Research On Scanning Robot For Pipeline Girth Weld

In order to guarantee the security and reliability of oil pipeline transportation, the pipeline girth weld needs to be tested. As an advanced method of non-destructive testing, automated ultrasonic testing plays an important role in pipeline welding defect testing. This article is based on the national 863project------"Underwater Tie-in Technique for Subsea Pipelines and Study ofAUT Testing Device Nationalization Technology" . The main task of this article is to make research in automated ultrasonic testing machine of pipeline girth weld------scanning robot.Analyzing and comparing the advantages and disadvantages of two keytechnologies of automated ultrasonic testing------phased array control technologyand TOFD technology, the phased array control technology is selected to test pipeline girth weld; The overall scheme of scanning robot is determined, the motion mode, the driving mode as well as the design performance are analyzed and the working process is introduced.Deep research is made in the structure of scanning robot. It is composed of four parts: flexible guide subassembly, movement mechanism, control box subassembly as well as probe adjusting mechanism. The static analysis model of scanning robot is established in order to deduce the general calculation formula of driving force at random position; The analysis model of scanning robot is simplified ensuring the center of gravity location unchanged, and the finite element analysis is carried on.The position servo module and communication module of probe adjusting mechanism control system are designed based on modular thinking. The single-chip microcomputer AT89C52, special motion control chip LM629 of superior performance and power actuation chip LMD18200 are selected, and the hardware circuit diagrams of single closed-loop servo system and communication system are designed.The motion simulation and analysis of scanning robot are carried on to verify the reliability of probe position in the radial direction of pipeline when scanning robot is running; The mathematic model of probe adjusting mechanism control system is established, and the simulation is carried on to verify that the position-control system has the good accuracy as well as the fast dynamic response characteristic.