Research On Synthetic Aperture Technology And Total Focusing Method Based On FPGA

In the field of high speed railway, nuclear industry, petrochemical and so on,defects due to fatigue, stress and friction generated from the workpiece,will grow bigger and shear as time goes on and cause major security incidents.Therefore,greater demands are being placed on online real-time detection of defects in the metal workpieces, to eliminate safety hazards.In the high-speed railway,non-destructive testing of internal defects in the wheel-rail using conventional ultrasound and phased array ultrasound technology, wheel drop detection and non-drop wheel detection have been widely used on-site.At present, industrial non-destructive testing based on conventional ultrasonic phased array is easy to implement and process,but the equipment is complicated and has low integrity.In recent years, more and more research are conducted in Total Focusing Method for its characteristic of high coverage and flexibility, which guarantee TFM can has high accuracy detection of a variety of complex materials.On the purpose of improving system integrity and imaging quality,this paper based on ultrasonic phased array technology, use Full matrix Capturing technology as the method to sample data, and use Total Focusing Method as algorithm to post-process sampling data.In this paper, we design the flow chart of algorithm and use MATLAB to testify it, use FPGA to realize the algorithm processing system to accelerate the processing speed,and combine Ultrasonic synthetic aperture technology with TFM to improve the imaging quality further.Firstly,we establish a basic mathematical model for FMC and use TFM as imaging algorithm, taking into account its simplicity and high precision, and verify and analyze the system by MATLAB.The result shows the mathematical model is correct and get high quality imaging, but time cost is high at the same time.Secondly,in order to improve the imaging speed, we use FPGA, a platform has capability of parallel processing,as platform to design and implement TFM processing system. By comparative analysis, we come to a conclusion that FPGA can not only ensure high quality imaging of defect, but also highly decrease the time cost.Finally, we combine the ultrasonic synthetic aperture technology and full matrix capture-total focusing method to get the image of defect, and analyze the result from the aspects of API and SNR.The result shows that this new system improve the imaging quality on the condition that ultrasound array probe keep the number of elements unchanged,Verify that the ultrasonic synthetic aperture can optimize imaging based on total focusing method.In a word, this paper lays a solid foundation for the further design of fast and high quality imaging based on total focusing method. It has a very good meaning to promote the real-time imaging development of miniaturization and integration.