提高无源声表面波扭矩敏感单元温度稳定性和传感系统响应速度的关键理论和技术研究

Due to the fact that the temperature characteristics of the surface acoustic wave (SAW) sensing element is unstable and the interrogation cycle is long, the performance of existing SAW dynamic torque sensor is poor and the sensing system can’t be used to measure the dynamic torque under different temperature fields. With the accumulated research experience during the SAW torque sensor study, the temperature stability of SAW sensor is improved and the technical problems of SAW resonant (SAWR) frequency fast scanning and multi-SAWRs interrogation, which have a great impact on the response of SAW torque sensor, are mostly solved. The laminated composite structure of ZnO/electrode/quartz was adopted. The theoretical model of torque sensing was established according to the Green function, FEM and perturbation theory. The impact of the structure parameters of the composite on the temperature and torque sensitivity was analyzed. The effect of temperature self-compensation was realized via optimizing the structure parameters. By analyzing the SAWR response, the relationship between the SAW energy entropy and the quality factor of SAWR was constructed and the response of the SAWR to an exciting signal was derived. A SAWR response detection method was proposed and a fast searching algorithm was designed. Based on the multi-frequency composite exciting technique, the technology solution of multi-resonators synchronous exciting and the corresponding analysis algorithm were studied. The reliability of the system was improved by doing all above. The SAW torque sensing prototype was developed with a uncertainty of 1%FS (k=2, temperature varying in the range: -20℃～85℃) and a response speed 100Hz which meets most of the requirements of the torque measurement.

针对目前声表面波(SAW)扭矩传感系统中因敏感单元温度特性和阅读器工作方式导致的测试精度低、动态特性差的现实问题，结合申请者前期研究基础，本项目着力研究提高扭矩敏感单元温度稳定性和系统响应速度的关键理论和方法。拟采用ZnO/电极/石英层状结构，通过格林函数、摄动理论和有限元仿真建立层状结构的扭矩敏感理论模型，分析多层结构参数对温度、扭矩敏感特性的影响，优化设计结构参数实现温度敏感的自补偿；从SAW谐振器响应信号着手，建立信号熵能量与谐振器Q值之间的函数关系模型，揭示响应信号随激励信号的变化规律，为SAW有效激励检测算法和快速查询算法设计提供理论基础和技术路线；研究基于多频复合激励技术的多谐振器同步阅读技术方案和分析算法，以适应差分式SAW扭矩传感器的快速解调。基于上述技术使设计的传感系统测量不确定度优于1%FS(k=2，温度范围-20℃～85℃)，响应速度达到100Hz，满足扭矩测量要求。

针对目前声表面波(SAW)扭矩传感系统中存在的温度稳定性和解调速度问题，本项目通过理论分析、数学建模和实验验证等手段研究了提高扭矩敏感单元温度稳定性和系统响应速度的关键理论和方法。基于传递矩阵方法，推导了多层介质板的广义格林函数；结合有限元、边界元理论与多层结构传播特性理论推导了复合结构SAW谐振器仿真方法，并通过仿真实验得到了ZNO/SiO2等复合层声表面波单端对谐振器的有效介电常数曲线、色散曲线、频率温度和扭矩响应曲线。分析了不同材料膜厚对温度、扭矩敏感特性的影响，优化设计了结构参数实现温度敏感的自补偿。分析了SAWR回波信号的包络特征；建立了SAWR回波信号的熵能量模型，并以回波信号的包络特征和熵能量作为两种特征参数，用作SAW回波信号聚类样本空间，利用K-Means聚类算法设计了SAW回波信号的识别算法。仿真与实验结果表明，当信号信噪比大于4dB时，该算法可以正确检测出85%以上的回波信号，对正弦干扰信号的误检率小于8%，实验结果表明所设计的方法能很好的区分SAW回波信号和干扰信号，有利于减少对无效信号的处理时间。基于软件无线电技术研究基于多频复合激励技术的多谐振器同步阅读技术方案和分析算法，利用软件无线电数字频率控制技术实现了多频复合信号的激发。设计了差分结构SAW谐振器的快速查询算法，以保证构成差分结构的两个SAW谐振器回波同时接收，减少传统解调方法中前后顺序接收而引入的测量误差；基于质心法设计了SAW回波信号快速解调方法，该算法在保证解调精度的前提下极大降低了对回波信号采样点数的要求，加快了解调速度。基于上述技术设计制作了SAW扭矩传感系统样机，并对试验样机进行了测试，实验结果显示设计的谐振器Q值大于7000，传感系统测量不确定度为0.68%FS(k=2，温度范围-20℃～85℃)，响应速度达到112Hz，满足扭矩测量要求。