弛豫铁电单晶融变效应及其低噪声矢量传感器研究

One of the most serious problem for the vector sonar is high self-noise of the vector sensor. The current solution is to directly replace the piezoelectric ceramic with the relaxor ferroelectric single crystal, which intends to use its higher piezoelectric coefficient and lower dielectric loss to reduce self-noise. But there is little effect. According to the research of the applicant, the dielectric properties of the single crystal present a significant change after joint with vibrator structure -joint effect- which directly impacts on the sensitivity and self-noise of the vector sensor. The current theory and method cannot reflect the joint effect, which leads to a great difference between theory and reality. In addition, the low-noise vector sensor cannot be obtained by simply replacing the active material while ignoring the coupling effects of other units and systems. The project studies the scientific issues of the joint effect impact on vector sensors. A new joint effect based theoretical design method of relaxor ferroelectric single crystal vector sensor is established, and the minimum self-noise system analysis theory of vector sensors including the influence of each unit and its noise coupling characteristics is setup as well. And then the multi-objective constrained optimization method is studied for low-noise purpose. This project is proposed to provide a complete self-noise theory analysis and low noise optimization design method for the relaxor ferroelectric single crystal vector sensor based on joint effect, which lays a solid theoretical foundation for breaking through the low-noise technology.

矢量传感器自噪声过高已成为限制矢量声呐发展的瓶颈之一，仅将压电陶瓷替换为性能更优的弛豫铁电单晶，实际收效甚微。申请人新近研究发现，弛豫铁电单晶与振子结构融合后会产生融变效应，介电性能发生显著变化，现有理论和方法均不能体现该效应产生的影响，导致设计与实际结果相差甚大；且仅替换有源材料进行低噪声设计是片面的，不能获得高性能低噪声矢量传感器。鉴于此，本项目通过深入研究融变效应在矢量传感器设计中产生影响的机理这一科学问题，提出不同于压电陶瓷的、弛豫铁电单晶特有的矢量传感器设计新理论；进一步建立包含各单元及其噪声耦合特性影响在内的矢量传感器最小系统自噪声分析理论，以低噪声为目标，研究各单元参数的多目标约束优化方法。拟建立一套完整的、基于融变效应的弛豫铁电单晶矢量传感器自噪声理论分析及低噪声优化设计方法，为突破低噪声技术瓶颈奠定坚实的理论基础，这对推进矢量声呐技术快速发展具有重要科学价值及研究意义。

本项目首次定义了弛豫铁电单晶与结构粘接后产生的融变效应，并对其行为机制理论上做出了解释，为不同于PZT的、弛豫铁电单晶特有的矢量传感器设计奠定了理论基础；建立了弛豫铁电单晶矢量传感器最小系统的自噪声理论分析模型，确立了影响低频段自噪声的主要因素为耦合噪声，为低频低噪声矢量传感器设计提供了理论依据；提出了基于梯度算法的多目标优化方法，验证了压电加速度计的灵敏度和谐振频率双指标提升效果，为传感器多目标参量优化问题提供了技术途径；试制了弛豫铁电单晶低频低噪声矢量传感器，经过第三方测试，等效噪声声压级在20Hz频段以上均低于Knudsen零级海况海洋环境噪声，分别达到了42.4dB@200Hz、53.0dB@63Hz（0dB=1μPa/√Hz），体现了良好的低频低噪声特性。