Multi-beam Imaging Sonar Transducer Array And Imaging Algorithm Design

Sonar is an important tool for humans to explore the ocean world,especially as land resources are gradually scarce nowadays,and countries are turning their goals to submarine resources,sonar research is becoming more and more important.Imaging sonar can image the actual conditions of the seabed,and it is widely used in military,civilian and other research fields.Therefore,the research of imaging sonar is of great significance.The TKIS-1 sonar previously developed by our laboratory is a single-beam mechanical scanning imaging sonar.Currently,more than 20 devices have been used in naval forces.TKIS-1 single-beam imaging sonar can meet the requirements of medium and long range detection,but it also has shortcomings that are difficult to improve: the scanning time is too long and the efficiency is low.Aiming at the shortcomings of TKIS-1 single-beam imaging sonar,the theoretical research of multi-beam imaging sonar is proposed.This thesis mainly focuses on the two key parts of multi-beam imaging sonar,namely the research of transducer array and imaging algorithm.The main work and research conclusions of this thesis are as follows:（1）This thesis introduces the working principle of TKIS-1 single-beam imaging sonar,conducts the imaging experiment,analyzes the advantages and disadvantages of TKIS-1 single-beam imaging sonar.Aiming at the shortcomings and new practical needs of TKIS-1 single-beam imaging sonar,a theoretical study of multi-beam imaging sonar is proposed,which provides theoretical guidance for the subsequent research and development of products.（2）According to the requirement of multi-beam imaging sonar,the design of transducer array is carried out,mainly including the working frequency,the number of elements and the distance between elements of transducer.The design results show that the operating frequency is 2.25 MHz,the number of array elements is 212,and the distance between elements is /2,and is wavelength.Analysing the model of transducer array signal after determining the relevant parameters.The signal-level simulation is carried out in thesis,which provides a theoretical basis for imaging algorithm design.（3）The imaging algorithm of multi-beam sonar is designed in this thesis.The conventional beamforming imaging algorithm is used to obtain the desired beamwidth.The simulation results show that the conventional beamforming can form a beam with a width of 1.8° in the direction of 75° under the parameters of 2.25 MHz operating frequency,212 array elements and half-wavelength array element spacing.But at the same time,the sidelobe amplitude is too high and the number of array elements is too large.Considering the size of the transducer and cost,the imaging algorithm of DC weighting and least square virtual array element beamforming is proposed.The simulation results show that the amplitude of sidelobes can be reduced by using DC-weighted beamforming,and the number of elements can be reduced by using least square virtual array element beamforming.And a beam with a width of 1.8° in the direction of 75° can be obtained by using 130 array elements.In the near-field situation,an imaging algorithm for near-field focused beamforming is proposed.（4）Designed the point target imaging simulation experiment in this thesis.The target imaging simulation experiments of conventional beamforming,DC-weighted beamforming,least-square virtual array beamforming and near-field focused beamforming are carried out to obtain imaging images that can display the distance and direction of the target.The simulation results verify that all the above algorithms can achieve target imaging.In order to verify whether the imaging algorithm meets the requirements,a resolution simulation experiment is carried out,and the results demonstrate that the resolution can almost meet the actual requirements.Finally,the scanning efficiency of multi-beam imaging sonar is analyzed,and the analysis results show that the scanning efficiency of multi-beam imaging sonar is about 10 times higher than that of TKIS-1 single-beam imaging sonar.To sum up,the thesis has basically completed the transducer array design and imaging algorithm design of multi-beam imaging sonar,and the theoretical design results meet the practical requirements.