Research On Sparse Sampling Method Of Addressing Excitation Ultrasonic Array

Traditional ultrasonic transducer array often uses the mode of simultaneous or delay excitation of each array element to generate different planar and focused wave fronts to obtain better detection results.However,the independent electrical connection between array elements leads to numerous electrode leads,and the complexity of electrical connection increases significantly,which increases the difficulty of transducer array preparation.At the same time,the mode of array element independent electrode leads is not flexible enough to control the excitation of subarray.In recent years,a new addressing excitation mode appears in the excitation of medical ultrasonic transducer array,which shows obvious advantages.However,the research on industrial ultrasonic transducer array is still in its infancy.This thesis takes full account of the differences between industrial ultrasonic transducer array and medical ultrasonic transducer array in detecting objects,transducer structure,transmitted acoustic power requirement,and applicability,and the feasibility of array addressing excitation composed of bulk piezoelectric ceramic array element by using minimal addressing array structure is verified.The addressing excitation principle,excitation logic,excitation timing,and excitation electrical characteristics of the array composed of bulk piezoelectric ceramic array element are studied.The addressing excitation transducer is fabricated,and the circuit system is designed and tested.At the same time,with the goal of reducing the amount of data collected by the addressing excitation ultrasonic transducer array,the sparse sampling technology and parameter reconstruction problem of the Finite Rate of Innovation(FRI)under this excitation mode are studied,and the sparse sampling and reconstruction framework of the addressing excitation ultrasonic array is established.The sparse sampling and parameter reconstruction of the received signals under different transmitting apertures are realized.Through the actual test,the key parameters of the echo signal are estimated accurately by using the sparse data obtained.The main research contents and conclusions of this thesis are as follows:(1)The excitation modes and characteristics of ultrasonic transducer array are analyzed,and the current situation and technical characteristics of addressing excitation modes in the field of medical ultrasonic detection are analyzed.Based on the full consideration of the different requirements of detection objects,array structure and electrical characteristics,a bulk piezoelectric ceramic addressing excitation scheme is proposed.On this basis,the development status of sparse sampling technology of ultrasonic transducer array is analyzed,and the FRI sparse sampling scheme and parameter reconstruction method for addressing excitation transducer array are proposed.(2)The acoustic field radiation characteristics of the bulk piezoelectric ceramic ultrasonic array were studied.The influences of geometry parameters,spacing and numbers of array elements on acoustic field radiation characteristics are analyzed through the directivity function model of the array.According to the acoustic field distribution characteristics of the array,the structure of the addressable excitation transducer array and the basic parameters of the array element are determined.(3)The current excitation mode of ultrasonic array is studied,and the row-column addressing design scheme which can realize the excitation of arbitrary aperture of single and multi-array element is proposed.On this basis,a 2+2 bulk PZT addressing excitation planar array with minimal array structure is designed and fabricated,and the performance of the array is tested.The addressing excitation control circuit is designed.The real-time opening and closing of the circuit composed of MOS electronic switches controlled by square wave signal is realized,the addressing excitation with different aperture is completed,and the feasibility and electrical performance of bulk array structure addressing excitation are verified(4)The basic principle of FRI sparse sampling theory is studied,and the FRI sparse sampling and reconstruction framework of addressing excitation ultrasonic array signal is given according to the characteristics of mathematical model of echo signal received by all array elements of addressing excitation ultrasonic array.The FRI sampling kernel based on Chebyshev II Low Pass Filter(Chebyshev II-LPF)is designed and trial-produced,and sparse sampling and parameter reconstruction of received echo signal under different aperture excitation are realized.(5)Using PZT-5H piezoelectric ceramics as the sensitive material of piezoelectric array element,the thesis fabricated and packaged the planar array of 2+2addressing excitation ultrasonic transducer,and gave the preparation process of each component of the transducer and the electrical performance test data of the transducer.The addressing control circuit of ultrasonic transducer,the generating circuit of ultrasonic excitation pulse,the receiving and processing circuit of echo signal,and the sparse sampling circuit are designed and manufactured,and the parameter reconstruction algorithm is given.The performance of the whole transducer system was tested on the built test platform.The center frequency of the transducer is 1MHz,and the aluminum test block was selected as the test object to realize the addressing excitation of any single array element,row and array elements,and all array elements in the single-channel excitation pulse generating circuit,and the echo signal under the addressing excitation mode was obtained.The transmitted acoustic power met the detection requirements.Taking the thickness of aluminum test block and hole defect as detection targets,addressing excitation and sparse sampling technology were adopted.The sparse sampling frequency is 219 KHz,and the measured data parameters were reconstructed.In the thickness test,the maximum amplitude parameter estimation error is 2.59%,and the maximum delay parameter estimation error is 1.37%.In the hole defect detection test,the maximum amplitude parameter estimation error is 7.48%,and the maximum delay parameter estimation error is 1.21%.