Table of Content

25 May 2021, Volume 32 Issue 10

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Development Status and Perspective Trend of Motor Cooling Systems

TANG Yong, SUN Yalong, GUO Zhijun, ZHANG Shiwei, YUAN Wei, TANG Heng, LIANG Fuye

2021, 32(10):  1135-1150.  DOI: 10.3969/j.issn.1004-132X.2021.10.001

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Cooling systems with high heat dissipation efficiency were the important foundations of restraining motor temperature rise, improving motor operation stability and prolonging motor life. The development status of air cooling, liquid cooling and evaporative cooling was introduced, which were commonly used in the cooling systems for motors. The advantages, disadvantages and application ranges of various motor cooling systems were analyzed and discussed. The research progresses in improving the cooling efficiency of motor heat dissipation system at home and abroad were reviewed. By combining the additional thermal circuit enhanced motor cooling system and the phase change heat dissipation technology, a new scheme to improve the heat dissipation efficiency of motors using phase change heat transfer devices was proposed. Finally, the development trend of the motor heat dissipation systems was predicted and prospected scientifically. 

Research on Multi-needles-multi-directions Cooperative Weaving Path Generation Method of Composite Preform#br#

CHEN Zhe, LIU Feng, WU Xiaochuan, DU Wudi

2021, 32(10):  1151-1156.  DOI: 10.3969/j.issn.1004-132X.2021.10.002

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The preform with convex polygonal section was fabricated using the multi-needles- multi-directions method, interference would occur between the x and y-direction fibers. A method of generating multi-needles-multi-directions cooperative weaving path was proposed. The shape characteristics of the cross-sectional profile of the preform were analyzed by using geometric abstraction. The combination of the laying direction of the sub-regions was discussed after dividing the cross-sectional profile, and the conditions for generating the interference-free weaving path of the cross-sectional profile were obtained. A typical preform was fabricated by the path generation method, it is found that the fibers laid in different directions will not interfere, and the fibers inside the preform are complete and will not overlap. The results show that the path generation method is rational.

Applications of a Ridgeline Extraction Method in Bearing Fault Diagnosis

CHEN Jian, YANG Bin, HUANG Kaixuan, CAI Kunqi, LIU Yuanyuan, LIU Xingfu,

2021, 32(10):  1157-1163.  DOI: 10.3969/j.issn.1004-132X.2021.10.003

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To solve the problems of low ridgeline identification ability and differences between the extracted ridge and the actual ridge in Crazy Climber algorithm, the Climbers movement rule and local optimal peak extraction method in the algorithm were improved. An improved Crazy Climber algorithm was proposed. First, STFT was applied to the time-domain signals to obtain the time-frequency matrix, and then the improved Crazy Climber algorithm was used to extract the time-frequency matrix to obtain the time-frequency ridge that might reflect the frequency changes with time. The simulation signal analyses prove that this method is superior to the original Crazy Climber algorithm. The method is used in the fault diagnosis of bearings, and the fault order is accurately extracted.

Bearing Fault Diagnosis Method Based on Small Sample Data under Unbalanced Loads#br#

HE Qiang, TANG Xianghong, LI Chuanjiang, LU Jianguang, CHEN Jiadui

2021, 32(10):  1164-1171,1180.  DOI: 10.3969/j.issn.1004-132X.2021.10.004

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Aiming at the problems that the bearing vibration signals were easily disturbed by unbalanced load and the small number of bearing fault samples, a bearing fault diagnosis method based on WGAN-GP and SeCNN was proposed. The bearing vibration signals were processed by short-time Fourier transform to get the time-spectrum samples that were easy to be processed by WGAN-GP, which were divided into training set, validation set and test set. Then the training set was inputted into WGAN-GP for adversarial training, new samples were generated with similar distribution to the training samples, and added to the training set to expand the training set. The expanded training set was input into SeCNN for learning, and the trained model was applied to the test set and output the fault recognition results. The analysis of the CUT-2 platform unbalanced load bearing data was carried out, and the experimental results show that the proposed method may accurately and effectively classify the bearing faults.

Experimental Research on Ultrasonic Assisted Internal Grinding of 40Cr15Mo2VN Bearing Rings#br#

YIN Long, ZHAO Bo, GUO Xingchen, ZHAO Chongyang

2021, 32(10):  1172-1180.  DOI: 10.3969/j.issn.1004-132X.2021.10.005

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In view of the difficulty in obtaining the low surface roughness and surface waviness of the bearing rings for the traditional machining method, a machining method using ultrasonic assisted internal grinding was proposed to improve the surface quality of the bearing rings. Based on the analysis of single abrasive grain trajectory in ultrasonic internal grinding, a theoretical model of surface roughness was established. The effects of various machining parameters on the surface quality of the bearings were studied by ultrasonic inner grinding of the bearing rings. The results demonstrate that the ultrasonic internal grinding significantly improves the surface quality of the bearings. Increase of the ultrasonic amplitudes may reduce the surface roughness and the surface waviness will decrease first and then increase. As the grinding wheel speed increases, the surface roughness and surface waviness will reduce first and then increase. Increased grinding depths and feed rates will increase surface roughness and surface waviness, but ultrasonic internal grinding may reduce the increases both of them.

Load Distribution of Double Nut Ball Screws with Consideration of Geometric Errors and Overturning Moment#br#

XI Jingyao, ZHOU Changguang, FENG Hutian, ZHANG Luchao

2021, 32(10):  1181-1190.  DOI: 10.3969/j.issn.1004-132X.2021.10.006

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A load distribution model of double nut ball screws was established by considering the geometric errors（ball size error, lead error and raceway profile error）and overturning moment. The force and displacement deformation curves of a typical 4010 ball screw were measured to verify the correctness of the theoretical model. The effects of axial loads, geometric errors and overturning moment on the load distribution of double nut ball screw were studied by simulation analysis. The results show that when the axial loads are of a constant, the overturning moment may cause the load distribution of double nut ball screws to deteriorate rapidly. The ball size errors and raceway profile errors may lead to the loads of the balls either increase or decrease. Due to the accumulation of the errors in the screw axial direction, the lead errors may lead to the increase of the load within one wide nut while the decrease of the load within the other side nut. When the error sizes keep constant, the influences of lead errors on the load distribution is greater than that of the ball size errors and raceway profile errors, namely the load distribution of double nut ball screws is more sensitive to the lead errors.

Experimental Study on Abrasive Dilatancy and Processing of Pneumatic Grinding Wheels under Non-uniform Curvature Surfaces#br#

SHI Meng, LI Zhuo, ZENG Xi, JI Shiming, HUANG Pengcheng, ZHENG Qianqian

2021, 32(10):  1191-1199.  DOI: 10.3969/j.issn.1004-132X.2021.10.007

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The cutting forces and the abrasive velocity in the contact area of the workpiece were changed when the SCA pneumatic grinding wheel was used to process the irregular curved surface. In order to solve the problems of uneven material removal at different curvatures of the workpieces, the modified Rowe dilatancy theory was proposed to establish the grinding wheel cutting force model, and the modified material removal model of the pneumatic grinding wheel under the non-uniform curvature surfaces was proposed herein. The model of SCA pueumatic grinding wheel was established by EDEM software. The influences of workpiece curvatures on contact forces and abrasive velocity in contact areas were analyzed when the amount of compression of grinding wheel was as 1.5 mm. The modified material removal model was verified by finishing experiments. The results show that the modified material removal model MAE(mean absolute error) is as 0.095, while the original material removal model MAE is as 0.291, The revised material removal model may be used for quantitative analysis in the SCA wheel polishing processes, scratches on the machined surfaces of the workpiece are significantly reduced.

Research on Attitude Estimation of Rocket Propellant Filling Robots Based on Lidar#br#

LU Yu, JIANG Zan, HONG Gang, DUN Xiangming

2021, 32(10):  1200-1204.  DOI: 10.3969/j.issn.1004-132X.2021.10.008

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To realize the demands of automatic docking in the filling processes of fuel propellant in the launch of carrier rockets, an attitude estimation algorithm was proposed based on single-line lidar. The two-dimensional lidar was rotated by a motor, and the three-dimensional point cloud information of the environment was collected. The target boards with special geometry shapes were identified by the proposed algorithm to determine the relative attiudes between the filling robots and the arrow valves, and the attitude estimation of the robots was realized based on artificial beacon. Finally, the reliability and accuracy of the proposed algorithm were verified by experiments.

Low-identification Dual Target Recognition Based on Feature Fusion

WU Yuan, XUE Peilin, YIN Guodong, HUANG Wenhan, GENG Keke, ZOU Wei

2021, 32(10):  1205-1212,1221.  DOI: 10.3969/j.issn.1004-132X.2021.10.009

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Aiming at the problems of low accuracy of low-identification target recognition by a single color camera, a scheme for simultaneously detecting an autonomous driving target was proposed by using a RGB camera and an infrared camera. In order to simultaneously extract the color characteristics of the color images and the temperature characteristics of the infrared images, the network structure was improved on the basis of YOLOv3 network to obtain a dual YOLOv3 neural network, and four feature fusion comparison experiments were designed to determine the optimal fusion scheme. A dual data set synchronous acquisition system was established, which collected color and infrared images for training and testing of the dual network. The validation set without network training was used to obtain four dual feature fusion models of average value and loss value. Experimental results show that the average accuracy of the dual-modal network model may reach 59.42% after 30 trainings.

Improved Genetic Programming Algorithm for RCMPSP

CHEN Haojie, DING Guofu, ZHANG Jian, YAN Kaiyin

2021, 32(10):  1213-1221.  DOI: 10.3969/j.issn.1004-132X.2021.10.010

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Aiming at the lack of optimization ability for priority rule scheduling, an improved hyper-heuristic genetic programming algorithm for the RCMPSP was proposed to evolve better priority rules. By analyzing the existing priority rules, a normalized attribute set and a top-level discriminant coding method for multi-project scheduling were constructed, and the NSGA-Ⅱ virtual fitness allocation method was applied to evaluate the population for achieving multi-objective optimization. A diversity population updating method was designed to enhance the search ability and avoid the defects that the traditional genetic programming was easy to fall into local optimum. The validity and feasibility of the proposed method were verified by the calculation experiments based on benchmark data set PSPLIB and the aircraft assembly line production instance.

Solution of Inverse Kinematics for 6R Robots Based on Combinatorial Optimization Algorithm#br#

JI Yangzhen, HOU Li, LUO Lan, LUO Pei, LIU Xubin, LIANG Shuang

2021, 32(10):  1222-1232.  DOI: 10.3969/j.issn.1004-132X.2021.10.011

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In order to solve the problems of multiple solutions, low accuracy and poor generality in inverse kinematics, a combinatorial optimization algorithm was proposed to solve the inverse kinematics for all kinds of 6R industrial robots. The kinematics models of the robot were established according to the classical D-H method. The objective function of the inverse kinematics was constructed by minimizing the pose errors with the principle of motion stability, and its fitness function was designed by linear weighing-sum method. An improved whale optimization algorithm for inverse kinematics was developed by using four methods including chaotic mapping initializing population, nonlinear updating of convergence factor, adaptive inertia weight and simulated annealing strategy. The combinatorial algorithm took the results of the whale optimization algorithm as the initial value, and then the inverse kinematics solution satisfying the accuracy requirements was iterated by the Newton-Raphson numerical method. The results of simulation experiments indicate that the performance of the improved whale optimization algorithm is greatly enhanced. Compared with the direct use of whale optimization algorithm for inverse kinematics, the combinatorial optimization algorithm has the advantages of faster solution speed, better stability and ultra-high accuracy, which also proves that the proposed algorithm is feasible and effective for inverse kinematics problems.

Rheological Behavior and Physically-based Constitutive Model of TNTZ Titanium Alloy#br#

ZHONG Mingjun, WANG Kelu, CHENG Jing, OUYANG Delai, CUI Xia, LI Xin

2021, 32(10):  1233-1239.  DOI: 10.3969/j.issn.1004-132X.2021.10.012

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The isothermal constant strain rate compression experiments of Ti-29Nb-13Ta-4.5Zr(TNTZ) titanium alloy in the range of deformation temperature 700~900 ℃ and strain rate 0.001~1 s-1 were carried out with Gleeble-3500 thermal simulator. The effects of strain rate and deformation temperature on the rheological stress of TNTZ titanium alloy were analyzed. According to the experimental data, the temperature rise values under different deformation conditions were calculated, and the law of deformation heat generation was analyzed. Comprehensively considering the influences of temperature on material self-diffusion coefficient and elastic modulus and the effects of strain on alloy rheological stress, a physically-based constitutive model was constructed based on strain compensation, and by multiple linear regression the functional relationship among material parameters and strain was fitted. The results show that the rheological stress of TNTZ titanium alloy increases with the increase of strain rate and decreases with the increase of deformation temperature. The temperature rise caused by deformation heat effect is positively correlated with strain rate and negatively correlated with deformation temperature. The physically-based constitutive model established by strain compensation has high prediction accuracy. The correlation coefficient R of the model reaches 0.964, and the average relative error is as 10.63%.

Investigation of Grain Size Evolutionin during Isothermal Local Loading Processes for Large-sized Titanium Alloy Components#br#

MA Qing, WEI Ke, LIU Zhiqiang

2021, 32(10):  1240-1247.  DOI: 10.3969/j.issn.1004-132X.2021.10.013

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In order to study the microstructure evolution rules in the isothermal local loading processes for large-sized titanium alloy components, the primary α-phase grain size variation processes of large-scale titanium alloy rib-web components during isothermal local loading were simulated and analyzed based on the internal variable microstructure model of TA15 titanium alloy. The local loading orders and integral loading mode were carried out as a comparison, so as to understand the microstructure evolution of the local loading. The results show that the transitional zones are affected by the transferred materials from the loading zones to unloading zones, the sizes of the primary α-phase grain after both of the loading steps are reduced, leading the sizes of the primary α-phase grains in this zone smaller than those zone away from the transitional zone. The switch of the first and second loading orders may change the quantity of transferred materials, so the loading order may affect the grain size variation processes on both sides of the die partition line. Compared with the integral loading mode, the grain size of local loading in the transitional zone is smaller. The grain size variation away from the transitional zone is almost indifference under above three loading methods.

Prediction Method of Cutting Loads of Shearers Based on Multi-source Data Fusion

YU Ning, SUN Yexin, CHEN Hongyue

2021, 32(10):  1247-1253,1259.  DOI: 10.3969/j.issn.1004-132X.2021.10.014

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To solve the problems of low accuracy using single sensor for cutting loads of shearers and improve the sensing ability of shearer running safety states, based on the applications of DBN, BR and PSO algorithm, a multi-sensor shearer drum load identification and prediction method was proposed. BR-PSO-DBN prediction model was constructed using 22 sets of test data monitored by idler shaft sensors, connecting frame pin shaft sensors and rocker strain sensors as input samples to predict the three directional loads and torque of drum cutting. Based on the experimental system of cutting loads, the field test was carried out, and the measured results were compared with the predicted ones. The results show that the measured curves are basically the same as the predicted curves, and the peak points correspond to each other. The prediction accuracy of the model for the three-way cutting loads of the drum is more than 83%, and the prediction accuracy of the roller torque is 95%, which indicates that the prediction model has high prediction accuracy and may provide reference for field applications to guide safety productions.

Study on High Precision and High Efficiency Preparation Processes of Frozen Sand Molds#br#

YANG Haoqin, SHAN Zhongde, LIU Feng, WANG Yifei,

2021, 32(10):  1254-1259.  DOI: 10.3969/j.issn.1004-132X.2021.10.015

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The high-precision and high-efficiency forming processes of frozen sand molds for casting were studied by using digital patternless casting precision forming technology herein. Based on the dimensional precision control and the analysis of local transient thermal field of the sand molds, the cutting parameters of frozen sand molds were jointly constrained, and the cutting parameters suitable for the processing and manufacturing processes of frozen sand molds were optimized. When the feed speed of cutting tool was as 100 mm/s, the spindle speed was as 4000 r/min, the depth of cut was as 4 mm and the cutting width was as 12.8 mm, the frozen sand molds prepared by digital patternless forming technology have higher dimensional accuracy and lower local transient temperature field in the cutting area of frozen sand molds. The cutting parameters are suitable for the long-term stable and low-temperature preparation processes of frozen sand molds, which may realize high-precision and high-efficient manufacturing of frozen sand molds.