Design And Key Technology Research Of Inspection Robot For Pipeline Girth Welding

Industrial pipeline is one of the basic equipment of modern industry.However,there are inevitable defects with different degrees in the butt joint welds owing to the harsh installation and application conditions.The defects must be identified to ensure the safe operation of in-service pipelines.With the rapid development of China’s industrial undertakings,enterprises’demand for inspection equipment has increased significantly.For the purpose of improving the applicability of flaw detection robots,reduce costs,and break the monopoly of foreign countries in this field,an industrial robot is expected to be fabricated,which enables the non-destructive weld inspection of large pipeline ring and suitable for China’s industry standards.According to the functional requirements of the weld inspection,the overall scheme,adsorption and movement modes of the robot are designed based on the environmental characteristics of the pipe wall.The 3-D mechanical structure of the robot is built with the emphasis put on the walking drive module,swing fine adjustment module,and the clamping device.The statics is numerically studied to ensure the robot operating normally on the pipe wall,and the minimum adsorption force of the single magnetic wheel is calculated,laying the foundation for the further hardware selection.Based on the comprehensive analysis of robot control requirements and characteristics,the control system with Delta series PLC as the control core is proposed,and the hardware facilities such as three motors and drives are selected.Then,the software framework is determined,and the main program is compiled and explained.Meanwhile,a visual and controllable remote wireless monitoring system is developed.A DC triple closed-loop speed control scheme for the robot’s driving system is introduced in this research.Through analyzing the characteristics of the DC brushless motor,a mathematical model of the motor with the corresponding controller is established,and the three-loop speed regulation is simulated by MATLAB.The current loop,speed loop and PID control position loop are optimized to solve the technical problems of system speed response,speed stability and anti-interference ability.The mathematical model of each controller is described,and the optimal parameter of each ring regulator can be observed from the data comparison.According to the numerical results,the performance of the speed control system is improved by using the mentioned control system.Therefore the method is verified to be reasonable.An experimental platform composed of a pipeline welding seam inspection robot prototype and control system is constructed to validate the presented numerical model,based on the relevant national standards and specifications.The test results of the control module show that the triple closed-loop combined with the PID control strategy can achieve a quick respond,indicating the rapid adjustment and favourable stability.After repeatedly testing of the robot,the running track with deviation range within±11mm can be obtained in both manual and automatic modes.Collectively,in addition to acquiring the optimal operating speed in various modes by the data analysis,the relevant factors that affect the robot speed control system,operating stability,and offset accuracy are clarified,and related suggestions for further improvement are given.In this research,theoretical approaches are employed to solve practical problems,which provides a reference for such engineering applications.