Table of Content

25 December 2017, Volume 28 Issue 24

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Parameter Optimization of Parallel Mechanisms Based on PCA

ZENG Daxing;WANG Juanjuan;FAN Mingzhou;YUE Xiaobo;HOU Yulei

2017, 28(24):  2899-2905. 

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A DELTA parallel mechanism was treated as the research object, the global conditioning index, the global isotropic and the global minimum singular value of the mechanism were solved to build multi-dimensional global performance indices. Based on PCA, the multi-dimensional global performance indices were dimensionally reduced, effectively integrated. Redundant data dimensions among kinematic indicators and target function dependence of weight coefficient were reduced to obtain more objective target function. The different structure parameter samples were analyzed by PCA thereby optimal structure dimensions were obtained based on the comprehensive global performance. The optimization results of PCA and the distribution of the performance index values were compared and analyzed, the best and the worst samples corresponded to the best and the worst performance areas of distribution map of every global performance index respectively, and then the effectiveness of applying PCA in parameter optimization of parallel mechanisms was verified. These contents of the research provide a new idea for multi-target optimization of the parallel mechanisms.

Torque Ripple Suppression of PMSM Applied for EPS Based on Motor Rotation Angle's  ILC

ZHAO Linfeng1;CHEN Jiushan2;CHEN Wuwei1;ZHANG Rongyun3

2017, 28(24):  2906-2913. 

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An EPS model was established based on PMSM. Due to factors such as the inherent non-sinusoidal magnetic flux distribution, cogging effects and current detection errors of PMSM, obvious torque ripples were caused. According to the characteristics that parasitic torque ripples were mostly a periodic function of the rotor position and the motor speeds in EPS system were not constant, an ILC algorithm based on corners was proposed to suppress the torque ripples of EPS in PMSM, and a large number of simulations and experimental verifications were carried out.The experimental results show that this scheme has significant inhibitory effects on the torque ripples of EPS.

Optimization of Hall Position Sensor for Permanent Magnet Synchronous Linear Motors

LI Bingran1;ZHANG Hui1,2;YE Peiqing1,2,3

2017, 28(24):  2913-2918. 

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There was a way to detect the positions of linear motors by detecting the magnetic field informations of linear motor movers. The principle of double Hall sensor position detection was introduced, and the cause of the installation errors was analyzed herein. In order to achieve the Hall sensor position detection error compensation, a method of using a 3D Hall sensor was proposed instead of a linear Hall sensor. In order to reduce external interferences, a fuzzy-neural off-line modeling method was proposed. Finally, the correctness of the compensation method was verified through the simulations and experiments.

Annoyance Subjective Evaluation Method of Automotive Interior Nonstationary Noises Based on Human Auditory Masking Effect

FENG Tianpei1;SUN Yuedong1;WANG Yansong2;ZHOU Ping1;GUO Hui2;LIU Ningning2

2017, 28(24):  2919-2924,2930. 

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Based on the collected interior noises of passenger cars running at accelerating or constant speeds, a subjective evaluation test of vehicle noise annoyance was conducted using anchored semantic differential method herein. Considering masking effect and questionnaire results of the sound quality subjective estimation experiments, the average values of time-varying psychoacoustic parameters of noise samples at constant speeds and the second half of the accelerating noise samples were calculated as independent variables, a regression mathematical relation among the average values and subjective evaluation results of annoyance was built using SVM technique. A masking effect based annoyance evaluation method (ME-AE method) was developed. Furthermore, by calculating average values of time-varying psychoacoustic parameters of all noise samples, a psychoacoustic metrics based annoyance evaluation method (PM-AE method) was developed using SVM. Results of leave-one-out and 10-fold cross-validating experiments suggest that the two annoyance subjective evaluation methods are effective in predicting vehicle interior nonstationary noises with high accuracy. And the proposed ME-AE method is more accurate and stable. Especially for predicting the annoyance of acceleration noises, the new method achieves greater improvements.

Study on Akima Curve-fitting Algorithm with Tool-path Based on Arc-length Parameters

ZHOU Peng1;WU Jichun1;ZHOU Huicheng2;YANG Shiping1;LIU Jingang1;MA Qiucheng1

2017, 28(24):  2925-2930. 

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In NC machining, tool-path was usually expressed by micro-line shocks, which might result in the magnitude of the cutter location(CL)points whose trajectory was unsmooth. The CL points were fitted into Akima spline curve with its advantages of smooth junction and the node points for over G1-continuity,thus the Akima curve-fitting algorithm preserving convexity for tool-path was proposed based on arc-length parameters. The algorithm was divided into two stages including CL points' searching and curve fitting.  Firstly the features of CL points, the error testing constraints including bi-chord error tests and tangent error tests for fitting the tool trajectory were used to judge the adjacent CL points by the threshold of the testing constraints, if they were satisfied with the threshold continue to search the next tool location point（TLP）, otherwise, CL points' searching might be suspended and the first and end points of the segment were attained, then the tangent vectors were calculated according to the first and end points in this segment to ensure the concavity and convexity of the fitted curves, and the arc-length was used to parameterize the CL points ,so that a section of Akima spline between the adjoining CL points which had paused to searching were generated. When this segment of Akima curve fitting was accomplished, then the end point of the section was regarded as the first point of the next section, as the circle to the end. The model of the shoe sole(consists of 75 CL points) were generated by ultilizing UG software. The different testing thresholds were set up to compare the Akima curves whose arc-length was parameterized with the Akima curves whose knots were parameterized and NURBS curves based on MATLAB programming and simulation experiments were used to validate effectiveness of the algorithm.

Research on Synchronous Structure Decoupling of Electro-hydraulic Load Simulators

LI Geqiang1,3;LIU Wei1;HAN Weifeng2;DENG Xiaozhong1,3

2017, 28(24):  2931-2939. 

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In order to study the extra torque problems of EHLSs, taking the valve control swing motor of EHLS as an object, a new principle of synchronous structure coupling was proposed, which was based on the analyses of the extra torque mechanism and influence factors. The concrete way was to design the load actuator into a compound bilayer structure, where the outer synchronous motor was used to track the bearing motor for position synchronization control, and the inner motor was used to load. Through the load actuator of the compound structure, the passive loads were modified into active loads, and the problems of extra torque were solved fundamentally. The principles of parameter matching, the design of the seals and the structures of the compound swing motors were given, and the rationality of the oil duct in the inner and outer motors was simulated and tested. Finally, through simulation analysis of EHLS under small gradient loading, the correctness and effectiveness of synchronous structure decoupling were verified.

Structure Design and Movement Principle of Wave Gliders with Webbed Wings

TIAN Baoqiang1,2;LI Linglong3

2017, 28(24):  2939-2943. 

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Through the introduction to flexible webbed wings and structure design, the movement principle of wave gliders with webbed wings（WGWW） was studied，and its driving force calculation model of flexible webbed wings was set up, based on the traditional wave glider researches. Gliding function of WGWW was verified through the WGWW prototype constructed and pool experiments. WGWW may overcome the shortcomings of traditional wave gliders, such as complicated structures, weak maneuverability and low driving efficiency, so it may be better applied in large scale, and long-term ocean environmental observation researches.

A Modified Optimality Criterion Method Based on Contrast Enhancement for Gray Scale Suppression

XU Xiaokui;GUO Baofeng;JIN Miao

2017, 28(24):  2944-2948,2956. 

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In order to suppress gray scale elements in density-based topology optimization, two kinds of contrast enhancement operators were proposed based on contrast enhancement strategy and introduced into the iterative calculation to modify the optimality criteria method. The contrast enhancement operator might enlarge the gray scale differences of the elements, drive the intermediate densities to the two ends of the range, and finally make the results convergence to the 0/1 material distribution. The effects of the proposed method were investigated with classical numerical examples. The results show that the optimization results with crisp boundaries are obtained by applying the proposed method.

Theoretical Analyses and Experimental Studies for Riveting and Assembly Processes of Automotive Hub Bearing Units

YANG Jun1;YANG Yunsong1;LI Wei1;XIAO Yunya2;ZHOU Zhixiong1

2017, 28(24):  2949-2956. 

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The theoretical analyses and experimental study for riveting and assembly processes of automotive hub bearing units were conducted. The theoretical calculation model of riveting and assembly forces and the finite element analysis model of riveting and assembly processes were established to study the effects of trajectories, inclination angles and duration times of the final riveting phase of the rivet head on riveting and assembly quality. The results show the riveting and assembly quality is optimal under processing parameters including a circumference trace, an inclination angle of 6° and a final riveting duration time of 0.8s of a rivet heat. Taking DAC2F10 automotive hub bearing unit as an example, it was assembled by the special machine tool developed by authors for riveting and assembly. The experiments show the theoretical calculation model of riveting and assembly forces and the finite element analysis model of riveting and assembly processees are rational. And the inclination angle of rivet head is optimized as 5.5°. The prototype automotive hub bearing unit is manufactured by the optimized riveting and assembly processes and the maximum service life examined by durability tests is nearly 200 000km, which shows the optimized riveting and assembly processes herein may greatly enhance the working life and reliability of automotive hub bearing units.

Automatic Analysis and Synthesis Method for Geometric Assembly Conditions of Moving and Fixed Platforms Based on Vector Sets

XIE Dongfu1;LUO Yufeng1,2;SHI Zhixin1;PENG Yanlan1

2017, 28(24):  2957-2963. 

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Based on the theory of position and orientation characteristics sets, an automatic analysis and synthesis method for geometric assembly conditions of moving and fixed platforms was proposed based on vector sets, and the main steps and flow charts were given. The example analyses show that the automatic analysis and synthesis method proposed in the processes of topology design of parallel mechanisms may synthesize more mechanisms, and the integrated mechanism is more general. In the processes of topology analysis and synthesis of parallel mechanisms, the proposed method reduces the dependence on designer's human experiences, inspiration and other factors, improves the efficiency of topology synthesis of parallel mechanisms, and facilitates the automatic analysis and synthesis of mechanical systems by computer.

Study on Force Tracking Control of EHA Active Suspensions

KOU Farong;WANG Zhe;DU Jiafeng;LI Dong;XU Jianan;HE Linglan

2017, 28(24):  2964-2970. 

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The mathematical models of 1/4 active suspension and EHA active suspension system were established, and the influences of brushless DC motor in EHA on the system were analyzed. A force tracking control strategy was proposed based on the main loop LQG ideal force controller and the internal loop motor current controller. The controller hardware of EHA active suspension was designed, and the simulations and bench tests were carried out.The results show that the force tracking control may make the actual active forces of the motor output real-time tracking of the ideal active forces, and the feasibility of the control strategy and controller is verified.

Effects of Variable Pitch Spring on Ride Comfort of Formula Student Racings

LUO Feng1;YANG Zhongjiong1,2;ZHOU Liqiang1,2

2017, 28(24):  2971-2975. 

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As the seats of formula student racings were rigid connected with frame, the vibration load might has great influences on the drivers. A characteristic curve fitting method of variable pitch spring was analyzed herein, and the variation laws of pitch with loads were obtained. Then, the effects of variable pitch spring on the ride comfort were analyzed, which were compared with linear spring, through random input experiments and determine input experiments. Experiments show that:(1) with the increase of speed, the maximum vertical vibration acceleration of each measuring points increases, while using variable pitch spring they are less than that using linear spring,(2) when the vehicle speed is as 50 km/h, the vertical vibration acceleration of the RMS value of the front axle measuring points and floor near the seat measuring points using variable pitch spring are reduced by 11.02% and 20.06% respectively and ride comfort and damping property are improved visibly comparing with using linear spring.

Inverse Kinematics Analyses of 3-finger Robot Dexterous Hand Based on Screw Theory

PEI Jiufang;XU Dezhang;WANG Hai

2017, 28(24):  2975-2980. 

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A novel inverse kinematics algorithm was proposed based on screw theory in order to improve operation efficiency of inverse kinematics for 3-finger robot dexterous hand. Taking Shadow 3-finger robot dexterous hand as an example, because inverse kinematics might not be solved directly by Paden-Kahan sub problem, an inverse solution of index finger(ring finger) was combined with algebraic solution and Paden-Kahan sub problem. The inverse solution of thumb was combined with numerical method and Paden-Kahan sub problem. Finally, validity and feasibility of the algorithms were proved by an example. Under the premise of ensuring accuracy, the algorithms have obvious geometric meaning, less computation, and high efficiency.

Hexapod Robot Dynamic Stability Based on Impedance Characteristics

AI Qinglin;XU Dong;ZHANG Libin

2017, 28(24):  2981-2989. 

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The hexapod robot might be instability when acted by an external force walking on the rough roads. To overcome this problem, a dynamic stability analysis method considering the external forces, the positions of the center of gravity, the dip angles of the bearing surfaces and the impedance characteristics of the robot were introduced. The theoretical model of the forward kinematics and the gravity of the robot were made to calculate the timely gravity centers of the robot and the positions of the footend. In order to simplify the calculation processes, the tip-over motion around the supported line was equivalent to mechanical rotation system. On the basis of the normalized energy stability margin, based on the impedance characteristics the dynamic stability model of the robots was presented to analyze the effect law of the different elements on the dynamic stability of the robots. The results show that the impedance characteristics of the robots improve the dynamic stability of the robots tremendously.

Path Planning of Spot Welding Robots in Sides of BIW Based on ACO-PSO

HOU Yangqiang1;WANG Tianqi1;LI Lianyu1;ZHANG Zhichen1;ZHAO Na2

2017, 28(24):  2990-2994. 

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A welding path planning algorithm was studied based on the tasks of multi-robot spot welding coordination in sides of BIW. An ant colony particle swarm hybrid algorithm was proposed for the tasks, to achieve the average distribution of multi-robot welding points and the optimal soldering path of single robot. Based on the analyses of the distribution characteristics of the sides of BIW welding points and the requirements of multi-robot coordination welding, a mathematical model of multi-robot coordination welding for the sides of BIW welding was established. A path planning scheme was designed based on ant colony particle swarm hybrid algorithm, and the planning results were obtained in MATLAB. Robot offline programming software ‘Robotstudio’ was used to build a multi-robot coordination welding workstations for the sides of BIW welding, and simulation tests were carried out on the planning results. The results show that the algorithm may realize the average distribution of welding points, shorten the welding paths and improve the welding efficiency effectively.

Matching Design and Folding Method for New Type Airbags in Coachs

WU Junting1;WU Jun1，2;CAO Libo1;WU Menghua1

2017, 28(24):  2995-3000,3012. 

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A new annular safety airbag was designed, and a new folding method of annular safety airbag model was developed. Taking a coach as reference, a driver side restraint system including the new annular safety airbag was established. Occupant injury data were compared and analyzed among the conditions of no airbag, the matching of traditional airbag and the matching of new airbag. Then the parameters of the new airbags were optimized. The results show that the driver's head and chest injury values decrease by more than 36% with matching the new airbag which may effectively reduce head and chest injuries in frontal collisions of coachs.

Fault Diagnosis Method Based on MED-VMD and Optimized SVM for Rolling Bearings

YAO Chengyu1;LAI Bowen1;CHEN Dongning2,3;SUN Fei2,3;LYU Shijun2,3

2017, 28(24):  3001-3012. 

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A method of fault feature extraction was proposed based on MED, VMD and fuzzy approximate entropy, and the optimized SVM was used to identify faults. The MED method was used to reduce the noise interferences and to enhance the fault feature informations in the fault signals, and the signals after noise reduction by VMD were decomposed, then, the fuzzy approximation entropy was used to quantify the modal components of fault feature informations after VMD, and the feature vectors were constructed, Finally, the extended particle swarm optimization(EPSO) algorithm was used to optimize the penalty factors and the kernel function parameters of SVM to complete the fault recognition classification. The proposed method was applied to the experimental data of rolling bearings, and the effectiveness of the method was verified. Compared with the feature extraction method based on local mean decomposition(LMD), it is shown that the proposed method may extract the features of rolling bearing faults more accurately and may identify different faults more accurately. Compared with SVM based on grid search algorithm and the least square support vector machines(LSSVM) based on EPSO algorithm, the proposed method has better classification performance and better diagnosis performance.

Pose Detection of Fillet Welds Based on Laser Displacement Sensor

HONG Bo1,2;YIN Li1,2;LI Yi1,2;LI Xiangwen1,2

2017, 28(24):  3013-3016,3023. 

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To solve workpiece offset and deflection problems of welded I-beam and box beam structures in automation production, a pose detection method of fillet welds was proposed based on laser displacement sensors. An arc length model of fillet welds was established, the effects of weld poses on arc length were analyzed. Based on Fourier analysis, a decoupling algorithm was put forward for pose detection, which realized the detections of lateral deviations, longitudinal deviations, groove angles and deflection angles of fillet welds. The pose experiments on the fillet welds with root gaps and tack welds were detected. The results show that the method has small detection error and good anti-interference capability, which has good application prospects in welding automation productions.

Research on Fatigue Life under Two Demension Random Stresses

TENG Ruipin;SONG Xiaolin

2017, 28(24):  3017-3023. 

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Based on Goodman formula and Miner damage rule, a calculation method of fatigue life was presented under two dimension random stresses considering influences of mean stress. The mathematical  models of the probability density function of equivalent stress and the equivalent stress of two dimension random stress were deduced whose mean stress and stress amplitude followed Gaussian distribution. By integrating with Gauss-Legendre integration formula, the fatigue life was studied under the stress. The change regulations of the equivalent stress with the change of the distribution parameters of mean stress and stress amplitude were analyzed. The equivalent stress was compared with that under one dimension random stress not considering influences of mean stress. The results show: with positive and negative direction changing of the mean values of mean stress“μm”, the equivalent stress will be influenced obviously. Negative μm will result in equivalent stress reduction, even less than it under one dimension conditions. Positive μm will result in rapidly increase of equivalent stress, even greater than it under one dimension conditions. When μm=0, the equivalent stress under two dimension is a little more than it under one dimension conditions.