Table of Content

25 January 2018, Volume 29 Issue 02

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Influences of Drum Cutting Load Disturbances on Shearer Height Adjustments

WANG Hui;SONG Yuning

2018, 29(02):  127-133. 

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Influences of drum cutting load disturbances on dynamic response characteristics of high mechanism during height adjustments of shearers were studied. According to the model of asymmetrical valve controlled cylinder, a transfer function model of height adjustment mechanisms was established. According to the working conditions of shearer, a load model of drum cutting load equivalent to height adjustment mechanism was analyzed. Conventional PID and fuzzy PID controller were used to control the mechanisms of different drum cutting loads and traction speeds. The results show that, fuzzy PID controller has better tracking performance, and the control effectiveness is less affected by cutting impedances and traction speeds.

Door System Stiffness and Error Analysis Considering Fixtures

SONG Kai1;HU Jinhua1;GAO Hui2;SHI Shaoliang1

2018, 29(02):  134-139,144. 

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As prediction accuracy was not high, and deviations were large for finite element simulations and tests, a new door stiffness analysis method was proposed, which considered test fixtures. Using theory of limit error synthesis, experimental error model was established by coupling test data collection errors and flexible deformation errors. A method was gave based on sensitivity analysis to calculate importances of error effects considering different station fixtures, and the common form of simulation error transfer model was deducted.  Finally, results show that the fixture has a great influence on deviations between tests and simulations，and verifies accuracy of the error model in an example of a car door.

Vibration Analysis of Cable in Launch Sonar Winch

ZHANG Tongxi;GONG Fangyou

2018, 29(02):  140-144. 

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In order to accurately simulate movements of suspended cable during the operations of aerial winchs, one type of hydraulic winch was used as a case study herein. A hanging swing mathematical model was set up based on pendulum theory. According to the vibration characteristics of flexible cables, nonlinear differential equation of vibrations of the cable was deduced and solved by explicit difference method. Through simulations, the swing angle variations of lifting loads under different excitation frequencies and the influences of hanging head displacements on the cables were analyzed, accuracy of the algorithm was proved herein. Conclusions drawn from this paper may provide theoretical basis for practical engineering designs and may be used for the air winch lifting system cable vibrations forecasting and reduction.

Static and Dynamic Characteristics of High-speed On-off Digital Valves

ZHAO Jinsong1, 2,3;ZHANG Chuanbi3;ZHAO Zining3;WANG Zhipeng3;YAO Jing1, 2,3

2018, 29(02):  145-150,157. 

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HSV series high-speed on-off digital valves were studied herein. In order to fully understand working performances and working principles of the valves, a mathematical model was built through mechanism modeling method. By MATLAB/Simulink, a simulation model was proposed and established. Based on this model, static and dynamic characteristics of the valves were analyzed. Thus, influence factors of opening/closing response times, valve's output flows, dead and saturated zones were analyzed. At last, static and dynamic characteristics mentioned above were verified by experiments. Experimental results show that the conclusions of static and dynamic characteristic analyses for the high-speed on-off digital valves are correct.

Sample Correlation Improvement Based High Speed Train Fault Diagnosis Method

ZHANG Kai;LUO Yilan;ZOU Yisheng;WANG Chao;SONG Xiaoxin

2018, 29(02):  151-157. 

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Ensemble empirical mode decomposition(EEMD) and variable predictive model based class discriminate(VPMCD) combined method was a effective method for mechanical fault diagnosis. For some insufficients such as the method might not apply small samples and with low recognition rates in diagnosing a high speed train, so the adaptability of VPMCD was improved by sliding window stepwise regression herein. Then, using relevancy and continuity of samples, recognition rate of this method was improved by pattern recognition including adjacent samples and smooth processing of samples. Experimental results indicate that the corrected method may reduce needs for samples, and increase recognition rate 20% at least.

Dynamics Modeling and Characteristics Analyses of a Two Rotational Parallel Mechanism with Revolute Joint Clearances

HOU Yulei;JING Guoning;DENG Yunjiao;YANG Yandong;ZENG Daxing

2018, 29(02):  158-165. 

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Based on the deficiencies of Lankarani-Nikravesh contact force model, a modified contact force model was proposed, and it was verified that the modified contact force model is effective. A parallel mechanism RU-RPR with revolute joint clearances was taken as research object, and the modified contact force model and modified Coulomb friction force model were used to calculate normal contact forces and tangential contact forces, respectively. Dynamics equations were established in form of differential algebra. Baumgarte stabilization method was added and the equations were solved by the fourth order Runge-Kutta method. Then effects of different friction coefficients on dynamic behaviours of the mechanisms were analyzed.

Design and Kinematics for a Not-fully Symmetric 3T1R Parallel Mechanism with Low Coupling-degrees

SHEN Huiping;XU Ke;YANG Tingli;SHAO Gouwei

2018, 29(02):  166-176. 

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A not-fully symmetric parallel mechanism with 3T1R motion outputs was designed. Coupling degree of the parallel mechanism was found bigger（κ=2）after its topological characteristic analysis was performed, for which solutions for its direct kinematics were more complicated. Therefore, a novel coupling-reducing parallel mechanism were proposed whose position and orientation characteristics and degree of freedom were unchanged with low coupling degree (κ=1). Further, one-dimension search algorithm was applied to solve its direct kinematics according to kinematics modeling principle based on ordered single opened chains. In addition, the workspace, rotation capability and singularity of this coupling-reducing parallel mechanism  were also analyzed according to the inverse kinematics. From the above analyses, the conclusions are drawn that the structures of this coupling-reduced mechanism are simple, and workspace and rotation capability of this parallel mechanism  are larger.

Fault Diagnosis Method for Rolling Bearings under Variable Rotate Speed Based on Time-varying Zero-phase Filter

CHEN Xiangmin;ZHANG Kang;JIN Fenghua;LI Luping

2018, 29(02):  177-185. 

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Aiming at the problems of extracting and separating fault modulation characteristics of rolling bearings from vibration signals of a gearbox under variable rotate speeds, a new fault diagnosis method for rolling bearings was proposed based on time-varying zero-phase filter. The gear mesh frequency was estimated from the vibration signals of faulted rolling bearings in gearbox by using chirplet path pursuit, and thus the shaft rotating speed of gearbox might be obtained by dividing the gear meshing frequency by the number of gear teeth, meanwhile, the analysis of Hilbert envelope demodulation was carried out to obtain the envelope signal of the vibration signals of faulted rolling bearings. And according to the shaft rotating speeds, each time-varying zero-phase filter was designed. Then each modulation signal was acquired by the analysis of time-varying zero-phase filter to the envelope signal. Lastly, the fault diagnosis of rolling bearings was carried out according to the order spectrum, which was obtained by using order analysis to each modulation signal on the basis of the shaft rotating speeds. Simulations and application examples indicate that the proposed method may effectively extract and separate each fault modulation characteristics of rolling bearings from a rotating speed changing gearbox.

Pulsation Characteristic Analysis and Tooth Profile Design of Double-circular-arc Helical Gear Pumps

LI Geqiang1,3;ZHANG Longfei1;HAN Weifeng2;DENG Xiaozhong1,3;FENG Yong1,3

2018, 29(02):  186-192. 

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Aiming at problems of large flow pulses, noises and serious oil trapped phenomenons of involute gear pumps, a gear pump with double-circular-arc helical gears as motion pair was proposed. Through comparison and analysis of their meshing characteristics, advantages of double-circular-arc helical gear drives were obtained. Taking sine curve as transition curve and on the basis of conjugate principles of gear meshing, equation of transverse profiles of double-circular-arc helical gear were solved. Equal area method was used to deduce the displacement of double circular arc gear pumps, then maximum and minimum instantaneous displacements of the double-circular-arc helical gear pumps were solved, thus the theoretical pulsation tended to zero. Flow pulsations of double-circular-arc helical gear pumps and involute helical gear pumps with the same gear parameters were compared and analyzed by using 3D dynamic mesh technology of Fluent. The flow pulsations of the former are much smaller than that of the latter.

Applications of Improved B-Spline Curves to 6R Robot Trajectory Optimization

DONG Jiajia;WANG Taiyong;DONG Jingchuan;ZHANG Yongbin;TAO Hao

2018, 29(02):  193-200. 

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A kinematics model of robots was established firstly by D-H frame method. Based on the analyses of trajectory planning processes, an improved B-spline curve was applied to the robot joint space trajectory interpolations. Secondly, after discussing the improvement reasons and elaborating the methods of improving the B-spline curves, the speed and acceleration properties， and the implementation details of the improved B-spline curves were given. Finally, simulation experiments were carried out on MATLAB 2014a platform, and the improved method was used to realize the circular trajectory. Results show that the method may improve the smoothness of robots in joint motions and spatial trajectories, and then optimize the trajectory motions of the robots.

Human-machine Interaction Manipulation Comfort Evaluations Based on Muscle Physiological Signals

HU Jing;QIAN Peilun;LIU Mingzhou;ZHANG Miao;ZHENG Da

2018, 29(02):  200-204. 

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Aiming at drawbacks of handling comfort evaluation methods, a method of man-machine interaction to evaluate handling comfort was put forward herein, which was based on characteristic parameters of muscle physiological signals. Using driving system as a typical example of man-machine interactions, experimental and data statistics were carried out. Through the regularization RBF network, the experimental samples of subjective comfort ratings and characteristic parameters of manipulator muscle physiological signals measured were studied and trained. Finally evaluation model of the handling comfort was established. Computational and experimental results demonstrate feasibility and applicability of the method.

Second-order Accurate Modeling and Experimental Studies of Rigid-flexible Coupled Flexible Manipulator

ZHAO Yan;RUAN Chengming;WANG Songwei

2018, 29(02):  205-210. 

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Based on dynamic boundary conditions and three deformation theories, a precise dynamics model of double-joint flexible manipulators with pseudo-modal method and Lagrangian method was established by Euler-Bernoulli beam model. Influences of the dynamic boundary conditions and deformation theory on theoretical modeling accuracy of the double-joint flexible manipulators were analyzed according to theoretical simulation results. It is verified that the model of rotating free beam is closer to the actual working conditions，by comparisons of double-joint flexible manipulator's modal frequencies of the experimental results and those from the theoretical model under different dynamic boundary conditions.

Anti-dead-zones and Friction Control of Space Robots with Recurrent CMAC

HUANG Xiaoqin1，2;CHEN Li1，2

2018, 29(02):  211-217. 

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Dynamics control of free-floating space robot systems with joint torque output dead-zones, friction and external disturbances were discussed. A recurrent CMAC and an adaptive dead-zone compensator were designed to track the desired trajectories of two joints. Friction double observers were designed to estimate the unmeasurable internal friction states, and dead-zone precompensator was designed to eliminate the impacts of joint torque output dead-zones. The recurrent cerebellar neural network model was applied to approximate uncertainty terms of dynamics equation including friction errors and external disturbances. The results of simulation show the efficiency of the proposed control method.

A Multi-chromosome Genetic Algorithm for Multi-depot and Multi-type Vehicle Routing Problems

CHEN Chengpin;HAN Shengjun;LU Jiansha;CHEN Qingfeng;WANG Cheng

2018, 29(02):  218-223. 

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Aiming at shortcomings of low efficiency and poor quality of solutions in the current multi-depot and multi-type vehicle routing problems, an integer programming model was established. A multi-chromosome genetic algorithm was proposed to unify the solution algorithms of the multi-depot and multi-vehicle problems, and traditional single depot and single vehicle problems. Several experiments were completed on the multi-chromosome genetic algorithm through calculation examples, and comparisons with the traditional algorithm results were carried out. Experiments show that the proposed algorithm exhibits high search efficiency and fast convergence speed, and has high quality and stability of the solutions, which verify effectiveness and practicability of the algorithm.

Structural Design of Finger Rehabilitation Exoskeleton Robots

WANG Jie1;GUAN Shengqi1;XIA Qixiao2

2018, 29(02):  224-229. 

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In order to meet rehabilitation needs of patients with finger injury, a finger-supported exoskeletal robot was designed based on planar linkages. Firstly, a kinematics model of the robot was established by analyzing the degrees of freedom of bionic finger movements. Secondly, main mechanical components and rotation angles of finger joints were used as space vector elements to solve robot workspace. Based on these, optimum sizes of each mechanical structures were obtained, and structural optimization designs of mechanical components were completed. Simulation results show that the robot may carry out bending and stretching movements in a certain range of angles, and may meet rehabilitation training of patients with finger injury.

Flattening Coefficient Model and Its Influence Factors of Small Roller Diameter Cold Rolling Mills

BAI Zhenhua1，2;XING Yu1;LI Boyang1;LIU Yaxing1;QIAN Cheng1;ZHAO Weiquan1

2018, 29(02):  230-236. 

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In the rolling processes, the mill work rolls with large “aspect ratio” and small absolute value of roll diameter had a greater level of work roll deflection problems. Considering characteristics of equipment and processing parameters on rolling mills, load distributions of the work rolls under horizontal bending was studied in detail, and a new roll flattening coefficient model was deduced. Taking a typical product as an example, changes of roll flattening coefficients were analyzed quantitatively when a single factor was changed in the horizontal displacements of the work rolls. In order to verify the model, a forecasting software was compiled based on the relevant theory, and the field experimental results were given herein.

Influences of Different Forming Processes on Setting Performances of Metal Seal

WANG Zhijian1;MA Zhen1;CHEN Yan2;ZHANG Shihong2;SONG Hongwu2

2018, 29(02):  237-241. 

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The cracks on the sealing surface of a new kind of metal seal in bridge plug formed by machining were studied, and the reasons were obtained by mechanics analysis and microstructure observation under different conditions. The hydraulic forming process for metal seals was proposed. The numerical simulation was employed to optimize the mold and process parameters of hydraulic forming, and hydraulic forming tests and metal seal tests were carried out according to the previous simulation results. The test results show that the quality of sealing surface is optimal when the pressure is as 180MPa and the holding time is as 5s, and there are no cracks on the surfaces after setting. The results of microstructure observation under different sealing surface conditions and mechanics analysis during hydraulic forming processes shows that the cracks may be eliminated by radial compressive stress of hydraulic forming. Therefore, the setting performances of metal seal may be greatly improved by hydraulic forming process comparing with original machining methods.