Field and Service Robotics - Corke P. and Sukkarieh S.(Eds) Part 15 potx

568 N. Elkmann et al. of water will be discharged into the sewer constantly. Legal guidelines require a sewer system’s structural and operational condition be inspected and recorded on a scheduled, regular and systematic basis. At present, structural condi- tion is usually detected by optical inspection (TV inspection or walk-through inspection).Conventional inspection methods cannot be used to inspect the Emscher sewer system because of its constant partial filling. The automatic inspection and cleaning systems to be designed as part of the project should effectively do away with walk-through sewer inspections. Hence, among other things, approval of the one-pipe sewer will depend on demonstrating that in- spection and cleaning can be done by using remote controlled or automatic systems. As part of the project, the following main components were designed and tested for their feasibility and fulfillment of the requirements: • Carrier system (motion kinematics, robot) for positioning along the sewer line; • Sensor and measuring systems for inspecting pipe condition above and below the water line as well as for detecting deposits; • Sewer cleaning system; • Media supply (power, data communication, water, etc.); • Control system, operation; • System navigation and positioning in the sewer; • Handling systems for positioning sensors and cleaning tools on and along the sewer wall. A large test station with various reinforced concrete pipes and different types of damage (e.g. cracks or spalling) was set up at the Fraunhofer Institute IFF in Magdeburg. The sensors for inspection were mostly new developments. In consultation with the Emschergenossenschaft, the Fraunhofer IFF has developed and built a prototype of the rough inspection system as well as a test prototype of the cleaning system and a test prototype of the inspection system in order to test these in a comparable, already existing sewer system (diameter 2300mm). 2InspectionStrategyand Systems The strategyfor automaticallyinspectingand cleaning theEmscher sewer system incorporatesathree-stage approach. In thefirststage,asmallswimming system called theSpy is employedinthe sewerfor rough inspection. It inspectsand measures theentiresewer line and conducts camera inspections,recording majorabnormalitiessuchaserosion, deposits, obstacles andleaks in thegas space. At thesametime, it checks whether thecleaningand inspectionsystemsdetailed belowcan be deployed. The Spymustbeable to position itself centricallyevenincurvedpipes in the sewercoveringalength of 600 m. Automated Inspection System for Large Underground Concrete Pipes 569 In the second stage, if necessary, the wheel-driven cleaning system eliminates deposits detected by the spy in the bed area and cleans the sewer wall before the inspection system is deployed. In the third stage, the inspection system (wheel-driven for diameters < 2000 mm, swimming for diameters > 2000 mm) inspects the sewer com- pletely, measuring the sewer (joint widths, pipe offsets, cracks) with greater accuracy than the Spy. For all three systems, concepts were designed and de- Fig.1. Spyprototype andtestofthe swimming inspection system in arealsewer veloped for their control, operation, introduction into and extraction from the sewer line as well as for their energy and water supply and data transfer. 2.1 Rough Inspection System (Spy) The Spy (Fig. 2) is an easy-to-operate, cable-guided swimming system for rough screening of the sewer line. The Spy detects corrosion, obstacles, de- posits and cracks. The Spy detects sewer conditions with little operating effort but with less precision than the inspection system. Fig.2. SensorsonSpy 570 N. Elkmann et al. Using a camera system, the Spy can visually inspect the gas space. It is equipped with several flashlights for illumination. Flashlights are used because they yield more light while consuming less power than floodlights. The Spy is additionally equipped with ultrasound sensors for sewer measurement in the water space. The Spy prototype must have smooth swimming behavior and lie stably in the sewer line even at higher flow velocity. The objective of the successful navigation tests was to position the Spy centrally in the current in order to create good conditions for geometry measurement. It was possible to determine the position of the Spy in the sewer and measure the sewer cross section in the gas space. 2.2 Inspection Systems In contrast to the Spy, the distinctive feature of the inspection system is its ability to achieve greater accuracy of measurement with its measuring sensors. Sensor systems are additionally integrated. Various concepts were developed for the carrier system. The two favored carrier systems are: 1. Floating systems for large sewer diameters and 2. Wheeled chassis for smaller sewer diameters The floating systems are convincing because of the high certainty of recovery. Their operational range is limited by the required water level though. Wheel- guided car systems are used when filling level is low or nominal diameters are smaller. The test prototype is modularly constructed and represents the Fig.3. Swimming inspection system Automated Inspection System for Large Underground Concrete Pipes 571 two favored carrier system concepts: Swimmer and Car. The Car test proto- type consists of the Swimmer and the additional wheeled chassis subsystem. Sensors for determining position in the sewer (laser ranging sensors and incli- nation sensors) and sensors for damage detection (laser scanners, ultrasound scanners, camera system, ultrasound crack sensor) were installed on the in- spection system. These sensors are either rigidly connected directly with the carrier system or they are moved by additional sensor kinematics. The rota- tion arm on the stern of the carrier system moves the ultrasound crack sensor along the sewer wall. Ultrasound scanners, laser scanners and camera system are mounted on a linear axis and can precisely measure the pipe profile over a length of approximately 1.5m. 3Positioning,PipeAxis Measurement Momentary position andorientation in thesewer have to be knownatthe time of anymeasurementswiththe Spyand with theinspectionsystem.Therefore, pipeaxismeasurement is an essentialprerequisitefor exactlyrepresenting and analyzing thesensordata. To this end, an algorithmwas developed, which, taking amodel of acomplete pipeasits starting point, measures thepipeaxis exactly. The totalerror of pipeaxismeasurement is arrived at by adding up theaccuracyofthe laserranging sensors,the tolerance andthe pipe’s surface conditionaswell as thesystematic error caused by theSpy system’s motion. Forthe laserand ultrasound scanners to detect damage,apositionalvalue of thepipeaxishas to be assigned forevery individual reading. Accordingly, when theaccuracyofmeasurement is being assessed, thesuperposition of position detectionand themeasuring method fordetectingdamage hastobe assessed. The inspectionsystem achievesagreater accuracyofmeasurement of its position in thepipebecauseitisstationary during measurement and, as such, only theaccuracyofthe laserranging sensors themselves playsaroleinthe overallmeasurement accuracy. Asensorsystem wasconceived,whichuses 15 laserranging sensors (5 aligned vertically and10horizontally)tocon- stantlyrecord position.The sensor distancedataisconverted into thesensor coordinate system. To measurethe pipeaxis, acylinder withanellipticalsurface areaisused to modelthe real pipewithits surfacequality andtolerances. Thisisclearly describedinthe Spy’scoordinate system by thecylinder axis,the radius and thediameter. The interpretation of themeasuring data wouldbeeasyifthe Spywereexactly in thecenterofthe pipewithout anydeviation in itsangles of alignment. In reality, thesystemstilt at yawand pitch angles are outof line withthe centerofthe pipe. Themeasuring points are notonastraight line butratheronasegmentasthe green measuring points in Fig. 4indi- cate.Hence an exactmodel of themeasurement hastobemade, whichallows forthe curvatureofthe pipe. Themodel is basedonthe correlation between 572 N. Elkmann et al. Fig.4. Coordinate system,difference between thereadingsinthe pipe model(green measuring points)and themodel with straightwalls (red measuringpoints). themeasureddistance, piperadius anddisplacement to thepipeaxisaswell as theyaw andpitch angles.Since this non-lineardependenceisknown, the alignmentofthe pipeaxiscan be determined from thedistancemeasurement. Thisalignmentthenmakes it possible to transform themeasuring points onto thecircularprojectionofthe pipeand consequently to determine theposi- tion of thepipeaxisinrelation to theSpy andthe inspectionsystem.The pipepositionisdeterminedfirstbymathematicallyresolving thenon-linear correlations. The determination of thepositionofthe pipeaxisisbased on using thepipeaxisalignmenttoplotthe measuring points on thecircular projection. Afterapplying this transformation, acircle with an offsetcenteris fit to themeasuring points.The displacementofthe axis of thepipevis-`a-vis theaxisofthe Spyisobtainedfrom this fit. In principle, this approachopens amethodfor measuring thepipeaxis, which is independentofthe pipediameteraswell as of theorientation andposition of themeasuring system.The method wasmodified to theeffect thatthe sen- soralignmentiscompensated forbyparable approximations.Corresponding calibrating measurements are takenonacalibrationrig. The system’s position alongthe axis of thesewer line is determined by mea- suring thelengths of cable uncoiled. In addition, thecamerasystem references thecurrent position at alljointswiththe camera system.Thisway,inaccura- cies caused by cable sagand slippage canbecompensated forand everysingle pipecan be approachedwithanaccuracyof ± 50 mm. 4 Types of Damage and Selected Sensor Systems for Damage Detection One focus of the project was the development of the sensor systems, which have the required accuracy of measurement under difficult conditions in the sewer and make it possible to take comparative measurements throughout the sewer’s period of operation (120 years). Automated Inspection System for Large Underground Concrete Pipes 573 Minimum requirements forsewer inspectioninGermany are stipulatedin self-monitoring regulationsissued by thestates. Legal requirements,techni- calspecificationsand negotiationswithlocal authorities have produced the inspectiontasks displayedinTable 1. The requirements of aone-pipeline are farmore demanding than thoseinthe technical guidelines. (*)Crackscausedbymechanicalstresscan be locatedthroughoutthe entire pipe.Cracksdetectedinthe upper section of thepipecan be used to calculate theextentofcracksinthe lowersection. Table1. Inspection tasksfor theinterceptorsparalleltothe Emschersewer system 4.1Chemical Corrosion Opticalmeasuring methodsdetect surfacecorrosionofthe concrete in the gas spaceand representpossible developments of damage.Asemiautomatic procedureconsisting of automaticand manual analysisbyanoperator is fa- voredfor corrosiondetectionand classification. The option of mapping the concrete wall comparatively withpreviousinspections is importantinorder to be able to mapany possible developmentofdamage.Several cameras are used to image thesewer wall completely. An image processing algorithmwithashort runtimeisusedtodetect ab- normalities immediately.The appearance of individual structural elements of thesurface is inspected forabnormalities,the measured number being more importantthanits precise characteristic. When avariable limit value is ex- ceeded,surface corrosionmay be likely. 574 N. Elkmann et al. Direct statements can be made about the possible occurrence of corrosion by comparing the distribution of the various proportions of gray tones in the readings with calibrated values or values already ascertained from previous inspections. Fig. 5 presents characteristic gray tone distribution curves for dif- ferent surfaces. Fig. 5 clearly shows the various curves for differently corroded Fig.5. Image of acorrodedconcrete surfacewithsuperimposedgrayscale curve forsubareas. surfaces.Clearly, differentlydamagedsubareas canbeidentified individually. The totalassessmentofpotential corrosionwould be obtained by averaging theentireimage space. In addition, laserscanners,whichmeasure thecrosssectionofthe pipe, are used to detect corrosionwithanaccuracyof ± 4mm. 4.2Obstacles,Sediments, Incrustations, Mechanical Corrosion Newly developedultrasound scanners withanaccuracyofmeasurement of ± 2mmare being used to detect obstacles,depositsand mechanicalerosionin thewater space. Fig. 6shows thetestsetup forgeometrymeasurement in thewater spacewith ultrasound scanners andascan image. 4.3Crack DetectioninConcretePipe First, digital image processing systemsare used to detect cracks in thegas space. Several cameras are used to identify cracks in thegas space. Automated Inspection System for Large Underground Concrete Pipes 575 Fig.6. Geometry measurements with ultrasound scanner(obstacles, sediments) In accordance with the requirements, cracks with a width of 0.5mm and up- ward have been positively identified and logged. While cracks can reach a long length, their frequently very narrow width makes great demands on the measuring system mapping them. Other measures such as comparisons with previous inspections and images of other cracks with known width as well as the superimposition of scales help make it possible to more closely de- termine crack width and thus more closely detect the type of damage. An important analysis module is automatic crack detection. It employs methods of image processing and pattern recognition in order to determine whether one or more cracks are possibly visible on a particular image or not. Particularly when there are small cracks, which an operator could overlook on the moni- tor, this automatic system constitutes a considerable advantage and increases the quality of the inspection results. Fig. 7 illustrates how different analysis modules identified a crack. In addition, each crack was graphically marked as a recognized structure for the purpose of presentation. The entire crack con- figuration was never identified. However, only the information of whether a Fig.7. Details of result images when different crack detection methodsare employed 576 N. Elkmann et al. crack may be present in a particular image or not is important for supporting the user. It follows from this that the automatic analysis module can already terminate the processing of the current image and inform the user once any crack segment has been found. Additionally, new acoustic methods (ultrasound, impact-echo) have been developed or adopted to detect cracks in the concrete in the gas and the water space. These acoustic systems are able to provide information on crack depth. The acoustic methods for crack detection additionally allow the following: • With the right sensor system, cracks can be detected in the water space too. • Cracks can be roughly classified (crack depth). • Spallings can be detected and wall thickness can be determined. Fig.8. Acoustic sensor systemsfor crack detection The use of these sensors sensor systems for crack inspection is completely new. 4.4 Deviation of Pipe Position Horizontal and vertical deviations of position and joint gaps have to be mea- sured. Laser scanners, aligned laterally or on the apex of the sewer, are used to detect and record the horizontal and vertical deviations of position. In the gas space, cameras measure the joint gap. Differences in joint width compared with earlier inspections indicate an axial displacement. Inconstant joint width along the pipe circumference indicates a deformation. Automatic measurement requires exact identification of the joint edges. To this end, image processing methods (segmentation, contour-finding) determine the pixels on the edges of the joint. Fig. 9 (a) shows a detail of the identified pixels. When the parameters have been suitably selected, the joint edges can be identified with an accuracy of a few pixels. If these pixels are used to apply ellipse approximations, which optimally approximate the number of points, the joint edges are obtained, which support automatic measurement of the joints. Automated Inspection System for Large Underground Concrete Pipes 577 Fig. 9 (b) shows a detail of the joint image with such ellipse approximations. A Hough transformation can be used to determine the ellipse approxi- mations. Since positioning and joint identification already identify the joint edges, the parameters of the corresponding ellipses are also approximately known. Thus, the search area of the Hough transformation can be restricted greatly, making efficient implementation possible. Fig.9. Image detail with detected jointedges:Whenmeasurementismanualthe jointwidth canbemarkedbyhand(a).Whenjointmeasurementisautomated, ellipse approximationsare placed throughthe jointedges (b). 5Summary andOutlook Since2002, theFraunhoferIFF as general contractorhas developedacom- prehensive conceptfor inspectionand cleaning systemsfor theEmscher sewer system.Not only have allthe relevantsubsystemsbeen identifiedbut they have also been designed in detail andsubjected to allnecessary testsinorder to be able to provide reliable informationabout their feasibility. Feasibility wasfullydemonstrated.Fociofdevelopmentwerethe carrier systemsfor movement alongthe sewerline guaranteeingmaximum recovery certainty,the pipeaxismeasurement andpositionsensing of thesystemsinthe sewerand thesensorsystemsfor detectingthe conditionofthe sewer’sgas andwater spaces.Differentsensorsystemshavebeen developedand tested in thetest stationaswell as in arealsewer.Erosion, incrustationsand corrosionofcon- creteare detected with great accuracy. Cameras detect axialdisplacement and laserscanners detect offsets in pipejointsinthe gas space. Apart from the cameras,differentsensors forcrackdetectioninthe gas andwater spacewere developedonanacousticbasis (e.g.ultrasound). [...]... the case for crops that are slowly growing and shallowly sown like sugar beet, carrots and onions In 1998, on average 73 hours per hectare sugar beet were spent on hand weeding in the Netherlands [4] The required labour for hand weeding is expensive and often not P Corke and S Sukkarieh (Eds.): Field and Service Robotics, STAR 25, pp 579–590, 2006 © Springer-Verlag Berlin Heidelberg 2006 580 T Bakker... pathconsists of l1 - c1 - l2 - c2 - l3 in this order, however c1 - c2 is determined in the first step and l1 , l2 and l3 are determined in the second step At the first step, set k at a certain value and calculate c1 for (θh − θs ) at the end of c1 Next, calculate c2 for (θe − θh ) in the same manner and connect c1 and c2 in direction θh In the second step, generate the path l1 - l2 - l3 between the end... installed and evaluated using experimental model called YAMAZUMI-2(YZ-2.Fig 12) and the pile of fragmented granite YZ-2 has same structure and function of a wheel loader The length between the front axel and the rear axel is 270mm and width of bucket is 250mm Size of the experimental pile is about 1000mm in width and 300mm in height Particle size of the pile is 5mm Two CCD cameras are attached to YZ-2 for... been conducted on automatic operation system of wheel loader [3, 4] These developed systems employed a guidance method or a teaching-playback method for traveling Path generation P Corke and S Sukkarieh (Eds.): Field and Service Robotics, STAR 25, pp 591–602, 2006 © Springer-Verlag Berlin Heidelberg 2006 592 S Sarata et al Dump Truck Pile Loader Fig 1 Wheel Loader Fig 2 V Shape Path function was not included... Christaller, Kirchner, Licht, Rome: ”Sewer Robotics , In: Proc From Animals to Animats 5, 5th Intl Conf On Simulation of Adaptive Behavior (SAB-98), R Pfeifer and B Blumberg and J.-A Meyer and S.W Wilson (eds), MIT Press, P 42 7-4 36, 1998 2 Kuntze H.-B., Haffner H.: Experiences with the Development of a Robot for Smart Multisensoric Pipe Inspection ICRA 1998: 177 3-1 778 3 Rome E., Hertzberg J.,Kirchner F.,... of c1 - c2 : Pt and the scooping point Pl with optimization on length of l1 - l2 - l3 Function Z for the optimization of the length l1 - l2 - l3 is defined in ( 5), 2 2 2 Z = l1 + l2 + l3 (5) Constraint conditions are C1 = (xl − xt ) − (l1 cos θs + l2 cos θh + l3 cos θl ) = 0 C2 = (yl − yt ) − (l1 sin θs + l2 sin θh + l3 sin θl ) = 0 (6) (7) Where xl , yl , xt and yt are x and y elements of Pl and Pt... Operation by Wheel Loader Shigeru Sarata1 , Yossewee Weeramhaeng2 , Akira Horiguchi3 , and Takashi Tsubouchi2 1 2 3 AIST, Namiki 1-2 -1 , Tsukuba, Ibaraki, JAPAN sarata-s@aist.go.jp University of Tsukuba, Ten-nohdai 1-1 -1 , Tsukuba, Ibaraki, JAPAN Sogo Security Service Co., Saitama, JAPAN Summary In this paper, as a part of research work on the autonomous loading operation by wheel loader at surface mines... combining data from a Real-Time Kinematic Differential GPS/GLONASS and odometry Tests conducted on a simulator and a small-scale robot show promising results Tests on the real forest machine are ongoing 1 Background and Introduction This paper describes an ongoing project of the design and development of an autonomous path-tracking forest machine This kind of product is part of a long-term vision in the forest... engineering and development for final prototypes The feasibility of automatic inspection and cleaning systems for the Emscher sewer system and the fulfillment of the legal requirements for inspection and cleaning have been demonstrated The research on and tests of the inspection systems, the sensor systems and the cleaning technology guarantee the inspection and cleaning required by law in a one-pipe sewer... in Mining Proc of IROS, pp43 9-4 45, 2001 2 Sarata, S.: Research and Development on Unmanned Loading Operation by Wheel Loader, Proc Rapid Mine Development, pp24 9-2 58, 2001 3 Gocho,T et al: Autonomous Wheel-Loader in Asphalt Plant, Proc 9th ISRAC, 1992 4 Oshima, H et al :Automation of Loading and Hauling Work in Mining and Quarry, Komatsu technical report, Vol.43, No.1, pp.2 7-3 9, 1997 (in Japanese) 5 Weeramhaen,Y . the measuring system mapping them. Other measures such as comparisons with previous inspections and images of other cracks with known width as well as the superimposition of scales help make it possible. chassis subsystem. Sensors for determining position in the sewer (laser ranging sensors and incli- nation sensors) and sensors for damage detection (laser scanners, ultrasound scanners, camera system,. automaticallyinspectingand cleaning theEmscher sewer system incorporatesathree-stage approach. In thefirststage,asmallswimming system called theSpy is employedinthe sewerfor rough inspection. It inspectsand measures