Design Of Phased Array Ultrasonic Beam Synthesis System Based On FPGA

The phased array ultrasonic nondestructive testing has the advantages of fast detection speed,high sensitivity,and can detect complex workpieces.It is the research hotspot in the field of ultrasonic detection.The most basic and important technique in phased array ultrasound nondestructive testing is sound beam synthesis.The beam synthesis technique includes two aspects of phased array transmission and reception.In this way,by controlling the delay time of the ultrasonic wave in the array,the beam can be deflected and focused,and a strong sound field is formed in the workpiece to be detected and reduced The sound field strength of the other areas of the workpiece,so as to obtain the detection resolution as high as possible.It can be seen that the time delay for controlling the emission of ultrasonic signals is the core of the beam synthesis technique.Based on the basic theory of acoustic wave,this paper analyzes the influence of the delay time precision of the array element and the phase of the sound beam,the deflection accuracy of the beam and the focal length of the beam focusing.The simulation results show that the higher the delay precision of the array element,the better the synthesis effect of the beam.At present,the structure of ultrasonic signal transmitting equipment is relatively simple,and there are some problems such as single output signal,rough waveform,low parameter accuracy and inconvenient adjustment of waveform parameters.The paper research and design based on field programmable gate array(FPGA)as the core with the direct digital synthesis of high-speed DA conversion(DDS)system,and further constructed a phased array ultrasonic beam emission system.According to the classic ROM look-up table DDS waveform generated in the process of FPGA requires a large amount of storage resources,This paper proposes a method to realize the occurrence of ultrasonic signal by using recursive iterative method.The method has the advantages of simple structure,low utilization of resources,and easy generation of ultrasonic signal.High precision ultrasonic signal,signal frequency,emission delay time and other parameters can be set flexibly,and then the synthesis of different beams,improve the phased array ultrasound detection capabilities and applicability to meet the different testing needs.The Cyclone IV series EP4CE6E22C8 of Altera Corporation was selected as the master chip,and a 16-channel phased array ultrasonic beam synthesis system was designed.The system can complete the 16-channel high-precision ultrasonic emission and 16-echo signal reception.The hardware system adopts the modular design method.The paper introduces the selection and circuit design of the component,including the FPGA core control circuit,the ultrasonic transmitting and receiving circuit,the data interface circuit and the system power supply circuit.On the basis of the hardware of the system,the design of ultrasonic signal generation,digital-to-analog converter drive,echo signal data reception and analog-to-digital converter driver is designed by Verilog HDL hardware description language,and the above-mentioned ultrasonic signal generation method is realized.The simulation of the software system is carried out,and the experimental test is carried out on the hardware platform.Finally,the simulation and experimental results are analyzed,and the accuracy of the parameters such as the occurrence of the ultrasonic signal and the correctness of the receiving system and the frequency of the signal and the delay time of the transmission are verified.