Abstract:[Objective]When the gear with constant relative curvature(CRC)transmission is in a mixed elastohydrodynam-ic lubrication state,the wear coefficient is not constant,and the traditional Achard adhesive wear model is no longer applicable.It is necessary to conduct adhesive wear analysis on CRC gears under mixed elastohydrodynamic lubrication.[Methods]Under mixed elastohydrodynamic lubrication,a dynamics model considering time-varying friction and a modified Achard adhesive wear model were established to calculate the adhesive wear depth of gears with constant relative curvature.The time-varying friction coefficient model was verified by comparing results with the experimental data.Through numerical examples,the effects of parameters such as modulus,input torque,and rotational speed on wear were discussed.[Results]The results show that the wear depth at the root of the driving and driven gears should be greater than that at the top of the teeth,and the wear depth at the pitch point was the smallest.The maximum wear depth occurs at the root of the tooth or at the boundary point of the meshing ar-ea of a single pair of teeth.Increasing the modulus,tooth width,input speed,and reducing input torque can effectively reduce wear depth.Increasing the transmission ratio or decreasing the relative curvature value under specific conditions can reduce wear depth.

Abstract:[Objective]A hybrid working mode underactuated manipulator was proposed to address the problem of difficulty in grasping coal foreign objects such as gangue and wooden blocks,which have irregular shapes and contours,large particle size variations,and thin volumes.[Methods]The manipulator used the envelope grasping and the parallel grasping to grasp irregular-ly shaped objects and thin objects,respectively.By parallel movement,the grasping space of the fingers was changed to adapt to the grasping of coal foreign objects in different particle sizes.Based on the movement process of fingers,grasping methods for coal foreign objects within different particle sizes were proposed.A contact force model for fingers was established,and the changes in contact force during the finger grasping were obtained,providing a basis for the stability study of the manipulator's grasping.[Results]The research results indicate that the manipulator is capable of grasping gangue and thin objects within the particle size range of 50-300 mm.

Abstract:[Objective]The coaxial dual-output cylindrical gear split-combined-torsion transmission system has the advantages of compact structure,light weight,and strong carrying capacity,and is widely used in aviation,shipbuilding and other fields.Although the coaxial dual-output cylindrical split-combined-torsion transmission system is symmetric in terms of local configuration principle,there is still a problem of uneven load distribution among the branches.The transmission system was analyzed from the perspective of statics.[Methods]Considering factors such as the torsional deformation of the transmission shaft,the support deformation and the meshing deformation of the gear pair,the principle of the meshing phase difference between the two pairs of the gear pair was analyzed,and the time-varying meshing stiffness of the cylindrical gear was calculated.Based on this,combined with the force balance conditions and deformation coordination conditions of the transmission configuration,the influence of the meshing phase difference between the gear pairs on the static load sharing characteristics of the transmission system was studied.[Results]The results show that the greater the meshing phase difference between the gear pairs is,the worse the static load sharing performance will be;the influence of the combined stage phase difference on the load sharing performance is greater than that of the split torsion stage;for the same stage gear pair,the influence of the phase difference of the right input branch of the inner output shaft branch on the load sharing coefficient is greater than that of the left input branch,and the influence of the phase difference of the left input branch of the external output shaft branch on the load sharing coefficient is greater than that of the right input branch.

Abstract:Yaw bearings and slewing bearings in wind turbine systems,rotating support bearings in aero-space launch towers,and slew bearings in cranes and excavators all exhibit characteristics of low-speed recipro-cating motion.Diagnosing faults in low-speed reciprocating motion bearings present significant challenges:the impact forces from damage contact are minimal at low speeds,resulting in weak damage impact signals.Further-more,the interference from deceleration and directional change impacts is substantial,and long signals covering multiple reciprocating cycles lack periodicity.To address these challenges,a method for diagnosing faults in low-speed reciprocating motion bearings is proposed.This method is based on modulation signal bispectrum(MSB)slice-wise overall averaging.The approach begins with signal resampling,which involves tracking zero-crossings in the rotational speed to resample vibration signals.Subsequently,it separates short signals from the resampled data based on encoder signals,forming a collection of short signals corresponding to individual recip-rocating cycles.Each short signal undergoes MSB analysis to generate the MSB bicoherence slice spectrum.The optimal carrier frequency and its associated modulation signal slice spectrum are determined from the bicoher-ence slice spectrum.Finally,an overall average of the MSB modulation signal slice spectra from the short signal collection results in the overall averaging feature.Validation of the method using fault test data demonstrates its effectiveness in diagnosing faults in low-speed reciprocating motion bearings.

Abstract:Aiming at the problem that the traditional ORB algorithm is difficult to realize the real-time and accurate grasp of the object by the robotic arm equipped with the binocular stereo vision,a robotic arm rec-ognition and grasping method based on an improved ORB algorithm was proposed.Firstly,the improved ORB al-gorithm was used to identify the target,and then the target was positioned according to the binocular stereo vi-sion optical axis parallel model.Then,the mathematical model of the robotic arm was established by using the standard D-H parameter method,and the inverse kinematics was solved.Finally,the obtained drive angles of each joint of the robotic arm were transmitted to the control end of the system.The end effector of the robotic arm was driven to complete the grasp of the target.The results show that compared with the traditional ORB algo-rithm,the improved ORB algorithm in this study can improve the speed and accuracy of target recognition and positioning,and effectively improve the real-time and accurate grasping of the robotic arm.

Abstract:In order to study the influence of gear eccentricity errors on the load sharing performance of each branch of the split torque and power confluence gear transmission system,the load sharing mechanism of the transmission system was analyzed.A coupled bent-torsional dynamics model with eccentricity errors was es-tablished by the lumped mass method,and the dynamic equation was solved by the Newmark-β method.The load sharing coefficient of each branch was calculated,and the variation of dynamic load sharing coefficients with or without eccentricity error was compared.Through two sets of numerical simulation,the influence of eccentrici-ty errors of different gears on load sharing coefficients of each branch was investigated.The results show that the eccentricity error of gears intensifies the amplitude fluctuation of load sharing coefficient of each branch of the system,and the load sharing coefficient of the right branch is smaller than that of the left branch in the closed-loop arrangement.When each level of gear eccentricity error acts independently,the influence of gear eccentrici-ty error on the load sharing coefficient of the branch where the gear is located is more obvious.When all levels of gear eccentricity errors act together,the load sharing performance of the power confluence stage is worse than that of the split torque stage,which indicates that the errors have the cumulative effect in the process of power transmission.It provides reference for the optimization of load sharing performance of the transmission system.

Abstract:[Objective]As an important strengthening process for gears,the quenching heat treatment will generate relative-ly high residual stress,which will further affect the meshing stiffness and dynamic performance of gears.Based on the analysis of the distribution law of quenching residual stress,the quantitative impact of residual stress on the meshing dynamic characteris-tics of gears was revealed.[Methods]A gear quenching simulation model was established based on the direct thermo-mechanical coupling method to solve the quenching residual stress.Combined with the single node method,this residual stress was regarded as the prestress to solve the time-varying meshing stiffness of the helical gear pair.Based on this,the lumped parameter method was used to establish a 10-degree-of-freedom dynamic model of the helical gear pair.The Runge-Kutta method was used for nu-merical solution,and the time domain diagram and frequency domain diagram of the dynamic load during the vibration response of the helical gear pair were obtained.[Results]Compared with the situation without considering the residual stress,the bending deformation of a single tooth becomes larger in the four-tooth meshing area and smaller in the five-tooth meshing area.The con-tact deformation does not change much,and the time domain peak values of meshing stiffness and dynamic load become larger,the dynamic load frequency domain amplitude spectral density at the meshing frequency increases.

Abstract:[Objective]The cycloidal pin gear reducer is popularized and applied for its high transmission ratio and compact structure.The transmission accuracy and smoothness of the cycloidal pin gear reducer is poor due to the high contact stress and low meshing stiffness between the cycloidal and pin gear.For the sake of further improving the load-bearing performance of the reducer,the analysis method was conducted to research the effect of structural parameters on the meshing stiffness by means of calculation and simulation.[Methods]In order to optimize its load-bearing performance,a mathematical analysis model of contact stress and meshing stiffness was proposed regarding the important structural parameters of cycloidal pin gear,as the design variables such as needle tooth distribution circle radius,eccentricity,and pin tooth radius;the VB.NET software was applied to calculate and analyze the influence of structural parameters of the cycloidal pin gear on the meshing stiffness,contact stress,meshing force,and torsional stiffness of the cycloidal pin gears pair.[Results]The results of calculation and simulation indicate that the meshing stiffness and torsional stiffness of cycloidal pin gear increase with the increase of the radius of the distribution circle and eccentricity and the decrease of the radius of the teeth.The research provides foundation for the design and optimization of the structure of cycloidal pin gear reducers.

Abstract:[Objective]Based on the theory of linear elastic fracture mechanics and dynamic simulations,a model was proposed to simulate the propagation of root fatigue cracks and calculate the mesh stiffness of gears with root cracks.This model was used to study the crack propagation characteristics in the roots of spur cylindrical gears and their impact on mesh stiffness.[Methods]Firstly,the initial crack location was determined through the dynamic simulation of gear dynamic meshing process.Then a tooth root fatigue crack propagation model considering real contact conditions was created,and the propagation path was simulated.Finally,the influence of different crack degree on the mesh stiffness was studied based on the crack simulation path.[Results]The results show that the fracture pattern of root crack is mainly open pattern,the initial crack mainly spreads towards the edge of the wheel,and the later crack evenly spreads towards the root of the tooth.The influence of cracks on the comprehensive deformation and mesh stiffness is greatest in the meshing process of the single tooth.At the same time,when the crack depth is small,the expansion path has little effect on the comprehensive mesh stiffness of the gear,and this effect is gradually obvious with the increase of the crack depth.

Abstract:[Objective]A 2-UPS/RRR parallel mechanism was created for the rehabilitation of the ankle.[Methods]The mechanism's three-dimensional model was created using SolidWorks software,and a moveable platform with an adjustable center of rotation was designed in accordance with various ankle rotation centers of different patients;the degree of freedom of the mechanism was calculated and analyzed using the helix theory,and the results were verified by using the Kutzbach-Grübler formula;the inverse solution equation for the mechanism's position and the polynomial equation were derived;the results were jointly simulated and verified using Matlab and Adams simulation software;the workspace of the parallel mechanism was solved using the limit search method.[Results]The results indicate that the mechanism can meet the rehabilitation training requirements of the human ankle joint.The research can provide reference for the subsequent physical prototype manufacturing.

Abstract:[Objective]The vibration analysis is an effective and widely used technology for monitoring the state of the rotating machinery.To better manage the health condition of various components in gear transmission systems,a vibration state monitoring framework for gear transmission systems based on the digital twin technology was proposed.[Methods]Firstly,the functionality and logical relation of each module in this technology framework were introduced from the physical layer,the data layer,the model layer,and the application layer,respectively.Secondly,the construction of the performance model and the behavior model for the gear transmission system was detailed.The performance model was used to simulate vibration signals,while the behavior model was utilized for updating the digital twin model.Finally,using a two-stage fixed-axis gear transmission system as an example,its digital twin system was established.Theoretical analysis and verification of various key technologies were conducted.[Results]The digital twin system achieves online vibration monitoring of the gear transmission system.The simulation response of the digital twin model shows close agreement with the measured vibration data,validating the effectiveness of both the performance and behavior models.This study provides valuable data support for the fatigue life prediction and reliability assessment of key components in the gearboxes,contributing to the advancement of digital twin technology in the monitoring of rotating machinery.

Abstract:[Objective]The feasibility of tooth profile reshaping to reduce the meshing shock and improve the fatigue life of gears was discussed for the meshing shock phenomenon of the rack and pinion mechanism of the oil pumping machine.[Methods]Firstly,the elastic deformation of gear teeth during the meshing was calculated based on the Ishikawa method.Secondly,four profile reshaping schemes were obtained by compensating the elastic deformation of gear teeth with the gear profile reshaping amount.Finally,the effect of each profile reshaping scheme was verified by the finite element simulation and the test comparison analysis.[Results]The results show that the gear reshaping amount within a certain range can effectively improve the fatigue life of gears and reduce the fluctuation of the contact stress,and the best reshaping amount is the theoretical reshaping amount.However,when the amount of reshaping is too small or too big,the fatigue life of gears will be little improved or even reduced.

Abstract:[Objective]To investigate the influence of the cutting speed,the depth of cut,and the feed rate on the residual stress of tooth surfaces during the form cutting of spiral bevel gears,a three-dimensional oblique cutting simulation model was established based on the characteristics of form cutting technology.[Methods]Single-factor and response surface methods were used for simulation to analyze the impact of each cutting parameter on the residual stress of the tooth surface.A response surface prediction model was developed to determine the optimal combination of cutting parameters,which was then validated through tests.[Results]The results indicate that the machined tooth surface is initially characterized by tensile stress,which rapidly transitioned to compressive stress along the depth direction before gradually diminishing to zero.Increasing the cutting speed enhances the surface residual tensile stress while slightly reducing the maximum internal compressive stress.The feed rate exhibites the most significant impact:the higher feed rate markedly increases the residual stresses on both the surface and within the hardened layer,accompanied by the greater stress penetration depth.Variations in the cutting depth demonstrates the minimal influence on the residual stress.The maximum relative error between predicted and test values of the tooth surface residual stress is 6.17%,validating the feasibility of simulation-based residual stress prediction in cutting processes.

Abstract:[Significance]Fault diagnosis technology is the key to ensure the operation efficiency of wind turbines and re-duce the operation and maintenance cost.As an important part of wind turbine,it is of great significance to understand its basic dynamic model for fault diagnosis.[Analysis]Through literature review,detailed fault diagnosis methods for key components of wind power drivetrain,namely the main bearing,gearbox,and generator bearing,were introduced.With more complex working conditions and harsher operating conditions,traditional fault diagnosis methods are limited,so the fault diagnosis of the wind power drivetrain under complex working conditions becomes more important.Combined with the development of fault diagno-sis of the wind power drivetrain under complex working conditions in the past five years,the current fault diagnosis methods of large-scale wind power drivetrain under complex working conditions were summarized in detail,and the main research and de-velopment directions of the wind power drivetrain fault diagnosis technology in the future were discussed.

Abstract:[Objective]To improve the internal(variable diameter,bending)passage ability of oil and gas pipeline cleaning robots,a multi-segment adaptive wheel-type pipeline cleaning robot was proposed.[Methods]The robot was designed with a two-segment structural configuration to reduce its turning radius.An extendable and retractable walking mechanism,formed by integrating a linear guide rail with a telescopic wheel assembly,was employed to enable adaptive movement within a certain range of pipe diameters.To ensure the operational stability of the cleaning robot inside pipelines,the motion process of the pipeline cleaning robot was simulated using Adams software,and its motion parameters were analyzed.The variation patterns of the robot's speed and wheel torque when passing through elbow pipes and pipes with varying diameters were thereby obtained.[Results]The speed of the robot will briefly increase to 1 146.9 mm/s when entering a 90° bend,and then decrease rapidly to 220 mm/s when exiting.In the continuous variable diameter pipe,the speed of the robot is maintained at about 520 mm/s,and the driving motor torque increases to 42.5 N·m with the decrease of the pipe diameter.The simulation data shows the correctness of the theoretical analysis and the rationality of the structural design.The tets results are consistent with the simulation results,further verifying the rationality of the pipeline cleaning robot design.

Abstract:[Objective]With the complexity of operational tasks,the dual-redundant robots have more operational flexibility and adaptability than the six-DOF robot arms.Aiming at the security problems in the information interaction and coordinated motion between the control systems of dual-redundant robots,a position-based alternate master-slave control strategy was proposed for a dual-redundant robot,with the master arm as"Leader"and the slave arm as"Follower".[Methods]A positional constraint relation was established for the master-slave control of a dual-redundant robotic system.Combined with the joint point tracking,real-time positional parameters during motion were captured.The mapping of each node position on the closed chain motion path of the dual-redundant robot system was realized based on the time interpolation.[Results]The test results show that the maximum error between the real-time tracking point parameters of each joint and the actual node position parameters of the dual-redundant robot system under arbitrary attitude is 0.465 mm,which realizes the virtual and real interactive trajectory mapping,and provides accurate position data for the application of collision detection algorithm in the actual dual-redundant robot system.

Abstract:A new type of seal ring bush silent chain(Zhenming chain)is brought forward and developed for the problem of severe vibration and high noise in the process of the motorcycle roller chain transmission.The structural innovation,mathematical modeling process and meshing principle of the silent chain are explained,and the RecurDyn dynamic simulation models of the new seal ring bush silent chain and a roller chain are estab-lished,which generate the operating wave curve caused by the polygon effect in the meshing process.The new seal ring bush silent chain is verified by variable speed and variable load wear test,noise test and road driving test.The results show that the noise of the new seal ring bush silent chain is lower than that of the roller chain,and the wear elongation of the new seal ring bush silent chain is lower than the roller chain.At the same time,it is proved that the innovative design scheme of the new seal ring bush silent chain is scientific and feasible.

Abstract: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 efficien-cy 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 ef-fects of different clearance sizes,clearance joint positions,and the number of the clearance joints on the dynam-ic 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.

Abstract:In order to improve the adaptability of the quadruped robot to the complex road surface,a quad-ruped robot with three degrees of freedom on one leg was presented.Firstly,based on the virtual prototyping technology,the ratio of the lower leg was optimized,and the best ratio of the lower leg was obtained,which took into account both the speed and the motion stability.Based on this,the waist length of the robot was optimized by using the optimization feature of the genetic algorithm and taking the space utilization rate as the objective function.Then,the forward kinematics analysis was carried out based on the D-H method.Finally,the Monte Carlo estimation of the foot reachable space was carried out by using the Matlab software.The ideal standing height and step length of the robot were obtained,which laid a foundation for the subsequent gait planning of the robot.

Abstract:In high power loaders,the drive axle is a key part of the drive train and its low power loss is crit-ical to maintain consistently excellent performance.Calculating its power loss is challenging due to the complexi-ty of its internal structure.A platform for calculating the power loss of the drive axle including the main reducer,the brake and the wheel-edge reducer was constructed in the Matlab platform,and the distribution of various power losses in the drive axle was obtained,while the accuracy of the calculation platform was verified accord-ingly through experiments.The results show that the calculation error is within 12%.The proposed modeling method and results provide important reference for the rapid and low-cost development of new generation drive axle products.