Abstract:The NVH noise performance of electric vehicles greatly affects driving comfort,and the NVH performance has become a key indicator for verifying the quality of their products;strengthening the research can greatly promote the high-quality development of reducers.Aiming at the problem that the noise data acquisi-tion environment of the noise test stand is highly disturbed and difficult to be eliminated,a noise signal decompo-sition based on variational modal decomposition(VMD)and fast independent component analysis(FastICA)and a background noise component identification and noise reduction method based on signal correlation analysis were proposed.The method firstly adopted the VMD to decompose the speed reducer mixed signal into multiple modal components,and then further separated and demixed the obtained modal components through the FastI-CA to obtain the multidimensional independent components.Finally,the multidimensional independent compo-nents were identified and filtered out by using the signal correlation analysis to reduce the noise and complete the separation of the background noise in the test.The results show that the proposed VMD-FastICA can correct-ly separate the background noise signal in the mixed signal,and effectively separate the noise.Through the re-ducer noise test stand 9 000 r/min speed conditions of operation test comparison,the decomposition filters out the background noise and reduces the sound pressure level by an average of 3.09 dB(A),with an average error of 0.32 dB(A),to further optimize new energy vehicle gearbox noise performance test methods,and to enhance the accuracy of the gearbox noise test to provide a technical guarantee.

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: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]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:[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]Considering the compact structural and internal/external excitations of the floating wind turbine drivetrain comprehensively,a 6.2 MW floating wind turbine compact drivetrain was taken as the research object to establish a rigid-flexible coupling nonlinear multi-body dynamic model.[Methods]The influence of base motion on the load-sharing perfor-mance of the floating wind turbine planetary gear transmission was analyzed.The influence law of component assembly error,main shaft's length,and bearing position on the load-sharing performance of the floating wind turbine planetary gear transmis-sions was clarified.This study can support improving the load-bearing capacity of the floating wind turbine drivetrain.[Results]The results show that the nonlinear coupling of foundation motion and environmental load has a negative impact on the load-sharing performance of planetary transmission system,and the impact increases with the increase of wind speed.It is found that the load-sharing coefficient of planetary transmission system increases monotonously with the increase of component errors.Specifically,the influence of assembly errors of different parts on the load-sharing characteristics is in descending order:plane-tary gear,sun gear,planetary carrier and inner gear ring.In addition,with the increase of the length of the main shaft and the dis-tance between the support point and the hub,the bearing load capacity of the planetary transmission system will be improved.

Abstract:[Objective]A path planning algorithm based on an improved dung beetle optimization algorithm was proposed to address the challenges in complex scenarios where traditional algorithms for robotic arm path planning often suffer from low efficiency and susceptibility to local optima.[Methods]Firstly,the robotic arm and obstacles were modeled using the bounding box method.An optimization function was established based on path length,joint motion smoothness,and collision avoidance.Secondly,the algorithm incorporated Logistic mapping for population initialization to enhance diversity and improved the heuris-tic mechanism to accelerate convergence.It introduced an adaptive polynomial mutation to escape local optima.Thirdly,the comparative simulations were conducted using basic dung beetle algorithm,jellyfish algorithm,grey wolf algorithm,whale algo-rithm,and the improved dung beetle algorithm in Matlab software.Finally,the real-world testing was conducted.[Results]The results indicate that the proposed algorithm is less prone to getting trapped in local optima,achieves faster convergence,shorter computation time,and higher optimization accuracy when solving robotic arm path planning problems.The algorithm's reliabili-ty is validated through the real-world testing.

Abstract:[Objective]To improve the automation welding production efficiency of steel columns and rib plates,a special welding torch moving mechanism has been designed.[Methods]Firstly,a cam linkage combination mechanism was designed to meet the moving trajectory and speed of the welding gun.Then a kinematic model of the mechanism was established.Secondly,based on the NSGA-Ⅱ algorithm,taking the transmission performance of the mechanism and the overall size of the mechanism as the optimization goals,a multi-objective optimization design of the connecting rod length was carried out under limited condi-tions,and the entropy weight method was used to select the optimal connecting rod length from the Pareto non-inferior solution set.Thirdly,the optimal roller coordinates were searched in the two-dimensional plane with the optimal rod length,and Matlab programming was used to obtain the convex contour line to verify that the cam pressure angle meets the design requirements.Fi-nally,based on the optimization results and combined with actual working conditions,the mechanism was modeled,and the Ad-ams simulation was used to obtain the working trajectory,speed and acceleration of the mechanism.[Results]The results show that the mechanism can meet the design requirements of welding trajectory and uniform speed welding as scheduled.At the same time,the optimized cam base circle radius is reduced by 29.79%compared with before optimization,and the speed and ac-celeration fluctuations are smaller.The correctness of the mechanism and the feasibility of the method are verified,and it pro-vides a reference design method for the design of other cam linkage mechanisms.

Abstract:[Objective]Robot inverse kinematics solution plays an important role in trajectory planning and control.The traditional inverse kinematics of robot was solved according to the kinematics equation and the mathematical theory,which has low calculation efficiency and has a certain impact on the control accuracy.In order to overcome these problems,an improved whale optimization algorithm was used to solve its inverse kinematics.[Methods]Improved whale optimization algorithm was proposed by integrating the mutation and selection operations of differential evolution algorithm into the whale optimization algorithm.The improved algorithm has good global search performance and fast convergence.Taking a 6R robot as the research object,improved whale optimization algorithm was used to solve its inverse kinematics.[Results]Results show that using improved whale optimization algorithm to obtain the inverse kinematics solution of the robot can simplify the solving steps and ensure the solution accuracy at the same time.

Abstract:[Objective]To address the issues of uneven residual compressive stress distribution and high surface roughness in gears after shot peening,this study investigates the effect of double shot peening on the surface integrity of 18CrNiMo7-6 car-burized gear steel.[Methods]A shot peening model with random shot distribution was established using Abaqus software.The effects of shot peening parameters such as shot velocity and shot diameter on the residual stress and surface morphology of the 18CrNiMo7-6 carburized gear steel were analyzed for both single and double shot peening.[Results]The results show that com-pared with single shot peening,double shot peening leads to more uniform plastic deformation on the material surface.The dou-ble shot peening significantly increases the residual compressive stress in the surface layer and shifts the depth position of the maximum residual compressive stress towards the surface,but has no significant effect on the depth of the residual compressive stress layer.Through variance analysis,when the shot coverage is 100%,using a lower shot peening intensity for the second shot peening process improves the uniformity of the surface residual compressive stress more effectively,with the maximum improve-ment reaching 28.76%.

Abstract:The magnetic drive equipment has advantages such as static sealing,overload protection and environmental friendliness,and its application is becoming increasingly widespread.Magnetic forces and torques between permanent magnets are the focus of the research on the magnetic drive technology.At present,many studies focus on establishing analytical models with three or four degrees of freedom to solve magnetic torques,but their applications have certain limitations.Based on the theory of the equivalent magnetic charge,a five degrees of freedom magnetic torque analytical model was established between circular magnets,and the in-fluences of factors such as relative displacement,eccentricity,and angle on the magnetic torque were analyzed.This model can solve magnetic torques of two axially magnetized magnetic tubes at any relative position and pos-ture.This study provides reference for the research and application of the magnetic drive equipment.

Abstract:[Objective]The existing intelligent fault diagnosis methods face challenges,such as model training relying on a large amount of labeled data,difficulty in obtaining fault data with different occurrence probabilities,and insufficient consider-ation of the impact of operating conditions.To address these challenges,a novel gearbox diagnosis method for adaptive inter-class and intra-class unbalanced fault data under varying working conditions was proposed.[Methods]Firstly,a gated local con-nection network was utilized to reduce the reliance on the labeled data and extract intrinsic features directly from the original da-ta.Secondly,a parallel mechanism of external and internal attention was designed to consider the distribution differences among inter-class and intra-class faults under different working conditions,adjusting the weights of extracted features accordingly.Fi-nally,focal loss function was employed to focus on minority and challenging samples,enabling high-quality mining of unbal-anced diagnostic information.[Results]The proposed method is demonstrated by six unbalanced gearbox datasets,which shows great effectiveness and superiority in identifying unbalanced fault data.

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.