Research on Oil/Gas In-pipe Inspection Robot

Journal of Shanghai Jiaotong University(Science), Vol E-10. No.3.2005.221-225Article ID:1007-1172(2005)03-0221-05Research on Oil/Gas In-pipe Inspection RobotSONG Yi-ran‘(宋一然), YAN GuO- zheng2(颜国正), XU Xiao-wun2(徐小云)1. Dept. of Electronic and Information Eng, Putian Univ., Putian 351100, China2. School of Electronic, Information and Electrical Eng., Shanghai Jiaotong Univ, Shanghai 200030)Abstract: A new type of in-pipe mobile robot was designed and developed on the basis of wheel in-pipe robot andcrawler in-pipe robot. The three sets of driving wheels circumferentially 120 apart in the cross section, both frontand rear driving wheels are distributed on the same parallelogram mechanism. The driving motor drives the threesets of driving wheels by worm couple, the regulating motor makes the three sets of driving wheels push againstthe pipe inwall with stable and adequate pressing force by the ball screw pair and pressure sensor, so the in-piptrobot can provide adequate and stable traction force. The robot mechanism is simple and small in size and workreliably. It is particularly suitable to the pipe with diameter 400-650 mm.Key words: in-pipe robot parallelogram machanism; pipe inspectionDocument code: AIntroductionsively against the wall of the pipe by springs andinkages. One typical approach is scissor-likeRecently pipe is used widely on the industry, structure with three wheels, one at the joint andagriculture and daily life. Natural gas and oil sup- the others at the end of the two limbsui].Thisply become one of the fundamental public services robot called MOGRER, has already commercialand its impact on the urban infrastructure is get- ized aimed at the application in the gas industry[ang larger. The urban oil/gas pipelines, as they Also, Fujiwara et aLta4l adopted similar approachare buried under the ground, are prone to external es. Kawaguchi et a/s) developed a mobile robotcorrosion usually derived by moisture and chemicalwith magnetic wheels which has special features inagent in soil, which causes material losses of thethe steering. Recently, hirose et al6) presented apipe wall. Also, cracks in the welded region andsummary of their works concerning various inpipethe damages from third parties such as construc-inspection robots developed themselves up to now.ion, electricity, sewage works are considered asone of the major reasons for pipeline failures. InThe robot to be presented in this paper hasthe inspection of urban gas pipelines, there are a three sets of driving wheel circumferentially 120lot of needs for autonomous inspection equipment apart in the cross section, the robot can providethat can run through inside the pipelinesadequate and stable traction force. Its mechanismUp to date, technology allows robots to be is simple and small in size and work reliably. It isbuilt small enough to go through pipelines with particularly suitable to pipe with pipe diameter 400mall diameter about 10 mm. Most of those sys-~650mm.tems have robots with drivve wheels pressed pas- 1 principle and structureof In-pipeReceived date: 2004-12-08RobotFoundation item: High Technology Research and DevelopmentFigure 1 gives the structure sketch of the in863) Programe of China( No2002AA442110): The Cooperative Fund of Pipe中国煤化工ure of pipe inspecYunnan Province and Shanghai JiaotongtionHmposed of lightingNiv. (No. 2001KABAAOOA025)CNMHGer, power supply,wE-mail,yong3090@yahoo.com.cnoptical fibre ringer, embedded computer, special222 NG Yi-ran(宋一然), YAN Guo-zheng(颜国正),etaloptical fibre and so on.the axile bush along the circle with 120 angle.The to-and-fro movement ofscrew nutaxial direction can drive the pushing bar do planemotion through the force sensor and theDriving wheelbush, the plane motion of the pushing barmake the parallelogram mechanism stretch or retrench so as to suit for the pipe with different di-ameter and to ensure the pipe robot wheels puagainst the pipe inwall with adequate pressingforce. The force sensor can indirectly measure thewheelpressing forobotinwall by checking the axial force between theFig 1 Setting drawing of the pipe inspection robotscrew nut and the axile bush, the detected forceLIghting lamp and) Wheeled leg( Specialsignal is compared with the expect value and theCCD cameramechanismoptical fibredifference value will be feedback to the regulatingmotor. Then the regulating motor will turn corre-sponding angle under the control of controller,sothe force F can be changed and make the detectedforce signal approach the idealized value and thepressing force between the robot wheels and thepipe inwall can approach the expect value also. Sothe robot can provide adequate and stable tractiond optical fibre ringer2 Design Main Pointsig. 2 The picture of pipe inspection robot2. 1 Geometric Constraints in PipelinesTypical configurations of pipelines are levelAs showed in Fig. 1, the in-pipe robot con- pipes, vertical pipes, elbows, branches, reducer,sists of two parts, one is for driving the robot, an- and valves. Most in-pipe robots can easily negoti-other is for regulating the parallelogram mecha- ate level pipe runs and can climb and descend pipesnism so the pressing force between the robot wheel with inclinations of 30 or less. Vertical pipe runsand pipe inwall can be adjustable. The moving for- are more difficult to achieve, and few robots todayward and back of the in-pipe robot can be accom- can perform this feat. Those pipeline configuraplished by the following processes the driving mo- tions gives geometric limitations and a robot shouldtor drives the worm which connects with the motor be designed to satisfy the limitations to traverseby holding screw, then the worm drives the three through pipelines successfully. among these, theworm wheels circumferentially 120 apart in the curvature of pipeline is the most important inforcross section. At last, the worm wheels drive the mation because the robot is caught when it is toorobot wheel through the chain wheel, so the robot long and tightening up when it is too thick. Thusrealize moving forward and back. The part for ad- each segment of the robot must satisfy the geomet-justing the pressing force is driven by the regulat- ric constraints in order to traverse pipelines. Nowng motor, the motor drives the ball screw. Owing let us consider a right angle elbow and derive con-to the screw nuts incapable of running along the straint equations for the design of a robot moduledirection of circle, the screw nut can only move to-Amply modeled as aand-fro along the axial direction of the ball screw中国煤化工Fig 3. Then, theThe screw nut connects with the axile bush bHHCN M H Ged cylindrical seg-force sensor. The pushing bar is connected with ments and we can derive relations among the diam-Research on Oil/Gas In-pipe Inspection Roboteter of pipelines, curvature, and the size of the while any one set of driving wheels meet duct orsegment. As illustrated in Fig 3, the worst loca- pit and losses the supporting force, the other twotion of the segment is where it is located inclined sets of driving wheels are still support the robot by45. In this situation, we can think about two cas- the parallelogram mechanism, so the drivinges:(a) Both ends of the segment are located on the wheels can not fall into the duct or pit The paral-traight parts of the pipelines.(b) Both ends of lelogram mechanism makes the wheel in-pipe robotthe segment are located on the curved part of the have some merit of the crawler in-pipe robot,sopipelines. Depending on the situations, we can de- the in-pipe robot has good obstacle performancerive the constraint equations to determine the size By all appearances, to ensure the in-pipe robot goof the segment.across duct or pit without any driving wheel fallinginto the duct or pit, the condition is the center dis-tance (see Fig. 1) between the front wheel and rearwheel must be greater than the width of the duct3 Wheeled Leg Mechanism and ItsMechanics AnalysisOne of the most important issues in the designof a driving vehicle is how to obtain theFig 3 Geometric constraints in elbowforce enough to pull the instrumentation as well ashe vehicle itself. Especially in vertical pipelinesIn case (a)the range of w can be derived as it is desirable to keep adequate wall pressing forcesfollowsin order to ensure sufficient traction forces. Exces-2/(1) sive forces may dissipate power and be in danger ofO