Abstract:In addressing the issue of identifying dynamic parameters for robotic arms,a trajectory optimi-zation method was proposed using an improved snake optimization algorithm.This method was innovatively built upon the conventional snake optimization algorithm by introducing adaptive adjustment operators in place of fixed coefficients.This adaptation enhanced the global search capability and convergence speed of the snake op-timization algorithm.The improved snake optimization algorithm was applied to the optimization design of excita-tion trajectories in the process of robotic arm dynamic parameter identification.The iterative reweighted least squares algorithm was employed as the parameter identification technique.In the experimental validation phase,a six-degree-of-freedom collaborative robot was chosen as the verification subject.The results demonstrate that,in comparison to conventional excitation trajectory design algorithms,the root mean square deviation of joint torques for the first three joints of the robotic arm decreases by 20.96%,while the root mean square devia-tion of joint torques for all six joints decreases by 23.58%.This verifies the effectiveness of applying the im-proved snake optimization algorithm to excitation trajectory optimization design,leading to enhanced accuracy in the dynamic parameter identification.

Abstract:In order to study the calculation formula of the electromagnetic torque and the transmission characteristics of the drum-type solid magnetic coupler(DSMC),a DSMC with 4 poles was taken as the research object.The magnetic equivalent circuit model introducing the induced current was established,combining with the Ampere's loop law and the 3-D magnetic effect to analyze and calculate the electromagnetic torque.The magnetic field distribution and the induced current distribution of the coupler and the mechanical characteristic curve under different input speeds were obtained by using the finite element simulation software.By moving the conductor rotor axially and changing the relative position of the two rotors,the effects of different meshing lengths on the electromagnetic torque were obtained.Finally,a test platform was built to verify the electromag-netic torque results obtained by the theoretical calculation and the finite element simulation.The experimental results are basically consistent with the above results.The model provides guidance for the design and optimiza-tion of the DSMC.

Abstract:In order to achieve accurate control of the lower extremity exoskeleton,the joint torque was ana-lyzed when the exoskeleton climbed the slope with different loads.Based on the third generation of the human-machine portable assisted exoskeleton robot of Southwest Jiaotong University,the exoskeleton dynamics model was established by the Lagrange method,and the calculation expressions of each joint torque were obtained.The lower extremity motion data was obtained by the 3D motion capture system,the driving torque required by the joint was calculated by the Matlab software,and the torque variation law was obtained during the process of climbing the slope.Finally,the three-dimensional exoskeleton model was established in SolidWorks software and imported into Adams software for dynamic simulation,and the reliability of the simulation results was veri-fied by comparing with the theoretical calculation results.The results of this study can increase the accuracy of the control results in the process of the exoskeleton climbing and the comfort of wearing the exoskeleton.

Abstract:The bearing performance and wear condition of the turning arm bearing of cycloidal reducers are closely related to the rotary accuracy and life of reducers.Aiming at the actual wear condition of a 150BX type cycloidal reducer bearing hole,first of all,the bearing model of the turning arm bearing was es-tablished,and the change rules of the maximum load and its direction were established.Then the motion models of the cycloidal gear and crankshaft containing manufacturing errors were established,the interfer-ence of the manufacturing errors on the movement of the turning arm bearing was analyzed,and the maxi-mum interference position on the turning arm bearing and the error selection method were obtained.The find-ings of this study provide a basis for the wear calculation of the turning arm bearing of the cycloidal reducer and the error selection of key components.

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]In the planetary gear system,the presence of the flexible pin shaft makes the nonlinear behavior in the gear transmission process more complex.To reveal the nonlinear dynamic behavior of the planetary gears in the wind power gearbox with flexible pins,a translational torsional coupling dynamic model and motion differential equations of the gear train were established.[Methods]Key factors such as the stiffness of the flexible pin,backlash,time-varying meshing stiffness,and error excitation were considered comprehensively.The influence of pin stiffness on the nonlinear dynamic performance of planetary gear was investigated by studying the dynamic meshing force,phase diagram,acceleration,Poincare diagram,and axis trajectory of sun gear and planetary gears.[Results]The results show that as the stiffness of the flexible pin decreases,the vibration acceleration and dynamic meshing force fluctuation range of the sun and planetary gears decrease and then increase.The motion of the sun gear and planetary gear transforms from periodic to quasi periodic when the stiffness of the flexible pin decreases.The stiffness of the flexible pin has a smaller impact on the floating range of the sun gear but a larger impact on the floating range of the planetary gear.The floating trajectory range of the planetary gear is greatly increased by reducing the stiffness of the pin shaft.

Abstract:[Objective]In response to the unclear lubrication characteristics of dynamically loaded journal bearings under misaligned journal states,a mixed elasto-hydrodynamic lubrication model for dynamically loaded journal bearings considering journal misalignment was constructed.[Methods]Based on the transient mixed lubrication model of journal bearings,the oil film thickness under journal misalignment was modified,and a metal surface roughness peak elastoplastic contact model was in-troduced to further couple the dynamics equation of the journal center with time-varying loads.A numerical solution scheme and model convergence conditions were designed to achieve lubrication simulation of dynamically loaded journal bearings with jour-nal misalignment.[Results]The results show that as the misalignment angle of the journal increases,the maximum oil film pres-sure and rough contact pressure significantly increase,exhibiting a specific nonlinear law.The minimum oil film thickness shows an approximately linear decrease,and the pressure and oil film distribution show significant non-uniformity with the in-crease of misalignment angle.The axis trajectory reflects that the journal's position in the misaligned state is lower than that in the alignment state of the journal.

Abstract:[Objective]Aircraft gears typically operate in extreme environments such as high temperatures,high speeds,and heavy loads,requiring excellent comprehensive performance.Surface integrity parameters have a decisive impact on gear fa-tigue performance.Rolling grinding is a finishing process that utilizes the mechanical action of abrasives to improve the surface integrity of workpieces.To improve the surface integrity and fatigue life of aviation gears,it is necessary to explore the behavior of the contact interface between the tooth surface and abrasive particles in gear rolling and polishing machining.[Methods]A simulation model for the barrel finishing of aerospace gears was established based on the discrete element method to analyze the material removal from the gear surface.A predictive model for the three-dimensional surface roughness Sa value of gear surfaces was developed.Barrel finishing experiments were designed for 14CrMnSiNi2MoA aerospace cylindrical spur gears.The evolu-tion of surface morphology and residual stress over time,before and after finishing,was analyzed.[Results]The results indicate that barrel finishing significantly reduces the surface roughness of aerospace gears and increases surface compressive residual stress.However,the finishing effects vary across different positions on the tooth surface,with the abrasive action strength on the tooth surface following the pattern:near the gear tip>pitch circle>near the gear root.

Abstract:[Objective]The existing research on diaphragm couplings mainly focuses on the mechanical performance of dif-ferent types of diaphragm couplings and the optimization of diaphragm size and shape through various optimization algorithms.There is relatively little research on the influence of diaphragm structural parameters on the mechanical performance of cou-plings under high torque and large deformation conditions.Therefore,a parameterized model of fan couplings was established through finite element analysis software Abaqus to explore the mechanical performance of nonlinear structures of fan diaphragm couplings under high torque and large deformation conditions.[Methods]The reliability of the simulation results was verified by analyzing the finite element stress results of the global model of the fan coupling.On this basis,different parameters of the waist structure of the membrane and the anisotropic stiffness and stress characteristics of the membrane under multiple membrane groups were studied,and the optimal combination of waist structure parameters and membrane layers under actual composite working conditions was obtained.And based on this combination model,multi-objective shape optimization of membrane struc-ture was carried out.[Results]As the number of layers in the membrane group and the parameters of the membrane waist struc-ture increase,the isotropic stiffness of the membrane continues to increase.The number of layers in the membrane group is in-versely proportional to the equivalent stress,and the parameters of the membrane waist structure are inversely proportional to the equivalent stress.By increasing the thickness of the stress concentration location on the membrane,it is possible to effectively re-duce the maximum equivalent stress,disperse stress concentration phenomena,and improve structural stiffness.

Abstract:Aiming at the problem of tooth surface twist of helical gears with longitudinal tooth crowing caused by the worm wheel grinding method,an anti-twist grinding method using an arc-shaped worm wheel was proposed.First of all,based on the generating process of the double-parameter envelope,a spatial meshing coor-dinate system between the worm wheel and the helical gear was established to calculate the contact line.Then,the twist values at different tooth width positions were calculated.The relation between the pressure angle devia-tion and the position value of the worm wheel was established,and the calculation process of the arc shape of the worm wheel was performed.Finally,an example was presented to verify the anti-twist dressing method.Com-pared with the deviation of the gear flank,the twist was compensated by using the arc-shaped worm wheel.The feasibility of the anti-twist grinding method was verified.

Abstract:Regarding the problem that the traditional near-field acoustic holography(NAH)has difficulty in reconstructing the sound field of the gearbox,this work makes full use of the cyclostationary characteristics of the radiated noise and combines the cyclostationary signal analysis with the equivalent source NAH algorithm to develop a sound imaging method for the gearbox.Firstly,the set of cyclic frequencies was estimated from the noise signal;secondly,the cyclic frequency of interest was selected,and the corresponding cyclic spectral densi-ty function was calculated;thirdly,the equivalent source NAH method was developed to reconstruct the poten-tial sound source of the gearbox.Finally,the effectiveness of the sound imaging method was justified by the sim-ulation and experimental data.

Abstract:In light of the problem of complex and diverse parameters and low optimization efficiency in the performance optimization of a solid disk permanent magnet eddy-current coupler,the dimensionless parameters of the disk permanent magnet eddy-current coupler were derived according to the dimensional analysis method.Six dimensionless parameters such as velocity parameter,magnetic density parameter,air gap parameter and di-mensionless number of main dimensions were obtained,which effectively reduced the workload of the analytical study;the correctness of dimensionless numbers was verified by the equation analysis method.The impact of each dimensionless number on the output torque of the permanent magnet eddy-current coupler was simulated by the 3D finite element.In order to improve the optimization efficiency,the structural optimization design was carried out by the response surface method to improve the utilization of permanent magnets,and the simulation results verified the effectiveness of the optimization.

Abstract:In order to enhance the operation capability of the robot end-effector and ensure the safety of human-robot interaction,a variable stiffness mechanism(VSM)with variable stiffness,energy storage,strong environmental adaptation,and safe human-robot interaction was proposed.Firstly,the principle of the mecha-nism to realize the variable stiffness function through the axial arrangement and interaction of multiple magnets was introduced,and several different stiffness modes were proposed.Then,the VSM was mounted on a 6-DOF robotic system to conduct a series of hammering collision experiments to demonstrate and analyze the excellent energy storage and adaptive capability of the VSM.In the meantime,relying on the robotic system,using Python software and finite element analysis,how to achieve the optimal hammering trajectory and the best hammering ef-fect through the VSM was explored.Finally,the potential damage to the robot caused by conducting a hard crash test chamber and how to adjust the VSM stiffness to mitigate this type of damage were also analyzed.The results show that the presence of the VSM can absorb most of the impulsive forces transmitted to the robot during its low stiffness phase,thus effectively avoiding the damage caused by the robotic system when performing similar tasks.

Abstract:The brake pad is one of the most critical safety part in the braking system,and it plays a vital role in ensuring drivers safety.In order to investigate the effect of braking conditions on the wear loss of disc brake pads,using Ansys Workbench simulation software,the wear simulation model was built based on the Ar-chard wear model;Archard wear commands were added through the APDL command flow to realize the wear simulation of the brake pad,so as to analyze and calculate the wear loss of the brake pad.The brake pad friction and wear test bench was built and five groups of different braking conditions were randomly selected for brake pad wear test,and the test results were compared and analyzed with the simulation results to verify the correct-ness of the simulation model.The results show that within the set parameter range,the effect of the brake pres-sure on the wear loss of brake pad is smaller compared to the effect of the initial brake speed;without the inter-vention of the external heat source,the individual effect of the brake pad surface temperature on the wear loss is smaller compared to the combined effect of other parameters such as initial brake speed and brake pressure on the wear loss of the brake pad.