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.

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]In response to the issues such as insufficient configuration innovation and incomplete kinematic performance analysis in existing 2-degree-of-freedom parallel mechanisms,the topological synthesis and kinematic performance studies on the novel single-loop translational parallel mechanisms were conducted,aiming to provide fundamental motion unit design theories for link-type modular robots.[Methods]Firstly,according to the topology design methodology of the parallel mechanism(PM)based on position and orientation characterization(POC),four single-loop translational spatial PMs consisting of two prismatic joints and five rotating joints were proposed,and their topological analysis was performed.Secondly,the symbolic positional positive and negative solutions,workspaces,and the singularities and their singular positions were derived for each of the four PMs and verified,respectively.Finally,the differential evolution algorithm was used to optimize the maximum workspace of the four mechanisms,and their maximum workspace were finally obtained.[Results]This single-loop translation spatial parallel mechanism can be used to design the unit of modular rod-type robots.This work lays a foundation for the design and its stiffness,kinematic error,dynamics analysis of the modular robot based on this unit.

Abstract:[Objective]The field modulated magnetic gear(FMMG)with the coaxial structure has a higher transmission capacity,which can be comparable with mechanical gears.While,the coaxial structure with the narrow and long air gap makes FMMG face the problem of heat dissipation.High temperature is easy to cause the performance degradation of the permanent magnets,or even demagnetization,and transmission failure.In view of the seriousness of the problem,a combined heat dissipation based on the pulsating heat pipe(PHP)and forced air cooling was proposed.[Methods]The PHP working process from start-up to dynamic equilibrium cycle based on the fluid-solid coupling simulation was analyzed.Influence of the liquid filling rate and other parameters on the equivalent thermal conductivity was discussed.The temperature field distributions of the FMMG under the different heat dissipation modes were analyzed.[Results]The finite element analyses and test results show that there are specific shortcomings for single PHP heat dissipation and single forced air cooling heat dissipation in FMMG,and the combined cooling method with both PHP and forced air cooling can dissipate heat more efficiently.This technology can provide support for the realization of high-power density FMMGs.

Abstract:[Objective]The global path planning algorithm for mobile robots currently faces challenges such as excessive inflection points,prolonged computation time,and inefficiency in complex environments.To address these issues,an improved A* algorithm was proposed and experimentally validated under complex environmental conditions.[Methods]Firstly,the traditional 8-neighborhood search of the A* algorithm was expanded to a 12-neighborhood search.Subsequently,based on the collision model derived from environmental heuristic information processing,the searched paths were categorized into four cost types,with the least-cost path selected as the optimal trajectory for the mobile robot.Finally,the optimal path obtained from the planning was smoothed using the cubic spline interpolation method.[Results]Test results demonstrate that,compared to the traditional A* algorithm,the improved A* algorithm achieves search speed improvements of 32.68%,33.40%and 20.17%in simple,moderate and complex environments,respectively.Additionally,the number of severe path deflections is reduced by 35.71%,43.67%and 47.58%in these environments.The obtained path has the advantages of fewer nodes,a shorter distance,and a smoother trajectory.

Abstract:[Objective]In order to understand the influence of side chains with similar topological structures on the decoupling and derived motions of parallel mechanisms,parallel mechanisms with similar topological structures were designed,and their topological characteristics and position equations were analyzed.[Methods]Firstly,based on the topology design method of parallel mechanisms using the position and orientation characteristic set theory,four novel single-loop spatial two-degree-of-freedom three-translation parallel mechanisms composed of similar branches were constructed.The design process was detailed,and the degrees of freedom were calculated.Secondly,kinematic models of these four mechanisms were established,and closed-form univariate octic(eighth-degree)equations for the forward kinematics were derived,with numerical methods employed to obtain numerical solutions.Symbolic inverse kinematic solutions were also derived analytically and verified.Finally,the intrinsic relation between the independently output motions and parasitic motions of the moving platform was analyzed.[Results]It is found that these single-loop two-degree-of-freedom three-translation parallel mechanisms are motion-decoupled and exhibit parasitic motions,making them suitable as main structures for lightweight three-dimensional vibrating screens.The results lay the foundation for dimensional optimization,workspace analysis,and dynamic analysis of such mechanisms.

Abstract:[Objective]To analyze the stage changing quality of small and medium-sized tractors equipped with hydro-mechanical continuously variable transmission(HMCVT)in the process of power changing,based on a HMCVT with continuously variable characteristic parameters,the traditional gear planetary transmission structure was changed into the traction planetary transmission structure,and a multi-stage HMCVT system was proposed.[Methods]Considering the influence of changing time and displacement ratio of the hydraulic system on the stage changing quality,AMESim modeling and simulation analysis of the multi-stage HMCVT system was carried out by adding a variable concerning which the characteristic parameters of the traction planetary array were continuously changing.When the change period t0=0.8 s was set in the simulation,multi-parameter adjustment analysis was carried out on the three evaluation indexes of the change period quality,such as velocity drop,impact degree and sliding power,in the characteristic parameter k 1.5-2.[Results]The design of the three-stage HMCVT system can reduce the maximum sliding power by 25.6%or the maximum impact degree by 20.84%by changing the value of the characteristic parameter k in the L and H stages.By changing the value of the characteristic parameter k in the S and L sections,the sliding work can be reduced by 6.68%,but the impact of changing the characteristic parameter k on the impact degree changes within 1%.The overall velocity drop will increase with the increase of the characteristic parameter k.The research results can provide reference for further improving the stage changing quality.

Abstract:[Objective]The high contact ratio(HCR)gear pair basically does not need to increase the weight of the gear de-vice to achieve an increase in carrying capacity and a smoother transmission.Therefore,the use of HCR gears instead of ordi-nary gears in the transmission system was proposed to improve the load carrying capacity of the gear system and reduce the vi-bration of the system.[Methods]Based on the potential energy method,the time-varying meshing stiffness calculation model of HCR gear was established,and the time-varying meshing stiffness and stiffness fluctuation between HCR gear and ordinary con-tact ratio gear were compared.The dynamic model of HCR gear system,including shaft segment,spur gear pair and bearing,was established by the finite element method.The dynamic characteristics of the HCR gear system and ordinary contact ratio gear system were compared in different speed conditions.[Results]The results show that compared with the ordinary contact ra-tio gear,the comprehensive meshing stiffness of HCR gear is significantly increased,and the stiffness fluctuation is significantly decreased.The root mean square and peak-to-peak values of dynamic meshing force and vibration acceleration of HCR gear sys-tem decrease significantly under different speed conditions.

Abstract:[Objective]To address the lightweight issue of electric drive axle housing,a specialized lightweight design method based on an approximate model and combinatorial optimization algorithm was proposed.Furthermore,the introduction of the 6σ reliability optimization theory aimed to enhance the stability of the axle housing.[Methods]Firstly,the design variables that have a significant impact on the performance of the axle housing were selected through sensitivity analysis.Secondly,a radial basis function(RBF)neural network approximation model of the axle housing was constructed based on test design data,followed by deterministic multi-objective optimization using a combination algorithm of the second-generation non-dominated sorting genetic algorithm(NSGA-Ⅱ)and the non-linear programming by quadratic Lagrangian(NLPQL).Finally,considering the influence of uncertain factors on the performance of the axle housing,6σ reliability analysis theory was introduced for reliability optimization design based on RBF neural network approximation model.[Results]The results indicate a 6.9%reduction in mass after optimized design,along with improved reliability in axle housing performance meeting 6σ standards.

Abstract:[Objective]Aiming at the problems of traditional rapidly-exploring random tree(RRT)algorithm in multi-degree-of-freedom manipulator path planning,such as the unguided search and the poor path quality,a heuristic RRT algorithm based on collision-free channels was proposed.[Methods]Obtaining collision-free channels in the workspace through a sphere-based wavefront expansion algorithm(Wavefront algorithm),setting up path targeting points,and utilizing the environmental information to inspire the tree growth instead of the traditional blind searching;the random point sampling function was improved,and the multi-dimensional Gaussian distribution model and Gaussian mixture model(GMM)of the path targeting points in the joint space corresponding to the joint angles were used as the heuristic terms,respectively,to guide the end-effector of the manipulator to direct the fast and stable expansion in the collision-free channel.[Results]Simulation and analysis results show that the heuristic RRT algorithm reduces the path search time and the number of iterations,and the path length is shortened by 39.32%compared with the traditional RRT algorithm.

Abstract:[Objective]In order to improve the accuracy of small-module gears,small-module gears are prepared by using 420 stainless steel powder as raw material and metal powder injection molding(MIM)process at a sintering temperature of 1 330-1 360℃.The injection blank with the best micro-morphology was taken as a prerequisite to study the effect of sintering temperature on the accuracy of small-module gears.[Methods]MLA650F field emission scanning electron microscope was used to observe the microscopic morphology of the gear injection blanks;JE 20 gear measuring center,Image J software,and Rockwell hardness tester were used to measure the accuracy,porosity,and hardness of the sintered gears,respectively.[Results]The results show that under 110 MPa injection pressure,when the sintering temperature is increased from 1 330℃to 1 350℃,the porosity of the gear surface decreases by 48.28%,the density increases by 5%,the hardness increases by 8.22%,the shrinkage continues to increase,and the accuracy is gradually improved;when the temperature is more than 1 350℃,the porosity decreases by 20%,the density decreases by 0.26%,the hardness decreases by 0.51%,the shrinkage rate increases slowly,and the accuracy of the gear gradually decreases;when the sintering temperature is 1 350℃,the gear has the best comprehensive performance,with a porosity of 1.5%,a density of 7.56 g/cm3,a hardness of 39.5 HRC,a shrinkage rate of 14.1%,and the highest accuracy level of grade 7 in the GB/T 2363-1990 testing standard.