Journal of South China University of Technology(Natural Science Edition)

Detection Method Based on Edge Feature with Binocular Vision for the Working Environment of Ｒobot

ZHAI Jingmei HUANG Jinzhou LIU Kun

2018, 46(3): 1-7. doi:10.3969/j.issn.1000-565X.2018.03.001

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The realtime information of the working environment is the important basis for intelligent decision of robot． For the instantaneity and adaptivity of 3D environment information detection，a detection method of the shape， size and location of the object or obstacle based on binocular vision is proposed． Firstly，the Otsu into Canny is integrated． It improves the efficiency of the target edge by down sampling and compressing gradient magnitude level． Secondly，an edge-point classification matching algorithm based on gray correlation is applied to classify and match the edge point． In addition， it improves the efficiency and accuracy of the algorithm at the same time． Then，based on the structure of point clouds， the automatic extract method for 3D geometry and the location information of contours based on edge curvature angle are proposed． The experiments of the robot autonomous operation in dynamic environment show that the methods proposed are able to obtain the 3D information of the object in the working environment． The planar size error is 0. 65%，height error is 1. 69%， and distinguishes the object or obstacle accurately． The robot completes the expected task according to the realtime location information of the object and the obstacle．

Material Ｒemoval Modeling and Trochoidal Toolpath

Control for Surface Polishing

WANG Qinghui XIE Liujie XU Chenyang CHEN Ｒuiqi ZHOU Xuefeng

2018, 46(3): 8-15. doi:10.3969/j.issn.1000-565X.2018.03.002

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By applying the material removal model of polishing with a flexible pad，a parameter control method of curved surface polishing with trochiod trajectory is proposed． First the contact state of a flexible pad and work-piece surface is determined． Pressure prediction model is then established by using the support vector machine method and the pressure distribution of contact area is founded． Then the material removal model is set up by using Preston equation． According to the relationship between radius and step，the trochoid trajectory can be divided into two cases: single-cycle with two overlapping regions and single-cycle with three overlapping regions． Based on the removal model，one single trochoid path is divided into two parts to overlap respectively and then the total overlapping is established according to the width of the overlapping region，so as to control the trochoid trajectory parameters to achieve the optimal removal overlapping． The results of removal rate simulation and robot polishing experiment show that the work-piece surface roughness reaches 0. 57μm after polishing，which indicates that the proposed parameter control method of trochiod trajectory is feasible for high precision curved surface polishing．

Nonlinear Observation of Projective Distance for

Spherical Image-Based Visual Servoing

YE Guoqiang LI Weiguang WAN Hao

2018, 46(3): 16-22. doi:10.3969/j.issn.1000-565X.2018.03.003

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Due to the design of invariant visual features，spherical image-based visual servoing (IBVS) can obtain good motion decoupling characteristics． But calculation of feature Jacobian matrix depends on unknown 3D distance of each observed target point． For the problem of online estimating the unknown 3D parameters in spherical IBVS， a nonlinear projective distance observation algorithm is proposed with persistency of excitation (PE) lemma． In this paper，kinematics of spherical features is firstly analysed with the unified projection model; then，an update law of states of vision system is designed with PE lemma，online observation of 3D distances is realized by exploiting the known camera motion and the measured image features． Furthermore， stability analysis of the observer is proposed． Simulative results show that the proposed algorithm can effectively realize the online estimation of 3D distances，and has a better estimation accuracy and dynamic characteristics compared with the indirect estimation method based on depth observation． Meanwhile， the dynamic convergence characteristics of spherical IBVS control can be effectively improved．

Crack Propagation Behaviors of Green Powder Metallurgy

Compacts Subjected to EdgeIndentation

YANG Dayong WAN Zhenping LU Longsheng

2018, 46(3): 23-28. doi:10.3969/j.issn.1000-565X.2018.03.004

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The green machining is an important approach for parts manufacturing of powder metallurgy，during which cracks and breakouts occur easily at the same time． The crack initiation and propagation behaviors of the green PM compacts subjected to edgeindentation are investigated to obtain the machined surface with high integrity． The results show that a crack initiates and spreads slowly along the indentation direction in a rectilinear form when the indentation load reaches a critical value． After that， the crack extends toward the outer surface of the specimen and eventually leading to the shedding of block materials encompassed by the crack． The crack is serrated in microlevel and forms a small angle with the indentation direction． Besides， the serrated crack does not penetrate into the machined surface． The crack propagation angle decreases with the increase of the interior angle of the indenter while remaining unchanged with the increase of the thickness of an indenter． The crack length increases significantly with the growth of the indentation thickness and increases as the growing of the interior angle of indenter when the interior angle is less than 70°，and then it barely changes with the angles that are larger than 70°．

Transient Dynamics Analysis for the Structures of the Excavator Based on Sub-Modeling Method

FENG Hao DU Qungui SUN Youping

2018, 46(3): 29-34,57. doi:10.3969/j.issn.1000-565X.2018.03.005

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In the analysis of transient dynamics of the excavator working device structure，not only the stiffness of both the hydraulic cylinders and the structures，but also the accurate stress of local structures (such as welded seams) applied in fatigue analysis should be taken into consideration． In order to meet these requirements，a global and refined model should be built for dynamics stimulation，which seems to be overwhelming and impractical． Therefore，a method that combines the global dynamic model with local sub-model is proposed to analyze the structural dynamics of the excavator working device． The global structures are simplified to more simple and efficient dynamic model with beam and spring model． Then， the sub-model with refined finite element is adapted to get the accurate local stress at the complex local structures． Finally， the comparison between the analysis and test results of an excavator shows that the error of the transient stress peak value between the calculation and test is less than 8%． The results show that the proposed method and model is correct．

Simulation Analysis on Mechanical Fatigue Life of

a Vehicle Exhaust System

WU Jie LIANG Peicong

2018, 46(3): 35-41. doi:10.3969/j.issn.1000-565X.2018.03.006

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To effectively improve the accuracy of total life analysis， the finite element method is used to predict the fatigue durability of exhaust systems in this paper． A method of the wholelifespan analysis based on dynamic responses is proposed by combining the nominal stress method with dynamic fatigue analysis． The method applies modal frequency response analysis to calculate the stress response to the structure under different frequency excitation．Ｒegarding the stress response as fatigue loads， the fatigue life of the structure is calculated on the basis of the fatigue characteristics of the material and the Miner linear cumulative fatigue theory． Taking a car exhaust system for the research object， its mechanical fatigue life under engine torque excitation and vibration excitation are analyzed． The simulation results show that the durability of the exhaust system meet the requirements．

Analysis of the Thermal Performance of Micro-Diameter Heat Pipes with Composite Wick

LI Yong XIE Peida ZHOU Wenjie LIAO Boliang HE Bolin CHEN Chuangxin

2018, 46(3): 42-48. doi:10.3969/j.issn.1000-565X.2018.03.007

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In this paper theoretical and experimental studies are conducted on three kinds of micro-diameter heat pipes (MDHPs， their outer diameter is 2 mm) with composite wick． The composite wicks consist of copper powdermesh (SMCP)，copper foam-mesh (SMCF) and mesh-mesh (MSM)． By referring to the capillary limit theory， the heat transfer power of the three kinds of MDHPs is analyzed and at the same time，maximum heat transfer capability under different filling ratios， the axial temperature distribution and the evaporation and condensation thermal resistances are analyzed． The results indicate that the maximum heat transfer capabilities of the three are 7W，with the corresponding optimum filling ratios of SMCP，SMCF and MSM being 110%，95% and 90% respectively， which are close to the theoretical values of capillary limit． The axial temperature differences of MDHPs increase with the heating power，and the maximum values are 4. 22，4. 20 and 4. 90 ℃ respectively． With the increase of heating power， the evaporation thermal resistance increases gradually． The change of condensation thermal resistance is small under low filling ratio． With high filling ratio，condensation thermal resistance of SMCP heat pipe fluctuates greatly，while condensation thermal resistances of SMCF and MSM heat pipes are relatively stable． When the filling ratios of the three kinds of MDHPs and their respective optimum filling ratios and heat transfer performance reach 7W， their evaporation resistances of MDHPs are 0. 437，0. 493 and 0. 591℃ /W，and their condensing heat resistances are 0. 167，0. 106 and 0. 110℃ /W，respectively．

A Prediction Scheme Based on Fast Diamond Search and Two Match Ｒegions in Compressed Video Sensing

YANG Chunling DAI Chao

2018, 46(3): 49-57. doi:10.3969/j.issn.1000-565X.2018.03.008

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Multi-hypothesis prediction (MH) is a key technique in compressed video sensing (CVS) predictionresidual reconstruct-algorithm． Unfortunately，when dealing with fast moving sequences，high computational complexity and low prediction accuracy are unavoidable． Besides，MH in measurement domain just employs the sum of absolute difference (SAD) principle to select hypothesis blocks，which usually introduces noise in the prediction blocks and decreases the reconstruction quality for neglecting the oneto-many relationship between the given measurement and original signals． To address these issues，this paper takes advantage of the motion features in video and proposes a multi-hypothesis prediction scheme based on fast diamond search with two matching regions (MHDS)． The MH-DS uses the fast diamond search method to search in two different directions for two optimal matching regions，where hypothesis blocks are obtained． MH-DS reduces the computational complexity of the searching process and get more effective prediction information． Moreover，a new matching criterion integrating mean square error (MMSE) with maximum pixels counting (MPC) is proposed in MH-DS in order to get more relevant hypothesis blocks． Simulative results show that the proposed MH-DS reduce the computational complexity of prediction process at reconstruction side and obtain higher prediction accuracy and higher reconstruction quality than the stateofthe-art CVS prediction methods．

Noise Ｒeduction of Chaotic Signals Based on Phase Space Ｒeconstruction and Singular Spectrum Analysis

CHEN Yue LIU Xiongying ＲEN Ziliang WU Zhongtang FENG Jiuchao

2018, 46(3): 58-64,91. doi:10.3969/j.issn.1000-565X.2018.03.009

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To reconstruct chaotic signals from noisy observation data，an adaptive noise reduction method based on phase space reconstruction and singular spectrum analysis (SSA) is proposed． Due to the noiselike nature of chaos， it is difficult to identify the number of the singular values corresponding to the signal components when applying conventional SSA method to chaotic signals． To address this issue， the number of the singular values is estimated by comparing the statistical difference between the chaotic signals and the noise in the phase space． Accordingly， an adaptive noise reduction algorithm is designed． Noise reduction experiments corresponding to both chaotic signals generated by computer and the monthly mean sunspot number series are carried out． The results show that the proposed method can precisely estimate the number of the singular values of the signals，and effectively reconstruct the original chaotic signals． Compared with the conventional chaotic signal denoising methods， the proposed method has advantages in terms of both noise reduction performance and phase portrait restructuring quality．

A Compact Super-Ｒegenerative Ｒeceiver with

Ｒeference-Class Accuracy of Frequency

ZHENG Weiguo CAI Min HE Xiaoyong

2018, 46(3): 65-71. doi:10.3969/j.issn.1000-565X.2018.03.010

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To overcome the poor frequency accuracy and selectivity of the conventional superregenerative receiver (SＲＲ)，a SＲＲ based on crystal has been proposed for low-data rate and low distance wireless sensor network (WSN)． This SＲＲ adopts a crystal oscillator (XO) as a superregenerative oscillator (SＲO) instead of the conventional LC or ＲC oscillator． With the help of the ultra-high quality factor of the crystal this SＲＲ has achieved the same accuracy and stability of working frequency as a crystal，and is immune to variations of process，voltage and temperature． A prototype chip， implemented in 0. 18-μm CMOS technology，utilizes a bi-direction driver to overcome the challenges of slow start-up and fully quenching，makes a reference XO work in a super-pre-generative manner，and then achieves sensitivity of －78dBm (1kb/s data rate)． The measured data show 50 times improvement on the frequency selectivity，and 7 ×10 －6 frequency error from the target frequency，which matches the reference-class accuracy． This receiver supplies a very compact solution with only a crystal being needed outside except several decoupling capacitors，which is suitable for WSN applications，e. g． wireless capsule endoscopy．

Modeling of Ultrasonic Wireless Electrical Energy Transfer System

LI Zhijian ZHUANG Ganlin WU Zhaohui LI Bin ZHANG Xiulai

2018, 46(3): 72-77. doi:10.3969/j.issn.1000-565X.2018.03.011

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Ultrasonic power transfer using piezoelectric devices is a promising wireless power transfer technology for biomedical implants． The depth of implantation is the key parameter of ultrasonic power transmission system． To explore the effect of depth of implantation on the power transmission efficiency，an ultrasonic power transfer system is designed underwater． The depth of implantation is simulated by the distance between the transmitter and the receiver． The output voltage of the receiver is acquired at different distances firstly and then analyzed by SPSS and Matlab software with statistics method． The linear regression model is established on the basis of analysis． The model is verified by means of the ultrasonic power transfer system． The experimental results show that the ultrasonic power transmission efficiency is related to the distance between a transmitter and a receiver． The output voltage of receiver decreases with the increase of distance． The proposed model has good prediction effect with the fitting degree greater than 95 percent and the prediction error less than 10 percent．

Design for the Steering Controller of Autonomous

Vehicles at the Limits of Handling

SUN Chuanyang ZHANG Xin XI Lihe CHEN Hongwei

2018, 46(3): 78-85. doi:10.3969/j.issn.1000-565X.2018.03.012

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This paper presents a path tracking steering controller based on the model predictive control (MPC) that simultaneously minimizes lateral path tracking deviation while maintaining vehicle stability for autonomous vehicles at the limits of handling． To improve the tracking accuracy， the course direction deviation is chosen for referential state，and the steadystate sideslip is used to calculate the course direction deviation instead of using the realtime sideslip． By using the lateral force of front tire as the input of the controller directly，and linearizing the rear tire force by the affine approximation， the computational burden can be reduced． The simulation results on a CarSimSimulink demonstrate that the present controller can operate the vehicle stably at the limits of tire adhesion，and has a better performance in tracking in comparison with the traditional controller．

A Fast Single Image Dehazing Algorithm Based on Dark Channel Prior

LIU Jieping YANG Yezhang WEI Gang

2018, 46(3): 86-91. doi:10.3969/j.issn.1000-565X.2018.03.013

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A fast and effective single image dehazing algorithm is proposed in this paper because of the low efficiency and the poor result in the sky region on the basis of the dark channel prior． Firstly，according to the color attenuation prior， the scene depth model is established to estimate the transmittance． Then，the rough transmittance is obtained on basis of local consistency and the dark channel prior． After that， the rough transmittance and the transmittance estimated by the scene depth model are fused to correct the transmittance of the sky region． Finally，the image is restored by means of the transmittance refined by guided filter，and the tone mapping is applied to the restored image． Experiments show that the proposed algorithm has high efficiency，which can also effectively improve the visibility and contrast of the restored image．

Flotation Foam Image NSCT Multi-Scale Enhancement with

Fractional Differential

LIAO Yipeng WANG Weixing FU Huadong WANG Huanqing

2018, 46(3): 92-102. doi:10.3969/j.issn.1000-565X.2018.03.014

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Considering the problems of low grey contrast，weak edges and noise interference for the foam image captured by the situation of the poor light in the floatation process，here is proposed a new foam image multiscale enhancement algorithm based on adaptive fractional differential and nonsubsampled contourlet transform (NSCT)． Firstly， foam image is decomposed through NSCT， the low frequency sub-band image is enhanced by combining the adaptive fractional differential order function constructed on the basis of pixel gradient feature，with the Tiansi operator which is improved by a set of brightness control parameters． Secondly，for high frequency sub-bands，threshold is adaptively computed according to the energy distribution，which is proposed to eliminate noise with the scale correlation coefficient，and the edge coefficients are enhanced by a nonlinear enhancement function． Finally， the processed image is reconstructed through NSCT． Enhancement experiment is performed by different kinds of bubble size images． Experimental results show that，compared to other current algorithms，the proposed algorithm is superior in improving the lightness，contrast，definition and comentropy of the foam image，and is successful in maintaining more texture details，which can also achieve much better performance to enhance bubble edges while removing the image noise． It lays a foundation for the subsequent foam image segmentation and edge detection．

Noise Ｒeduction of Snoring Sound by Using Traditional Spectral Subtraction and Wiener Filter

PENG Jianxin TANG Yunfei

2018, 46(3): 103-107. doi:10.3969/j.issn.1000-565X.2018.03.015

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A method to improve the signalto-noise ratio (SNＲ) of snoring sound is proposed in combination with the traditional spectral subtraction and Wiener filter in this study． Firstly， the noisy snoring signals are slightly enhanced by traditional spectral subtraction by projecting the noisy snoring to noise space and signal space by a method of subspace projection so that the SNＲ is obtained． Then a transfer function of Wiener filter from SNＲ is obtained． Finally，when the snoring sound processed by traditional spectral subtraction is filtered by the Wiener filter， the noise in snoring sound can be further reduced． The results of the simulation of snoring sound with additive white noise show that the method used in the study gets a higher SNＲ than that by the traditional subtraction or Wiener filter． It is proved that the method can do better than the one of traditional subtraction or Wiener filter in noise reduction．

Analysis and Experimental Validation of the Mixed-Order Ambisonics Ｒeproduction

MAI Haiming XIE Bosun JIANG Jianliang

2018, 46(3): 108-118. doi:10.3969/j.issn.1000-565X.2018.03.016

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Ambisonics is a series of spatial sound systems based on spatial harmonics decomposition and each order approximation of sound field． Both the accuracy of directional information reproduction and the complexity of system increase as the order of Ambisonics increases． Considering that the horizontal resolution of human hearing is higher than that of vertical direction，mixed-order Ambisonics reconstructs horizontal sound field with higher order spatial harmonics，while vertical sound field with lower order spatial harmonics is reconstructed，and thereby a compromise is reached between the perceptual performance and the complexity of system． By taking the 28 +1 layer-wise loudspeaker layout for example， the present work analyzes the binaural pressures in mixed-order Ambisonics reproduction and compares with the case in conventional high-order Ambisonics． When the corresponding binaural pressures in two systems are also compared for various target source directions，the results indicate that，for appropriate design and feasible loudspeaker layout，mixed-order Ambisonics improves the horizontal localization performance，and at the same time maintains the same off-horizontal localization performance as the high order Ambisonics． A series of virtual source localization experiments on Ambisonics reproduction validate the analysis．

Influence of the Number of Loudspeakers on Sound

Pressure Error for Ambisonics Ｒeproduction

JIANG Jianliang XIE Bosun MAI Haiming ＲAO Dan LIU Yang

2018, 46(3): 119-126. doi:10.3969/j.issn.1000-565X.2018.03.017

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As analysis on freefield pressure error and binaural pressure error in Ambisonics reproduction yields different results，and the results from binaural pressure error are closer to those of auditory perception． In this work，the influence of the number of loudspeakers on the pressure error in Ambisonics reproduction is evaluated by analyzing the binaural pressure error． The results indicate that，near the frequency limit given by Shannon-Nyquist spatial sample theorem，increasing the number of loudspeakers from low limit L2 to (L + 1)2 or (L + 2)2 reduces the error in reproduction effectively． Increasing the number of loudspeakers to more than (L +2)2 or increasing frequency to higher range，however，makes the relationship between the binaural pressure error and the number of loudspeaker complicated． The results of this work revise the conclusion of some previous work．

Docker Cluster Scheduling Strategy Based on Genetic Algorithm

LIN Weiwei WANG Zetao

2018, 46(3): 127-133. doi:10.3969/j.issn.1000-565X.2018.03.018

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Docker cluster technology is a new scheme for building a cloud computing platform because of its lightness，simple deployment and high efficiency． In order to improve the load balancing performance of traditional Docker cluster scheduling strategy and increase the capacity of multi task concurrent scheduling，a genetic algo

rithm based Docker cluster scheduling strategy is proposed in this paper． This strategy will merge into a multi task scheduling group，and generate the corresponding scheduling results as individuals． Then by combining the task load mode， the current node load state and hardware performance and by calculating the load balancing value as the fitness of individuals，the genetic algorithm is finally selected as the global optimal solution of scheduling results．

Experimental results show that compared with the popular Docker swarm spread strategy and weight scheduling strategy， the proposed strategy has significantly improved load balancing performance and multitask scheduling efficiency．

A Study of an Improved Pseudo Generator Design of Ｒandom Number and Performance on the Basis of a Logistic Map of Histogram Homogenization Method

LI Di WEI Demin

2018, 46(3): 134-141. doi:10.3969/j.issn.1000-565X.2018.03.019

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The logistic map can be used to generate pseudo random numbers． However， the data generated directly cannot take on a good uniformity． Based on the characteristic of random numbers generated directly by the logistics map pseudo random generator (LM-PＲNG)，an improved pseudo random number generator (ILM-PＲNG) is designed based on a histogram homogenization method，and the performance of LM-PＲNG and ILM-PＲNG is researched by parameters tests，uniform test and unique test． At 0. 05 level，the results of three kinds of number scales show that the first moment of random numbers generated by LM-PＲNG can pass the tests when N =103，N = 104 and 60% N = 105． The second moment，variance and uniform failed in the test． 93. 3% of the samples can pass the unique test． Meanwhile， random numbers generated by ILM-PＲNG can pass all the tests in this research． The parameter and uniform characters are getting better with the numbers getting larger． As a new kind of PＲNG， the ILM-PＲNG can overcome the lack of the original logistic generator and can be used to generate uniform pseudo random numbers more satisfactorily．

Characteristic Frequency Acquisition Algorithm of Burst Signal Based on Amplitude-Time Inflection Point#br#

2018, 46(3): 142-148. doi:10.3969/j.issn.1000-565X.2018.03.020

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