Design And Implementation Of An Automatic Measurement System For The Wall Thickness Of A Tank Structure

With the rapid development of automation technology,automatic detection has become an important development direction of detection technology.Tank structure parts are widely used in aerospace,national defense industry and other fields.In order to ensure the reliability of the tank structure parts,it is necessary to test the thickness of the work-piece before it is put to use.At present,manual ultrasonic thickness measurement is often used in the detection of such work-pieces.The detection results often depend on the experience of the detection personnel.Manual measurement has high labor intensity and low efficiency with large human errors.In this paper,according to the characteristics of the tank structure and the influencing factors of ultrasonic thickness measurement,an automatic ultrasonic thickness measurement system is designed.The starting point of this paper is to build an automatic detection system based on the traditional manual ultrasonic thickness measurement principle to replace the manual detection.The automatic detection system can improve the measurement efficiency and reduce the measurement error to ensure the measurement repeatability.First of all,the overall scheme of the system is designed according to the rotation characteristics and testing requirements of the tank structure.The main body of the scanning system is a six degree of freedom manipulator and a rotary table.The main measuring instrument is an ultrasonic thickness gauge.The system is controlled by host computer.According to the function of the test system,the overall structure of the software is designed.The main factors influencing the measurement results are analyzed.Secondly,according to the inspection requirements,the scanning mechanism is designed and selected.The executive end of thickness measurement is designed according to the characteristics of contact ultrasonic thickness measurement.The executive end of thickness measurement realizes the collection of contact force,the adaptive adjustment of measurement angle,the supply of coupling agent and other functions.The position and attitude between tool coordinate system and work-piece coordinate system are calculated.According to the characteristics of the shape and surface of the tank structure,this paper presents a kind of segmented adaptive point distribution method for the tank structure.The point distribution method distributes the curvature and arc length of the characteristic curve of each shape and surface.The method carries out curvature adaptive point distribution for each segmented shape and surface.Through the example of segment function,the relationship between the adaptive degree and the measurement error of this method is analyzed.The whole collision free measurement path is designed and studied.Finally,the performance of the system is tested after the system is developed and debugged.The results show that the automatic thickness measurement system of the tank structure can meet the requirements of the automatic detection.The system improves the detection efficiency and reduces the measurement error.The system has good universality.