最新刊期
卷 47 ， 期 8 ， 2023
- 摘要：In order to study the effect of pressure field characteristics on the lubrication and sealing of a heavy-haul locomotive gearbox, a simulation model of the gearbox internal pressure field is established by considering the sealing structure at the vent based on the computational fluid dynamics and the lattice Boltzmann method. Then the simulated results extracted at the vent are compared with the test data to verify the correctness of the simulation model. At last, the influence law of different factors on the gearbox internal pressure field is studied with this validated simulation model. The results show that the gear speed and gear steering have a great effect on the internal pressure field of the gearbox. The absolute values of the mean pressure difference or the mean values of the pressure at all the monitoring points are positively and nonlinearly correlated with the gear speed. The change of the gear steering will change the pressure difference between the upper and lower points of the gear meshing area. The pressure difference is larger when the gear rotates forward, and the gear steering also has a great impact on the pressure of other monitoring points. However, the immersion depth of the driven gear and the lubricating oil temperature (dynamic viscosity) have little effect on the gearbox internal pressure field. It can provide a theoretical basis for the operation and maintenance of the locomotive and the rational allocation of the lubricating oil.关键词：Locomotive;Gearbox;Pressure field;Computational fluid dynamics;Lattice Boltzmann method
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发布时间：2023-08-22 - 摘要：Modeling gear grinding surface roughness is an essential basis for understanding gear integrity. Due to the complex macro shape of the grinding wheel and workpiece and the difference in local grinding conditions during gear grinding, the direct transfer of the classical surface grinding roughness modeling method is limited. Therefore, this study proposes a method for modeling the surface roughness of gear form grinding, considering the variation of local grinding strips. According to the grinding mechanism of form grinding, the grinding motion relationship between the grinding wheel and the gear is analyzed. The motion trajectory equation of abrasive particles at different local positions under the influence of macro geometric shapes is derived. A grinding wheel model considering the random distribution characteristics of abrasive particles in the complex shape of grinding wheel is established. Based on the generation mechanism of grinding surface roughness, the surface roughness of formed grinding teeth is obtained by an iterative algorithm. The forming grinding test of 12Cr2Ni4A gear material after carburizing and quenching is carried out. The results show that the prediction model of the surface roughness of formed grinding teeth presented in this study agrees with the experimental results. The model can well reflect the surface roughness distribution along the tooth profile under the local grinding strip difference. The work of this study puts forward a new understanding of the formation mechanism of the surface roughness of the formed grinding teeth and provides more reference and basis for the follow-up research.关键词：Surface roughness;Gear;Form grinding;Gear steel
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发布时间：2023-08-22 - 摘要：In order to solve the problem of tooth surface eccentric load caused by shaft deflection angle of large internal meshing gears of the shield machine, the tooth surface equation of comprehensively modified tooth surface is given, and the method of neural network combined with orthogonal test is proposed to screen and predict the tooth surface modification parameters. In this method, the tooth profile modification and tooth direction modification are no longer regarded as independent variables, and the eccentric load on the tooth surface can be transformed into the load evenly distributed on the tooth surface. Through the contact analysis of the modified gear by the finite element method, it is found that this method can effectively reduce the excessive local stress on the tooth surface caused by the shaft deflection angle and reduce the transmission error. The optimal tooth surface modification parameter value can be found at one time, which avoids the high cost of meshing experiment for the internal meshing gear of large shield machines.关键词：Gear modification;Orthogonal test;Neural network;Large internal gear
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发布时间：2023-08-22 - 摘要：In order to study the meshing efficiency of the gear pair under the actual working conditions, the force and kinematics of the contact surface of the gear pair are analyzed, the lubrication state of the gear pair is judged by combining the theory of elastohydrodynamic lubrication, and the relationship between the elastohydrodynamic lubrication and the mixed lubrication state is established. The mathematical model of the dynamic friction factor is used to obtain the friction factor of the gear pair at different meshing positions along the meshing line. From the point of view of force, the calculation formula of gear pair meshing efficiency is deduced, and the dynamic sliding friction factor is introduced to obtain the result of gear pair meshing efficiency that conforms to the actual working conditions. Combined with the simulation analysis software, the influence of the transmission ratio and the number of pinion teeth on the sliding friction factor and the meshing efficiency of the gear pair is analyzed. The results show that the calculation method of the gear pair meshing efficiency based on dynamic sliding friction factor is in good agreement with the actual working conditions, which has certain guiding significance for gear transmission design.关键词：Friction factor;Gear transmission;Transmission ratio;Meshing efficiency
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发布时间：2023-08-22 - 摘要：In order to study the vibration characteristics of fine high tooth gears, a pair of standard gears and fine high gears are taken as comparative experimental objects, and the translation torsion dynamic model of a spur gear transmission system is established. The finite element method is used to solve the time-varying meshing stiffness of fine high tooth gears, and the influence of load on the stiffness is analyzed. The vibration response of gears is calculated by Newmark-β time integration method. The dynamic loads of bearings and gear meshing excitation of standard gears and fine high gear transmission systems are compared, and the dynamic loads of input and output bearings of two pairs of gear systems at different speeds are solved. The results show that the meshing of fine high gears is two-tooth three-tooth alternating contact, and the change of stiffness is weakened. The dynamic load fluctuation amplitude of the bearing is significantly lower than that of the standard tooth, the meshing frequency and its frequency doubling amplitude are significantly reduced, and the meshing force between the teeth is reduced.关键词：Fine high tooth;Meshing stiffness;Dynamic characteristics;Meshing excitation
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发布时间：2023-08-22 - 摘要：Gear vibration and noise are important parameters that affect the transmission performance. The vibration and noise control of the gear transmission system has become a very important field. Presently, the main methods of vibration control of the gear transmission system are increasing coincidence, shape modification, displacement, damping, etc. In this study, a novel method of staggered tooth phase of gears is proposed, the meshing principle of staggered phase tuning gears is studied, the calculation formula of time-varying meshing stiffness of staggered phase tuning gears is derived, and the mapping relationship between staggered phase and vibration response is studied. The experimental scheme of the parallel shaft spur gear pair with different staggering phases is designed, the experimental study of vibration reduction effect of gear pair with different staggering phases is carried out, and the experimental results are compared and analyzed with the simulation results.关键词：Time-varying meshing stiffness;Vibration response;Vibration control;Method of gear staggering phase tuning
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发布时间：2023-08-22
Theory·Research
- 摘要：A five degrees of freedom manipulator for automatic retractable vehicle-mounted wheelchairs is proposed. Firstly, the mathematical model of the manipulator is established according to the D-H method, and the forward and inverse kinematics analysis is carried out. When the inverse kinematics analysis is carried out, the analytical method and the back propagation (BP) neural network are used to solve the problem respectively. Secondly, the quintic polynomial interpolation method is used to plan the joint space trajectory of the manipulator, so as to realize the smooth and impact-free movement of the manipulator. Then, the workspace of the manipulator is analyzed based on the Monte Carlo method, and the point nephogram of the workspace for the end positioning of the manipulator is obtained. Finally, virtual simulation experiment is carried out for specific vehicle-mounted application scenarios. The simulation results show that the design of the manipulator is reasonable, the movement is flexible, and it meets the application requirements, which will provide a theoretical basis for the development and application of the prototype.关键词：Kinematics analysis;BP neural network;Monte Carlo method;Trajectory planning;Workspace
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发布时间：2023-08-22 - 摘要：Random wind speed causes frequent load fluctuations in the wind turbine gearbox transmission system, resulting in complex structural deformations and gear deflections, which aggravate the risk of gear contact failure. A novel method to improve the fatigue performance of wind turbine gearbox transmission systems considering the stochastic uncertainty of environmental parameters is proposed. The mapping relationship among wind turbulence intensity-gear modification parameter-gear long-term contact fatigue damage is reconstructed by the surrogate model method based on the dynamic model of the wind turbine transmission system considering global loads. And then, a multi-stage gear modification parameter optimization function considering the probability distribution of wind speed is established and the optimizing fatigue performance is compared. The results show that the long-term gear contact fatigue damage value of the low-speed stage sun gear is more than 0.7, which is one of the weak parts of the high-reliability design of the wind turbine gearbox transmission system. The long-term gear contact fatigue damage values of optimizing gears have been reduced significantly, in which the low-speed stage sun gear has been reduced by 11.37%, so the fatigue performance has been improved significantly.关键词：Wind turbine gearbox;Transmission system;Environmental parameters;Fatigue damage;Performance optimization
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发布时间：2023-08-22 - 摘要：To reduce the wear of gear tooth surface and improve its transmission performance, a composite modification design method is proposed, which is based on the Sine-SSA-BP model and used to verify the influence of modification on gear wear. According to the Archard wear model, tooth wear is calculated. The threshold and the permissible gear wear are used as the criteria to reconfigure and modify the gear tooth. The new tooth surface coordinate equations are derived respectively. Moreover, the sparrow search algorithm (SSA) improved by the Sine chaotic mapping is used to optimize the back propagation (BP) neural network, and the accuracy of Sine-SSA-BP is verified by comparing it with the traditional BP, so as to characterize the implicit relationship between the modification parameters and the gear wear. The distribution law of gear wear under the influence of modification parameters is further investigated. Finally, the optimal modification parameters are obtained through the iterative solution, and the composite modification design is carried out. The influence of modification design on the gear wear is compared and analyzed. The results show that the contact state of the tooth is significantly improved, and the gear wear is significantly reduced after the composite modification design. This method is conducive to reducing the early wear failure probability of gears and can provide theoretical reference for the anti-wear design and parameter optimization of gears.关键词：Transmission gear;Wear analysis;Modification design;Surrogate model
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发布时间：2023-08-22 - 摘要：Compared with serial mechanisms, parallel mechanisms have the advantages of good rigidity, high precision, stable and compact structure, which are suitable for the field of surgery. A (5R)OC-URR parallel mechanism with two rotational and one translational degrees of freedom and remote center of motion (RCM) is proposed which can be used for the body structure of minimally invasive surgery and has the characteristics of partial motion decoupling. The position analysis model of the mechanism is established, and the analytical expression of position of the inverse solutions is derived. On this basis, the desired workspace of the mechanism is defined for the task of minimally invasive surgery. Using the evaluation index of local motion/force transmissibility, the definition and calculation method of average transmission index in the desired workspace of the mechanism are given. Aiming at maximizing the average transmission index, a constrained optimization model of mechanism dimensional parameters is established, and the accelerating grey wolf optimization (AGWO) algorithm is employed to solve the problem. The test of numerical examples shows that the comprehensive performance of AGWO algorithm in solving constrained optimization problems is better than that of the compared algorithm. The results of mechanism optimization design show that the optimization model and algorithm are feasible and effective. The research work in this study can lay a theoretical foundation for the practical application of the mechanism.关键词：Parallel mechanism;Remote center of motion;Evaluation index of transmissibility;Dimensional optimization;Grey wolf optimization algorithm
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发布时间：2023-08-22 - 摘要：Aiming at the low bearing capacity of the 3R series mechanical leg configuration, the leg configuration is improved, and two 3-DOF parallel leg configurations of 2R1T are proposed. A virtual prototype is built by Adams software with the same main structural dimensions, the same constraints and drives are added, a leg configuration is selected according to the comparison of the force of the linear actuator during loading, and the overall prototype design is completed. The leg coordinate system is established, the kinematics of the leg structure is analyzed by the vector method, the virtual prototype built by Adams software is used for simulation verification, the error between the theoretical value and the simulation value is small, and the correctness of kinematics is verified, which lays a foundation for further research and analysis.关键词：Quadruped robot;Parallel mechanism;Kinematics analysis;Vector method;Simulation verification
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发布时间：2023-08-22 - 摘要：The performance wagon is the key stage mechanical equipment to realize rich performances and diversified changes on the stage, which can carry actors or scenery. In order to solve the problem of low intelligence and poor flexibility of the traditional performance wagon, which can not walk or rotate arbitrarily according to the designated path in accordance with the program arrangement, a new type of performance omnidirectional vehicle form based on nested structure is proposed. The structure is composed of an inner and outer nested double ring frame, and the relative motion and combined motion of the nested inner and outer double rings are realized by meshing the large gear ring of the outer ring with the tension adjustment of the inner ring and driving the pinion components. The omnidirectional vehicle for the proposed structure is designed. Based on the kinematics principle, the kinematics analysis system is carried out for the omnidirectional vehicle, and the kinematics model is established. On this basis, the track estimation is carried out and the three-dimensional model is established to analyze the dynamics of the omnidirectional vehicle. An omnidirectional vehicle platform based on the nested structure is built for system experiment and tests. The results show that the omnidirectional vehicle based on the nested structure has good mechanical performance, and can realize trajectory motion with good robustness and high precision.关键词：Omnidirectional vehicle;Performance equipment;Kinematic analysis;Nested structure;Track tracking
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发布时间：2023-08-22
Design· Calculation
- 摘要：It is of great significance to establish a cylindrical gear bending fatigue life prediction model with a wide range of applications and easy calculation. Through the gear bending fatigue test combined with the simulation results of the finite element model, the energy accumulation curve at the root of the tooth under different stress amplitudes is calculated. On the basis of the energy accumulation curve, the fracture cumulative energy curve under different stress amplitudes is obtained, and a cylindrical gear bending fatigue life prediction model is proposed based on the Palmgren-Miner linear cumulative damage theory and the above curve. Combined with the test results of gear bending fatigue tests under different stress amplitudes, the test results are all within the ± 3 life factor scatter bands, which proves that the model can accurately predict the gear bending fatigue life.关键词：Cylindrical gear;Energy accumulation;Fatigue life prediction;Fatigue test;Finite element analysis
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发布时间：2023-08-22 - 摘要：The transmission efficiency of belt continuously variable transmission (CVT) generally fluctuates around 80%. In order to further improve transmission efficiency, gain economic benefit and reliability, domestic all-terrain off-road vehicle (ATV) is taken as the study object which presents problems such as low transmission efficiency, rubber belt slipping under heavy load condition and short working life of belt in the running test. The structure of the rubber belt CVT is simplified, and the influences of three key components, driving wheel limit spring, centrifugal fly hammer and slave wheel pressure torsion spring, on the performance of CVT are analyzed by using CVT experimental bench. The results show that the efficiency of rubber V-belt CVT is improved by optimizing the stiffness of the spring and the mass of centrifugal fly hammers, and reasonably matching parameters. This study provides some reference of experimental analysis method and performance data for the design of high efficiency rubber V-belt CVT.关键词：Rubber V-belt;CVT;ATV;Experimental study;Performance test
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发布时间：2023-08-22 - 摘要：In order to reduce the radiation and conduction noise of the end face of spur gears, on the basis of previous studies, the polymer materials with viscoelastic properties, acrylic ester and polyurethane, are selected and evenly coated on the end face of spur gears. The noise reduction results of different materials and different coating thicknesses are compared. The test results show that the selected polymer materials can reduce the radiated noise of spur gears. Within a certain thickness range, the noise reduction increases with the increase of the coating thickness of the material.关键词：Spur gear;Noise control;Viscoelastic material
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发布时间：2023-08-22 - 摘要：Due to its own structural characteristics, a harmonic drive system has a wide range of nonlinear factors, such as flexible deformation, friction and external uncertain interference. Most of the traditional controllers simplify the system to a certain extent, or do not consider the nonlinear external disturbance, resulting in that the performance of the designed controller cannot achieve the desired results. In order to improve the accuracy of the system, the dynamic model of the harmonic drive system is established considering the nonlinear stiffness and nonlinear friction of the system. Based on the test data, the parameters of the model are identified by the least square method. Radial basis function （RBF） neural network is used to approximate the nonlinear friction and external uncertain disturbance torque of the system on-line, and an adaptive inversion controller based on RBF neural network is proposed. Using Lyapunov stability theory, the convergence of the closed-loop system is proved. The simulation results show that, compared with the ordinary Back-stepping control, the proposed RBF neural network adaptive inversion control can effectively approach the system nonlinear friction and external unknown disturbance after being subjected to external unknown disturbance, and its peak value of tracking error can be quickly stabilized to 0.000 82 rad. The Back-stepping control is sensitive to external unknown interference, and the peak value of its tracking error increases to about 0.012 3 rad. The proposed RBF neural network adaptive inversion control can suppress the influence of parameter dynamic changes and external disturbances on the transmission accuracy of the system, and improve the transmission accuracy of the system.关键词：Harmonic drive system;RBF neural network;Back-stepping control;Transmission accuracy
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发布时间：2023-08-22 - 摘要：In order to study the transmission performance of slotted-type eddy-current couplers with radial misalignment, based on the theory of the equivalent magnetic charge theory, the copper which cuts the magnetic field line in motion is equivalent to permanent magnet. Combining with Coulomb's law, a calculation model of output torque is established in this study. The analysis of magnetic flux density, copper loss and output torque of couplers are all simulated by finite element software, and the maximum allowable value of radial misalignment is obtained. The results show that with the increase of radial misalignment, the induced magnetic field decreases during operation, which results in the increase of the magnetic flux density, the decrease of the copper loss and the torque, and the fluctuations of the copper loss and the output torque changing with time become more and more obvious. When the radial misalignment is less than 6 mm, the torque generated by the couplers can almost be remained accurately and the fluctuation of the torque is relatively stable.关键词：Slotted-type eddy-current couplers;Radial misalignment;Equivalent magnetic charge;theory;Magnetic flux density;Copper power loss
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发布时间：2023-08-22 - 摘要：The supporting stiffness analysis of the eight-cable 6-DOF cable-driven parallel robot is conducted, and the force/position hybrid control is carried out on this basis. Firstly, the cable-driven parallel robot is described systematically. Secondly, a kinematic analysis is conducted according to the principle of vector closure. The force of the mobile platform is analysed, and the static equilibrium equation is derived by Newtonian mechanics. After that, the relationship between the load change and the position change is described by the stiffness matrix in the operational space, the analytical expression of the supporting stiffness is deduced, and the influencing factors of supporting stiffness are analysed. Moreover, the factors of system stiffness, mobile platform posture accuracy and force control stability are considered, integrating the force/position hybrid controller. The simulation results show that the position error of the mobile platform is effectively reduced by the force/position hybrid control strategy, which is designed based on the stiffness analysis. Finally, the accuracy and effectiveness of the stiffness model and the force/position hybrid control strategy are verified by experiments.关键词：Cable-driven parallel robot;Supporting stiffness;Force/position hybrid control;Mobile platform;Position
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发布时间：2023-08-22 - 摘要：Increasing the fatigue life of the laminated coupling helps to enhance the working stability of the transmission system. To this end, this study establishes a quasi-static mechanical analysis model of the laminated coupling under the action of external torque, and grasps the stress change law of the dangerous part of the lamination. The fatigue life of the laminated sheet is obtained using the S-N curve method. Response surface models of spacer thickness, inclination angle and excess with respect to fatigue life of the laminations are developed by the Box Behnken method. Finally, a study on the optimization of the structure-process parameters of the coupling is carried out. The results show that when the intermediate shaft thickness is 14 mm, the inclination angle is 85.75°, the excess amount is 0.126 mm, and the fatigue life of the coupling is increased by 15.0% compared with the original structure, which ensures the stability and reliability of the shaft system.关键词：Laminated coupling;Quasi-statics mechanical analysis model;Fatigue life;Response surface model;Structure optimization
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发布时间：2023-08-22
Test·Analysis
- 摘要：In order to monitor the running state of the gear test-bed, find the running faults in time and effectively, and ensure the stable operation of the equipment, a state monitoring method of the gear test-bed based on digital twin is proposed. By establishing the digital twin model of the gear test-bed, the running state of the gear test-bed under normal operating conditions is simulated in real time, so as to realize the state monitoring, fault judgment and operation state prediction of the gear test-bed equipment. The comparison of the test results of the closed power flow gear test-bed shows that the digital twin simulation results of the gear test-bed are basically consistent with the test results of the gear test-bed. This technology can restore the operating conditions of the gear test-bed under normal operating conditions, so as to realize the state monitoring of the gear test-bed, and provide a new method for fault diagnosis and state monitoring.关键词：Digital twin;Gear test-bed;Condition monitoring
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发布时间：2023-08-22 - 摘要：The main drive gearbox of the coke dry quenching (CDQ) elevator in a steel plant has experienced serious failure after serving a period of time in service. The process of maintenance shows that the pinion shaft and the bearing of the final stage are most severely damaged. For further research of damage causes, this study will calculate the capacity and life of the bearing by KISSsoft software, and meanwhile build a 3D model of the CDQ elevator gearbox for the finite element analysis (FEA) by using software Inventor Nastran. As a result, the weakness of the structure about the gearbox is identified and the optimization is implemented contrapuntally. According to the comparison before and after maintenance, the improvement effect is obvious.关键词：CDQ elevator gearbox;Finite element analysis;Inventor Nastran
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发布时间：2023-08-22 - 摘要：A bilateral wrist joint training and rehabilitation mechanism is designed to meet the requirements of bilateral passive training better than unilateral active training. The rehabilitation mechanism adopts two spatial reverse double crank parallel sub mechanisms. The forward kinematics of the mechanism is analyzed in the spherical coordinate system, and the motion relationship of the two platforms is obtained. The Euler angles of the rolling, pitching and virtual yaw motions of the two platforms are measured, and the front and back muscles are measured simultaneously in the three motion modes. The experimental data shows that when the mechanism is rolling, the angular displacements of both platforms are equal in magnitude and opposite in direction, while the mechanism is pitching, the angular displacements of both platforms are the same in magnitude and direction. The maximum and average electromyography （EMG） values of anterior and posterior muscles measured during the bilateral active training are 319.65 mV and 352.2 mV higher than those measured during the resting state, and 155.9 mV and 184 mV higher than those measured during the unilateral passive training, respectively. The above results show that the developed bilateral training machine has mirror symmetry, can play a training effect on the wrist joint, and the training effect is better than that of the unilateral training.关键词：Stroke;Bilateral training;Wrist rehabilitation;Mirror symmetry
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发布时间：2023-08-22 - 摘要：Aiming at the current problem of low grinding efficiency of domestic ball screw grinding, a new type of ball screw grinding device is proposed. On this basis, a four-factor three-level quadrature test is designed for the four main process parameters of grinding torque, grinding speed, grinding time and abrasive particle size in the grinding process of the lead screw; a set of optimal process parameters is obtained by taking the surface roughness of the lead screw as the detection index. Then the friction torque measurement test is carried out on the ball screw before and after grinding. The effect of grinding on friction torque performance of the ball screw is explored.关键词：Ball screw pair;Grinding;Friction torque;Surface quality
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发布时间：2023-08-22
Development·Application
- 摘要：In order to address the problems of installation inconvenience and high cost of traditional encoder for speed measurement, the estimation method of instantaneous speed of rotating machinery based on vibration acceleration is studied and summarized. The present work recapitulates the basic principles of six popular instantaneous speed estimation algorithms, investigates these six speed measurement methods through the speed test of industrial helical gearboxes under different working conditions, and analyzes their advantages and applicability. The results show that the vibration acceleration signal indirectly contains the speed information of the gearbox, which can be used to accurately estimate the instantaneous speed of the gearbox, and which is of great significance for the condition monitoring and control of the gearbox in operating conditions.关键词：Tacholess measurement;Vibration acceleration;Gearbox speed;Condition monitoring
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发布时间：2023-08-22
Review
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