Ultrasonic Inspection Of Welded Joints Based On Robotic Arm Mechanism

Welding is a commonly used material processing method in industrial production,and it is widely used in the field of processing and manufacturing such as aerospace,automobile,and rail passenger cars.In order to ensure stable performance of the welded parts,the welded joints need to have good corrosion resistance,good high and low temperature resistance,and good mechanical properties.In order to ensure the quality of the welded joint,it is important to perform the weld joint inspection after welding.In order to ensure the credibility of welding quality evaluation and improve the detection efficiency,non-destructive testing methods are often used in industrial production to test and evaluate the quality of welded joints.Ultrasonic testing is a commonly used non-destructive testing method,because it has a wide range of applications,no harm to people,high sensitivity,and computer programming to visualize ultrasound data for analysis,therefore,it is widely used in industrial production for quality evaluation of welded joints.In this paper,for the common scanning mechanism,when detecting welding with complicated shape changes,it is not easy to perform.It is proposed to use a weld ultrasonic inspection method based on passive mechanical arm scanning.By using the flexible movement of the arm,the ultrasonic probe is mounted on the end of the arm and the hand-held probe is used to detect the welding.It can be used to detect welding with complex shape changes.Compared with the traditional scanning mechanism,it has simple and flexible operation.The complex surface has the advantage of good shape,and it also provides accurate probe position information.In this paper,according to the mechanical arm structure used in the experiment,the design of the angle information acquisition system is carried out.The design part takes the angle sensor to collect the angle data at the joint of the mechanical arm,selects the appropriate angle encoder and data acquisition card,and then selects The reading method of the angle sensor data converts the pulse data into angle data to realize accurate positioning detection.According to the principle of space coordinate system transformation and the D-H algorithm of the manipulator,the expression between the end position of the arm and the joint rotation angle is derived,and the theoretical end position calculation model is obtained.Then analyze the factors that may cause errors,and analyze the weights of the factors that cause the errors through MATLAB to establish a matrix with error compensation.In order to solve the error compensation quantity matrix,the error judgment quantity is set,the experimental data is collected,the error between the calculated value of the ideal model and the actual data is calculated,and the error judgment quantity is taken as the objective function,and the genetic compensation algorithm is used to solve the error compensation quantity solving matrix.The model is updated after the error compensation amount is obtained.After the model is updated,the error between the calculated value and the actual value is less than 10%,which is in line with the experimental requirements.After the calculation of the end position calculation model of the arm is performed,the arm is ultrasonically detected by the arm,and after the A-scan signal is analyzed for a brief analysis,the C-scan is performed on the welding to obtain a C-scan image,which will be calculated from the image information.The diameter of the nugget is compared with the actual value,and the difference is less than 0.5 mm.The experimental results show that the ultrasonic inspection and nugget diameter determination of the welded joint can be performed by the mechanical arm detection system.