强耦合水声换能器阵发射超指向性研究

The research of transmitting superdirectivity of strongly coupled underwater acoustic transducer arrays can develop the great potential of transducer arrays with low frequency and small size. It can result in much sharper transmitting directivity pattern and much higher directivity index compared with conventional transducer arrays. It helps to obtain the innovative ways to increase the transmitting sound level of underwater acoustic transducer arrays with small size and create the conditions for active sonar systems to detect long-range targets. Based on the foundation of previous research results, the principle and method of the transmitting superdirectivity of strongly coupled underwater acoustic transducer arrays will be deeply investigated in this project. The contents of research mainly include the following aspects. First, the methods of global optimization and modal synthesis to obtain transmitting superdirectivity of underwater acoustic transducer arrays will be researched. Secondly, the methods of increasing the robustness and transmitting efficiency of superdirectivity of underwater acoustic transducer arrays with appropriate constraint and optimization of the driving voltage weight and suitable modal combination and systhesis. Tradeoffs among the parameters such as the transmitting directivity, robustness, efficiency and bandwith will be made to ensure the underwater acoustic transducer array with relatively high transmitting directivity index, good robustness and efficiency, wide bandwidth, and obtain larger transmitting sound level. At last, experiments in the anechoic water tank and lake will be conducted to verify the transmitting superdirectivity of underwater acoustic transducer arrays and make the researched principle, method and technique achieve good application performance.

对强耦合水声换能器阵发射超指向性的研究可以充分发掘低频小尺寸水声换能器阵的巨大潜力，使基阵相比于常规阵列发射指向性更尖锐，指向性指数更高。获取提高小尺寸水声换能器阵发射声源级的创新途径，为主动声纳远距离探测目标创造条件。本课题拟在已有研究成果的基础上，对强耦合水声换能器阵发射超指向性形成的原理与方法进行深入的研究。研究内容主要包括利用全局寻优以及模态合成等方法对强耦合水声换能器阵进行发射超指向性形成；通过对水声基阵驱动电压加权合理约束优化以及对辐射声波模态适当组合叠加等方法提高发射超指向性形成的稳健性及发射效率。在发射指向性与稳健性、发射效率、带宽等参数之间寻求一个比较好的折衷，既保证水声基阵有比较高的发射指向性指数，稳健性、发射效率也较高，带宽较宽，发射声源级更大。然后进行消声水池及湖上实验，对水声基阵的发射超指向性进行实验验证，使研究的原理、方法和技术获得良好的应用效果。

为了发掘低频小尺寸水声发射换能器阵的巨大潜力，使基阵相比于常规阵列发射指向性更尖锐，指向性指数更高，本课题对强耦合水声换能器阵发射超指向性形成的原理与方法进行了深入的研究，利用全局寻优以及模态合成等方法对换能器阵进行发射超指向性形成。项目研究按计划进行,达到原定目标。主要研究内容和取得的研究成果有：.1、研究了利用有限元方法对单个弯曲圆盘换能器及其阵列的声辐射特性进行了建模与计算。设计制作了一种低频小尺寸的弯曲圆盘换能器，在消声水池实验测量得到圆盘换能器的谐振频率和发射电压响应，与仿真计算结果一致。.2、利用声场建模跟优化算法相结合的方法计算了弯曲圆盘换能器阵列各阵元的驱动电压加权，使得阵列获得良好的发射超指向性。分别利用常规波束形成加权和优化波束形成加权对8元均匀直线阵的发射指向性进行了仿真计算，优化加权结果相比于常规波束形成加权结果，旁瓣高度降低，主瓣宽度变窄，阵列发射指向性指数更大。.3、对多瓣圆环换能器的发射超指向性形成进行了深入的研究。通过利用模态合成的方法求解多瓣圆环换能器各阵元的驱动电压加权，使得整个圆环换能器形成发射超指向性。以多瓣圆环单极子、偶极子、四极子为基础，通过控制它们各阶模态的加权系数使圆环换能器获得不同的发射超指向性。.4、在消声水池中测量了由8个弯曲圆盘换能器组成的直线阵在不同阵元间距下的发射指向性，结果表明利用优化加权能够使直线阵获得发射超指向性性能。还制作了八瓣圆环换能器的原理样机，在消声水池中测量了八瓣圆环换能器在0阶、1阶、2阶模态以及多阶模态合成下的发射指向性，实验结果表明八瓣圆环换能器可以通过模态合成的方法获得良好的发射超指向性性能。