Table of Content

25 February 2018, Volume 29 Issue 04

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Design of Energy Conversion Mechanism and Jumping Stability of a Locust-like Jumping Robot

WANG Huan;JI Aihong;DAI Zhendong;LI Li;HE Wei;SHEN Huan

2018, 29(04):  379-384. 

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A new type of robots which might achieve continuous jumps was developed by simulating the ways of locust-kick jumps. On the basis of the energy conversion mechanism investigations during jumping processes, the torsion spring bounce mechanisms were designed. The torsion spring completed the continuous leg contractions and take-off processes under the combined actions of geared motor and fuselage tracks, which meant the robots might achieve stable landing to ensure multiple jumps. In order to enhance the ability of jumping robots to jump on different surfaces, the roles of mat and claw used by locusts were researched in different surfaces by establishing a grasping model, and the bionic jumping base structure was designed integrated adhesive mat and claws.

Abnormal Vibration Fault Diagnosis of Cars Based on “Source-path-receiver” Model

BEI Shaoyi1;ZHAO Jingbo1;LEI Weining1;WANG Wei1;DENG Shuchao2

2018, 29(04):  384-389. 

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Based on the “source-path-receiver” model, abnormal vibrations under specific speeds of the vehicles were studied by tests. Then, the excitation source was determined from the wheel assemblies by vehicle vibration tests, body/wheel assembly partial frequency tests and frame/body modal tests were carried out to determine the abnormal vibration amplification paths. On the basis of identification the abnormal vibration causes, this paper respectively proposed reasonable improvement measures from two aspects of vibration source elimination and transfer path improvement, and provided practical cases and system solution for similar problems in engineering.

Applications of Optimization Parameters VMD to Fault Diagnosis of Rolling Bearings

MA Hongbin;TONG Qingbin;ZHANG Yanan

2018, 29(04):  390-397. 

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First, the leapfrog algorithm was used to search the optimal combination of influence parameters.The optimal parameters was selected after the search. Variational modal decomposition of optimized parameters was used to process fault signal. The eigenmode function was obtained. In order to verify whether the parameters obtained by the leapfrog algorithm were the optimal parameters, the Best Eigenmode function was selected to analyse envelope. The characteristic frequency of envelope spectrum was compared with the actual fault frequency. The matrix was formed with the obtained modal function. The singular value of the signal was obtained by using singular value decomposition. As input of ultimate learning machine,the singular value was used to Classify fault types. The simulated and measured signals were analysed by the variational modal decomposition of the optimized parameters. The feature information can be extract, and the type of fault was Identified. The result shows that this method has some practical significance and practical value.

Abrasive Flow Machining Experiments Based on Uniform Design Method

QIAO Zemin1,2;ZHANG Xinming1;LI Junye1;WEI Lili1;ZHAO Weihong1

2018, 29(04):  398-402. 

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According to the abrasive flow machining principles, taking tank engine nozzle as the research object, using uniform experimental design method, the better abrasive particle flow tests of processing parameters(abrasive particle diameter, abrasive concentration, processing time and grinding fluid acid-base properties) were selected by uniformly dispersed, through the optimization variables, objective function was obtained, and the optimal abrasive flow machining parameters were obtained. The experimental results show that using the uniform design scheme may save 70% of the time comparison with orthogonal design after the uniform tests, the surface roughnesses within the nozzle workpiece holes decrease, the abrasive flow machining experiment aims are reached, and the regression optimized processing parameters may be further reduced the nozzle orifice surface roughnesses. The mathematical models of surface roughnesses,  material properties and processing time may provide the technical supports for abrasive flow productions.

Design of Ultrasonic Gear Lapping Vibration Systems for Bevel Gears with Shaft

YANG Jianjun1，2;GUO Haojie1;ZHU Derong3;LI Jubo1

2018, 29(04):  403-408. 

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In order to meet  the requirements of ultrasonic resonance frequencies for bevel gear lapping systems, the designs for three type of compound ultrasonic horns with simplified bevel gear model were carried out based on wave propagation theory. A unified mathematical model of resonance frequency equation was established to compare the displacement magnification factors and the maximum stresses among the three type of compound ultrasonic horns. An ultrasonic vibration system of the compound ultrasonic horn combined with ultrasonic transducer was analyzed with modal and harmonic response by using finite element(FE) method. In the end, impedance analysis and vibration frequency testing were carried out to verify the theoretical design. The results show that the realistic resonance frequency is as 23.269kHz with the small error 1.17% compared with the design frequency. The validity of theoretical design for ultrasonic gear lapping systems was verified by experimental tests and FE analysis.

Thrust Characteristics of Synthetic Jet Underwater Based on Numerical Method

JIA Lianchao1,2;GENG Lingbo1,3;HU Zhiqiang1;YANG Yi1,2;WANG Chao1

2018, 29(04):  409-416. 

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The numerical method for the simulations of the flow fields and thrusts of synthetic jet underwater were studied herein. The effects of grid resolution, the first height of the boundary layer and the turbulence model on the thrusts of synthetic jet underwater were debated in detail. It is found that the thrusts are not sensitive to the grid resolution and the turbulence model. The numerical results of the thrusts are well consistent with the experimental data, indicating the effectiveness of the numerical method in the simulations of synthetic jet underwater. The efficiency of the actuator under different L/D conditions are numerically studied. The results show that the efficiency is the highest when L/D is near 4. When L/D deviates from 4, the efficiency decreases. A mathematical model of the thrusts of synthetic jet underwater was established. And a nozzle deflectable synthetic jet actuator was designed. The thrust enhancement characteristics of synthetic jets were interpreted using this model through the comparison among the thrusts of the nozzle deflectable actuator under the deflection angle of 0 and 90 degree.

Subharmonic Vibrations and Bifurcations of Vibro-impact Systems with Progression

LYU Xiaohong1, 2

2018, 29(04):  417-422,428. 

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A mechanics model of the vibro-impact systems with progressive motions was established. Types of impacts between the vibration exciter and the cushion, and conditions of progressive motions of the slider were analyzed. Judgment conditions and motion equations of four probable motion states presented by the systems were put forward. Based on bifurcation analysis of two-dimensional parameters, existence regions and distribution laws of different types of periodic motions of the systems were obtained in the exciting frequencies and precompression parameter planes. Bifurcation processes of 1/n subharmonic vibrations were analyzed in detail. When the exciting frequencies increase, bifurcation processes of 1/n subharmonic vibrations become more complicated due to the occurrence of non-smooth bifurcations of the periodic motions, incuding real-grazing bifurcations, bare-grazing bifurcations, or saddle-node bifurcations. Moreover, the effects of precompression are relatively large.

Localization and Driving Speed Detection for Construction Vehicles Based on Binocular Vision

TONG Zhixue;ZHAO Tao;HE Lile;WANG Xiaowei

2018, 29(04):  423-428. 

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According to the characteristics of low speed and high slip ratio of construction vehicles，a method was proposed based on binocular sequence images in order to quickly detect the relative positions and actual speeds of the vehicles. The vehicle-borne binocular vision sensors were used to collect the image sequences of the surrounding environments continuously. And the distances from the environment feature points to the origins of the camera coordinate systems were calculated through matching the captured each frame binocular images using speeded up robust features(SURF)，so as to achieve vehicle relative locations. Meanwhile, the feature points of two adjacent frames were tracked and matched based on SURF，and the matching feature points were divided into far points and near points according to different depths of the fields . The rotation matrix and translation vector of the coordinate systems in vehicle motions were calculated by using the far points and the near points respectively, and then optimized them by Levenberg-Marquardt method. Finally, the velocities of the vehicles were estimated according to optimized rotational matrices and translation vectors. The results of outdoor simulation test show the effectiveness and feasibility of the proposed method.

Dynamics Modeling and Model Test Verification of Tank Multi-body Systems

HAO Bingfei;WANG Hongyan;RUI Qiang;WANG Qinlong

2018, 29(04):  429-433,440. 

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In order to study the driving vibration characteristics and off-road maneuverability of tanks, the topology of tank dynamics systems was analyzed by virtual prototyping technology and multi-body dynamics modeling method. Tank multi-body dynamics system was built and the random road model was built by means of harmonic superposition method. To verify the credibility of the model, under the stable driving conditions, the automobile platforms and high speed road environments were selected respectively, the model simulations and real vehicle tests were compared. The results show that tank dynamics multi-body model may reflect the vibration characteristics of the real vehicles. The model provides a reference model for the study of tank vibration characteristics. The method of real vehicle tests may be used to verify the dynamics characteristics of simulation model.

Influences of Key Structural Parameters of Hydraulic Piston Pump on Cavitation

GAO Dianrong1;SUO Xiaoyu1;CAI Qianling2;WU Shaofeng1;LIANG Yingna1

2018, 29(04):  434-440. 

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In order to focus noises, vibrations and component corrosions caused by the cavitation in hydraulic plunger pump, a numerical simulation was conducted through full cavitation model and k-ε turbulence model to study the distribution of gas-phase volume fraction at various positions in plunger chamber and the generation mechanism of the distribution and the cavitation at relief grooves. The relation between depth of level 1- relief groove with its gas-phase volume fraction and impulse frequency in plunger pump. The results reveal that cavitations occur mainly at the intake areas, and the gas-phase volumes get to the largest fraction at the moment while water touching the inlet of port plate, and reducing dip angle of the sloping plate the gas phase volume fraction and its lasting period are decreased. Increasing the depth of level 1-relief groove wakens the cavitation, but it strengthens the peak pressure and pressure pulsation rate.

Radial Dynamic Characteristic Parameter Identification of Rolling Joints in Ball Screw Feed Systems

ZHU Jianmin;ZHENG Zhouyang;HU Yujia;ZHOU Yanan

2018, 29(04):  441-449. 

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In allusion to the problems that the radial dynamic characteristic parameters of rolling joints were difficult to determine in ball screw feeding systems, a method to identify the radial dynamic characteristic parameters of rolling joints in assembled feed systems was proposed. The screw was simplified as an Euler-Bernoulli beam to create its radial vibration equation under the excitation of harmonic vibration forces, the experiments were designed to obtain the measurement points' radial vibration displacements of the ball screw, combining with the theoretical values calculated by the radial vibration equation of the ball screw to establish the optimization goal function, and then the radial stiffnesses and the radial damping parameters of the rolling joints were identified by using AFSA. Taking a self-developed ball screw feed drive test bench as the research object, the radial stiffnesses and radial damping parameters of its guide pair, the ends of bearings，and its rolling joints in ball screw assembly were identified by using the proposed method. The experimental results demonstrate that the maximum errors of measurement point radial vibration displacements between the calculated values and the tested ones are as 3.0% based on the parameters of rolling joints calculated by the proposed method, and verify the correctness and validity of the proposed method.

Dynamics Modeling and Drive Parameter Prediction of a 5-DOF Wheel Grinding Manipulator Arm

RONG Yu1,2,3;LIU Shuangyong3;WANG Hongbin1;HAN Yong3

2018, 29(04):  449-456. 

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A new type of 5-DOF manipulator arm was proposed based on the 2-UPS+UPU mechanisms. The explicit expression between the wrist movement states and the joint driving parameters was given, and the peak prediction model of servo motors for driving speeds and torques was obtained. Calculations show that the peak value of the driving motors' speeds is as 25.1r/s, and the peak value of the driving motors' torques is as 6.2N*m. Using a design scheme of the manipulator arm and its structure parameters as an example, and the calculation results show that the example's driving motor peak speed is as 18.7r/s, and the example's driving motor peak torque is as 4.73N*m. The predicted peak power of the example's servo motors is as 700W. The driving parameters' peak prediction model of the manipulator arm is more reasonable.

Tool Life Prediction in Titanium High Speed Milling Processes Based on CNC Real Time Monitoring Data Driven

YUAN Guangchao;BAO Jingsong;ZHENG Xiaohu;ZHANG Jie

2018, 29(04):  457-462,470. 

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A large number of multi-source heterogeneous data existed in the monitoring data due to the inconsistency of the data structures of the different equipment in the workshops, which were difficult to collect and monitor through a single communication protocol. To solve this problem, a data model of machine-tools, communication frameworks and access strategies were developed to realize multi-source heterogeneous data acquisition based on the OPC-UA and MTConnect herein. Carbide tools were easily damaged and quick-wear in high speed machining(HSM) of titanium alloys, as it was difficult to predict the remaining useful tool life in real time.Therefore, a BP neural network model based PCA method was developed to reflect the relationship among machine conditions and the parameters of the tools. The model realizes the monitoring and predicting of important informations of tool healthy conditions based on RUL.

Message Dissemination Methods for Implicit Human-Machine Interactions Based on Industrial Internet of Things

YANG Lin;LI Wenfeng;DUAN Ying;LUO Yun;YANG Wenchao

2018, 29(04):  463-470. 

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For the features of industry 4.0 ecosystem, interactions among human and internet of things (IoT)-based manufacturing resources were reconfigured temporary, and the network topology of human-IoT was complex and dynamic. To address the issues in crowdsourcing and social self-organized smart devices in industrial internet of things (IIoT), an efficient and clear human-IoT implicit interaction mechanism was designed. Moreover, considering the factors of human in IoT interactions, based on concepts of machine social networks, a message dissemination method in social device-to-device network was proposed. Finally, a case study of implicit interactions for car wheel customized manufacturing was illustrated. And by using the classic method of Caveman for social network modeling and probability theory, average delivery rate and number of connection for wireless body networks were introduced as matrices to analyse performance of proposed mechanism. The simulation results show that, the maximum average completion rate of proposed message dissemination is improved by 7% compared with the random message forwarding mechanism. Under the given user satisfaction rate, the numbers of directly connected smart devices may be calculated quantitatively. The results may be used to provide the theoretical basis of the parameter selections for human-computer interaction systems in IIoT.

Characteristic Modeling and Optimization Method of Underwater Hydraulic Spindle Drilling Processes for In-situ Machining Systems

CHEN Yongliang1;PENG Tao1;LIU Deshuai 1;WANG Zhijiang2

2018, 29(04):  471-476. 

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Aiming at the low efficiencies in low speed drilling using high speed hydraulic drive spindles for in-situ friction stitch welding processes, a characteristic modeling and off-line optimization method of the underwater hydraulic drilling spindles in-situ machining systems were put forward. The drilling parameters and data were obtained by several tests. The optimal cutting parameters were obtained by the fitting based on BP neural network and genetic algorithm based optimization . The optimal parameters were used as the initial inputs for on-line optimization. The results show that the underwater drilling and the optimal cutting parameters may be effectively used in in-situ drilling processes, which shorten the on-line optimization time of drilling processes and improve the drilling efficiencies.

Mechanism and Simulation Experiments on Twin-roll Thin-strip Vibration Casting

DU Fengshan1,2;SUN Minghan1,2;HUANG Shiguang1,2;WEI Jieping1,2;HUANG Huagui1,2;XU Zhiqiang1,2

2018, 29(04):  477-484. 

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A set of 160mm×150mm vibration casting machines were designed and manufactured in order to carry out the research on the product quality of twin roll strip casting processes.The effects of vibrations on the crystal nucleation and cast microstructure were studied.The distributions and growth rules of the cast microstructures in the solidification zones under the conditions of vibration and non-vibration were compared and analyzed. It is pointed out that improving the vibration frequencies may effectively promote the grain refinement. At the same time, according to the requirements of industrial experiments, a three-dimensional flow field-temperature field coupling finite element simulation model of molten pools was established by using CFD software.The results show that increasing the vibration frequencies and amplitudes may enhance the “mixing” effects of the cast rolling molten pools, which may promote the grain refinements and restrain the segregations. It is found that the solidification point positions(i.e. Kiss point height) are not distributed along the width direction of the plates in the castrolling processes. As a result, the longitudinal inhomogeneous extensions are the direct factors to induce the cast rolling oblique cracks. And the Kiss point position will be moved up with the increase of the amplitudes and the frequencies.

Research on Annular Gradient Multi-cell Structure Crashworthiness under Multi-impacting Cases

ZHANG Yong;ZENG Yi;XU Xiang;LIN Jiming;LAI Xiongming

2018, 29(04):  485-492,498. 

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In view of the facts that traditional uniform multi-cell structure existed the defects of high peak forces when they were impacted and instability because of global bending in the oblique collisions，a novel annular gradient multi-cell tube with gradient material distribution was proposed herein. Firstly, theoretical model of the mean crushing forces about annular multi-cell tubes was derived. Then, relevant experiments were carried out to validate the accuracy of theoretical model. Furthermore, numerical simulation method was used to investigate the energy absorption performances of annular gradient multi-cell structures and corresponding uniform multi-cell structures under the multiple impacting conditions. The results show that the gradient multi-cell structures have better energy absorption capacity and load-bearing characteristics than that of the uniform multi-cell structures, especially, the crashworthiness of gradient multi-cell structures presents more obvious advantages under the large angle impact conditions. Besides, the peak forces and the energy absorption capacity of the gradient multi-cell structures gradually reduce and reach convergence with the increase of gradient exponent, meantime, thickness interval of gradient structures also has important influences on crashworthiness of the gradient structures.

A Shape Prediction Model of Eight-high Rolling Mills and Its Applications

BAI Zhenhua1,2;ZHAO Weiquan1;ZHANG Miaoxing1;LI Boyang1;LIU Yaxing1;GUO Zhensheng3

2018, 29(04):  493-498. 

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Based on the analysis of the structural characteristics of eight-high rolling mills, from the two aspects of the metal plastic deformation model and the elastic deformation model of the roll systems, a shape prediction model suitable for eight-high cold rolling mills was developed by fully combining the equipment and process features of eight-high rolling mills after the coupling between the two models. The corresponding calculation flow chart of the shape was provided. Also, the model was applied to the actual production of 1450 eight-high cold rolling mills of a cold rolling factory, thus the corresponding software for shape prediction was developed. Good results were achieved after in the field applications. The shape closure rates are reduced greatly, this technology brings large economic benefits and has the further values of popularizations and applications.