Table of Content

25 June 2021, Volume 32 Issue 12

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Design of Ultrasonic Weak Impact Energy Guide Device and Infrared Thermal Image Detection#br#

XU Zhangjing, LIU Zhiping, DU Yong, WU Hao

2021, 32(12):  1387-1394.  DOI: 10.3969/j.issn.1004-132X.2021.12.001

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Contacts among ultrasonic horn and surface of CFRP complex structure were line contacts. During excitation and detection, coupling efficiency was low, and contact stress was concentrated, while secondary damage occurred easily. Based on Huygens principle and dual-source interference enhancement effect, a design method for surface-contact dual-source excitation energy steering device was propose herein. A finite element model was established by ABAQUS. Influences of different excitation device size and excitation methods on temperature rise of the tube damages were analyzed. Design parameters of the curved dual-source device was determined, and a control experiment for the excitation device was set up to verify the pararneters. The results show that the maximum temperature rise of crack damages is increased by about 35.8%, and the curved dual-source excitation device may avoid stress concentration and effectively reduce risk of secondary damages.

Research Status Analysis of Adhesively Connection Technology in Aerospace Industry#br#

GUO Lei, LIU Jianhua, ZHANG Jiapeng, LI Xiayu, ZHANG Xiumin, XIA Huanxiong

2021, 32(12):  1395-1405.  DOI: 10.3969/j.issn.1004-132X.2021.12.002

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Aiming at current inadequate researches of adhesive assembly technology in aerospace products, especially in precision electromechanical products in China, the application types for adhesive connection technology in aerospace and application characteristics  of ultra-high/low temperature resistance, sealing, versatility, stability/low creep, and low volatility were briefly introduced. Research improvement of mechanism, key processes, static/dynamic mechanics properties, and fatigue and aging characteristics of adhesive bonding were summarised and analysed. Finally, development tendencies of the aerospace adhesive technology in the aspects of process parameter quantization, dynamic mechanics property investigation, and advanced adhesive equipment were pointed out.

Dynamic Fit of Injection Mechanisms for Squeeze Casting Machines Based on Friction Model#br#

ZHU Qian, YOU Dongdong, ZHU Quanli,

2021, 32(12):  1405-1413.  DOI: 10.3969/j.issn.1004-132X.2021.12.003

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Fit clearance was a key factor affecting service and process control of injection mechanisms, in order to study the fit clearance of injection mechanisms, a friction model of the injection mechanisms was proposed. Friction model and numerical simulation were integrated based on secondary development of MSC.MARC software. The results of numerical simulation integrated with friction were compared with those of ordinary numerical simulation without considering friction and the injection experiments to verify effectiveness and accuracy of numerical simulation integrated with friction. Multi-cycle injection processes for the injection mechanisms of 2500 kN squeezing casting machine were simulated, and the changing rules of the fit clearance were studied. In stages of injection and punch return, changes of the fit clearance are severe. In solidification stage, changes of the fit clearance are gentle. Main reason for drastic changes of the fit clearance is the uneven axial temperature distribution in shot-sleeve.

Analysis of 5-DOF Parallel Driving Mechanisms and Their Position Resolution

ZHANG Jingzhu, SHI Hanqing, WANG Tao, HUANG Qingxue, JIANG Li

2021, 32(12):  1414-1422，1431.  DOI: 10.3969/j.issn.1004-132X.2021.12.004

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 A multi-branch coupled parallel driving mechanism with three translations and two rotations was proposed. Degree of freedom and motion characteristics of end for the mechanism were analyzed based on position and orientation characteristics set method. Inverse kinematics model of the mechanisms was established by homogeneous transformation method. Full Jacobian matrix of parallel driving mechanisms was solved. Forward kinematics model was established based on the Newton iterative method, and theoretical model was verified by simulation. Reachable workspace of the mechanisms was drawn by CAD variational geometry method. Global position sensitivity coefficient index of the mechanisms was defined, and the influences of resolution for the driving system on the position resolution of the mechanisms under specific working conditions was analyzed systematically.

Binocular Camera Calibration Based on BP Neural Network Optimized by Improved Genetic Algorithm#br#

ZHANG Fengfeng, ZHANG Xin, CHEN Long, SUN Lining, ZHAN Wei

2021, 32(12):  1423-1431.  DOI: 10.3969/j.issn.1004-132X.2021.12.005

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The BP neural network has the problems of low accuracy and poor convergence in the binocular camera calibration processes. A method was proposed to solve these problems to complete the calibration of binocular camera based on BP neural network optimized by improved genetic algorithm. First, the Trajkovic operator with multi-lattice fusion algorithm was proposed for corner detection. A matching algorithm of homonymous corner combining point-to-point spatial mapping and grid motion statistics was proposed. Then, the pixel value of the homonymous corner was extracted and the actual 3D coordinate value was calculated, and the crossover and mutation probability and selection operator of genetic algorithm were improved. Finally, the improved genetic algorithm was used to optimize the BP neural network, and the pixel value and the 3D coordinate value were used as the input and output of the BP neural network respectively, so as to complete the calibration of binocular camera. The results show that average calibration prediction errors before and after optimization are as 0.66 mm and 0.08 mm respectively, and the average calibration prediction error was reduced by 88%. The number of calibration test iterations before and after optimization is as 736 and 169 respectively, and the iteration speed is increased by 3.4 times after optimization. The improved genetic algorithm optimizes the BP network and achieves good results, which basically meets the requirements of binocular camera calibration. 

ADRC for Electro-hydraulic Position Servo Systems Based on Dead-zone Compensation#br#

WANG Lixin, ZHAO Dingxuan, LIU Fucai, LIU Qian, ZHANG Zhuxin

2021, 32(12):  1432-1442.  DOI: 10.3969/j.issn.1004-132X.2021.12.006

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Aiming for the problems of proportional valve dead-zone, parametric uncertainties, and unknown external disturbances in electro-hydraulic position servo control systems, a cascade controller which was composed of ADRC and dead-zone inverse compensation was designed. Firstly, the valve dead-zone was pre-compensated by an inverse model which was established based on experimental identification. Then, according to the characteristics of the system, the first-order ADRC was designed. “general disturbances” were estimated by an improved ESO and compensated by a nonlinear control law in real-time. The results of co-simulation and experiments show that the proposed cascade controller effectively compensates the proportional valve dead-zone, improves dynamic performances and position tracking accuracy of the system.

Reliability-based Design Optimization Strategy for Structures by Universal Generating Functions#br#

ZHOU Jinyu, ZHU Dawei, WANG Zhiling

2021, 32(12):  1442-1448.  DOI: 10.3969/j.issn.1004-132X.2021.12.007

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In order to improve accuracy of RBDO, a new RBDO method was proposed based on UGF. On one hand, dynamic mapping among design variables and probability indexes was established through a series of response surfaces, which eliminated inner cycle of traditional double cycle algorithm. On the other hand, UGF was introduced for reliability analysis to avoid disadvantages of low precision or non-convergence of the traditional moment methods in dealing with non-normal random variables and highly nonlinear performance functions. At the same time, combined with non-uniform discretization technology, analysis accuracy may be improved under given calculation costs. The examples show that the proposed method is reasonable, feasible, and robust.

Design and Research of Refrigeration Linear Compressor Spring Assembly

CHEN Hongyue, ZHANG Zhanli, LIN Qingzhu

2021, 32(12):  1449-1455.  DOI: 10.3969/j.issn.1004-132X.2021.12.008

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To reduce volume of spring assembly and meet stiffness requirements of refrigeration linear compressor, a cylindrical arm coil spring was designed based on spiral of Archimedes. Variation of radial and axial stiffness, stress characteristics, and equivalent mass of scroll arm plate spring, and a new type cylindrical arm coil spring were analyzed and compared by finite element analysis method. Axial stiffness characteristics of both type springs were verified experimentally, and the new type of cylindrical arm coil spring was applied to spring assembly. Research results show that the cylindrical arm coil spring has large radial stiffness, axial stiffness, and constant dynamic stiffness. The improved spring assembly provides greater axial stiffness and reduces volume and mass of spring assembly effectively. 

A Fault Diagnosis Method of Mechanical Equipment Based on FKCH-TM and Thermal Images#br#

HE Zhiyi, SHAO Haidong, CHENG Junsheng, YANG Yu,

2021, 32(12):  1456-1461，1478.  DOI: 10.3969/j.issn.1004-132X.2021.12.009

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 Aiming at problems of dimensionality disaster and structure information destruction in thermal imaging fault diagnosis of mechanical equipment, a fault diagnosis method of mechanical equipment thermal images was proposed based on FKCH-TM. Firstly, flexible kernel convex hull(FKCH) of each class in feature tensor space was defined. Then, the optimal hyperplane between the FKCH was found, and FKCH-TM model was built. Finally, thermal images of mechanical equipment under different fault conditions were directly used as the input of FKCH-TM for fault diagnosis. Experimental results show that the proposed method may identify and diagnose the faults of mechanical equipment accurately and stably.

Motion Planning of Mobile Manipulators Based on RRT with Sparse Nodes

LI Yaozhong, WANG Shuting, JIANG Liquan, MENG Jie, XIE Yuanlong,

2021, 32(12):  1462-1470.  DOI: 10.3969/j.issn.1004-132X.2021.12.010

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Traditional motion planning of mobile manipulators had problems such as without considering docking errors and low efficiency. A novel motion planning method of mobile manipulators was proposed based on RRT with sparse nodes. Influences of positioning errors for the mobile platforms on motion planning were analyzed, and an error compensation method was developed based on coordinate transformation. Aiming at addressing excessive searching in local spaces by RRT algorithm, a regression filtering mechanism was improved to avoid repeated expansion of nodes. Then, considering validity of boundary nodes, the random point boundary extension mechanism was proposed to greatly decrease collision detection time. Experimental results demonstrate that the proposed algorithm improves efficiency of motion planning.

Liquid Metal Based Flexible Sensors for Soft Manipulator towards Human-Machine Interaction#br#

LIU Huicong, YANG Mengke, YUAN Xin, SUN Lining, JIN Guoqing,

2021, 32(12):  1470-1478.  DOI: 10.3969/j.issn.1004-132X.2021.12.011

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Flexible strain and bending sensors based on liquid metal were designed by 3D printed micro-channel herein. Strain sensors were integrated into glove which was used to detect posture of human hands, and bending sensors were integrated into soft manipulator which was used to control posture of the soft manipulator. To realize soft manipulator with human-machine interaction, sensing glove with strain sensors and soft manipulator were combined. Experiments verify that the sensing glove may control the posture of the soft manipulator and the bending degree of each finger.

Stiffness Enhancement Method for Complex Thin-walled Parts Driven by Principal Stress Field#br#

ZHANG Weinan, DAI Ning, GUO Ce, YU Yi, GONG Sai

2021, 32(12):  1479-1485.  DOI: 10.3969/j.issn.1004-132X.2021.12.012

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Aiming at the problems that stiffness enhancement effectiveness of traditional reinforcing methods such as intersecting parallels stiffener was not always optimal in complex thin-walled parts, a stiffness enhancement method for complex thin-walled parts was proposed. Bionic principle of Victoria Warren vein layout was explored based on main stress field model, and an optimization method for lightweight stiffness enhancement of complex thin-walled parts driven by principal stress field was proposed. Experimental results show that the specific stiffness of the complex thin-walled parts generated by this method increases by 33% when mass of the structure is almost equal to that of the traditional intersecting parallels stiffeners.

Position and Stiffness Control of Pneumatic Series Elastic Joints for Bionic Jumping Robots#br#

SHEN Shuang, LEI Jingtao, ZHANG Yuewen

2021, 32(12):  1486-1493.  DOI: 10.3969/j.issn.1004-132X.2021.12.013

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A kind of series elastic joints driven by pneumatic artificial muscle(PAM) was proposed. Based on the Chou model of PAM, a dynamic model of series elastic joints was established, and joint stiffness was derived. The relationship between the joint stiffness and internal pressure of PAM and stiffness of elastomer was obtained. The control algorithm of BP neural network tuning PID parameters(BP-PID) was designed, and the research on position and stiffness control of pneumatic series elastic joints was performed. The simulation results show that BP-PID control is better than PID control, tracking errors of joint positions are changed from 0.58° to 0.10°, and tracking errors of joint stiffness are changed from 0.026 N·m/rad to 0.005 N·m/rad. The experimental results show that the average tracking error of planning position signal is reduced from 0.347° to 0.117°, and the average tracking error of joint stiffness is reduced from 0.024 N·m/rad to 0.019 N·m/rad.

Viscoelastic Rheological Properties of Polymer Melts in Cross-scale Extrusion Processes#br#

LIU Kui, WANG Minjie, ZHAO Danyang, LI Hongxia

2021, 32(12):  1494-1503.  DOI: 10.3969/j.issn.1004-132X.2021.12.014

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A molecular theory-based rheological model was established to describe micro-scale effect on viscoelastic rheological properties through dynamic viscoelastic property measurements under micro-scale conditions. The model might reflect influences of characteristic channels on the stress state of viscoelastic flow processes. The existence of micro-scale effect weakened viscoelastic rheological response of polymer melts and promoted relaxation processes of molecular chains. The micro-scale effect included in the rheological model was characterized by coefficient sizes of micro-scale effect and ratio of storage modulus and loss modulus. A smaller value of the coefficient for the micro-scale effect indicates a more remarkable effect of the characteristic scale on the viscoelastic properties. Smaller ratio of coefficients for viscoelastic micro-scale effect shows an apparent influence of characteristic scale on the relaxation processes.

Electrochemical Corrosion Performance of Laser-arc Hybrid Surfacing Layers for High Nitrogen Steel#br#

RUI Wei, BAI Di, QI Tong, DU Shaofeng, YANG Zhikun, LIU Fengde, ZHANG Hong

2021, 32(12):  1503-1511.  DOI: 10.3969/j.issn.1004-132X.2021.12.015

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The effects of different welding parameters on surface corrosion behavior of surfacing weld were studied by electrochemical corrosion method. Research results show that corrosion resistance of surfacing layers increases firstly and then decreases with the increase of surfacing current I, laser power P, and surfacing speed v. Nitrogen content of welds is higher as I=220 A, P=3.2 kW, v=0.8 m/min, passive film on sample surfaces has better stability and the strongest pitting resistance. It is found from the corrosion morphology of the sample as I=260 A or v=0.6 m/min, pitting pits on the weld surfaces are large and dense, and corrosion ditch is formed, the dendrites in the welds tend to grow continuously and expand outward. When power increases to 3.2 kW, coarse columnar dendrites in the welds transforme into uniform and fine dendrites, which improves the corrosion resistance.