最新刊期
卷 48 ， 期 9 ， 2024
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Contact Characteristics Analysis of Tooth Surface Microscopic Morphology Based on the Fractal Theory
摘要：How to effectively calculate the contact stiffness of the joint surface and analyze the influence of the joint surface stiffness on the dynamic characteristics of the overall structure is one of the important subjects in the study of mechanical structures. However, at present, the fractal theory is simply applied to the calculation and analysis of the joint surface stiffness, and it is difficult to comprehensively analyze the microscopic contact characteristics. Therefore, it is urgent to propose a new method to calculate the contact stiffness of the tooth surface and to analyze the microscopic contact characteristics. Based on the W-M （Weierstrass-Mandelbrot） function, a three-dimensional solid model of the microcosmic joint surface of the tooth surface was constructed, and a new method for fractal representation of the rough surface profile based on the fractal dimension D and the tooth surface roughness was proposed, considering the influence of roughness on the stiffness. The contact deformation mechanism of asperities was discussed, and the law of contact stiffness changing with the deformation of asperities was revealed. The research shows that in the same roughness of the micro-joint surface, when the asperity deforms to the same level, the larger the fractal dimension D is, the greater the contact stiffness will be. In the joint surface with the same fractal dimension and different roughness, the smaller the roughness of the joint surface is, the greater the contact stiffness will be.关键词：Rough surface;Roughness;Fractal theory;Contact stiffness model- 17
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发布时间：2024-09-23 - 摘要：A splash lubrication simulation model of a planetary gear train was established based on the moving particle semi-implicit （MPS） method, and it was verified by experiments to explore the splash lubrication behavior of the planetary transmission. Through the simulation, the oil distribution characteristics, the number of lubricating oil particles in the engagement zones, and the churning loss of the rotating components were studied. The results show that in the rotation of the planetary gear train, the interior space of the gearbox can be divided into three regions: the oil-pool region, the oil-dragging region, and the oil-poor region. The number of oil particles in different engagement zones and the churning torque of each component show periodic variations during the planet gear passes through the three regions. The numbers of oil particles in the inner and outer engagement zones reach the peak when the planet gear runs into the oil-pool region, and both drop rapidly to a minimum value after entering the oil-poor region. The churning torque of the planet gear rises sharply to the peak after entering the oil-pool region and keeps the peak value until the planet gear enters the oil-dragging region, then the churning torque turns to fall until stabilizing at a very low level when the planet gear enters the oil-poor region. Different from the planet gear, the churning torque of the planetary frame drops sharply when one of the planet gears enters the oil-pool region and rises rapidly when that planet gear enters the oil-dragging region and the next one has not entered the oil-pool region. The churning torque of the sun gear is small and insensitive to the planet gear positions. Among the total churning power of the planetary gear train, the sum of the three planet gears accounts for about 60%, followed by the planetary frame, and the sun gear accounts for the least.关键词：MPS;Planetary gear train;Splash lubrication;Oil distribution;Churning loss
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发布时间：2024-09-23 - 摘要：Aiming at the problems of the standard rapidly exploring random tree (RRT) algorithm in a complex environment, such as blind expansion, falling into local search, easy planning failure, low sampling success rate, and long paths, an adaptive goal-oriented strategy combined with an alternative strategy for regional sampling and an improved RRT algorithm of the greedy pruning strategy was proposed. Based on the kinematics of the manipulator, the envelope was used to simplify the manipulator model to improve the efficiency of collision detection. The adaptive goal-oriented strategy solved the problems of blind search, low search success rate, and difficult convergence of the RRT algorithm in complex environments; the regional sampling alternative strategy solved the problems of the RRT algorithm easily falling into local search, low sampling success rate, and long sampling time; the greedy pruning strategy eliminated redundant nodes and shortened the path, improved the path quality, and enhanced the robustness of the algorithm. In the Matlab and robot operating system (ROS), the obstacle avoidance simulation planning was carried out for different scenarios. The results show that the average search success rate of the improved RRT algorithm has increased by 82.4%, the average sampling success rate has increased by 67.5%, and the average path planning success rate has increased by 70%. The average time efficiency is increased by 81.9%, and the average path length is shortened by 63.05%. Finally, the practicability and effectiveness of the algorithm were further verified by the trajectory planning of the physical manipulator.关键词：Welding manipulator;Collision detection;Adaptive goal orientation;Alternative strategies for region sampling;Greedy pruning
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发布时间：2024-09-23 - 摘要：A method based on the polynomial interpolation combined with the segmental planning was proposed for the trajectory planning of redundant mobile manipulators. The kinematic analysis was carried out by considering the manipulator and the mobile platform as an integrated system, a generalized form of the geometric Jacobi matrix and its pseudo-inverse were derived. In the trajectory planning process, the trajectory running time and the spatial distance travelled by the end of the mobile manipulator were taken as the optimization objectives, the velocity and acceleration constraints of each joint were also taken into account, and a genetic algorithm was used to optimize the trajectory of the redundant mobile manipulator. The simulation results demonstrate that the trajectory of the optimized motion is smooth, and the displacement and velocity curves of the joints of the mobile platform and the manipulator are continuous and stable, which verifies the feasibility and effectiveness of the method.关键词：Mobile manipulator;Trajectory planning;Geometric Jacobi matrix;Genetic algorithm
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发布时间：2024-09-23 - 摘要：Replacing the hydraulic oil in hydraulic motors with the natural water will lead to an increase in the leakage of the wheel train and a decrease in the volumetric efficiency of motors. In order to improve the volumetric efficiency of the non-circular planetary gear hydraulic motors, the influence of axial clearance between the wheel train and the distribution plate on the volumetric efficiency of the motor is quantitatively analyzed. Firstly, according to the principle of the gap leakage in the rotating plane and the friction force in the fluid, the leakage and power loss formula between the wheels were derived, so as to calculate the optimal solution of the axial clearance of the motor under 30 MPa pressure difference. Secondly, on the basis of considering the manufacturing error, based on the dynamic grid and user-defined function (UDF) programming technology, the leakage amount and volumetric efficiency of the motor under different axial clearances were detected and analyzed, and the theoretical volumetric efficiency of the motor under the same conditions was calculated. The two were compared to obtain the change trend and the minimum value of motor volumetric efficiency under different working conditions. The results show that from the calculation results of selecting the axial clearance value, when the flatness of the wheel is 0.01 mm, the volumetric efficiency of the motor is not less than 77.28% within the working pressure difference of 30 MPa. It provides a basis for the structural improvement of subsequent motors.关键词：Hydraulic motor;Non-circular planetary gear;Axial clearance;Volumetric efficiency;Dynamic grid
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发布时间：2024-09-23 - 摘要：The printing speed, registration accuracy and print quality of the printing machine are deeply affected by the dynamic characteristics of the gripper mechanism. The gripper mechanism is mostly composed of a cam mechanism and some connecting rods, where joint clearances inevitably exist. The stability, work efficiency and lifespan of the mechanism would be reduced by the joint clearances. Taking a cam-linkage mechanism as the research object, a dynamic model of the mechanism with multiple clearance joints was established. The effects of different clearance sizes, clearance joint positions, and the number of the clearance joints on the dynamic responses of the mechanism were analyzed. The results indicate that all the above factors have an impact on the transmission accuracy and stability of the gripper mechanism, and the interaction between multi clearance joints has a significant impact on the dynamic characteristics of the mechanism. This study provides reference for the structural optimization design of printing machines with clearance joints.关键词：Gripper mechanism;Clearance joint;Cam-linkage mechanism;Dynamic characteristics
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发布时间：2024-09-23
Theory·Research
- 摘要：A novel 2PRU-PRUR parallel mechanism with one translational and two rotational (1T2R) degrees of freedom and without parasitic motion, and its mobility and motion characteristic were analyzed by means of the screw theory. The output axis of the moving platform designed as the deviation type can enhance the orientation capability of the mechanism. The orientation of the end-effector output axis was depicted by using the spherical attitude angles (the azimuth and tilt angles), and the symbolic solutions for the inverse displacement analysis were proposed. The screw theory was used as a mathematical tool to establish the definitions and computing methods for the local and global transmission performances indices of the mechanism. Based on the performance evaluation and workspace analysis, a constrained many-objective optimization model was constructed to formulate the design problem of dimensional parameters, and multi-objective evolutionary algorithms were employed to solve this problem. To enhance the optimization performance of the algorithm for solving the problem, a vector-angle-based many-objective differential evolution (VaDE) algorithm was proposed, which can balance comprehensively the convergence and distribution of the individuals. At the same time, the VaDE was utilized to solve the many-objective optimization problem, and multiple Pareto optimal solutions were obtained. The research results can provide reference for the dimensional synthesis and practical application of the proposed mechanism.关键词：Parallel mechanism;Transmission performance;Many-objective optimization;Vector angle;Differential evolution algorithm
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发布时间：2024-09-23 - 摘要：A dual-modulation axial magnet gear motor （DAMGM） was proposed to address the shortcomings of the axial magnet gear motor （AMGM）, which has a large overall size and low torque density（≤70 kN·m/m3）. Two magnetizing rings on the high-speed and low-speed sides were used to modulate the low-speed rotor in the DAMGM, and the non-magnetic parts in both magnetic magnetizing rings were permanent magnets, effectively improving the output torque of the low-speed rotor. In addition, compared to the existing AMGM, the drive motor was placed inside the high-speed permanent magnet rotor of the DAMGM, reducing the overall axial size and significantly improving the torque density of the low-speed rotor（150 kN·m/m3）. Aiming at the problems of long calculation time and serious waste of computer resources in the existing 3D finite element method, a 3D analysis method of DAMGM based on the cylindrical coordinate system was presented. According to three boundary conditions of the magnetizing ring, the mathematical and physical models of the modulated DAMGM air gap magnetic field and electromagnetic torque were established. The calculation results are not only accurate （compared with the 3D finite element method, the average calculation error is less than or equal to 5%）, but also the calculation time is short （only 1/10 of the 3D finite element method）, facilitating the analysis, comparison, and optimization of different parameter structures in the DAMGM.关键词：Axial magnetic gear motor;Air gap magnetic density;Electromagnetic torque;Three-dimensional analysis method
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发布时间：2024-09-23 - 摘要：In response to the optimization problem of meshing regions caused by the S-shaped tooth profile in the harmonic gear drive, a method for effective edge-conjugate tooth profile design was proposed. This method effectively avoids the difficulties of solving the complex S-shaped tooth profile equation. The convex tooth profile of the S-shaped tooth profile was taken as the base tooth profile. Tooth profiles of the flexspline and circular spline were designed using both the traditional backlash adjustment method and the effective edge-conjugate method. The meshing characteristics and contact stress of the tooth profiles designed by the two design methods were compared and analyzed through the plane numerical analysis and the finite element modeling. The research results show that the effective edge-conjugate tooth profile design method can achieve both quadratic and two-point meshing, increasing the gear's meshing angle and meshing arc length. The total number of meshing teeth per revolution is increased by 15.78%, with 55% of the flexspline teeth participating in the meshing, thereby enhancing the load capacity of the harmonic gear drive. Moreover, the effective edge-conjugate method leads to an enlargement of the contact area, reducing the maximum contact stress between the tooth profiles by 24.36%, which effectively decreases wear between the flexspline and circular spline tooth surfaces.关键词：Harmonic gear drive;S-shaped tooth profile;Effective conjugate point;Meshing characteristics
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发布时间：2024-09-23 - 摘要：A human lower limb rehabilitation device based on a planar five-bar mechanism was introduced, aiming at meeting the early, mid and late rehabilitation training needs of stroke patients who are bedridden after surgery. This device has the characteristics of simplicity and reliability, and can be placed at the end of the bed or moved with the patient's walking. The device mainly consists of a lower mobile platform, a manual lifting component, an upper power transmission mechanism, and left and right training mechanisms. Sensors were attached to the universal joint brackets of the ankle and knee joints, allowing real-time collection and feedback of the patient motion information. Through kinematics analysis and Adams software simulation, the results show that adjusting the initial phase of the double crank of the device can change the motion track of the joint points, thus obtaining the range of motion of human lower limb joints under different motion modes, achieving the purpose of horizontal training and walking training, and meeting the training needs of patients in different rehabilitation stages.关键词：Lower limb rehabilitation device;Planar five-bar mechanism;Structural design;Kinematics analysis;Adams simulation
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发布时间：2024-09-23 - 摘要：The flexible arm of moxibustion robots was designed and simulated, and the flexible arm was made of thermoplastic polyurethane (TPU) and segmented bellows, including the bending section and the elongated section. Using Abaqus CAE analysis software, the structural dimensions such as the wall thickness and the corrugated angle of the bellows were optimized, the kinematics simulation analysis of the flexible arm was carried out from the relation between bending angle and air pressure and flexibility, and the mechanical properties of the flexible arm were calculated and analyzed. The results show that the robot's flexible arms designed for the moxibustion application can meet the requirements of the load capacity and the flexibility.关键词：Moxibustion robot;Flexible arm structure;Bellow;Simulation design
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发布时间：2024-09-23 - 摘要：The motion trajectory of the crusher working device during the working process was planned, and combined with the research theory of robot robotic arms, a crusher working device model based on the improved D-H method was established. A kinematic model was established, the forward kinematic analysis on the model was performed, and the joint angles of the rotary platform, boom, and bucket at different positions in space were obtained through inverse kinematic solutions. The motion trajectory of the working device was planned by using a fifth degree polynomial curve, a seventh degree polynomial curve, and a ninth degree polynomial curve in the joint space. On the Matlab platform, a D-H parameter model of the working device was built using the Robotics Toolbox and three methods were simulated to obtain the angle, angular velocity, and angular acceleration variation curves of the joint rotation. Comparative analysis shows that the seventh degree polynomial programming angular acceleration curve is smooth, continuous, without abrupt changes and small fluctuations, which can ensure the continuity and smoothness of the working device movement.关键词：Hydraulic crusher;Trajectory planning;Polynomial interpolation;Kinematic analysis
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发布时间：2024-09-23
Design· Calculation
- 摘要：In order to study the influence of diaphragm thickness on the torque transmission and misalignment compensation performance of wind turbine couplings, the overall finite element model of the coupling was established, the stress nephogram under the combined action of torque, axial displacement and angular displacement load was obtained, and the feasibility of the finite element simulation analysis was verified by combining with the actual broken position of the diaphragm. The stress response of each diaphragm thickness under different loads was given, the influence of different loads on the stress of each diaphragm thickness was analyzed, and the influence of preload force and contact friction coefficient on the performance of the coupling was discussed. The results show that the increase of diaphragm thickness can improve the torque transmission capacity of the coupling, but will weaken its misalignment compensation capacity. The influence of different loads on the stresses of different diaphragm thicknesses is different, and the comprehensive performance of the coupling is the strongest when the diaphragm thickness is 3 mm. The influence of bolt preload on the performance of the coupling is great, while the influence of contact friction coefficient between diaphragms on the performance of the coupling is smaller.关键词：Wind turbine coupling;Diaphragm thickness;Finite element simulation;Stress analysisCoupling performance
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发布时间：2024-09-23 - 摘要：This study takes the shift process of a commercial vehicle equipped with an automated mechanical transmission (AMT) as the research object, with the aim of reducing shift shock and shortening shift time. Simulink was used to construct a shift control strategy without the participation of synchronizers, which includes dynamic coordination of power sources and active synchronization control of motors based on optimal control principles. Then, AMESim was used to establish a complete vehicle shift simulation model. Taking the shift from fifth gear to sixth gear as an example, a comparative analysis of the shift performance between AMESim and Simulink joint simulation and traditional shift strategies was conducted. The simulation results show that the synchronization time is reduced by 21.42% during the shift process, the maximum impact is reduced by 24.88%, and the entire shift time is reduced by 18%. Finally, the control strategy proposed in this research was validated in real-time using the dSPACE semi physical simulation platform.关键词：Automated mechanical transmission;No synchronizer structure;Gear shift impact;Motor control;Gear quality
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发布时间：2024-09-23 - 摘要：On the basis of analyzing the movement law of the three-dimensional and five-direction braided yarn, the composite box was designed to be composed of two parts of the braided base and the box wall. On this basis, the braiding and forming principle of the three-dimensional and five-direction braided box was obtained. According to the braiding principle and the yarn movement law, the three-dimensional solid model of the braided box was established, and the finite element analysis of the three-dimensional and five-direction braided box was carried out. The stress of matrix and fiber in the braided composite box was studied by stress and strain analysis results. Under the assumption of ignoring the influence of friction, bearing and other factors on the system, the motion equations of the two-stage gear transmission system with a box body were established, and the numerical analysis of the two-stage gear transmission system was carried out by the Runge-Kutta method to study the influence of excitation on the dynamic characteristics of the assembling and weaving system.关键词：3D and five-direction box braiding;Composite material;3D solid model;Two-stage gear transmission system
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发布时间：2024-09-23 - 摘要：It is difficult to solve the binding force of motion pairs of over-constrained mechanisms. This study attempted to decompose the constraint term in the d'Alembert principle into two parts, static constraint and dynamic constraint. The static constraint under constraint conditions and the dynamic constraint of the equilibrium inertial force were obtained separately, and the total constraint force of the example was solved through the superposition of the two. Taking three pairs of uniform transmission rod space RCCR mechanism as the research object, the binding force was solved by the above method, and the solution results were compared with the dynamic simulation results. The results show a good consistency.关键词：D'Alembert principle;Overconstrained;Space RCCR mechanism;Dynamic binding force
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发布时间：2024-09-23 - 摘要：Comprehensively utilizing various technical means, such as vibration signal analysis, endoscopy, macroscopic observation, metallographic analysis, scanning electron microscopy (SEM) analysis, energy dispersive spectroscopy (EDS) analysis, and mechanical performance experiments, a fault diagnosis and cause analysis were conducted for the radial cracking phenomenon along the tooth groove of a certain type of wind power gearboxes. The abnormal vibration was revealed through vibration signal analysis, and the characteristics of abnormal vibration was determined through spectrum analysis and time domain feature extraction. The fault location was confirmed through endoscopic inspection. After disassembly, SEM inspection were used to confirm the presence of a large-sized inclusion at the crack source, and the composition of the inclusion was determined through EDS, further analyzing and determining the entire process of gear penetration cracking. By comprehensive analysis, the cause and location of the fault were determined, which provides scientific basis for equipment maintenance, and improves production efficiency and equipment life, while reducing fault loss and maintenance costs.关键词：Wind turbines;Fault diagnosis;Cause analysis;Fault closed-loop;Gear cracking
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发布时间：2024-09-23
Test·Analysis
- 摘要：To design a curvilinear cylindrical gear with arbitrary tooth surface contact pattern, a method for determining the radius of a disc-shaped milling cutter for machining the curvilinear cylindrical gear was proposed based on the reverse determination of the required dimensions of the contact pattern. Firstly, the mathematical model of the tooth surface of the curvilinear cylindrical gear was introduced. Secondly, a mathematical model for calculating the contact patterns was established. Then, taking four curvilinear cylindrical gears machined by double-edged milling cutters with different radii as examples, the relation graph between the radius of the disc-shaped milling cutter and the contact patterns was studied. Finally, the radius selection of the disc-shaped milling cutter was achieved through interpolation. This method can skip the gear trial processing, reduce the manufacturing cost of gears, and lay the foundation for the design and manufacturing of fixed-setting face-milling curvilinear cylindrical gears.关键词：Curvilinear cylindrical gear;Disc-shaped face-milling cutter;Contact pattern;Mathematical model
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发布时间：2024-09-23 - 摘要：In order to better assist patients with wrist injuries in rehabilitation, a wrist rehabilitation trainer was designed. Firstly, the structure of the rehabilitation trainer was designed based on the biological motion mechanism of the wrist joint and the bionic principle, and the design of the flexible compensation joint of the wrist joint was added. After that, the kinematic model of the wrist joint was established based on the flexible compensated joint, and the working space of the trainer was obtained. Then, the virtual prototype platform was built, and the joint drive impedance controller was designed for joint simulation test. The influence of friction parameters, damping parameters and human-machine contact load on the impedance control performance was analyzed through the simulation test to verify that the joint control can be realized, and the working space of the compensated joint was compared and analyzed to verify the rationality and feasibility of the structural design of the trainer and to provide a theoretical basis for the production of the next physical prototype.关键词：Rehabilitation trainer;Wrist joint;Kinematic simulation;Dynamic model;Joint simulation
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发布时间：2024-09-23 - 摘要：In the design of the micro-positioning platform, a three-dimensional bridge-type amplification mechanism capable of generating high displacement amplification ratio was introduced. On this basis, a four-bar symmetric guiding mechanism was incorporated to effectively reduce the parasitic displacement at the output end. This design allows the micro-positioning platform to fully leverage the advantages of both mechanisms. By applying the strain energy theory, the second theorem of Castigliano, and Lagrange's theorem, the static and dynamic mathematical models of the micro-positioning platform were established. The theoretical analysis revealed the influence of key dimensions on the displacement amplification ratio of the platform. Through calculation, the amplification ratio and natural frequency were determined to be 19.90 and 193.26 Hz respectively, under the optimal parameters. Finite element analysis was used to verify the amplification ratio and natural frequency, resulting in relative errors of 4.3% and 5.9% respectively. This confirms the superior performance of the improved micro-positioning platform proposed in this study, as well as the accuracy of the theoretical analysis method. It provides theoretical guidance for the mathematical modeling of flexible micro-positioning platforms with amplification mechanisms.关键词：Three-dimensional bridge-type amplification mechanism;Four-bar symmetrical flexible mechanism;Flexible micro-positioning platform;Castigliano's second theorem;Finite element simulation
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发布时间：2024-09-23 - 摘要：In response to the issue of excessive sampling data and poor fault feature extraction performance in the fault diagnosis process of gearbox rolling bearings, a regularized orthogonal matching pursuit (ROMP) algorithm was proposed based on the maximum correlation kurtosis deconvolution (MCKD) for the diagnosis of bearing weak fault signals. Firstly, to achieve adaptive selection of parameters in the MCKD and ROMP algorithms, an improved grey wolf optimization (IGWO) algorithm was introduced. Then, the IGWO was used to denoise the original signal through MCKD processing. Finally, IGWO-ROMP was utilized to reconstruct the signal and diagnose bearing faults through envelope analysis of the signal.Verified by simulation signals and experimental results, this method can effectively extract bearing weak fault components, providing a new approach for the diagnosis of bearing weak fault signals.关键词：IGWO;MCKD;ROMP;Bearing fault diagnosis
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发布时间：2024-09-23
Development·Application
- 摘要：Robot dexterous hand can mimic human movements to realize multiple tasks in complex scenarios, which is a key technology for developing intelligent humanoid robots. Focusing on the research history of robotic dexterity, the current research status of multi-fingered dexterity was elaborated, and the evolution process and research progress of dexterity were analyzed. The classification and characteristics of dexterous hands were discussed in terms of the number of degrees of freedom, drive mode, mechanical transmission mode and sensing technology, and the future development trend of dexterous hands was envisioned.关键词：Robot dexterous hand;Bionic technology;Mechanical transmission;Perception technology
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发布时间：2024-09-23
Review
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