China Mechanical Engineering

Research on Obstacle Avoidance by Virtual Force for Redundant Robot

CHOU Wu-Qing, WANG Shuo

2011, 22(24): 2899-2902.

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This paper present a new method of obstacle avoidance for redundant robot with tool-tip restrictions. This method introduced virtual force and kinematic of multibody system into obstacle avoidance.The robot avoided obstacle in real-time based on the obstacle avoidance force and the attraction of mission path. Obstacle avoidance algorithm improves accuracy and efficiency by the partition of operating area and the accurate computation of obstacle avoidance force. The approach implements collision avoidance without kinematics optimization and improves the real-time performance.

Research on Associated Network Construction of Rapid Extended Manufacturing Tasks Based on Multi-view Model

GUO Yu, AN Bei, LIAO Wen-He

2011, 22(24): 2903-2908.

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A method for constructing an association ship among different sub-tasks in rapid extended manufacturing for weapon production was studied, the paper put forward a way to build associated network model of sub-tasks in the extended manufacturing system, and defined a multi-view model of extended sub-tasks(EST) based on structure, function,process, and management.A principle on how to analyze the association of EST was given,which can complete qualitative and quantitative analyses of different size of EST. Finally,a case was given to validate the validity of the method.

Design and Experiment of Double-motor Synchronous Control System with Variable Friction Load

HU Hong, LI Le-Bao, ZHANG Yi, WANG Ling

2011, 22(24): 2908-2914.

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For the influences of friction load for a double-motor synchronous control system in actual operation,this paper built a math model of the double-motor's synchronous control system and a Stribeck friction model firstly.Then based on the analyses of the advantages and shortcomings of all kind of control methods and control algorithm,a scheme of synchronous control for double-motor was presented,which used fuzzy PID to control the double-motor's relative by the method of relative

coupling control,and compared it with normal PID's.

The simulation and experimental results show that the synchronous control system of relative coupling with fuzzy PID is better than the normal

PID's,which has better anti-interference and synchronization control precision.

Semi-finished Milling Tool Path Optimization Algorithm for Irregular Free-form Surfaces

GUO Guang-Li

2011, 22(24): 2914-2917.

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This paper focused on the tool path optimization algorithm of a free surface on the coordinate of CNC machining. The optimization algorithm can be applied to semi-finishing conditions for high speed milling free surface curvatures. The design surface can be obtained from optimizing the tool path by offsetting an angle. The final cutting tests of different processes show the optimization algorithm has a good effect, and can fully meet the needs of precision verifying the reliability of the algorithm.

Dynamics Analysis of Flexible Rotor System Based on Wilson-θ Method

HEI Dai, ZHENG Mei-Ru

2011, 22(24): 2918-2922,2965.

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Dynamics model and equation of a nonlinear flexible rotor-bearing system were established based on rotor dynamics. A method consisting of Wilson-θ method and the predictor-corrector mechanism and Newton-Raphson method was proposed to determine unbalanced response of dynamics system. Taking the stiffness of flexible rotor as the control parameter, nonlinear dynamic responses of rotor system were obtained by the proposed method. The stability and bifurcation of the periodic motion of system can be analyzed by the Floquet bifurcation theory and Poincaré map. Numerical results reveal periodic, 3- periodic, quasi- periodic, 5- periodic, jump solution of the system.

Reliability Allocation of High Speed Motorized Spindle Based on Improved Fuzzy AHP Method

SHU De-Xin, LIU Hong-Zhao

2011, 22(24): 2923-2927.

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An improved fuzzy analytic hierarchy process(AHP) method was applied to allocate the reliability of the high-speed motorized spindle of a CNC machine tool whose reliability indexes can be qualitative and quantitative and multi-hierarchic. By establishing the AHP structure of reliability allocation from many uncertain factors affecting the allocation of reliability, the weights of each unite of system

were analyzed and calculated quantitatively,and the rational allocation of system was finished according to the weights.The results are basically consistent with the actual situations.It shows that the method has good practical and is able to provide a basis for the spindle design.

Simultaneous Localization and Mapping Algorithm of a Mobile Robot Based on Extended Kalman Filter

LOU Xiao-Chun

2011, 22(24): 2927-2930.

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For mobile robot simultaneous localization and mapping(SLAM) key issues,an improved

SLAM method based on extended Kalman filter was presented.Through the

establishment of the observation model based on line features,the prediction and

state-updating of the SLAM were formulated,the computing cycles were designed based

on the number of feature points and the simultaneous localization and mapping were realized.Experimental results show that the method is effective and feasible.

Simulation Analysis and Optimization of Friction Separation Mechanism of Mailing Machine

JIANG Jian-Dong, DAO Guo-Xin, DIAO Ying-Di, ZHANG Li-Ban, XU Fang

2011, 22(24): 2931-2936.

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According to the deficiency of existing friction separation mechanisms of mailing machines,this paper proposed a new type of friction separation mechanism,analyzed the conditions of friction separation and obtained calculation formula of the pressure roller's gap adjustment.A dynamics simulation model of this mechanism

was established by LS-DYNA software and the speed,acceleration and the positive

pressure of the envelopes,friction forces suffered in the separating process were analyzed by finite element simulation.The problem of how to classify the envelope thickness through the adjustment of the angle of pressure roller, and the influences of different heights

of supporting roller and transmission speeds on the effectiveness of envelope

separation were studied in order to optimize the related parameters of this friction separation mechanism.The results show that the matching method of classifying envelope thickness, adjusting supporting roller's height and conveyer speed can increase greatly

the effectiveness and efficiency of the separation mechanism.

Incipient Rub-impact Fault Diagnosis of Rotor System Using Improved HHT

WANG Xiang, WANG Zhong-Sheng

2011, 22(24): 2937-2940.

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For suppressing the problem of setting two parameters in EEMD with difficulty,the standard deviation of added white noise and the number of ensemble trials, a general method of setting the two parameters was given through the experimental analyses. And then, taking the rubbing fault signals of rotor as objects, an improved HHT algorithm was presented. This method was also validated by real rub-impact case, and was compared with basic HHT algorithm. The results show that improved HHT is more precise. 

After-sale Quality Loss Evaluation and Early Warning Method of Universal Engineering Products Based on Fuzzy Comprehensive Evaluation and BP Neural Networks

LI Jin-Cai, YIN Chao, LIU Fei

2011, 22(24): 2941-2946,2976.

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In view of the after-sale quality loss of universal engineering products is affected by multiple factors and it has difficulties in evaluation and early warning.

An after-sale quality loss evaluation and early warning method for universal engineering

products was put forward,which was based on fuzzy comprehensive evaluation and BP neural networks.Meanwhile,the evaluation index system for after-sale quality loss was founded.Subsequently,some of the key technologies were studied, including fuzzy comprehensive evaluation, three layer BP neural networks forecasting for the after-sale quality loss.Finally, the method was successfully applied in after-sale quality loss evaluation and early warning in a universal engineering products manufacturer of Chongqing,

and good results were obtained.

A Processing Method for Measuring Data of 3-D Welding Seam Based on Active Framework

YANG Jian-Zhong, WANG Bao-Shan, HUANG Ke, BANG Fang-Yu

2011, 22(24): 2947-2953.

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In order to realize precise laser welding of the large-scale aerospace structure, a “5+2” axes laser welding & measuring system, as well as a processing method for measured data based on the active framework were developed. According to homogeneous coordinate transformation, local position and normal of 3-D welding seam were converted into global data to establish its geometric model which was reflected on the machine tool's reference coordinate. Then, the machine tool's geometric errors were analyzed and compensated. Finally, a welding experiment based on the aerospace structure simulacrum was carried out. Through online measurement, data processing, geometric modeling, and actual welding, the proposed method was verified to meet the requirements.

Design of a New Vertical Rotary Paper-cutting Device 

LIU Zi-Jian, XIE Zong-Min, LV Cheng

2011, 22(24): 2953-2957.

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A method of vertical rotary tipping paper-cutting was proposed and a new vertical rotary tipping paper-cutting device consisted of paper-cutting blade and paper-cutting drum was designed. The curve of cutting edge, the groove of paper-cutting drum and the performance of the device for cutting tipping were researched and the accuracy and rationality were verified by a virtual prototype simulation and experiment. A new method was provided for the design of high-speed paper-cutting device. The device was used in tobacco industry and could cut tipping paper in high-speed and great efficience.

Its life is prolonged and the practical value is great.

Analysis of Stepper Motor Velocity Saturation Nonlinearity

XU Gong-Wei-1, 2, XU Fang-１, ZHANG Lin-1

2011, 22(24): 2958-2961.

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The velocity saturation nonlinear characteristics of stepper motor tracking control with the describing function method was studied herein. Research results

show that, along with the rotation excitation field amplitude or frequency of the

stepper motor increases, stepper motor output will gradually appear distortion

component; when the product of excitation magnetic field amplitude and frequency is greater than a certain value, stepper motor output appears complete distortion. If distortion degree is

bigger,the stepper motor output nonlinearity is stronger and frequency characteristics

are worse.Step motor digital servo valve velocity saturation nonlinearity simulation

proves the effectiveness of the analyses.

Modelling and Validation of Vertical Vibration with 6 Degrees of Freedom for 4-high Hot Strip Mill Stand

MA Wei-Jin-1, LI Feng-Lan-2, WANG Dun-Yuan-1, XIONG Shi-Bei-2

2011, 22(24): 2962-2965.

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A lumped mass model with 6 degrees of freedom for the vertical vibration of 4-high hot strip mill stand was proposed, and then its modal frequencies were calculated by MATLAB package. Field vibration testing results confirm that the numerical calculation is relatively accurate. This vertical vibration model can be used for dynamics simulation and structural dynamics modification, which provides important theoretical and practical significances for mastering and understanding the vibration characteristics of 4-high mill stand, avoiding vertical self-excited vibration, enhancing rolling efficiency and improving product quality.

Research on Energy-saving Methods for Hydraulic Speed-regulating Curcuit Based on Multi-pump

WEN De-Sheng, GUO Gao-Feng, DU Xiao-Jie, XU Tian, DIAO Chao

2011, 22(24): 2966-2969.

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Based on a new hydraulic component(multi-pump),several noval speed-regulating circuits were proposed.The core component of these circuits is multi-pump in which more pumps with different flows are formed.It has more inlet

ports and more outlet ports,according to various working conditions of the actuator needed,it changes the connection of pipes,which makes the pumps output power match the

load power reasonably,by doing so,the problem of too much power loss can be

solved.The operating principle of single-acting multi-pump and double-pressure throttle

speed-regulating circuit,the double-acting multi-pump digital control inlet throttle speed-regulating circuit and the double-acting multi-pump digital control stepless speed-regulating circuit were stated,then the power performance of the multi-pump digital control inlet throttle speed-regulating circuit under constant load was analyzed.The results show

that these curcuits reduce the loss of power and improve the efficiency.

Research and Development of Electronic Servo Tri-axis Multi-position Transfer System for Large-scale Press

SHU Ren-Miao-1, TANG Dui-Bing-1, XU Liang-Liang-1, ZHONG Ta-Sheng-2, JI Xue-Dong-2, LIU Shi-Hao-1

2011, 22(24): 2970-2976.

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In order to achieve automatic feeding and station conversion required by a large-scale multi-stage press machine,a large-scale electronic servo three-axis multi-stage feeding system was researched and developed.In the process of research & design,an overall design solution was proposed at first

based on a systematic approach, effectively solving the difficulties resulted by many

influence factors for designing such a complex feeding system, and leading to an orderly design manner.Then the feeding system was modeled by a three-dimensional design software of Solidworks,and was simulated by the kinematics software of ADAMS and the finite element analysis software of ANSYS. Finally, a physical prototype of the feeding system was built, which verified the feasibility and reliability of the proposed design solution. 

Research on Water Jet Propulsion Theory of Positive Displacement Pump

YANG You-Qing-1, GU Xiao-Jun-1, SHU Yu-Quan-2

2011, 22(24): 2977-2981.

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The composition and work principles of a positive displacement pump (PD pump) WJP were introduced and the comparative analyses were made between the positive and negative displacement pump (ND pump) WJP. Based on the traditional WJP theory, a study of introducing correction coefficients of momentum/kinetic and the impact factors of boundary layer and pump suction was carried out to investigate the energy transformation and the theory of PD pump WJP, such as the calculation of thrust and efficiency. The related conclusions are extended to design high performance PD pump WJP units.

Tolerance Synthesis Modeling and Simulation Based on DOF of Geometric Variations of Features

HU Ben-Qing-1, WANG Can-1, JING Hui-2, HUANG Mei-Fa-2

2011, 22(24): 2981-2985.

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Aimed at the AFR specified in the stage of design, a mathematic model that can be used to tolerance synthesis simulation in CAT was established based on the geometric features' variations of DOF. Two steps were involved in the course of tolerance synthesis modeling: the relationships among each feature's DOFs with AFRs were explicitly formulated with homogeneous matrix transforms and the synthesis equations were obtained with the matrix inversion technique. An engineering example, gear pump, was introduced to test the proposed method. The synthesis equations between the backlash spacing and the corresponding features' DOFs were obtained, and the distribution of each feature's DOFs was calculated by the method of Monte Carlo. The results show the validity and practicability of the method proposed.

Packing Pressure Control in a High-accuracy Plastic Injection Molding Machine Based on CMAC and PID Compound Controller 

CA Kan, YING Ji, CHEN Zi-Chen, WANG Shuo

2011, 22(24): 2986-2989.

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Aiming at serious problems of controlling

packing pressure in injection molding processes with traditional PID algorithm,

such as pressure overshoot,static error,time delay etc.,a mathematical

model of the packing pressure system in injection process was

established.Considering the behaviors of system,a new control device with

CMAC and PID compound controller was designed.

The experimental results show that,compared to traditional PID control,

CMAC and PID compound control improves the pressure overshoot,static error and time delay of the packing pressure significantly,and makes notable progresses on quality and repeatability of products.

Mechanics Principle of Controlling Trip Shape by Means of VC Roll

LI Wei-Min, CHOU Beng

2011, 22(24): 2990-2992.

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On the basis of experiments and FEM simulation,the influence law of control pressure and oil chamber length on the dead

crown and its distribution rule was discoursed. In rolling mills using VC roll as the backup

roll,the mechanics principle of controlling trip shape with VC roll is that the bulging effect of VC roll can reduce the contact area between working roll and backup roll,thereby

causes a moment opposite bending deformation of backup roll at both ends of the working roll.The key technique is in selecting an appropriate oil chamber length so that the equivalent crown zone should not appear.

Thermal Response of Functionally Graded Piezoelectric Coatings on Sphere and Cylinder Shells

SHU Xiao-Beng

2011, 22(24): 2993-3000.

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By solving the piezothermoelastic control

equations and using the recursive relations between layers, the explicit piezothermoelastic solutions were deduced for functionally graded piezoelectric coatings on hollow spheres and circular cylinders.The solutions are accurate for multi-layered functionally graded piezoelectric coatings. If a continuous functionally graded piezoelectric coating was divided

to many layers,a approximate solution will be obtained and converged to the

accurate solutions when the number of layers increased.Piezoelectric effects were ignorable on the stresses in substrate,

but very obvious on the stresses in coating.Increasing the number of layers

in coatings does not decrease the maximum stress,but obviously decreases

the jump of circumferencial stresses between layers and reduces interfacial

stress concentration.However,interfacial strenghth is weakened because the radial stress between coating and substrate increases with the number of layers. 

coating;

Overall Efficiency Optimization of Duel-state Continuously Variable Transmission

HAO Yuan-Zhi-1, 2, SUN Dong-Shu-1, QIN Da-Tong-1, YIN Yan-Chi-1

2011, 22(24): 3001-3005,3022.

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Aimming at highest efficiency of CVT,an optimization algorithm was designed by considering the efficiency of engine and the main dissipation component of CVT.Duel-state hydraulic torque converter(TC)

was also included in the algorithm.Control strategy based on power demands

was designed in order to realize higher efficiency of the whole system.The highest efficiency operating conditions which satisfied the power demands were set to be the control objective.As a result,

the best economical efficiency is available.While the power demands exceed the maximum output power under the current vehicle speed,the maximum output power conditions

were set to be the control objective,and then the best dynamic performance is available.

TC ideal control line was calculated,based on which a practice operating line was designed. The results of simulation show that by adopting the designed optimal strategy,fuel consumption decreases nearly 3%, TC lock time reduces 11% in start-acceleration,and the maximum output power increases 2.3%. 

Analysis of Dynamic Fatigue Reliability of Active Suspension Based on Random Optimal Control

WANG Ji-Dong-1, 2, MEI Xue-Qing-1

2011, 22(24): 3006-3011.

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Using the theory of random vibration and random optimal control, a calculation method of statistical law of random dynamic load on suspension parts for the two-degree vehicle model was deducted. The probability model of random dynamic load under variational velocity of the vehicle was established. An analysis method of the dynamic fatigue reliability of suspension parts based on random optimal control was proposed. The simulation results show that the random dynamic load on the active suspension parts is in evidence bigger than that on the passive suspension parts, and that the dynamic fatigue reliability of the active suspension parts in use is smaller than that of the passive suspension parts. This illuminates that the reliability of the active suspension parts is reduced than that in the passive suspension parts.

Thoughts of Mechanical System Condition Monitoring Technology under IOT

YAN Xin-Beng, ZHANG Ru-Lei

2011, 22(24): 3011-3015.

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The latest progresses in mechanical system condition monitoring technology under the IOT was reviewed and presented.The montiorability-based design basic theory is fundamental to develop mechanical system condition monitoring technology under the IOT.A study of on-line monitoring sensors and

their systems according with IOT features guarantees the development of mechanical system condition monitoring technology in IOT.The establishment of the standard system of mechanical system condition monitoring technology can provide the technical support to the development of mechanical system condition monitoring technology under IOT.

Current Status and Development Trends of Vibration-based Piezoelectric Generator

SHU Chi-Ya, CHEN Ren-Wen, LEI Xian

2011, 22(24): 3016-3022.

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The current status of piezoelectric generator was reviewed,including the working principles and the species of piezoelectric elements.The energy scavenging circuits and the strategies for increasing the operating frequency range were focused.

Some application examples were illustrated and the trends were pointed

out according to the problems in current researches.With the development of microelectronic and micromachining technology,the piezoelectric generators will be widely used in powering MEMS,wireless sensor networks and low dissipation electronic devices.

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