最新刊期
卷 47 ， 期 7 ， 2023
- 摘要：In response to the problems of no suitable constraint conditions in the optimization process of tooth profile modification of cycloidal pin wheel transmission, difficulty in determining the modification amount of cycloidal gear tooth profile in reverse engineering, and the inability to obtain the meshing interval when studying the characteristics of cycloidal pin wheel transmission, research has been conducted on the method for determining the meshing intervals of cycloidal gears. Firstly, the stiffness analysis is performed to determine the main components that affect the stiffness. Then, through the contact stiffness analysis of the key components, the torsional stiffness model of the needle roller bearing, the tapered roller bearing and the meshing point of the cycloid are established respectively.On this basis, the torsional stiffness equation of the cycloid with needle roller bearings, tapered roller bearings and with the torsion angle of the whole machine as variables is deduced.Finally, according to the continuity principle of meshing points, all the meshing intervals whose sum of torsional stiffness of meshing points is approximately equal to the torsional stiffness of cycloidal wheels are calculated, and according to the principle that the initial meshing point of cycloidal wheels does not change with the increase of load, the feasible meshing intervals under different loads are finally screened. The analysis results of this method are basically consistent with the actual situation, and there is no need to disassemble the reducer, which can provide necessary reference data for the design and optimization of cycloid pin gear transmission.关键词：Cycloid pin gear transmission;Torsional stiffness;Meshing interval;Industrial robot
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发布时间：2023-08-14 - 摘要：The full tooth flank contact characteristic of the line contact spiral bevel gear transmission is sensitive to errors. To obtain the influence of error factors on transmission contact for line contact spiral bevel gears, the contact simulation analysis with error factors is carried out. Firstly, based on the cutter head approximation machining method, a tooth flank mathematical model of the line contact spiral bevel gear is developed, and the correctness of this model is verified. Then, based on this model, the influence of installation errors and pitch deviation for line contact spiral bevel gears with different accuracy levels are analyzed, and the change law of the contact stress and deformation for the mating flank are obtained. The results show that, due to error factors, the line contact spiral bevel gear transmission will produce edge contact, which is mainly shown at the top, and then at the toe, not obvious at the root and the heel. Among the various errors analyzed, the pitch deviation and the pinion axis error have the great influence on the contact stress and deformation of the tooth flank, followed by the shaft spacing error and the shaft angle error, and finally the gear axis error. The research results can provide reference for the error control and modification design of the line contact spiral bevel gear.关键词：Spiral bevel gear;Line contact;Pitch deviation;Installation error;Contact simulation
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发布时间：2023-08-14 - 摘要：To synthesize a class of 2T2R parallel mechanisms with optimal transmission and large tilting ability, a type synthesis method for parallel mechanisms is proposed by combining the screw theory and the limb construction method. Taking the 2-RPS mechanism as the basic limb, the screw theory is used to classify the constraint types of the new limb, and the limb construction criterion is given to ensure that the degrees of freedom of the parallel mechanism remain unchanged. Combined with the characteristics of motion/force transmission of the mechanism, the limb with the maximum transmission index is selected by using the screw theory, and the 2T2R parallel mechanism with the optimal transmission is synthesized. Finally, the kinematics analysis of a novel 2-RPS-UPS parallel mechanism is carried out, and the workspace of the mechanism is solved by Matlab. The results show that the synthesized parallel mechanism has optimal transmission and large tilting ability.关键词：Parallel mechanism;Type synthesis;Screw theory;Optimal transmission;Large tilting ability
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发布时间：2023-08-14 - 摘要：According to the principle of cycloid generation, the gear rotating guide bar mechanism is designed. The motion matrix equation of the mechanism is given by the method of rotation vector differentiation, and the influence of the number of cycloid lobes and the position of the rocker on the motion characteristics of the mechanism is studied. The results show that the lobe number of the hypocycloid only affects the rotating guide-bar on the angular velocity pulsation, but has little effect on the velocity pulsation. There will be two spike pulses on the angular velocity of the rotating guide-bar when the oscillating slider is located at the axisymmetric line on the sharp corner side, which however would be only one at other locations except center of the hypocycloid. The position of the rocking block only affects the phase angle of the planetary gear during uniform acceleration motion of the rotating guide rod, but it has no effect on the phase angle of the planetary gear during uniform deceleration motion.关键词：Differential of rotational vector;Hypocycloid;Rotating guide-bar mechanism;Kinematic characteristics
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发布时间：2023-08-14 - 摘要：A set of mechanism synthesis universal model is presented in this study. Given the expected straight-line and a fixed pivot, this model can solve the synthesis problem of the straight-line guide mechanism when the instant center tends to infinity in the coupler plane. In addition, mechanism synthesis formulas are derived and an example of mechanism optimization method is given. Based on the synthesis model, an infinite number of straight-line mechanism solutions that can satisfy the expected straight-line requirements are obtained. Then feasible solution regions are computed by imposing constraints. According to the design requirements, the designer can find promptly the optimal straight-line mechanism meeting constraints from an infinite number of mechanisms. The demonstration shows that this method provides a new way for straight-line mechanism synthesis with instant center at infinity, the synthesis process is simple and intuitive, and has universality. It is suitable for computer aided design of straight-line mechanism with second-order and third-order, which is beneficial to improve the design quality and compress the design cycle.关键词：Straight-line mechanism;Instant center at infinity;Mechanism synthesis;Solution region;Computer aided design
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发布时间：2023-08-14 - 摘要：The bevel gears are the core components of inter-axle differential. The reliability of the bevel gears will affect the differential function and transmission capacity between different drive axles. Focusing on improving the fatigue life of bevel gears from the point of gears' backlash control, the issue that the selection of backlash for bevel gears are ambiguous during the actual application is resolved. Adopting a modular design concept, establish a backlash control dimension chain, and propose a method of adding steps on the input shaft to accurately control the backlash of bevel gears; through the fatigue life test rig of the interaxle differential bevel gear, the optimal control range for the total backlash of the interaxle differential bevel gear is explored to be [0.30, 0.60] mm; it is known that the change in backlash has a significant impact on the contact fatigue life of bevel gears and the bending fatigue life of tooth roots, and reasonable backlash control can increase the contact fatigue life of tooth surfaces by 29%. The research provides theoretical and experimental basis for improving the fatigue life of bevel gears in the inter axle differential.关键词：Inter-axle differential;Bevel gear;Backlash control;Fatigue life;Bench test
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发布时间：2023-08-14
Theory·Research
- 摘要：To solve the problems that the conventional planetary gear wheel hub reducer has many parts, large axial dimensions and complicated installation around the wheel system when the vehicle requires a relatively large transmission， and taking the electric car as the research object, this study proposes a new type of wheel hub drive reducers based on single-stage nutating transmission, describes the working principle and transmission process, completes the structural design and transmission efficiency calculation, and establishes the virtual prototype model. The finite element analysis is carried out to discuss the location and cause of the maximum contact stress of the mechanism under a static load. The reliability and rationality of the structure are verified.关键词：Electric car;Wheel hub drive;Nutating transmission;Structural design;Finite element analysis
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发布时间：2023-08-14 - 摘要：In order to achieve accurate grasping of the target object with fewer drives, a metamorphic manipulator with single drive and multi-mode is proposed by combining metamorphic principle with the kite-straight-line mechanism. The manipulator can change its two working modes including linear parallel grasping and adaptive envelope grasping by one motor. Firstly, the equivalent mechanism of the metamorphic manipulator in different configurations is derived based on the law of minimum resistance. Variable topological structures are described using topology diagram and corresponding kinematic models of the manipulator in different configurations are established. Secondly, the relationship between the contact force of each knuckle and the input force of the manipulator is established according to the principle of virtual work. The elastic coefficient of the elastic element is optimized by analyzing the influence relationship between the elastic element and the envelope grasping stability. Finally, the correctness of the proposed static model is verified through a combination of numerical calculation and virtual simulation, which can provide reference for the design and application of this type of metamorphic manipulator.关键词：Metamorphic mechanism;Single drive;Manipulator;Kinematics;Statics
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发布时间：2023-08-14 - 摘要：According to the theory and method of topological design of the parallel mechanism (PM) based on position and orientation characteristic (POC) equations, a novel three-translation (3T) parallel mechanism for grasping is proposed. Firstly, the design process of the entire PM is described and the main topological features of the mechanism are analyzed. It is proved that the mechanism contains two sub-kinematics chains (SKCs） whose coupling degree equals 0. Secondly, according to the kinematics modeling principle for parallel mechanism based on topological features, the direct kinematics problem (DKP) and inverse kinematics problem (IKP) of the mechanism are solved according to the order of SKC. Then, according to the singularity analysis method based on SKC theory, the first and second kind of singular configurations in each SKC are analyzed. Finally, the task workspace with the optimal internal velocity transmission factors index of the mechanism is analyzed and selected. This study lays the foundation for the stiffness, dynamics and engineering prototype design of the mechanism.关键词：Parallel mechanism;Sub-kinematics chain;Coupling degree;Velocity transmission factor;Workspace
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发布时间：2023-08-14 - 摘要：By observing the movement characteristics of each foot when hexapod crawls in reality, according to this feature, an innovative three segment spatial crankshaft is designed. Connect the three sections of the crankshaft in this space with the front, middle and rear feet in turn. The connecting parts with each foot are designed into different spatial linkage mechanisms. In order to ensure the motion coordination of each foot when crawling, the kinematic parameters of the spatial crankshaft and its connected mechanisms are analyzed. Based on the coordinated motion parameters, the hexapod structure is modeled, and the walking coordination is simulated by Catia. At last, real objects are produced for motion test. Therefore, the feasibility of spatial crankshaft transmission structure is verified.关键词：Hexapod;Spatial crankshaft;Spatial linkage;Structural Modeling;Dynamic Simulation
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发布时间：2023-08-14 - 摘要：In this study, a new type of power-function-sine flexure hinge is proposed. The calculation formula of compliance and rotation accuracy of the flexure hinge is derived by using Castigliano's second theorem. The finite element simulation analysis and theoretical value calculation of compliance and rotation accuracy are carried out by taking different parameter values. The relative error is less than 10%, which verifies the correctness of the calculation formula. The influence of curve equation parameters of the flexure hinge on the performance of the flexure hinge is analyzed. The results show that the minimum thickness has the greatest influence on the performance of the flexure hinge. In addition, the ellipse and hyperbola are compared with the new hinge. The results show that the ellipse flexure hinge has the greatest compliance, but the rotation accuracy is the smallest; the hyperbolic flexure hinge has the highest rotation accuracy, but the lowest compliance. By introducing the compliance accuracy ratio β, through analysis and comparison, it is known that under the same L and the changing d, the value of the power function sine flexure hinge β is 2.68 times and 1.237 times higher than those of elliptical and hyperbola flexure hinges respectively. With the same flexure hinge diameter and the changing length, the value of the power function of sinusoidal flexure hinge β is 2.60 times and 1.18 times higher than that of elliptic and hyperbolic flexure hinges respectively. It shows that the power function sinusoidal flexure hinge has more advantages in comprehensive performance.关键词：Flexure hinge;Power-function-sine;Compliance;Rotation accuracy;Finite element analysis
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发布时间：2023-08-14 - 摘要：Based on the intrinsic geometry, a new type of mechanism with single degree of freedom is designed which can translate along the intersecting line. According to the theory of azimuth feature set, the degree of freedom of the mechanism is calculated and its kinematics are analyzed. A coordinate system is established to solve the forward and inverse position solutions of the mechanism and it is verified. Based on the schematic diagram of the mechanism, a three-dimensional model is established with a specific dimension parameter, and the kinematics simulation is carried out in Recurdyn. The output characteristics of the terminal running trajectory are analyzed, and the feasibility of the mechanism is verified.关键词：Intersecting line;Parallel mechanism;One degree of freedom;Kinematic simulation
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发布时间：2023-08-14 - 摘要：A 4-CPS/UPU parallel mechanism used in the field of parallel machine tools is proposed. Based on the screw theory, the kinematic and constrained screw system of the parallel mechanism is established. The mechanism has five degrees of freedom and can realize the function of three shifts and two rotations. The degree of freedom is verified by the modified K-G formula. The forward and inverse solutions of the parallel mechanism and the working space are analyzed. The simulation analysis is carried out by Adams software. The workspace of the mechanism is continuous without cavity, and its shape is similar to that of a pyramid, which is regular and symmetrical; the smooth displacement and velocity curves obtained by simulation show that the mechanism has good kinematic performance, which provides a certain theoretical basis for its parametric design in the field of parallel machine tools.关键词：4-CPS/UPU parallel mechanism;Degree of freedom;Position inverse solution;Positive position solution;Workspace;Adams software
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发布时间：2023-08-14
Design· Calculation
- 摘要：In order to better reveal the influence of tooth root crack failure on the dynamic characteristics of the gear system, the whole process of failure mechanism analysis—gear system modeling—crack failure test is carried out. Firstly, considering the more realistic tooth root transition curve and effective tooth thickness reduction limit line, a more rigorous crack gear tooth model is established, the meshing stiffness calculated by the traditional potential energy method is improved, and the stiffness of 6 kinds of cracks with different depths is studied. Secondly, in view of the shortcomings of the traditional lumped parameter model, a finite element dynamic model of the gear-rotor system is established based on the Timoshenko beam element theory. Finally, the Newmark-β method is used to solve the dynamic response of the gear system with normal/different depth crack faults, and compared with the experimental results considering the influence of rotational speed. The results show that when there is a crack in the tooth root, the acceleration response has a periodic impact characteristic, and the side frequency phenomenon in the frequency domain occurs near the meshing frequency and its harmonics; the strength of impact components in both the time and frequency domains is positively correlated with crack depth and rotational speed. The simulation results and the measured signals show consistent characteristics, which verify the correctness of the method in this study.关键词：Time-varying meshing stiffness;Tooth root crack;Finite element model;Vibration characteristic analysis
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发布时间：2023-08-14 - 摘要：Accuracy and fatigue life are important factors restricting the development of domestic robot reducers. In order to improve the efficiency of fatigue life test, it is very important to select appropriate load torque for accelerated life test. In this study, according to the real working condition of a certain robot reducer on the industrial robot, the maximum load torque of the robot reducer without failure is obtained through calculation and simulation, and the accelerated life test is completed on the basis of this. Firstly, the calculation model is built by using SolidWorks software, the maximum static torque is calculated and the appropriate load mass is preliminarily selected. Then the Adams software is used to simulate the pendulum of fatigue test load. According to the maximum static torque and the maximum dynamic torque, the load quality and rotation acceleration and deceleration time are calculated. An orthogonal experiment is designed to combine the two to obtain the load mass and rotation acceleration and deceleration time that can complete the accelerated fatigue test with the highest efficiency. Besides, the correctness of simulation calculation is verified by experiments. The results show that the load static torque has a great influence on the test time, and the test time of the robot reducer is significantly shortened after selecting the appropriate load mass, the rotation acceleration and the deceleration time, which improves the test efficiency of robot reducers. It provides a theoretical basis for the accelerated life test of robot reducers.关键词：Robot reducer;Accelerated life test;Load torque;Test time
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发布时间：2023-08-14 - 摘要：The synchronous belt drive is the main drive form of the driving mechanism of the transplanter. Based on the low stability of the traditional trapezoidal tooth-shaped driving mechanism of the transplanter during seedling separation, it is easy to cause bad tooth skipping and tooth disengaging. A virtual prototype model of the seedling separation device driving mechanism is established by the rigid-flexible coupling multi-body dynamic simulation method to analyze the dynamic characteristics of periodic dynamic load stress variation, transverse vibration, and transmission error of the synchronous belt. The results show that the stress distribution of the straight-toothed synchronous belt (STSB) is more uniform than that of the high torque drive (HTD) and the traditional trapezoidal toothed synchronous belt. The minimum stress value is 59.16 N/mm2, and the minimum amplitude of transverse vibration is 33 mm. The transmission error is small, and the transmission is smooth. It provides reference for dynamic simulation and tooth profile optimization of the driving mechanism of the transplanter.关键词：Dynamic characteristic;Tooth profile;STSB
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发布时间：2023-08-14 - 摘要：Aiming at the stiffness adjustment of the continuous manipulator designed by the deformed Miura origami mechanism, the influence of geometric parameters on the stiffness of the origami robot arm is discussed. Firstly, based on the bar-and-hinge model method, the taper angle and length of the three sets of origami robot models are maintained, pressure is applied to the robot arm, the bending stiffness of the manipulator in the state of extension and contraction is analyzed by the Matlab simulation program, and the corresponding bending stiffness ratio is calculated. The results show that when the number of edges of the polygon on the end face of the manipulator is increased from 5 to 7, the bending stiffness ratio increases with the increase of the number of polygon edges, so that the origami manipulator is rigid and flexible in the state of extension. Secondly, the force-displacement relationship of the origami manipulator is further modeled using the principle of virtual work, the relationship between the cone angle and the load force of the manipulator is clarified, and the three groups of origami manipulators with different cone angles are also analyzed. Finally, a conclusion is drawn that with the increase of the cone angle, the resistance to external forces is not always increasing. That is, the change of the cone angle has an impact on the load performance of the manipulator.关键词：Miura origami mechanism;Continuous;Stiffness adjustment;Bar-and-hinge model;Principle of virtual work
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发布时间：2023-08-14 - 摘要：Under the alternating load, the chain of high-speed heavy-duty bucket hoist passes through hundreds of thousands or more shocks, and the final failure mode is mainly chain plate fatigue fracture. There is no report on this kind of chain fatigue tester at home and abroad. Through force analysis of chain plate, theoretical basis is provided for elastic-plastic analysis after extrusion, analysis of residual stress, calculation of displacement under elastic-plastic state, and actual working condition test etc. Through the design of extruded-hole mandrel with different interference, statistical analysis is carried out on relevant data to further explore the range of interference of extruded holes, and tensile test is carried out on extruded-hole chain plate with certain interference to verify whether the tensile strength of chain plate will be affected.关键词：High speed and heavy load;Chain plate;Fatigue;Elastic-plastic;Residual stress;Extruded hole mandrel
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发布时间：2023-08-14 - 摘要：In order to design the globoidal cam deceleration mechanism with good performance and improve the transmission performance, the working surface equation and conjugate contact equation are deduced based on the space conjugate contact principle. The constant parameters of globoid cam are preprocessed by using Creo software, and the parametric design of globoid cam deceleration mechanism is completed. According to the finite element method, the first six modes of the reducer mechanism are analyzed. The orthogonal experiment method is used to design the experimental scheme. The influence of pressure angle, rotary pitch radius, roller radius and roller width on the sensitivity of the constraint mode of the reducer mechanism is quantitatively analyzed by statistical theory and variance analysis. The results show that the variances of pitch radius and roller radius of turntable are 0.021 and 0.043 respectively, both of which are less than 0.05 and sensitive to the constraint mode of globoidal cam, followed by the pressure angle and the roller width. The results provide a basis for the study of vibration and noise of globoidal cam mechanism design.关键词：Orthogonal test;Globoidal cam reduction mechanism;Parametric design;Constrained mode
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发布时间：2023-08-14
Test·Analysis
- 摘要：Aiming at the RV reducer spindle force problem, and based on the Romax force analysis of the main bearing, it is found that due to the different magnitude and span of the impact parameters, the influence degree of each parameter on the spindle bearing force cannot be determined. Based on this, a fuzzy comprehensive evaluation method is proposed. The results show that the number of cycloidal wheel pins and the radius of cycloidal wheel pitch have the greatest influence on the force of the main bearing. The entropy weight method and grey relational degree are used to verify the influence degree of each parameter on the bearing capacity of the spindle. The results obtained by the fuzzy comprehensive evaluation method are consistent with the results obtained by the entropy weight method and grey relational analysis method, which verify the effectiveness of the fuzzy comprehensive evaluation method.关键词：Force;Fuzzy comprehensive evaluation;Spent information;Entropy weight method;Grey correlation degree
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发布时间：2023-08-14 - 摘要：The development of the self-propelled wrap-around packaging robot can significantly boost the technological progress of the industry. This research introduces a self-propelled wrap-around packaging robot with a new working mode. For this packaging robot, the AGV equipped with a 6-DOFs robot arm to construct a mobile robot arm is used as the main body. The packaging film fixing device and the film drawing frame are loaded on the AGV, to realize the complete autonomous wrapping work. On the basis of introducing the overall structure of winding packaging robot, the working process of typical objects winding packaging with a mobile manipulator is analyzed and kinematics modeling is conducted. A simulation analysis system is developed based on the mathematical model of the mobile robot arm and the model of winding typical objects. The calculation and simulation results show that the wrap-around packaging robot can complete the wrapping work of packaging film and meet the design requirements. The related work provides a basis for the practical application of the self-propelled wrap-around packaging robot.关键词：Packaging robot;Wrap-around packaging;Mobile robot arm;Kinematic modeling;Simulation
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发布时间：2023-08-14 - 摘要：The new version of the gear accuracy standard GB/T 10095.1—2022 has been released, and the standard of accuracy of rack is written with reference to the gear accuracy standard. The manufacturing technology and the processing accuracy of racks have changed greatly, so the standard of accuracy of rack has been revised. The main differences between the 2022 version of the standard of accuracy of rack and the 1988 version are: terms and symbols; definition of total tooth profile deviation; measurement of the rack pair; adding the parts detection method of flame cutting large modulus racks for lifting and lowering of offshore platforms, as well as five measurement tools that can be used in the production process of racks. Analysis is conducted concerning the added and the revised parts.关键词：Rack;Accuracy grade;Coordinate measurement
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发布时间：2023-08-14 - 摘要：Based on the linear laser displacement sensor, this research constructs a device which can measure the multiple deviations online of large gears. In this device, the tooth profile of the gear can be scanned by the linear laser displacement sensor, and the data of any tooth surface of the gear can be measured. The tooth profile curve of the gear can be fitted based on the least square method, and compared with the ideal model of the gear, the tooth profile and tooth distance deviation of the gear can be calculated by combining the radial polar coordinate angle comparison method. The measuring device proposed in this research is small in size, light in weight and easy to carry. The measuring method adopted is efficient and the gear deviation measured is accurate and reliable.关键词：Line laser displacement sensor;Non-contact measurement;Deviation analysis;Online measurement
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发布时间：2023-08-14 - 摘要：A rolling bearing fault diagnosis model based on two-step transfer learning and EfficientNetV2 (TSTE) is proposed for the real fault diagnosis environment in engineering, where the scarcity of available data leads to the low accuracy of the intelligent diagnosis model in bearing health status diagnosis. Firstly, the model is trained on the full life time bearing data set and then the model shallow weights are freezed to train it on the multi-condition bearing data set for the first transfer learning. Secondly, by constructing a class-imbalance dataset, the impact of scarcity of available data on fault diagnosis performance is studied in actual fault environments is studied. Then, the synthetic minority oversampling technique (SMOTE) oversampling method and the edited nearest neighbors (ENN) under the sampling method are proposed to expand the fault data, reconstructing the class-imbalanced dataset into a class-balanced dataset. Finally, the model is trained on the class-balanced dataset, freezing the model's bottom weights and training the model deeper for a second transfer learning, enabling the model to take control of the failure characteristics of the balanced dataset. The experiments are evaluated by a variety of metrics, while comparing it with other methods, and using the Grad-CAM method for feature visualization. The results show that the proposed method is able to transfer the fault diagnosis knowledge accumulated by the model in a laboratory environment to actual engineering equipment. It is suitable for the diagnosis of rolling bearing faults in situations where test data is scarce.关键词：Rolling bearing;Two-step transfer learning;EfficientNetV2;Class-imbalance;Resample
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发布时间：2023-08-14
Development·Application
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