distribution of flexible working points in the task space before and after optimization is compared. The results show the proportion of flexible working points of the optimized robot increases significantly， which verifies the effectiveness of the optimized design method.关键词：Cooperative robot;Flexibility;Size optimization;Particle swarm algorithm
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发布时间：2022-09-26 - 摘要：Based on the study of the ankle rehabilitation mechanism， a 3-DOF rigid flexible coupling parallel ankle rehabilitation mechanism is proposed， which solves the problems of poor compliance and large inertial impact existing in the present rehabilitation institutions. The forward and inverse kinematics solutions of the parallel rehabilitation mechanism are solved， and the correctness of the calculation results is verified. Furthermore， the Jacobian matrix of the mechanism is solved， the relationship between the rope speed change of the mechanism and the speed change of the moving platform is analyzed， and the position change and speed change of the mechanism are simulated and analyzed. The results show that the designed mechanism moves smoothly， can meet the requirements of ankle rehabilitation training， and also provides a theoretical basis for the research and development of the follow-up control system.关键词：Ankle rehabilitation;Parallel mechanism;Kinematics;Rope driven
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发布时间：2022-09-26 - 摘要：The climbing pinion is an important part of the jacking system of a self-elevating platform. The key of structural design of climbing pinions is gear parameter selection and tooth shape design. Gear parameters such as large modulus， small teeth， large pressure angle and positive modification coefficient are usually selected. In tooth profile design， the influence of contact ratio and normal backlash on the normal meshing operation of climbing pinions and leg racks should be considered so as to meet the basic requirements of continuous operation of pinions and racks. After the tooth profile design is completed， three methods are used to analyze the tooth strength of climbing pinions， and a comparison is conducted. It is pointed out that the finite element method can be used as an effective method for checking the strength of large module gears.关键词：Climbing pinion;Tooth profile design;Contact ratio;Normal backlash;Strength analysis
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发布时间：2022-09-26
Design· Calculation
- 摘要：In order to improve the sealing performance of the high-speed gearbox sealing device， this study analyzes the non-contact labyrinth sealing of the high-speed gear transmission commonly used in petroleum， chemical and other fields. By establishing a numerical calculation model， the influence of factors such as the number of sealing teeth sealing differential pressure， oil-air mixture concentration，and position of oil slinger on the leakage of oil return ports and oil leakage ports of each sealing cavity is analyzed， which has guiding significance for the design of non-contact labyrinth sealing for high-speed gearboxes.关键词：Non-contact labyrinth sealing;Number of sealing teeth;Sealing differential pressure;Mixture concentration;Position of oil slinger
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发布时间：2022-09-26 - 摘要：A herringbone gear transmission system with star gear train is taken as the research object. In order to find the cause of system resonance， a modal-analyzing 3D finite element model is established to analyze the modal characteristics of herringbone gear transmission system of star gear train. Firstly， according to the experimental results of star gear train， the resonance caused by rotational frequency excitation and meshing frequency excitation is the main part of the vibration amplitude of the system. According to this phenomenon， a 3D finite element model is established based on the meshing stiffness matrix to analyze the modal characteristics of the system. The results show that the rotational frequency resonance mode and meshing frequency resonance mode obtained by simulation are uniquely corresponding to the experiment data， and the meshing frequency resonance mode is mainly represented by the fifth pitch diameter vibration mode of the inner gear and the torsional vibration mode of the coupled gear pair. This finite element model provides a valuable reference method for resonance prediction and resonance cause analysis of herringbone gear transmission system with star gear train.关键词：Planetary gear system;Herringbone gear;3D finite element model;Modal characteristics
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发布时间：2022-09-26 - 摘要：Gear noise has become an important index to check the gear processing quality， and it is also a common problem in gear application. In order to effectively solve the noise problem of gears in use， a method which can appropriately increase the helix angle of helical gears to reduce the gear meshing noise is adopted. Taking the first stage motor shaft and helical gears of the door controlled reducer as the analysis object， the model is established and simplified by three-dimensional software， and the sound pressure level of 19°~23° helical angle gear meshing is simulated using the acoustic module in Comsol Multiphysics software； the meshing sound pressure levels of 19°~23° helical angle gears under no-load and loaded conditions are measured with UT353 decibel instrument from close to and 1 m away. The test results show that by improving the helix angle， the reducer noise is optimized by 2~6 dB， and the optimization effect under loaded conditions is better than that under no-load condition. Finally， the stability of mass production of motor shafts and gears is ensured by limiting the use times of cutting tools.关键词：Gear;Helix angle;Noise
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发布时间：2022-09-26 - 摘要：Differential is one of the important parts of automobile transmission system. The analysis of its fault mode and the control of it have always been the focus in the automotive industry. Thus， an analysis and investigation process of the abnormal noise problem is systematically expounded based on a CVT sedan low-speed steering condition. The reproduction of the abnormal noise problem is realized through the differential performance bench. Combined with the disassembly analysis of the fault parts， the potential mechanism and solution of differential abnormal sound problem are proposed. Through the optimization of planetary shaft positioning assembly method and processing technology， the abnormal sound of the differential of the vehicle is accurately and effectively eliminated, which has certain engineering guidance value for the solution and investigation of NVH（Noise， Vibration， Harshness） and abnormal sound problems of the transmission system under transient working conditions of the vehicle.关键词：Differential;Abnormal noise;Planetary gear;Axle shaft gear;Planetary gear shaft
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发布时间：2022-09-26 - 摘要：As rack-and-pinion is the key driving part of rack railway， mastering the wear condition and law of the gear rack pair tooth surface during the operation of the gear rail vehicle is conducive to ensuring the smooth and safe operation of the gear rail vehicle. For this purpose， the process of variable mounting distance transmission of rack-and-pinion in the form of Strub rack railway is analyzed， and the key parameters of variable mounting distance transmission are calculated accordingly； by introducing the mounting distance step and slip distance step， the continuous transmission process of rack and pinion pair with variable mounting distance is discretized， and the mathematical model of wear volume and wear depth of tooth surface of variable installation distance rack-and-pinion is constructed； in order to verify the accuracy of the mathematical model， rack wear test is carried out； combined with concrete examples， the influence of different parameters on tooth surface wear is analyzed to obtain the key factors affecting the wear of tooth surface and their influencing rules. The results show that the measured value of tooth surface wear depth is consistent with the theoretical value of the model， which verifies the accuracy of the model. As the wear at the top of the rack teeth is the most serious， choosing the gear with larger displacement coefficient is conducive to reducing the wear of the rack tooth surface.关键词：Rack railway;Variable mounting distance;Rack-and-pinion;Wear model
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发布时间：2022-09-26 - 摘要：Parallel mechanism has the advantages of large stiffness，fast response and high precision， which is suitable for suspension field. A new type of parallel mechanism for automobile multi-link suspension is proposed， the kinematic model of the mechanism is established， combined with the screw theory， the spatial motion characteristics of the mechanism are analyzed through the pose parameters， and the screw amount representing the motion is approximately even. Combined with the kinematics concept of the automobile suspension， the wheel positioning parameters are given using the homogeneous transformation matrix. The instantaneous kinematic analysis method of the suspension is proposed using the screw theory.关键词：Parallel mechanism;Multi-link suspension;Pose parameters;Kinematics
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发布时间：2022-09-26 - 摘要：The Parasitic Motion and workspace of a new 2-PRU/PUU parallel mechanism are analyzed. Firstly， the degree of freedom of the mechanism is analyzed according to the spiral theory， and then the correctness of the results is judged by the modified Grübler-Kutzbach formula. Secondly， by establishing the kinematics mathematical model of 2-PRU/PUU parallel mechanism， the mathematical relationship between the Parasitic Motion and the position and pose of the moving platform is deduced. On this basis， the inverse position solution of the mechanism is calculated using the three-dimensional space coordinate vector method. Finally， the limit boundary search method is used to calculate the workspace in Matlab software， and Adams software is used to simulate the moving platform centroid motion parameters of 2-PRU/PUU parallel mechanism. The research provides theoretical and data support for scale synthesis， error analysis and practical engineering application of the mechanism.关键词：2-PRU/PUU parallel mechanism;Spiral theory;Parasitic motion;Position inverse;Workspace
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发布时间：2022-09-26
Test·Analysis
- 摘要：Based on the motion mechanism and biomechanics of human lower limb joints， the structure， function and motion law of human bones and joints are introduced. A simplified mathematical model of human lower limbs is established， and the posture coordinate equations of hip， knee and ankle joints are obtained. UG is used to establish the model； Adams and OpenSim are used to simulate the test； the lower limb joint angle， step height and step length curves are obtained. With the help of Xsens DOT commercial wearable sensor， the experimental results show that the simulation results are similar to the experimental results， and the joint angle， step height and step length curves are consistent with the actual human walking test results. The results show that the simplified model and simulation test are reasonable and effective and they are in line with the walking process of human lower limbs. It provides a simplified research method for sports testing， rehabilitation medicine and exoskeleton design.关键词：Lower limb joints;Attitude equation;Simulation test;Experimental test
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发布时间：2022-09-26 - 摘要：Aiming at the problem that the vibration signal of planetary gearboxes has strong non-stationary characteristics， few fault samples and the dependence of traditional deep learning on data， an intelligent diagnosis method for planetary gearboxes based on continuous wavelet transform（CWT） and model agnostic meta learning（MAML） is proposed. First， the vibration signal of the planetary gearbox is converted into a time-frequency image through CWT， which effectively expresses the non-stationary characteristics of the planetary gearbox； then， the ability of “learning to learn” of MAML is used to train small samples of time-frequency images， and finally the “unseen” faults of planetary gearboxes are tested. Through fault diagnosis experiments of planetary gearboxes under different sample sizes， working conditions and noise environments， a conclusion is drawn that the proposed method has higher recognition accuracy， generalization and robustness compared with other methods.关键词：Planetary gearboxes;Continuous wavelet transform;Model agnostic meta learning;Few shot learning;Fault diagnosis
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发布时间：2022-09-26 - 摘要：The effects of induction quenching with different current frequency on the surface hardness， tooth root hardness， tooth core hardness， hardness gradient and metallography of gear shafts are analyzed and discussed by carburizing， tempering and induction quenching experiments of heavy-duty gear shafts. The results show that carburizing， quenching and tempering and induction quenching of 18Cr2Ni4WA steel gear shafts can effectively improve the surface hardness of the workpiece to more than 58 HRC， and improve the hardness gradient value of hardened layer. Improve the metallographic structure of hardened layer， and ensure the best hardness of the tooth core， so as to increase the bending fatigue strength of gear shafts. Therefore， a heat treatment method is provided for the low carbon alloy steel gear material containing more Cr， Ni， W and Mo after carburizing， which can improve the product quality.关键词：Heavy duty gear shaft;Induction hardening;Hardness of tooth core
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发布时间：2022-09-26 - 摘要：For service robots， security reconnaissance vehicles， etc. their mobile range is large and working space is complex. The drive system is vulnerable to impact， blocking or overload due to external impact， thereby resulting in tooth fractures and large bending of support shafts. The application of micro servo drive system is greatly limited. Aiming at this problem， a clutch structure is proposed to protect miniature reducer in this study. Using the finite element method， basic parameters of the spring and the protection threshold of the clutch structure is designed. Then， the threshold is captured and verified through the clutch performance test rig. Experimental results show that the miniature reducer can realize the clutch function accurately under the overload condition， and the measured clutch protection threshold is in good agreement with the design threshold. The clutch structure can limit the maximum threshold of the gear load， enable the gears of the miniature reducer to work within the design load range and improve the working reliability of the miniature reducer.关键词：Miniature reducer;Gear transmission;Clutch structure;Overload protection;Spring
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发布时间：2022-09-26
Development·Application
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