X射线实时影象探伤管道机器人的关键技术

1、中文摘要X射线实时影象探伤管道机器人的关键技术这篇论文介绍了一种检查大口径管道焊接连接的机器人系统，它被发展作为X射线实时图象检查法 RTIIT的自动化平台。该机器人在管道内可以独立寻找并确定焊接接缝位置，在同步控制技术的控制下可以完成对焊缝进行质量检验的任务。该机器人系统安装有一个小的焦点和具有定向波束的X射线管，因此可以获得清晰度较高的焊接接缝图像。关于该机器人系统个别的关键技术也将被详细说明。它的结构是（？） 关键词：X射线探伤、实时影象、机器人0 介绍与射线照相检查方法（RET）相比较，X射线实时图像检查法（RTIIT）有许多优势，比如较高的效率、较低的成本，更容易实现自动化和对焊接缺

2、陷进行即时评估。此外，最新的技术允许X射线RTIIT被用在对管道进行无损检测（NDT），并且这个方法的检查品质和RET1，2是一样的。因此，无损检测设备，通常用于管道检验的基于RET的设备，需要通过改造变成基于X射线实时图像检查法的。使用X射线实时图像检查法对管道进行无损检测一定要有一个自动化平台，X射线探伤实时影象管道机器人（irtipr）就是为该目的而设计的。事实上，除了已经被解决的涉及X射线探伤实时影象管道机器人的问题之外，一些集中在机器人的智能控制的关键技术也出现在这篇论文中。，例如，机器人在管道内的独立动作，同步控制技术和在管道内外之间信息交流配合，我们也将机器人的结构（ ？ ）。1

3、 机器人的工作原理这个X射线探伤实时影象管道机器人由管道内和管道外两部分组成，结构详见图1。管道外的部分由图像采集处理系统（8，9，10），管道外同步旋转机构和它的驱动系统（11，12）组成。图像扩大器由管道外旋转机构来推动并围绕管道中心旋转进行采集焊接图像及通过图像采集卡将图象信号传达给图像处理计算机。管道内的部分由管道内电脑（1）、电源和换流器系统（）、行走及其驱动系统（）、X射线系统（）、管道内同步旋转机构及其驱动系统（,6）和焊接接缝独立寻找及定位系统（）。X射线系统中的X射线管由管道内的旋转机构推动围绕管道的中心旋转。图1 X射线探伤实时影象管道机器人的结构机器人主要工作原理说明如下

4、：在焊接接缝独立寻找及定位系统的控制下管内爬行器完成工作位置的定位，并在定位的位置上处于等待的状态。当它收到从管道外由低频电磁波传达的指令信号时，管道内的电脑立即操纵X射线系统的控制器来实现管道外的控制。管道内和管道外的旋转机构由同步控制技术控制围绕相同的管道中心旋转并按旋转-照射-旋转的方式完成焊接接缝检查。 机器人的控制系统与工艺步骤的工作原理相比，X射线irtipr的控制系统主要由一些关键技术组成，例如以X射线图象标准检查程序为基础的同步控制技术和以数据合成及低频电磁波传递为基础的焊接接缝独立寻找及定位技术。2.1 管道内和管道外旋转机构的同步控制技术根据 X射线实时图象检查法的技术要求

5、，X射线管和图像增强器必须围绕同时地同一个中心旋转。因为X射线irtipr采用无线的工作方式，机器人管道内同管道外的部分是不可能的由电缆连接着的。如何在管道内外旋转机构的控制系统之间实现同步信息通信，或如何实现同步控制，变成必须被解决的关键技术。同步旋转可以被描述为：当管道内的旋转机构带动X射线管到旋转角时，管道外的旋转机构也带动图像增强器同时绕同样的中心旋转到相同的角度（图2）。因为金属管道的遮挡作用和无线的特征，现有的通信手段很难完成在管道内外控制信息的通信（,5）。根据X射线探伤实时影象管道机器人的特殊性，我们提出这同步控制方案如下：将一个垂直于焊接接缝的标准检查程序导线设置在X射线管的

6、照射窗上；当 X射线照射到焊接接缝时，标准检查程序导线也在管道外的电脑上成像。只要管道内和管道外旋转机构处于同步的位置，即X射线管的照射窗和图像增强器的轴是重合的（=0）（图2），标准检查程序导线成像在电脑屏幕的中心位置。标准检查程序导线的成像和标准检查程序的中心线重合，看图3。当管道内旋转机构旋转角时，在屏幕上标准检查程序导线的成像偏离标准检查程序中心线，距离为H 。距离H被用作管道外旋转机构控制系统的错误输入使调节自身旋转运动直到这距离H为零或小于指定值，管道外旋转机构同步动作可以被实现。试验和模拟证明以上同步控制技术是正确的。这种同步动作满足X射线探伤实时影象管道机器人的技术要求。这种方

7、法以 X射线当做观测信号源，管道内和管道外的旋转机构同步动作信息通过X射线图象的标准检查程序导线偏离标准检查程序中心线距离确定，从而执行同步动作.这种方法已经申请发明专利。图2 同步旋转机构 图3 X射线图象的标准检查程序导线焊接接缝的独立寻找及定位技术独立寻找并定位意味着在管道内机器人没有任何其他干涉仅借助于传感器自动地决定哪里是工作位置.这种控制方式就是“智能控制”。寻找及定位系统的精确度和可靠性与机器人是否可以实现在管道内独立行动有直接关系。如果这个系统是无效的，机器人将在管道中“死亡”或“迷路”6。 大略地说，检测焊接位置接缝方法如下：（1）利用编码器或圆弧测定器；（）利用焊接接缝表面

8、伸出凹面变化的位移所引起位移；（）利用焊缝表面接缝导电；（）利用放射性同位素（比如射线信号源）；（）利用观测；（）利用低频电磁波。因为这种方法受许多因素的影响，例如：行进时刹车、管道内的环境、人为的因素、放射性的伤害、定位的精确度和效率，仅仅使用一种方法是不能获得满意效果的。考虑到焊接接缝的规则排列,即每个焊接接缝的间距大约12m,和各种位置检测方法优点和缺点,以多种成象设备为基础的焊接接缝独立寻找及定位系统被提出来改善和提高精确度、效率和可靠性的局限。多种成象设备由圆弧测定器、CCD摄像机和低频电磁波的接收器和发射极组成。系统的框图如图4。图4 焊接接缝独立寻找并定位系统系统采用定位反馈来提

9、高定位的效率。反馈成像构成的视觉反馈系统实现精确的定位。合成数据以三种测量数据为基础，圆弧测定器的数据、低频电磁波以及图象，使用优先估计算法处理数据。根据三种定位法的特征，上述数据在不同的范围分别地有效。如果x1表示圆弧测定器的测量数据，x2是低频电磁波，x3是图象。X表示机器人在管道的内实际位置，各个焊接接缝的间距是12m。那么，三种测量数据的有效作用范围如下：x1 ,12m；x20.1m ,1m；x3 -10cm,10cm，最后的定位目标是x3 = 0.三种测量数据有效范围描述如下：当距离x1相距焊接接缝位置是大于100cm时，使用圆弧测定器是为了提高定位效率，并且机器人在管道内以高速移动

10、；当数据x2是小于100cm时，控制器变成低频电磁波，并且让机器人以低速度移动；当焊接接缝进入这图象范围时，采用图象伺服系统获得精确的定位。数据合成规律可以表示为：X = X1 如果（x3 > - 10）且（x3 < 10），那么X =x3；以上方法实现了模糊控制并且完美地解决了精确度以及定位效率之间的矛盾。定位精确度的测试结果在±3毫米内，可以满足这设计要求。低频电磁波的传递除了定位的作用，低频电磁波还被利用于传送管道内外部分之间的开关信号。考虑它的危险，X射线系统经从管道外遥控操纵。因为这机器人是无线的以及考虑到金属管道的遮挡作用，其他的方法不能完成管道内外部分之间传

11、送开关信号的任务。所以低频电磁波被采用来发送操作命令到管道内控制x射线系统。3 结论这X射线irtipr的关键技术是保证为X射线rtiit实现自动化。如果一个机器人采用没有电缆的工作方式且它的管道内外旋转机构同步控制技术没有被解决，它根本不可能为X射线rtiit实现自动化。焊接接缝独立寻找及定位技术是有形的具体化的智能机器人，也保证了机器人工作的高可靠性。低频电磁波实现了管道内外部分控制系统之间在金属管道遮挡条件下的信息交流，并且起到了闭环的控制系统的作用。以这些关键技术为基础的X射线irtipr可被用于对这大口径管道（在6601400mm）的检查，工作距离大约2km，工作速度在18m / m

12、in.因为这机器人安装有一小的焦点以及定向波束X射线管，与其它X射线管相比可以获得较高的清晰度的焊接接缝图像。这些关键技术在测试中被证明是完美地满足了X射线rtiit的技术要求。英文摘要Key Techniques of the X2ray Inspection Real-timeImaging Pipeline Robot This paper presents a robotic system for weld-joint inspection of the big-caliber pipeline , which is developed for the purpose of being

13、 utilized as automation platform for X-ray real-time imaging inspection technique (RTIIT) . The robot can perform autonomous seeking and locating of weld-seam position in-pipe , and under the control of synchro-follow control technique it can accomplish the technologic task of weld inspection. The r

14、obotic system is equipped with a small focal spot and directional beam X-ray tube ,so the higher definition image of weld-seam can be obtained.Several key techniques about the robotic system developed are also explained in detail . Its construction is outlined.Key words : X-ray inspection ； real-tim

15、e imaging ； robot0 IntroductionCompared with radiographic examination technique(RET) , X-ray real time imaging inspection technique(RTIIT) has many advantages such as higher efficiency ,lower cost , better feasible automation and weld-defects evaluation on-line. Furthermore , up to date technology a

16、llows the X-ray RTIIT to be used in Non-Destructive Testing (NDT) of pipelines , and the inspection quality of this Technique is as good as that of the RET1 ,2 . Therefore ,NDT equipments , which are used commonly in pipeline inspection and basing on the RET , need to be renovated by basing on the X

17、-ray RTIIT. To employ the X-ray RTIIT in NDT of pipeline there must be an automation platform , and X-ray inspection real-time imaging pipeline robot ( IRTIPR) is designed for the purpose. In fact , besides the problems that have been resolved3 and are involved in the X-ray IRTIPR , several key tech

18、niques are presented in this paper , in which we address the robot focusing on its intelligent control, i . e.the autonomous motion in-pipe , the synchro-follow controltechnique and the communication of cooperation between in-pipe and out-pipe , and we also outline the construction of the robot .1 C

19、omposing and Working Principle of the RobotThe X-ray IRTIPR consists of the two parts of in-pipe and out-pipe , as illustrated in Figl 1. The out-pipe part is composed of image collecting and processing system (8 ,9 ,10) , out-pipe synchro-rotary mechanism and its driving system (11 ,12) . The image

20、 intensifier is driven by the out-pipe rotary mechanism to rotate round the center of pipeline to collect weld image and transmit video signal to image processing computer by image-collecting card. The in-pipe part is composed of in-pipe computer (1) , power and inverters system (2) , walking and dr

21、iving system (3) , X-ray system (4) , in-pipe synchro-rotary mechanism and its driving system (5 ,6) and weld-seam autonomous seeking and locating system (7) . The X-ray tube in X-ray system is driven by the in-pipe rotary mechanism to rotate round the center of pipeline.Fig.1 The structure of X-ray

22、 IRTIPRThe main working principle of the robot is explained as follows : Under the control of weld-seam autonomous seeking and locating system the in-pipe crawler finishes the localization of working position , at which the in-pipe crawler is in a state of waiting. When it receives the command signa

23、l from out-pipe , which is transmitted by low frequency electromagnetic wave , the in-pipe computer operates immediately the controller of X-ray system to realize its out-pipe control . In sequence the in-pipe and out-piperotary mechanisms are controlled by the synchro-followcontrol technique to rot

24、ate with the same center of pipeline and finish weld-seam inspection in the manner of rotating-irradiating-rotating.2 The Control System of the RobotAccording to the technologic process of working principle , the control system of X-ray IRTIPR is proposed and mainly made up of several key techniques

25、 such as the synchro-follow control technique based on the X-ray image of benchmark lead wire , the weld-seam autonomous seeking and locating technique based on data fusion and the communication of low frequency electromagnetic wave.2. 1 The Synchro-follow Control Technique of In-pipe and Out-pipe R

26、otary MechanismIn the light of the technologic requirement of X-ray RTIIT , the X-ray tube and the image intensifier must be required to rotate synchronously with the same center. Because the X-ray IRTIPR adopts wireless working manner , i . e. there is no tether cables linking in-pipe with out-pipe

27、 parts of the robot . How to realize the synchro-message communication between in-pipe and out-pipe control systems of rotary mechanism , or how to realize synchro-control , then becomes a key technique that must be solved.The synchro-follow rotating can be described as : when the in-pipe rotary mec

28、hanism drives X-ray tube to rotate an angle of , the out-pipe rotary mechanism drives image intensifier to rotate the same angle synchronously with the same center too (Fig12) . Because of the shielding function of metal pipeline and wireless feature , the means of communication existed is difficult

29、 to accomplish control-message communication between in-pipe and out-pipe parts4 ,5 . According to the particularity of X-ray IRTIPR , we put forward the synchro-control scheme as follows : a benchmark lead wire perpendicular to weld-seam is placed on the irradiation window of X-ray tube ; when the

30、weld-seam is irradiated by X-ray , the benchmark lead wire is also imaged in out-pipe computer. As long as the in-pipe and out-pipe rotary mechanisms are in a synchronous position , namely the axis of irradiation window of X-ray tube is coincident with that of image intensifier (= 0) (Fig12) , the i

31、mage of benchmark lead wire is in the middle position of computers screen , i . e. the image of benchmark lead wire is coincident with the position of benchmark center-line ( H = 0) , see Fig13. When in-pipe rotary mechanism rotates an angle of , the image of benchmark lead wire will deviate from be

32、nchmark center line on the screen , the distance is H. Then the distance H is used as an error input of control system of out-pipe rotary mechanism to regulate its rotating motion. Until the distance H is zero or smaller than appointed value , the synchro-follow motion of out-pipe rotary mechanism c

33、an be realized.The test and simulation prove that the above-mentioned synchro-follow control technique is correct . The synchro-motion satisfies the technologic requirement of X-ray RTIIT.The method utilizes X-ray as vision source , and the synchro-motion message of in-pipe and out-pipe rotary mecha

34、nisms is transmitted by the screens distance that the X-ray image of benchmark lead wire deviates from the benchmark center line , thus the synchro-motion is performed. The method has been applied for invention patent .Fig12 The synchro2rotary mechanism Fig13 The X2ray image of benchmark lead wire2.

35、 2 Weld-seam Autonomous Seeking and Locating TechniqueAutonomous seeking and locating mean that the robot determines automatically where is the working position in-pipe with the help of sensors but without any ones inter-meddling. This control-manner is actually“intelligent”. The precision and relia

36、bility of seeking and locating a system have direct relation with if a robot can realize autonomous motion in-pipe. If this system is disabled , the robot will take the place of the accident of“death”or“lose the way”in-pipe6 .Generally , methods for detecting the position of weld-seam are as follows

37、 : (1) Utilize encoder or cyclometer ; (2) Utilize the displacement caused by the protrusion-concave changing of weld-seam surface ; (3) Utilize if the zone of weld-seam conducts electricity ; (4) Utilize radioactive isotope ( such as ray source) ; (5) Utilize vision ; (6) Utilize low frequency elec

38、tromagnetic wave.Because these methods are influenced by many factors such as walking wheels skid , the in-pipe environment , manmade factors , radioactive injury , locating precision and efficiency , satisfactory result cant be obtained when one of the methods is used alone.Considering weld-seam re

39、gular array , i . e. the space between each weld-seam is about 12m , and advantages and disadvantages of each position-detection method , one system of weld-seam autonomous seeking and locating based on multi-sensors is put forward to improve and enhance the precision , efficiency and reliability of

40、 localization. Multi-sensors consist of the cyclometer , CCD camera and the receiver and emitter of low frequency electromagnetic wave. Systematic block diagram is depicted as Fig14.Fig14 Weld-seam autonomous seeking and locating systemThe system adopts position feedback for enhancing the efficiency

41、 of localization. Vision servo is structured with image given feedback for realizing accurate localization.The data fusion based on three kinds of measure-data , which are the data of cyclometer , low frequency electromagnetic wave and vision , adopts the estimate-algorithm with priority to process

42、data. In terms of the characteristics of three localization methods , the above data have different effective function region respectively. If X1 represents the measure-data of cyclometer , X2 of low frequency electromagnetic wave , X3 of vision. X represents the actual position in-pipe of the robot

43、 , the space between each weld-seam is 12m. Then , the effective function regions of three kinds of measure-data are as follows respectively : X1 1m ,12m ; X2 0. 1m ,1m ; X3 -10cm ,10cm , the final localization goal is X3 = 0. The data fusions rule of three kinds of measure-data is described as : wh

44、en the distance X1 away from weld-seam position is greater than 100cm , the cyclometer is employed for localization in order to enhance the efficiency , and let the in-pipe crawler move at a high speed ; when the data X2 is smaller than 100cm , the“attention”of the controller changes into the method

45、 of low frequency electromagnetic wave , and let the in-pipe crawler move at alow speed ; when the weld-seam enters the vision range , the vision servo is adopted for accurate localization.The data fusions rules are expressed as :X = X1 if ( X3 > - 10) and ( X3 < 10) , then X = X3 ;The above-m

46、entioned method that is realized with fuzzy control and datafusion has perfectly solved the contradiction between the precision and the efficiency of localization. The test result of localization precision is within ±3 mm , which can meet the design requirement . 2.3 The Communication of Low Fr

47、equency Electromagnetic WaveBesides the function of localization , low frequency electromagnetic wave is still utilized to transmit the off-on signal between in-pipe and out-pipe parts. Considering its dangers , the X-ray system is often operated with remote control from out-pipe. Because the robot

48、is wireless and in view of the shielding function of metal pipeline , other methods cannot accomplish the mission that transmits the off-on signal between in-pipe and out-pipe parts. So the low frequency electromagnetic wave is adopted to transmit operation command for in-pipe computer to control th

49、e X-ray system.3 ConclusionKey techniques of the X-ray IRTIPR are assurances for X-ray RTIIT to realize automation. If a robot adopts the working means of having no cable and the synchro-follow control technique of in-pipe and out-pipe rotary mechanisms being not solved , it will be impossible for the X-ray RTIIT to realize automat