Optimization Design Of 1D Sparse Array For Ultrasonic Phased Array

Ultrasonic phased array imaging technology can control the time (phase) relationship between each arrays when each array element transmits (or receives) sound waves. So that it can realize the deflection and focus of acoustic beam, and complete the acoustic imaging. Compared with conventional ultrasonic methods, it has many characteristics such as rapid and flexible deflection, excellent mechanical reliability and so on. According to the present domestic and foreign research progress of ultrasonic phased array inspection technology, the design of ultrasonic phased array transducer and multi-channel ultrasonic transmitting and receiving system have become the two key technology of phased array inspection. As the electronic control core of phased array ultrasonic testing system, multi-channel ultrasonic transmitting and receiving system has realized many key technologies of beam control of time and space. The array transducer is the key part of ultrasonic phased array system, and it takes a direct contact with test object, which has a direct impact on the performance and imaging quality of phased array detection.In the design of ultrasonic phased array, it is common to eliminate the grating lobe by shrinking array element spacing, or increasing density of array element, in order to solve the problem of fuzzy imaging space. But it also brings a drawback which will improve the cost of the array, increase the difficulty of production and make a serious effect of mutual radiation between arrays, it is evident in the design of large-scare array transducer. And then sparse array is the effective way to figure out these problems. Based on the Matlab software, this paper puts forward an improved particle swarm optimization (PSO) algorithm by the simulation and optimization of different 1D sparse array, to calculate their array patterns which can reflect the spatial resolution and contrast resolution of the image and find out sparse array with good acoustic performance close to the reference array.Experimental analysis indicates that the PSO algorithm provides an effective reference for sparse array optimization design.Combined with the MRLA, the improved PSO algorithm not only makes sparse array maintain a high spatial resolution, at the same time, but also improves contrast resolution, and solves the problem that the sparse array optimized simply by the PSO algorithm has a poor consistency. Based on mixed programming of MATLAB and Visual Studio 9.0, a ultrasonic phased sparse array control platform have been developed, which can not only control any aperture, and any number of valid array elements of sparse array transducer, but also realize optimization design and performance evaluation of sparse array with different aperture. Then based on this platform, a ultrasonic phased sparse array detection system has been designed.Through the sparse array detection system, this paper has used the sparse array optimized by two kinds of algorithm and the reference array with corresponding aperture, to test and compare typical weld defects test blocks containing pores, slag, lack of fusion, lack of penetration, crack have been made by artificially with different thickness, and then established database of typical sparse array and weld defects. Defect detection experiments show that the PSO algorithm combined with MRLA, can increase imaging spatial resolution of sparse array, at the same time, improve contrast resolution of detection imaging, and provide high quality ultrasonic testing image.