Research On The Application Of Data Compression Technology For Electromagnetic Rail Flaw Detection

In 21st century,high speed and heavy haul railways become more and more important.People pay more and more attention to railway safety.Rail inspection comes to be an important part to ensure the safety of train running.Low speed manual rail flaw detector has been difficult to meet the needs of rail inspection with the continuous updating of railway mileage records and the rapid development of high-speed railway technology,the demand for high speed testing equipment is more and more urgent.Now the main flaw detection method is ultrasonic flaw detection,it need rail bonding and oupling agent for testing which affect the speed of detection,so it's more and more difficult to meet the needs of the main train line detection.Eddy current testing is a kind of nondestructive testing,its principle is to obtain the information of the measured conductor by changing the electromagnetic characteristics of the measured conductor which has the advantages of high speed,non-contact.High speed inspection of rail must use a higher sampling frequency,resulting in a larger amount of data whichwill cause tremendous pressure on storage and transmission.This paper focuses on the design of the compression algorithm and the embedded system based on the electromagnetic rail flaw detection.This system receives the detection data sent by the FPGA flaw detection device,then preprocesses the data and compresses the data,finally saves the data to the database through the HTTP request.The mainstream views as follows:(1)Study the basic principle of electromagnetic eddy current testing and the basic knowledge of data compression theory.Expound the relationship between data compression and the information theory,analyze the multiple indexes of evaluating the compression performance of data,and study the thoughts and characteristics of several common data compression methods.(2)Construct ARM-Linux embedded system for electromagnetic rail flaw detection data compression.The hardware platform takes S3C2440 as the core,and constructs the minimum system circuit,memory and communication interface circuit.Develop Bootloader to boot start the operating system,transplant Linux3.18.24 kernel,build file systems using busybox 1.22.1 and YAFFS2,transplant the libcurl dynamic library required by HTTP communication and the serial communication the software of rzsz to build a complete environment for the program.(3)Design of data compression algorithm based on LZW and Deflate,receive the inspection data sent by the FPGA flaw detector through UDP communication,use libcurl to write InfluxDB through the HTTP request after the measured data is compressed,and view the data through the Grafana finally.The comparison of the measured data before and after compression shows that the compression algorithm of the electromagnetic rail flaw detection data is effective.