China Mechanical Engineering

A Bias Corrected Response Surface Method and Its Applications to Reliability-based Design Optimization

Zhan Zhenfei, Yang Junqi, Shu Yajing, Yang Ren-Jye

2016, 27(07): 853-858.

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In simulation-based vehicle design, the Bayesian inference based model extrapolation method was further investigated,that was previously proposed by the authors, and a systematic bias corrected model extrapolation and RBDO under uncertainty was introduced. A real-world lightweight design problem of vehicle was employed to demonstrate the validity of the proposed method.

BP Neural Network State Observation and Backstepping TrackingControl of Model-free Robotic Manipulators

Li Guang, Fu Hao

2016, 27(07): 859-865.

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A model-free trajectory tracking control algorithm was proposed for multi-link robotic manipulators with friction damping and model parameter uncertainties based on the backsteeping techniques. An adaptive BP neural network state observer with modification items was used to obtain the unmeasured states and approximated the system model online.Then,a backstepping tracking controller was developed, which took advantages of the observed state values and dynamics.Based on Lyapunov stability theory it is proved that presented controller can guarantee the tracking accuracy and all signals involved are bounded. Finally, it demonstrates that the strategy is effective by the simulation of tracking expected trajectory.

A Firefighting Six-legged Robot and Its Kinematics Analysis of Leg Mechanisms

Jin Zhenlin, Zhang Jinzhu, Gao Feng

2016, 27(07): 865-871.

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Firstly,a six-foot parallel firefighting robot was proposed and the whole conceptual design was accomplished. Secondly, based on the evolution of 2UPS+UP parallel mechanism,a novel three degrees of freedom leg mechanism with self-protection function was proposed.Then,leg mechanism kinematics was analyzed and the equation for inverse position and velocity mapping relationship were presented. The workspace of manipulator was analyzed and its three-dimensional graphic was drawn.At last,the influences of drive mechanism geometrical parameters on obstacle ability and walking speed were revealed,and a reasonable set of graphical parameters was designed.The hexapod robot proposed herein has good protective properties and broad application prospects especially in fire, nuclear plant leak,earthquake and other disaster relief.

Positioning Error Compensation Method of Industrial Robot Based on Closed-loop Feedback of Position and Orientation#br#

He Qingxi, You Zhenzhou, Kong Xiangdong

2016, 27(07): 872-876.

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In order to improve the absolute positioning accuracy of an industrial robot，a position compensation method was proposed herein based on closed-loop feedback of the position and orientation of the end effector. The compensation utilized a laser tracker to monitor the position and orientation of the robot，by measuring the optical tooling points (OTPs) fixed on the end effector，and calculated the deviations of the position and orientation by registering nominal coordinates and the measured coordinates of the OTPs. The industrial robot system communicated with the laser tracker system by industrial LAN，and adjusted the position and orientation of the robot according to the deviation data. The experiments attached in end verified the compensation method，which shows that the location errors are reduced to 0.05mm in maximum，and the orientation errors are reduced to 0.012 degree in maximum.

Synchronous Coupling Control Method of Electronic Gearbox

Han Jiang, Wu Lulu, Tian Xiaoqing, Xia Lian

2016, 27(07): 877-881,887.

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Firstly, an EGB generative control error calculation formula was deduced from the perspective of geometry, combining EGB movement control model in gear machining process. Then, the reasons of generative errors were analyzed. After that, an EGB synchronous coupling control method was proposed, and the synchronous coupling control model was built. In addition, the simulation analysis of control model was carried out, and the control effects of the synchronous coupling control mode and asynchronous manner were compared. Finally, the control model was applied in gear cutting numerical control system which was developed independently with EGB. The simulation and experimental results show that the method can promote generative control precision of EGB effectively.

Research on Noise Diagnosis Technology Based on HELS Method#br#

Liu Congzhi, Wang Lingyan, Ren Bingyu, Ma Luping, Liu Weiqun, Hu Guangdi

2016, 27(07): 882-887.

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The noise diagnosis technology based on HELS applied the Helmholtz equation for noise diagnosis. It transformed the superposition of sound pressure into superposition of a set of linear independent functions. Then the method of least squares was used to reestablish the surface pressure of the sound source according to the known noise signals. The paper innovatively established a new type of HELS-PSO model to research the noise source identification and sound field reconstruction in order to improve solution accuracy. In the experiments the speakers were as simulated noise source and verified by experiments. The experimental results verify the effectiveness and efficiency of the algorithm and the accuracy of the new algorithm is higher than that of the traditional HELS algorithm.

Research on Novel Parallel Micro-motion Precision Platform with Flexible Hinge

Li Shihua, Han Xueyan, Ma Qixiang, Li Fujuan

2016, 27(07): 888-893.

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Based on 3-RPC parallel mechanism, a new 3-PRC parallel micro-motion platform driven by piezoelectric ceramic transducer was put forward and its structure was optimized. The position of the platform was analyzed by using vector method and the theoretical coupling errors of the platform were put out. The motion decoupling characteristics of the platform were researched and analyzed by using the finite element analysis method. At last the prototype was produced and tested. The results show that the parallel micro-platform can achieve three-dimensional movement with high precision and good motion decoupling characteristics in the micron scale.

An Improved Estimation Method of Permanent Magnet Synchronous Spindle Motor Speed

Huang Keyuan, Jiang Zhi, Huang Shoudao, Yang Weixing

2016, 27(07): 893-898,938.

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This paper analyzed the model of permanent magnet synchronous spindle motor，and put forward an improved speed sensorless speed estimation method of permanent magnet synchronous spindle motor. This method corrected the estimated speed values according to the errors between the estimate current and actual current，and presented the selecting principle of the correction parameters，the motor speed might be accurately observated. Experiments show that motor acceleration performance is good，the speed accelerates from zero to rated speed (6000r/min) within 1s，during high speed running the control precision is high，resistance to impact load ability is strong，good robustness，and suitable for wide speed range，under less than 2% of rated speed the motor can be still loaded with stable operation. The experimental results verify the feasibility and effectiveness of the method.

Research on Construction Method of Objective Function for Multi-objective Topology Optimization in Structures

Zhang Jingxin, Liang Wei, Xia Yang

2016, 27(07): 899-903.

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For multi-objective topology optimization of structural materials，this paper presented a generalized average distance method to study the objective function construction method of multi-objective topology optimization based on mathematical programming. Several methods using the average distance of the evolution were introduced to change multi objectives into single objective,and the topology optimization of a automobile suspension control arm was taken as an example by a variety of methods that were evoluted in the simulation research. The results show that：a variety of methods using the average distance method can flexibly construct the objective function of the multi-objective optimization，and find a way to make better the construction objective function .The average distance concept may be applied to the design of structure optimization for multi-objective topology.

Application of LMD-ICA to Fault Diagnosis of Rolling Bearings

Bian Jialei, Zhu Chunmei, Jiang Zhanglei, Lü Junyan

2016, 27(07): 904-910.

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The classical ICA could only be applied to overdetermined blind source separation problem, which meaned the source of the observed number should be not less than number of signal source,according to this feature,a new method of LMD combined with ICA was proposed. With the approach,collected single-channel vibration signals were first operated with LMD，each components then were rearranged to build a virtual channel noise based on cross-correlation criterion, the virtual channel noise with collected signals was input into ICA,using FastICA algorithm based on negative entropy realize the separation between source signals and noise signals was realized so as to achieve the noise reduction purpose. At last, spectrum analysis method was used to compare the two signals before and after noise reduction.The noise of the signals is filtered out in a certain degree，and the spectrum is less burr，and the fault characteristic frequency is more obvious，which is advantageous for the fault feature extraction,experimental analyses prove that the new denoising method proposed herein is valid.

Human Gait Events Fast Recognition Method via Surface Electromyography

Chen Jiangcheng, Zhang Xiaodong, Yin Gui

2016, 27(07): 911-916,924.

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Real-time and accuracy detection of human motion during active training stage were required for lower limb rehabilitation robot. A dynamic surface EMG based human gait events fast recognition method was proposed. Firstly，the surface EMG generation model was established and the skeletal muscle activity during gait was analyzed，the gait event perception method with surface EMG intensity and its variation was put forward. Then，an ANFIS model was built to recognize the supporting phase and swing phase, which used the dynamic surface EMG signals of vastus lateralis lie in the both of left and right thigh as the signal source.The experimental results show that the average correct rate may reach 95.3% compared with results detected from force plate，the average time errors for heel strike (HS) and toe off (TO) timing detection are 21.4ms and 24.5ms respectively. Moreover，the method proposed also shows a strong robustness against the surface EMG difference between gaits.

Online Measuring Method of Fatigue Crack Growing Length Based on Image Processing Technology

Gao Hongli, Zheng Huanbin, Jiang Wei, Qi Zicheng,

2016, 27(07): 917-924.

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Based on image processing technology, a fatigue crack growing length online measuring method was proposed herein to obtain high precision crack length data by applying direct, reliable,accurate method in the fatigue crack propagation test.Firstly,a series of digital images in the process of fatigue crack propagation was collected by high-speed switching industrial camera that consists of a large scale area array CCD and a macro micro lens, and the morphological characteristics of fatigue crack image were analyzed. Then, sub-pixel edge detection method was used to detect the prefabricated crack edge in order to obtain the fatigue start position. Secondly, the crack region was divided into multiple square sub-images from fatigue crack start point to right specimen edge.The sub-images were segmented to binary images by adaptive image segmentation method based on grayscale statistics. The crack skeleton could be obtained by connecting the binary crack images applying the single-domain growing algorithm. Finally, system calibration and online measuring experiments of crack lengths were done. The experimental results indicate that the proposed method is of non contact,high precision, with strong anti-interference ability, and experimental data is stable and reliable. The measuring precision of crack length reaches 0.03mm, which can satisfy the international standard of fatigue crack propagation test.

An Aleatory and Epistemic Mixed Uncertainty Model Considering Parametric Correlation and Its Reliability Analysis

Zheng Jing, Jiang Chao, Ni Bingyu, Fan Song

2016, 27(07): 925-933.

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A probability and evidence hybrid uncertainty model considering parametric correlation was proposed and a corresponding reliability analysis method for problems with both aleatory and epistemic uncertainties was studied.Firstly,sample correlation coefficients were introduced to describe the correlation among probability variables,evidence variables as well as probability and evidence variables. Correlated parameters were transformed into independent ones through a matrix transformation and an equivalent probability-evidence hybrid model was built. Then the hybrid model was transformed into a series of probability-interval models in subspaces and a nested optimization analysis iterative format was summarized to obtain the failure probability interval. At last, three numerical examples were provided to verify the validity of the proposed method.

Optimization of Valve Timing of a Kerosene Engine Based on RSM

Zhang Wei, Mao Jianguo, Wei Tete, He Xiaoming

2016, 27(07): 933-938.

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Using optimization method of response surface based on the simulation, modified kerosene engine valve timing multi-objective optimization problem was studied. A simulation model of the engine performance was established with the intake, exhaust timing, ignition advance angle as optimization variables and with the improvement of brake power and brake special fuel consumption as the design optimization target. The results show that: relative to this gasoline engine, intake valve opening timing of modified kerosene engine must be postponed, the exhaust valve closing time must be postponed, and ignition timing must be advanced for better engine performance; and applications of response surface methodology can improve the efficiency of optimization.

Lubrication Characteristics Analyses of Ferrofluid Bearing Based on CFD Simulation

Li Ting, Ma Jien, Zhang Yu, Fang Youtong

2016, 27(07): 939-944.

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Ferrofluid bearing had a series of advantages, like high speed, good sealing, strong bearing capacity, etc.,which complied the needs of high-speed railway. A three-dimensional model of ferrofluid bearing was built and the simulation about the bearing and thermodynamic characteristics were carried out based on CFD. And then, further analyses of the influences of eccentricity were made, which laid the foundation for subsequent design of ferrofluid bearing.

Design of Extruder Flow Channel Based on Fluent

Lin Lihong, Jia Xiaoyan, Ma Tiejun,

2016, 27(07): 944-950.

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In order to reach the quality demands of extruder rubber and solve the disadvantage of “try and error”, the extruder head flow channel was designed based on the combination of experiences and numerical analyses. The simple flow channel and improved flow channel were designed by experiences and liquid mechanics, a mathematical model was made and the flow behavior of rubber was analyzed by Fluent. The results turn out the improved damping is better than simple damping on distributary function. The parameters of damping were set, the influences of variables on flow behavior and outlet velocity were analyzed and the flow channel structure was optimized by these effects. The extrusion experiments were made，the reasons of errors were analyzed and the following research directions were indicated.

Decoupling Control of Speed and Torque of a Hydraulic Wind Turbine

Zhang Yin, Kong Xiangdong, Chen Lijuan, Ai Chao, Li Hao

2016, 27(07): 951-956.

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Taking a hydraulic wind turbine as the research object, the high power quality output as a goal, the decoupling control of the speed and torque in the unit was conducted.The mathematical models for the hydraulic transmission system fixed displacement pump-variable motor were established. Based on the hydraulic transmission system, the key factors affecting the quality of the unit electric energy output were explored, the coupling problem of the multiinput-multioutput system was analysed, and the control method of feed-forward decoupling compensation was used to decouple. The control laws of variable motor and proportional throttle valve to the output speed and output power of the hydraulic system were analysed, and the speed and torque decoupling controller was obtained based on high power quality in hydraulic wind turbine. Taking a 30kVA hydraulic wind turbine semi-physical simulation platform as the simulation and experimental platform, the proposed control method was researched. Simulation analyses and experimental results show that the decoupling control of output speed and torque in hydraulic wind turbine is realized, and the steady speed control of hydraulic transmission system and the smoothing control of transmission power fluctuation may be achieved effectively. The results lay the foundation for the control of high quality electric power output and the improvement of the grid friendly performance in the hydraulic wind turbine.

Second-order Hydrodynamics Computation and Response Characteristic Analysis for a Semi-submersible Offshore Floating Wind Turbine

Peng Chunjiang, Hu Yanping, Cheng Junsheng, Shen Yiping

2016, 27(07): 957-964.

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A second-order hydrodynamics computation method was proposed based on the quadratic impulse response function technique for offshore floating wind turbines. Firstly，the quadratic transfer functions were calculated using the direct integration method through three-dimensional potential theory. Secondly，the quadratic impulse response function technique was applied to compute the second-order hydrodynamics in terms of the quadratic transfer functions and wave elevation. Lastly，the resulting second-order hydrodynamics was acted on the integrated dynamics model of offshore floating wind turbine in time domain. So the excitation response of the second-order hydrodynamics might be computed. Taking the DeepCwind semi-submersible platform supporting the NREL 5-MW offshore baseline wind turbine for case，the verification of the second-order hydrodynamics computation method presented was conducted,and various excitation responses were calculated and analyzed. The results show the slow drift force and mean drift force have notable influences on semi-submersible platform，but the sum frequency second-order force can be neglected.

Study on Structure and Properties of ZrO2-8%Y2O3 Thermal Barrier Coatings Prepared by Atmospheric Plasma Spraying

Wang Lin, Feng Yanling, Yu Hao, Li Fei, Zhong Yinghong, Lu Xin, Ji Yaping, Feng Zezhou

2016, 27(07): 965-969,993.

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Thermal barrier coatings （TBCs） which consisted of a NiCoCrAlY bond coat（BC） and a ZrO2-8%Y2O3 top coat（TC） were prepared. BC was prepared by high velocity oxygen fuel (HVOF) and TC was prepared by atmospheric plasma spraying（APS）. The microstructures of TBCs were investigated thoroughly by scanning electron microscopy（SEM）. The thermal conductivity and thermal insulation property of TBCs were tested mainly. The results show that the interfacial adhesion between the top coat and the bond coati is fine. The interfacial adhesion between the bond coat and substrate is also fine. The thermal conductivity of TBCs is as 0.99W/（m·K）at 1100℃. The thermal insulation effect can reach 155℃ at the test temperature of 1100℃ and air flow under the condition of 4m3/h.

Numerical Simulation and Experimental Study on Rotary Roll Forging for a New Al-Zn-Mg-Cu Alloy Cup#br#

Ma Junlin, Gao Shiheng, Li Ping, Xue Kemin

2016, 27(07): 970-975.

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In order to study the influences of mechanics properties of a new Al-Zn-Mg-Cu alloy cup formed by rotary roll forging, the initial height-diameter ratios of 0.4, 0.8 and 1.2 cylinders deformation were researched by numerical simulation and experiments. The metal flow, equivalent strain and temperature distribution of the cylinders in the process of rotary roll forging were simulated by FEM. Then the corresponding experiments were carried out, and the tangential and radial mechanics properties in the cup chassis were tested respectively.It is found by FEM analyses that, the amount of grid distortion in the area contacted with top die is larger than others. And the thermal effects in the forming process are obvious. The results show that, when height-diameter ratio of initial cylinder is 0.8, the strength in cup chassis comes to 507MPa, which increases 64.4% compared with the base metal strength. The strength in chassis of the new Al-Zn-Mg-Cu alloy cup may be improved by the isothermal rotary roll forging. Meanwhile, the height-diameter ratio of initial cylinders can affect the chassis strength greatly.

A Tire Model for Contact Ground State Considering Drivingand Overturning Torques at Axle Head

Wang Chen, Huang Haibo, Liu Jinpeng, Li Hongyu

2016, 27(07): 975-981.

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The lateral deformation was considered utilizing Euler beam and divided tire into slices in lateral direction. The displacements of belt elements were computed with two-variables Fourier series. The profile of tire cross-section was described as quadratic function. The model was verified by comparing longitudinal and lateral forces with tests. The results show that the model is more precision and efficiency. The methodology for building tire 3D contact model can be provided to explore the tire wear and mechanics behaviors.

Aerodynamic Drag Reduction Method of Vehicle Body Based on Non-smooth Surface and Vortex Interference

Yang Yi, Zheng Meng, Huang Jianfeng, Nie Yun

2016, 27(07): 982-987.

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A body aerodynamic drag reduction method was discussed by combining the non-smooth surface morphological structure with active control of the flow field.Decorating pit type non-smooth surface on the vehicle rear end of MIRA straight back model，and on the basis of the non-smooth model，a vortex generator with variable jet velocity was equipped in the pit array to control rear air flow of model, improving the trailing vortex structure. Through three models' (smooth model, non-smooth model, non-smooth model with eddy injection) numerical simulations of three dimensional flow field，some parameters（such as airflow velocity, pressure, and the turbulent kinetic energy） of the models with different tail morphological characteristics were obtained， the difference of aerodynamic drag coefficient of different models under different wind speeds and the drag reduction effects under different jet velocities were compared. Changes of tail flow field parameter were analyzed, aerodynamic drag reduction mechanism and the effects of eddy-jet agitation of non-smooth body were elaborated.Results show that through a optimized combination which consists of passive drag reduction of the non-smooth form and active drag reduction of the eddy effusion, the aerodynamic drag of MIRA straight back model is effectively reduced.

A Mixed Flow Channel CFD Simulation Method for Vehicle Torque Converter

Liu Shucheng, Xing Qingkun, Li Weiwei, Zhang Jing

2016, 27(07): 989-993.

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In a complex dynamic process of hydrodynamic converter for vehicle, the work phase shift might occur at any time. Without identifying the changes of flow field in time, it could become difficult to simulate the transient flow performance. Based on traditional converter CFD channel model and bladeless channel model, a new hybrid-flow-channel CFD simulation model of hydrodynamic torque converter was established. This model might automatically identify the work phase and phase transition of torque changing, coupling and power reverse transfer. According to whether the stator wheel was idling or not, it automatically selected the appropriate model channel. A series of simulations and experimental studies of steady state and dynamic characteristics of a torque converter were conducted to validate the credibility of hybrid-flow-channal simulation model. The results show that the CFD simulation method of hybrid channels of the hydrodynamic torque converter is of high accuracy for the steady and dynamic simulation of the converter.

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