基于垂直线阵的水下三维成像系统设计

Design of Underwater 3D Imaging System Based on Vertical Line Array

针对传统三维声呐硬件系统复杂、计算量庞大的特点,本文设计了一种基于垂直线阵的水下三维成像系统。相比于传统二维面阵成像声呐,垂直线阵成像声呐阵元数较少,硬件电路较简单。但是,垂直线阵扫面时间过长的缺点使得系统成像速率较慢,无法满足实时成像的需求。为解决此问题,本文提出了一种多频率发射波束形成算法,该算法通过优化垂直阵列的发射过程,有效地减少了系统发射阵列的波束发射次数,从而缩短了系统扫描时间,提升了成像速度。系统硬件部分由发射模块、接收模块、电源模块以及显示模块4个部分组成。系统通过FPGA控制120路信号的同步采样,在波束形成计算中使用并行子阵分级波束形成算法再次提高了系统的运算速率。为了验证系统的性能指标,本文先后对系统进行了波束形成仿真测试以及水下环境的实际成像测试。经测试,本文设计的垂直线阵三维声呐成像效果接近同等指标的二维面阵成像声呐,系统成像帧率较高,满足了三维声呐低功耗、小型化、实时成像的需求。

Aiming at the problem of complex structure and huge amount of computation of the traditional 3D imaging sonar,a design of underwater 3D imaging system based on vertical line array is proposed.The imaging sonar system which based on vertical line array has less array elements than the traditional imaging sonar which based on 2D planar array,so this system has a simple hardware structure.But the imaging sonar system which based on vertical line array also has a serious drawback,that is,the scan time is too long.So that the vertical line array imaging sonar can’t meet the needs of real-time imaging.In order to solve this problem,a multi frequency transmit beam forming algorithm is proposed.This algorithm can effectively reduce the beam launch times of the system by optimizing the launch process of the vertical array,thus reducing the scanning time of the system and improving the imaging speed.The hardware structure of the system is composed of four parts,which are the transmitting module,the receiving module,the power module and the display module.FPGA samples high speed for 120 channels of acoustic signal,and uses the parallel subarray beamforming algorithm improving the calculation speed of beam forming.In order to test the performance of the system,two tests have been carried on,which are the beam forming simulation test and the actual imaging test of underwater environment.Experimental results shows that this system has the same imaging ability as the traditional 3D imaging sonar based on 2D planar array,and the system meet the needs of low power consumption,miniaturization and real-time imaging.