Research On Precision Detection Technology With Anti-interference Combined AC And DC For Broken Wire Of Steel Cable

Steel cable is a ferromagnetic metal component with light weight,high tensile strength and good flexibility.It is widely used in elevator,ropeway,bridge and other fields.However,it is prone to have defects such as corrosion,abrasion,broken wire and so on,which will cause great potential risks.Therefore,it is necessary to design and implement a set of precise detection system for detecting broken wire of steel cable.Additionally,in the actual working environment of steel cable,the system may be subject to various interference signals of different frequency,which greatly affects the detection results.Therefore,the objectives of research are to improve the anti-interference capability of the detecting system and implement the precise detection for the positions and quantities of broken wire.The main research contents are as follows:(1)The research on the theoretical scheme on the magnetic flux leakage detection.Through analyzing the characteristics,types of flaws and scrap standards about the steel cable,it is determined to take the broken wire as the main research object.On this basis,through comparing different magnetic excitation methods,different sensors and different signal processing methods,we put forward a theoretical scheme,which includes the generation of magnetic flux leakage signal through combined AC and DC excitation,collection of flux leakage signal using Hall sensor,suppression of system noise by using lock-in amplifier circuit,and determination of the positions and quantities of broken wire by designing software algorithm.(2)The simulation study of magnetic flux leakage field.Through establishing the finite element model of the probe and simulating the basic structure of the probe,the magnetic excitation and sensing parameters,we design an excitation device and a magnetic shield device,and then optimize the strength of permanent magnet and AC excitation strength,the amplitude of AC excitation and the value of lift distance.Moreover,through simulating and analyzing the width,depth and position of broken wire,we obtain the relationship between the magnetic leakage strength and parameters of broken wires,which provides guidance for the design of algorithm on the detection of broken wire.(3)The overall design,realization and test of the system.We propose a hardware solution firstly based on the AC and DC compound magnetic field excitation and the orthogonal vector lock-in amplifier circuit to improve the anti-interference capability of detection system,and first of all,we realize the design and manufacture of the main board circuit.On this basis,we design the program about the module drive,the algorithm about the slope and threshold detection and the program about interface display and then realize the output of the positions and quantities information of the broken wire.Finally,we fabricate the base and frame of the probe and build the experimental platform,and then carry out 30 repeated experiments on a steel cable with 3 broken wires artificially set.The results show that the positioning accuracy is ±1mm and the recognition accuracy of 2,3 and 4 broken wires is 96.7%,100% and 100% respectively.And more importantly,under strong interference condition of 100 Hz,the output of this system is still normal,which proves that the anti-interference effect is reliable.