Table of Content

10 March 2016, Volume 27 Issue 05

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Compensation for Cutter Errors of Spiral Bevel Gear CNC Machining

Han Jiang, Yang Qingyan, Zhang Kuibang, Xia Lian

2016, 27(05):  569-576. 

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The deviation of the profile that cutter blade used a straight profile to instead the truly, that would impact the machining accuracy of spiral bevel gear tooth surface, during CNC machining process. This paper analyzed the principles of CNC machining spiral bevel gear first, and then a mathematical model of the blade to the tooth surface was built; after that based on the space meshing theory the actual cutter blades were calculated; the relationship among cutter radius and tooth flank errors was establised; the actual tool truncate errors were deduced. Finally, according to the spiral bevel gear machining principles the tool errors were compensated. The compensation results was verified based on simulation and prove the algonithm is reliable.

Research on Grinding Wheel Loading Detection Based on Thermogram Detection and Segmentation Technology

Guo Li, Jiang Zhishun, Shang Zhentao

2016, 27(05):  577-583. 

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According to the grinding wheel loading detection problems, a method was proposed for detecting the grinding wheel loading based on the active infrared detection technology and the thermogram segmentation technology. Three methods including the threshold segmentation, the edge detection and the region growing were used to segment the thermogram, the features like the amounts and states of the grinding wheel loading were extracted. The experimental results show that: the distribution of the grinding wheel loading swarf extracted by the threshold segmentation method presents a “segregation” phenomenon, and the selected threshold value is affected the loading features deeply. The edge detection method has overcome the “segregation” phenomenon, but there still exist some problems such as the edge is not complete and the positioning of the edge is not accurate. The results of the RGS method based on the gradient threshold filtering are more objective and accurate. The test result errors of the grinding wheel loading detection between the RGS method and the microscopic photography were given. The RGS method can realize active quantitative detection of the grinding wheel loading.

Speed Sensorless H_∞ Control for PMSM Based on Energy Function

Wu Zhongqiang, Wu Changhan, Jia Wenjing, Zhao Liru

2016, 27(05):  583-588. 

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The speed sensorless H∞ control method for PMSM was researched based on the energy function. In order to control the speed of motor rotator effectively, firstly the Hamilton model of the PMSM was shaped when there was not disturbances, and the rotator speed might reach the expected value. When there were disturbances, a H_∞ controller was designed based on the Hamilton function. An observer was designed using the method of expansion plus feedback based on the Hamilton function and used to measure the angular speed of rotator, and the speed sensorless shape plus H∞ control were achieved. The simulation results show that the shape plus H_∞ control based on the observer can estimate the angular speed accurately, and restrain the disturbances of system, and control the rotator speed effectively.

Type Synthesis of Fully-decoupled and Fully-isotropic 1T1R Parallel Robotic Manipulators

Chen Hai, Cao Yi, Qin Youlei

2016, 27(05):  589-595. 

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Based on the screw theory, a method of structural synthesis of fully-decoupled and fully-isotropic one-translational and one-rotational(1T1R) parallel mechanisms was proposed, the parallel mechanism adopted with driven-chain whose output link was provided by independent motors. Firstly, according to the prescribed characteristics of each mechanism limb, a methodology was proposed that made use of the screw theory to synthesize desired forms for both of the direct and the inverse Jacobian matrices. Secondly, according to the features both of the direct and the inverse Jacobian matrices, the actuation screws, actuated screws and mobile un-actuated screws of every limb were confirmed at first based on the reciprocal screw theory, and the leg structure was obtained. Then the structural synthesis of each kinematic chain for fully-isotropic 1T1R parallel robotic manipulators was performed in the light of different connectivities of the limbs. Finally, the anticipant manipulators were synthesized by using the rules and regulations of fully- isotropic parallel mechanisms and a lot of parallel mechanisms were obtained. Many of fully-decoupled and fully-isotropic 1T1R parallel mechanisms were synthesized by using the above method. Kinematical analysis about one of manipulators designed here show that the method is reasonable and correct.

Ant Colony Optimization of STEP-NC Process Route Based on Dynamic Update of Taboo Manufacturing Features

Huang Fengli, Gu Jinmei, Zhang Libing, Xu Chunguang, Wang Haiyan

2016, 27(05):  596-602. 

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In view of the process route generation and optimization problems of the manufacturing features in STEP-NC, ant colony optimization method of process routes with dynamic update of taboo manufacturing features was proposed, which was to make the replacement rate minimum of machine tools, fixtures and tools as the objective function. First, the manufacturing features were decomposed in accordance with manufacturing process, and then the process route optimization problem was converted to the order of manufacturing features. According to the processing hiding relationship in the machining process and the rigid constraint matrix, a dynamic update method of taboo manufacturing features was put forward in the process of generating process route. Taboo manufacturing features dynamic updating method was combined with ant-cycle model of ant colony algorithm, which was to solve the optimization problem of parts processing route. Application examples show that the proposed method may solve the rigid constraint processing problems better in the optimization process of the machining process route.

Door Closing Force Calculation Considering Door Assembly Deviations

Song Kai, Liu Jiuwu, Cheng Aiguo

2016, 27(05):  602-608. 

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For the inaccurate analyses of automotive door closing force simulation caused by assembling deviations,a approach to accurately calculate the door closing force was proposed.Firstly, by establishing appropriately mechanics model of the components in the process of closing the door, the door lock that impacted the closing force out of several other factors was taken for example, and the probability statistics distribution of door lock's positional errors in the process of assembling was gained by Monte Carlo simulation.Combined with the door lock's positional assembling errors in the calculation of the closing force of the mathematical model, the probability distributionof the door closing force was obtained. Then the closing force tests on the prototype were done.The test results show that the calculation accuracy of the door closing force that combined with the door assembling deviations is improved.

Analyses of Dynamic Coupling Characteristics and Structural Noise of Multi-Megawatt Wind Turbine Gearbox

Yang Changhui, Xu Taojin, Wu Canyuan

2016, 27(05):  609-614,621. 

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Wind-turbine gearbox was one of the most important components of wind-turbine, its dynamic performance had direct impact on the whole system. A coupled nonlinear dynamic FE model containing gears-shafts-bearings-housing for a multi-megawatt wind turbine gearbox of planetary gear transmission was built comprehensively to perform the coupled modal analysis of the whole gearbox with Lanczos method. In consideration of the nonlinear factors of the time-varying mesh stiffness of spur and helical gears, gear errors and gear mesh impact, the dynamic response of the system was studied using direct integration method under the effects of internal excitation. The vibration displacement, velocity and acceleration as the dynamic evaluation indexes of the wind turbine gearbox were obtained, and the structural noise was also analyzed. All results provide useful theoretical basis for dynamic optimization of multi-megawatt wind turbine gearbox system.

Optimization Design of Capture Latch in Space Docking Mechanism

Tang Shuren, Chen Baodong, Liu Zhong, Kang Zhiyu, Tang Ping

2016, 27(05):  615-621. 

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Space docking mechanism was an important portion to realize space docking between aircrafts. As a key component of docking mechanism, capture latches were used to carry out following actions: capture and release. The bolt-spring mechanism in capture latch was quite hard to design as a typical multi-object system. This paper analyzed the movement orderliness of bolt-spring mechanism and built its mathematics model, then simplified those nonlinear equations on the basis of engineering requirements. After that, penalty function and stochastic tactic distribution model were used to improve the standard genetic algorithm, and the calculations were completed and the results were checked by ADAMS simulation method. At last，capture latch tests indicate that capture force reduces and capability improves observably. Finally, capture latch put across China on-orbit space docking test, and attested upwards optimization design successfully.

Optimization Identification for Dynamic Characteristic Parameters of Sliding Joints Based on Response Surface Methodology

Wang Zhonghou, Yuan Keke, Li Gang

2016, 27(05):  622-626. 

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In allusion to the difficulties to determine dynamic characteristic parameters of sliding joints, and the complexity and large calculation quantity of the current method, a new method combining the response surface and experimental modal analysis was proposed to identify the dynamic characteristic parameters. The sample points were acquired by experimental design to construct the polynomial response surface model. The relative error between the results of the calculated response surface and the actual test was taken as the  objective function. An adaptive simulated annealing algorithm was employed to optimize parameters of the function.Modeling, experiments and parameter identification were conducted with the sliding joints between column guide way and slide carriage of the experimental machine tool. The analytic results indicate that the parameter identification achieves high precision and significantly improves the efficiency.

Measurement of  Particle Mass of  Resonant Fatigue Crack Propagation  Test  Vibration  System  Based  on Soft-measuring  Technology

Gao Hongli, Liu Hui, Zheng Huanbin, Liu Huan

2016, 27(05):  627-634. 

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The  particles of resonant fatigue crack propagation test vibration  system were composed of multiple different shapes and material components,which largely limited  the direct measurement of particles mass.A soft-measuring method was  proposed herein to measure the particle mass of this kind of vibration system. Firstly, three degrees of freedom vibration system mechanics model and the dynamics equation were established and the system natural frequency equation concerning system natural frequency, spring stiffness and particle mass was derived. The specimen stiffness under different crack  lengths was  calculated by finite element  method and the system natural frequency under different crack lengths  was  measured through frequency measuring experimental method.With substituting resonance frequency value under different crack lengths and the corresponding specimen stiffness into system frequency equation, the over determined equations were derived by taking the particle  mass  needed to  identify  as the unknown variables, the least-squares solution was obtained by solving the over determined equations,and this vibrating system particle mass  were obtained by further subsequent processing. The related experiments  were  performed to verify the accuracy of the proposed method.The experimental results  show  that the maximum error of main vibration mass is  as  6.76% and the proposed method has theoretical significance and application values.

Internal and External Parameter Calibrations of a Camera Based on Convex Relaxation Optimization Algorithm

Ke Fengkai, Chen Youping, Xie Jingming, Zhang Dailin

2016, 27(05):  634-639,657. 

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The similarity between the real object and the reconstructed model and the precision of the 3D point cloud were determined by the accuracy of the internal and external parameters of the camera. A convex relaxation algorithm was proposed to deal with the problems of camera calibration. Each monomial in the polynomial optimization problem was replaced by its corresponding linear item and some semi-definite matrix inequalities were added. The global optima could be approximated or achieved by solving one or more semi-definite programming problems. The experimental results confirm the feasibility and the accuracy of this algorithm. Moreover, the algorithm can be applied to the problems of camera calibration and some other polynomial optimization problems in multiple view geometry.

Speed PI Parameter Auto-tuning Based on Closed-loop Adaptive Identification

Zhang Peng, Wang Wenge, Fu Xia, Nie Ting

2016, 27(05):  639-645. 

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In order to solve the problems of speed PI parameter tuning process needed to be adjusted repeatedly or had low efficiency for PMSM servo system, a practical method of speed PI parameter auto-tuning was proposed based on the closed-loop AKF system identification. Though speed closed-loop input excitation, the signal-to-noise ratio and actual output of closed-loop identification sequence under different frequencies were analyzed, then the discrete model of closed-loop controlled objects was identified by AKF algorithm, and finally by genetic algorithm the optimal speed PI parameters were searched through simulation. Simulation and experimental results show that the presented algorithm can effectively suppress the influences of the measurement noise disturbances on system identification accuracy, and the recognition result can reflect the dynamic input-output characteristics of the actual system, moreover, excellent response and high accuracy have appeared after speed optimization and it is convenient to the practical industrial applications.

Experimental Study on Recognation of Bulk Materials Level by SVM Posterior Probability

Tian Mingrui, Hu Yongbiao, Jin Shoufeng

2016, 27(05):  646-651. 

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A image-based method for bulk level detection in bulk loading operations was proposed herein. The method first divided the image to several non-overlapping sub-blocks, then each blocks were filtered by a homomorphic filter, converted to binary image, abstracted the binary co-occurrence matrix, and recognized by SVM according to their texture features. In recognition process, a target-proportion model of the blocks which located between the boundary of bulk and the background was found based on SVM posterior probability. The model combined the SVM bulk level fitting results and the SVM posterior probability values was used to segmentation process in these boundary-blocks. Experimental results indicate that the recognition errors of the contour and the bulk level are reduced by 42% and 56% compared to the SVM recognition algorithm, average errors are as 0.4517pixel and 0.2586pixel respectively. The running times of the proposed method is as 0.2s under MATLAB. 

Modeling and Experimental Research of Workpiece Spindle Speed Optimization in CNC Camshaft Grinding

Yang Shouzhi, Deng Zhaohui, Wu Guiyun, Liu Wei, Wan Linlin, Peng Keli

2016, 27(05):  652-657. 

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According to the constant speed camshaft grinding mathematical model in X-C axis, the equations of horizontal feed displacement and velocity of wheelhead, cam workpiece spindle theory speed were established. Based on the machine capacity constraints of CNC camshaft grinder, the allowed values of workpiece spindle speed were calculated with integration reverse method, where the values of horizontal feed velocity, acceleration or jerk of wheelhead exceeded the limit in the corresponding corner section. Then the calculated values of workpiece spindle speed were replaced with the theoretical speed value of constant speed camshaft grinding on the corresponding corner section. With the workpiece spindle speed curves before and after optimization, the camshaft grinding experiments were carried out. The experimental results indicate that: using the optimized workpiece spindle speed, the maximum cam lifting errors and maximum adjacent errors of the camshaft decrease compared to that processed by the theoretical constant speed; and the surface roughness also decreases. It shows that optimization method can improve the processing quality of the precision and efficient camshaft grinding.

Research on Dynamics Model and Properties of Bellows Type Vibration Isolator with Negative Pressure

2016, 27(05):  658-662,668. 

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Low frequency vibration isolator was studied herein. According to the unique features of negative pressure and the good elastic performance of rubber, a new concept of bellows type vibration isolator with negative pressure was proposed. The qualitative analyses of negative pressure isolation theory were carried out. Through mechanics modeling and theoretical simulation analyses and the experimental results indicate that the vibration isolator system has a more ideal nonlinear elastic curve. At the same time,impacts of the negative pressure and the effective area on performance were studied. Results show that, the bellows type vibration isolator with negative pressure has a strong practicability.

Design and Simulation Analysis of New Semi-active and Multiplication Process Heave Compensation Device

Xu Tao, Liu Qingyou, Dai Juan, Li Wei

2016, 27(05):  663-668. 

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Combined with the compensation principles of semi-active heave compensation device, a multiplication process traveling block hook heave compensation system was designed,which was driven by double driven gear-two tooth face straight rack mechanism, and its working principles and compensation process were analyzed. Then coupled with the AMESim simulation software the compensation mathematical models of system components were establish such as heave compensation hydraulic cylinder, hook load, gas liquid accumulator and driven gear-straight rack. The simulation results show that: the whole compensation efficiency of new heave compensation system can reach 95.6% and the compensation effect is good, the system energy consumption curve shows a trend of rising because the compensation motor running. With the increases of radius of driven gear in the compensation system, the hook heave displacement decreases gradually and the compensation effect is improved, and have the smaller influences on the system's energy consumption. With the proportion coefficient increases, the curves of the hook heave displacement and system energy consumption show a trend of increases firstly and then tends to slow. With the increase of platform heave cycle, the compensation effect becomes good and system energy consumption reduces; with the increase of hook load, the system energy consumption increases linearly.

Design  of  Path Planning Algorithm for Automatically  Fiber  Placement  for  Sculptured  Surfaces

Meng Shuyun, Zhao Dongbiao, Lu Yonghua

2016, 27(05):  669-673,679. 

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Aimed at path generation for automatically fiber placement of sculptured surfaces,an algorithm called WEM  was proposed.A family of wraps as the reference lines were adaptively generated based on the surface shape. According to the process data of the fibers for composite tow, fiber placement path were obtained,which formed  fixed placement angle with the corresponding reference curve.This algorithm might be applied in the kind of free-form spline surface with parametric method description. The simulation shows that the algorithm is feasible and effective.

Fault Diagnosis Method for Rotating Machinery Based on AMD

Shi Peiming, Su Cuijiao, Zhao Na, Han Dongying

2016, 27(05):  674-679. 

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Aiming at the problems of fault diagnosis for rotating machinery, a fault diagnosis method for rotating machinery was proposed based on AMD herein. As long as the frequency components of signals were known, signals with different frequency components might be decomposed into single frequency signals using the AMD method, especially to decompose a signal with closely spaced frequency components. For the fault feature frequency prediction in rotating machinery fault diagnosis, AMD method might be used to extract fault feature frequency signals in mechanical vibration signals and the frequency spectrum was obtained. If the frequency spectrum contains the fault feature frequency, it shows that the faults exist in mechanical vibration signals. The analysis of the rolling bearing fault signals and the comparison with empirical model decomposition(EMD), it shows that the AMD method is effective and more rapid, accurate than EMD.

Analyses of Characteristics of a PWM Digital Flow Valve

Huang Jiahai, Guo Xiaoxia, Li Taotao, Quan Long, Wang Shengguo

2016, 27(05):  680-684. 

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Digital hydraulic valve had the advantages of reliability, low sensitivity to contamination, which was controlled by PWM and was limited in hydraulic system by the small and discontinuous flows. A two-stage digital flow valve was presented，where the pilot stage was as high-speed on/off valves and the main stage was as a cartridge valve based on flow-displacement feedback principles. There were features of simple structure, high energy efficiency, piloted digital control, continuous output flow. The working principles and a simplified mathematical model were presented. The performance of the valve was investigated by means of simulation. The results show that the digital valve working principles are feasible and the valve output flow can be continuously changed by adjusting the duty ratio of the PWM signals supplied to pilot valve. There are important significance to further research and improvement of the valve.

Influences of Coupling Bearing's Random Parameters on Eigenvalues of Double Rotor System

Meng Hua, Liu Baoguo, Li Gege

2016, 27(05):  680-684. 

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The stochastic problems in the eigenvalue of the complex double rotor system were analyzed by the dynamic stochastic differential equation. The eigenvalues of double rotor system was calculated with the whole transfer matrix method. After that, the relationship between the eigenvalue including its mean and standard deviation value and the random parameter's variation coefficient was investigated with Monte-Carlo method considering the effects of random parameters such as coupling element's mass, stiffness and damping coefficient. Meanwhile, to improve the effectiveness of this research, the conclusion was verified individually on double rotor system with one or two coupling bearings.

Critical Time Point  Identification  for  Global Dynamic Stress Based on Spectral Element Interpolation  of  Solution  Space

Zhang Yangang, Mao Huping, Su Tiexiong, Li Kun, Wang Jun

2016, 27(05):  688-693. 

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According to the complexity and high-cost characteristics  of dynamic  analyses  in the   structural dynamic optimization processes,a  critical time points identification method for solution space of global dynamic stress based spectral element interpolation was proposed.The most dangerous time points of the structure dynamic response were found.The modal stress distribution was obtained  by using the modal superposition method,and then, the solution space domain of the global dynamic stress was computed.The Lagrange interpolation techniques were applied in the solution space domain to get the high precision function of the global dynamic stress. The absolute maximum points, that is, the critical time points,were found by executing the global DIRECT optimizer. Last, two examples of 124-member plane truss and the structure  subjected  to uniform and concentrated force were used to illustrate the feasibility and validity of the proposed method.

Adaptive Sliding Mode Control of Robotic Manipulators with External Uncertain Stochastic Vibration

Yao Laipeng, Hou Baolin

2016, 27(05):  694-697. 

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To address high precision tracking control problem of robotic manipulators with external uncertain stochastic vibration, an adaptive sliding mode control strategy was proposed. The stability of the closed-loop system was proved by Lyapunov stability theorem. By using saturated function instead of symbolic function of the controller, the controller could effectively eliminate the chattering phenomenon. Simulation results confirm that the proposed adaptive sliding mode controller has higher robustness, stability, precision to track the desired trajectory compared to conventional PID controller.

Process Analysis of Cold Occlusive Precision Forging for a Certain Type of Planetary Gear

Wang Jiulin, Li Ping, Tian Ye, Xue Kemin, Wang Changkai

2016, 27(05):  698-703. 

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Combined with numerical simulation and physical experiments, a study of differential planetary gear formed by occlusive cold extrusion was conducted. The deformation process, metal flow field and forming load were analyzed. And based on the floating die technology, the combination structure of three dies was designed. The results show that the small end of tooth is first filled, and the presence of overflow tank at the top of the large end of tooth significantly improves the metal flow conditions. Compared to the absence of overflow tank, the total forming load reduces from 9550kN to 5576kN and the clamping force reduces 50.72%, only as 2464kN. Finally, the experiments were conducted and the results show that the gear is full filled with smooth surface.

Research on Axial Cushing Behaviors of Inner Stiffened Hat-section Structure

Mo Yimin, Su Dong, Shi Zhihua, Xu Min

2016, 27(05):  704-709. 

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Dynamic axial compression simulation and drop-weight tests were carried out to study the crushing behaviors of inner stiffened hat section structure. First, the influences of inner stiffening on the hat-section structure were analyzed in theory; then, according to simulation results and experimental verification, the crushing behaviors of the inner stiffened hat-sections structure were analyzed. It is found that inner stiffening can greatly increase the energy absorption abilities of the hat-section structure, it is good for failure phenomena, stability and lightweight.