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matlab中英文翻译文献

matlab中英文翻译文献
matlab中英文翻译文献

附录英文原文

Scene recognition for minerescue robot

localization based on vision

Abstract:Anewscenerecognition system waspresented base donfuzzy logicand hidden Markov model(HMM) that canb eapplied in minerescue robot localization during emergenc ies. Thesystem uses monocular camera to acquire omni-directional images ofthe mine environment where the robot locates. By adoptingcenter-surround differencemethod, the salient localimage regions are extracted from the images as natural landmarks.These landmarks are organized by using HMM to representthe scene where the robot is,and fuzzylogicstrategyis used to match the scene andlandmark.By this way, the localizationproblem,which is the scenerecognition problem in t hesystem,can be converted into the evaluationproblemof HMM. The contributionsofthese skills make the system havetheabilitytodeal with changes inscale, 2D rotation and viewpoint. The results ofexperimentsalsoprove that the system hashigher ratio of recognition and localizationin bothstaticanddynamicmine environments.

Keywords: robotlocation;scene recognition;salientimage; matching strategy;fuzzy logic; hidden Markov model

1 Introduction

Search and rescuein disasterarea inthe domain ofrobot i s a burgeoning and challenging subject[1]. Minerescue robotwas developed toenter minesduring emergencies to locate possibleescape routes for those trapped inside and determine whetheritissafefor humanto enterornot. Localization is a fundamental problem in this field.Localization methodsbased on camera canbe mainly classified intogeometr ic, topological or hybrid ones[2].With its feasibility andeffectiv eness, scene recognition becomes oneof the important technologies of topological localization.

Currentlymost scene recognition methods are basedongloba limage features andhave twodistinct stages:trainingoff line and matchingonline.

During the training stage,robotcollectstheimages of theenvironmentwhere itworks and processes the images to extrac tglobalfeaturesthat represent the scene. Someapproacheswere used to analyze thedata-set of image directly and some primary features were found, suchas the PCA method [3]. However,thePCA methodisnot effective in distin guishing the classes of features.Anothertypeofapproach usesappearancefeatures including color, texture andedge density torepresent the image.For example, ZHOUe tal[4]used multidimensional histograms to describeglobal appearance features. This method issimple butsensitiveto scaleand illumination changes.Infact, allkindsofglobal image features are sufferedfrom the change of environment.

LOWE [5] presenteda SIFTmethodthat uses similarity invariant descriptors formed by characteristic scaleandorientationat interest pointsto obtain thefeatures.The featuresare invarianttoimagescaling, translation,rotationandpartially invariant toillumination changes.But SIFTmay generate 1000 or more interest points, which may slowdown the processordramatically.

During thematching stage, nearest neighborstrategy(NN)is widely adopted for its facility and intelligibility[6]. But it cannotcapture the contribution ofindividualfeature for scenerecognition.Inexperiments, theNN is not good enough to expressthe similarity between twopatterns. Furthermo re,the selectedfeaturescan not represent the scene thoroughlyac cording tothe state-of-art patternrecognition, whichmakes recognitionnot reliable[7].

So inthis work a new recognition system is presented,wh ich is more reliable and effective if itisused in a complexmin eenvironment. In this system,weimprove the invariance by extractingsalient local image regions as landmarksto replace thewhole image to deal withlarge changes inscale,2D rotatio nand viewpoint. And the number of interestpoints is reducedeffectively,which makes the processing easier.Fuzzy recognition strategy is designed to recognizethe landmarks inplaceof NN, which can strengthen the contribution of individual feature for scene recognition.Because of itspartial information resuming ability, hidden Markov model is adopted to organizethose landmarks, which can capture the structure orrelationship among them.Soscene recognitioncanbetransformed to theevaluation problem of HMM,whichmakes recognition robust.

2 Salientlocal imageregions detection

Researchesonbiological vision system indicate that organism(likedrosophila) often pays attentionto certain speci alregions in the scenefortheirbehavioral relevance or local i mage cues whileobservingsurroundings [8]. These regions can be takenas natural landmarks to effectivelyrepresentand distinguish differentenvironments.Inspiredby those,we use center-surrounddifference method to detectsalient regions in multi-scale image spaces.The opponenciesof color and texture a re computedtocreatethe saliency map.

Follow-up,sub-imagecenteredat the salient position in S is taken asthe landmark region. The sizeof the landmark regio ncan be decided adaptivelyaccording to thechanges of gradient orientation ofthe local image[11].

Mobile robotnavigation requires thatnatural landmarks should be detected stably whenenvironments change to someextent. To validate therepeatability on landmark detection ofourapproach,we have done some experiments onthe cases ofscale, 2D rotation and viewpointchanges etc. Fig.1 shows thatthedooris detected for its saliency when viewpoint changes. More detailedanalysisand results aboutscale and rotation canbe found inour previousworks[12].

3 Scenerecognitionand localization

Differentfrom other scenerecognitionsystems, our system doesn’t need training offline.In otherwords,our scenes are not classifiedinadvance.Whenrobotwanders, scenes ca pturedatintervals of fixed timeare used to build the vertexof atopological map,which represents the place where robot locates. Although the map’sgeometriclayout isignoredby

the localization system, itis useful for visualization anddeb ugging[13]and beneficialtopath planning.So localization m eanssearchingthe best match of currentscene onthemap.In thispaper hiddenMarkov model is usedto organize the extracted landmarks from current scene andcreate thevertex o ftopologicalmap forits partial informationresuming abi lity.

Resembled by panoramic vision system, robot looks aroundto get omni-images. From

Fig.1 Experimenton viewpoint changes

each image, salient local regions are detectedand formed to be a sequence, named aslandmark sequencewhose order is the sameas theimage sequence. Then a hidden Markov modelis creat ed basedon the landmark sequence involvingk salient local image regions,whichis taken as the description of theplacewhere the robot locates. In oursystemEVI-D70 camerahas a view field of ±170°.Considering the overlap effect,we sample

environment every 45° to get8images.

Let the 8images as hiddenstateSi(1≤i≤8),the created HMMcan be illustrated by Fig.2.The parameters of HMM,aij andbjk, areachieved by learning, using Baulm-Welch algorith m[14].The threshold of convergence is set as 0.001.

Asfor the edge of topological map,we assign it withdistanceinformationbetween two vertices. The distances can be co mputed according toodometry readings.

Fig.2 HMM of environment

To locate itself on thetopological map,robotmust ru nits‘eye’ onenvironment andextract a landmark sequence L1′ ?Lk′ , thensearch the map for the bestmatched vertex(scene). Different from traditional probabilistic localization[15], in oursystem localizationproblem canbeconverted tothe evaluationproblemof HMM. The vertex withthe g reatest evaluation value, which mustalsobe greaterthan a threshold,is taken as the best matchedvertex,whichindicates the most possible placewhere therobot is.

4 Match strategy based on fuzzylogic

One ofthe key issues in image matchproblemistochoosethe most effectivefeatures ordescriptors to represent theoriginal image. Due torobot movement,those extracted landmarkregions will changeatpixel level. So, the descriptors orfeatureschosen should be invariantto some extent according tothe changes of scale,rotationand viewpointetc. In this

paper, weuse 4 features commonly adopted in thecommunity tha tare brieflydescribed as follows.

GO:Gradient orientation.It hasbeenproved thatilluminati onand rotation changes are likelyto have less influence onit [5].

ASMand ENT:Angular secondmomentand entropy,whichare twotexture descriptors.

H: Hue,which is used to describe the fundamental information of the image.

Anotherkey issue in match problem isto choose a good match str ategy or algorithm.Usually nearest neighbor strategy (NN) isus ed to measurethe similarity between twopatterns. But we havefound in theexperiments that NN can’t adequately exhibit theindividual descriptor orfeature’s contributionto similarity measurement.Asindicatedin Fig.4, theinput image Fig.4(a) comes fromdifferent viewof Fig.4(b). But the distancebetw een Figs.4(a)and(b)computed by Jeffereydivergence is larger than Fig.4(c).

To solve the problem,we design a new matchalgorithmbased on fuzzy logic forexhibiting the subtlechangesof eachfe atures. The algorithmis described asbelow.

And the landmark in thedatabase whosefusedsimilarit ydegree ishigherthanany others is taken as the best matc h.The matchresultsof Figs.2(b)and(c) are demonstra ted by Fig.3.As indicated,this method canmeasure the similar ity effectivelybetweentwo patterns.

Fig.3Similarity computedusingfuzzy strategy

5Experiments and analysis

Thelocalization system has been implemented onamobile robot, which is builtby ourlaboratory.Thevision system is composedof aCCD cameraandaframe-grabberIVC-4200. The resolutionofimage isset to be400×320and thesample frequency issetto be 10 frames/s. Thecomputers ystem is composed of1GHz processor and512M memory,which i scarriedbytherobot. Presently the robot works in indoor environments.

Because HMM is adopted to represent and recognize the scene, our system has the abilityto capture the discriminationabout distribution of salient local imageregions and distinguish similarscenes effectively. Table 1shows therecognition result of static environments including 5laneways and a silo. 10 scenes are selected fromeach environment and HMMs arecre ated for each scene.Then20 scenes arecollectedwhen the robot enters eachenvironmentsubsequently tomatch the 60

HMMs above.

In the table, “truth” means that the scene to be localized matches withthe right scene (the evaluationvalueofHMM is 30% greater thanthe second high evaluation). “Uncertainty” meansthat theevaluation valueof HMMisgreaterthanthesecondhigh evaluation under 10%.“Error match” meansthatthe scene to belocalized matches withthe wrong scene. In the table, the ratio of error match is 0. But it is possible that the sceneto be localized can’t match any scenesandnewvertexes are created. Furthermore, the“ratio of truth” aboutsilo is lower bec ausesalient cues arefewer in this kind of environment.

Inthe periodof automaticexploring, similar scenes can be combined. The processcanbe summarized as: when localization succeeds, thecurrent landmarksequenceis added to theaccompanying observation sequenceof the matched vertexun-repeatedly according to theirorientation (including the angle oftheimagefrom whichthe salientlocal region and the headi ng of the robotcome).The parameters ofHMMarelearned again.

Compared with theapproaches using appearancefeatures of the wholeimage(Method2, M2),oursystem (M1)uses local salient regionsto localizeandmap, whichmakes it have more tolerance of scale,viewpoint changes caused by robot’sm ovement andhigher ratioofrecognition andfewer amount of verticeson thetopological map. So, oursystemhasbetter performanceindynamicenvironment.These can be seen in Table 2. Laneways 1, 2, 4, 5 are in operationwhere some miners are working, which puzzle therobot.

6Conclusions

1) Salient localimagefeatures are extracted to replace the whol

eimageto participatein recognition, whichimprovethetolerance of changesin scale,2Drotation and viewpoint of environmentimage.

2) Fuzzy logic isusedtorecognize the local image, and emphasize theindividual feature’s contributiontorecognition, whichimprovesthe reliabilityof landmarks.

3)HMMis usedto capturethe structure or relationship of those localimages,which converts the scene recognition problem into theevaluation problem of HMM.

4)The results from the above experimentsdemonstratet hatthe minerescue robotscene recognition system has higher ratio of recognition and localization.

Future work will befocused on using HMM todeal withtheuncertainty of localization.

中文翻译

基于视觉的矿井救援机器人场景识别

摘要:基于模糊逻辑和隐马尔可夫模型(HMM),论文提出了一个新的场景识别系统,可应用于紧急情况下矿山救援机器人的定位。该系统使用单眼相机获取机器人所处位置的全方位的矿井环境图像。通过采用中心环绕差分法,从图像中提取突出的位置图像区域作为自然的位置标志。这些标志通过使用HMM有机组织起来代表机器人坐在场景,模糊逻辑算法用来匹配场景和位置标志。通过这种方式,定位问题,即系统的现场识别问题,可以转化为对HMM的评价问题。这些技术贡献使系统具有处理比率变化、二维旋转和视角变化的能力。实验结果还证明,该系统在静态和动态矿山环境中都具有较高的识别和定位的成功率。

关键字:机器人定位;场景识别;突出图像;匹配算法;模糊逻辑;隐马尔可夫模型

1 介绍

在机器人领域搜索和救援灾区是一个新兴而富有挑战性的课题。矿井救援机器人的开发是为了在紧急情况下进入矿井为被困人员查找可能的逃生路线,并确

定该线路是否安全。定位识别是这个领域的基本问题。基于摄像头的定位可以主要分为几何法、拓扑法或混合法。凭借其可行性和有效性,场景识别成为拓扑定位的重要技术之一。

目前,大多数场景识别方法是基于全局图像特征,有两个不同的阶段:离线培训和在线匹配。

在训练阶段,机器人收集其所工作环境的图像,并处理这些图像提取出能表征该场景的全局特征。一些方法直接分析图像数据得到一些基本特征,比如PCA 方法。但是,PCA方法是不能区分特征的类别。另一种方法使用外观特征包括颜色、纹理和边缘密度来表示图像。例如,周等人用多维直方图来描述全局外观特征。此方法简单,但对比率和光照变化敏感。事实上,各种全局图像特征,所受来自环境变化的影响。

LOWE提出了SIFT方法,该方法利用关注点尺度和方向所形成的描述的相似性获得特征。这些特征对于图像缩放、平移、旋转和局部光照不变是稳定的。但SIFT可能产生1 000个或更多的兴趣点,这可能使处理器大大减慢。

在匹配阶段,近邻算法(NN)因其简单和可行而被广泛采用。但是它并不能捕捉到个别特征对场景识别的贡献。在实验中,NN在表达两种部分之间的相似性时效果并不足够好。此外,所选的特征并不能彻底地按照国家模式识别标准表示场景,这使得识别结果不可靠。

因此,在这些分析中提出了一种新的识别系统,如果使用在复杂的矿井环境中它将更加可靠和有效。在这个系统中,我们通过提取突出的图像局部区域作为位置标志用以替代整个图像,改善了信息的稳定性,从而处理比率、二维旋转和视角的变化。兴趣点数量有效减少,这使得处理更加容易。模糊识别算法用以识别邻近位置的位置标志,它可以增强个别特征对场景识别的作用。由于它的部分信息恢复能力,采用隐马尔可夫模型组织这些位置标志,它可以捕捉到的结构或标志之间的关系。因此,场景识别可以转化为对HMM评价问题,这使得识别具有鲁棒性。

2 局部图像区域不变形的检测

生物视觉系统的研究表明,生物体(像果蝇)在观察周围环境时,经常因为他们的行为习惯注意场景中确定的特殊区域或者局部图像信息。这些区域可以当作

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