Research And Design Of Distributed Acoustic Emission System Based On ZYNQ

As an emerging non-destructive testing technique,acoustic emission testing offers the advantage of lower cost and wider applicability than traditional non-destructive testing techniques.Acoustic emission inspection systems simply install an acoustic emission sensor at a suitable location on the object to be tested to capture and process the acoustic emission waves released when cracks or fracture damage occurs in a material component,allowing real-time detection of the location of damage during use and monitoring of the dynamic expansion of the damage.Conventional acoustic emission systems are limited by their bulky portability,poor channel expandability,single function and many wired communication cables,making them difficult to use in increasingly complex and diverse detection scenarios.In order to solve these problems,this thesis investigates and designs a ZYNQ-based distributed acoustic emission system using the "FPGA+ARM" architecture to achieve distributed multi-node time synchronisation and acoustic emission signal acquisition and processing,and finally locate the source of acoustic emission.The system uses a wireless self-organising network module for data transmission.The ZYNQ-based design and implementation of this acoustic emission system has the advantages of high speed parallel signal processing capability,good design versatility and reusability,strong channel expandability,versatile functionality and high synchronisation accuracy.The main work of this thesis is as follows:Through the theoretical study of the acoustic emission system,the software and hardware design of the ZYNQ-based distributed acoustic emission system is determined.The hardware selection of the acoustic emission sensor,preamplifier,ZYNQ main control board,AD converter,GPS receiver and wireless transmission module was completed according to the design requirements.In response to the commonly used distributed system GPS timing synchronisation method relying too much on the PPS second pulse signal and the problems of signal loss,non-flip and desynchronisation of the second pulse signal,this distributed system design implement ts the DPLL-based PPS frequency doubling synchronisation module.The DPLL-based PPS multiplier synchronisation module is designed to reduce the synchronisation errors of the sub-nodes by providing a signal that is still synchronised with the PPS inside the FPGA when the PPS signal is lost.This thesis then goes on to complete the design of the clock management synchronisation module for the system sub-nodes.The time management synchronisation module provides a high precision synchronised time reference for the subsequent signal processing of each sub-node.In view of the single function of commercially available acoustic emission systems,most acoustic emission systems only do acoustic emission signal data acquisition,but do not extract the characteristic parameters of the acoustic emission signal and other problems,this thesis studies the design and implementation of sub-node acoustic emission signal acquisition and processing module,and its simulation to verify.The signal acquisition and processing module includes several sub-modules such as AD acquisition control,digital filter,envelope extraction,feature extraction,SD card storage and wireless transmission.A test platform is built to validate the system on board and verify the functionality of important modules to meet the design requirements.The QT visualisation software was designed based on Chan’s TDOA localisation algorithm,with the software interface displaying the acoustic emission source location and acoustic emission characteristics.The whole distributed acoustic emission system was tested in a lead break experiment and the results were analysed.The system was experimentally tested and found to meet the design requirements.This thesis has 73 figures,8 tables and 84 references.