用于车载自主导航系统激光多普勒测速仪关键技术研究

In the vehicle navigation system, the native defects of the traditional speedometer affect the measurement accuracy. In the project, Laser Doppler technology for the vehicle self-contained navigation system is deep researched based on the optical Doppler effect. For one thing, multipoint layer technique is put forward for dual-beam model to solve the problem that it can not work in the status of out of focus, for another, the technique of beam splitting and reuse is proposed for the classical reference beam model to improve the efficiency for laser energy utilization. And two types of laser Doppler velocimeter (LDV) with different structure are designed using the above two kinds of technique. Then, some frequency domain technology such as fast Fourier transform, frequency spectrum refinement and frequency spectrum correction are also used to enhance the extracting accuracy of Doppler frequency. Measurement error of the LDV and methods to reduce the error in various situations are put forward. In order to determine the measurement accuracy degree, the estimation of parameters and their Cramer-Rao Lower Bounds (CRLBs) of the Doppler signal are investigated. The aim of the project is developing a new laser velocimeter with high measurement accuracy, large measuring range, rapid dynamic response, and good repeatability to offer the guarantee for the vehicle self-contained navigation system based on analyzing the physical mechanism of the new structure and relative engineering technology.

车载导航系统中传统测速方式的固有缺点严重影响导航精度，该项目基于光学多普勒效应深入研究可用于车载自主导航的激光多普勒测速技术，提出多点分层技术解决传统双光束差动系统不能进行离焦测量的难题，另外将分光再利用技术用于参考光结构增大光能利用率，并基于上述两种技术分别设计两种不同结构的激光多普勒测速系统；采用快速傅里叶变换、频谱细化和频谱校正相结合的技术提高多普勒频率的提取精度；分析系统实时测量的误差并针对各种误差提出控制措施；为了判断测量准确度，研究激光多普勒测速参数估计的克莱姆－拉奥下限。项目旨在通过对新型结构物理机制和相关工程技术的分析，研制出精度高、测速范围广、动态响应快和重复性好的激光测速系统，论证新型结构的可行性，为车载自主导航系统的发展提供有力保障。

在导航系统中，已有的测速方式(加速度、全球定位系统等)存在误差累积、动态响应能力差等缺点，已经不能满足导航日益发展的要求。激光多普勒测速具有精度高、空间分辨率好、动态响应快、测量范围大、非接触测量等特点，已成为当今速度测试技术的重要发展方向。本项目对可用于车载自主导航激光多普勒测速仪的关键技术进行了深入研究。首先，基于条纹模型对双光束系统控制体的体积进行理论计算及仿真模拟，选择了合适的光学参数并合理布置多个光学探头，利用多点分层技术设计多点分层差动激光多普勒测速系统；为了提高光能利用率，增强多普勒信号，利用分光再利用技术对典型参考光结构进行改进并设计了新型参考光结构的激光多普勒测速系统；其次，分析了车载激光多普勒测速系统实时测量的各种误差因素，着重研究了固态表面的运动散斑、大加速度等引起的多普勒增宽而带来的测量误差，并针对各种因素提出相应的误差控制措施；为了给车载自主导航系统提供三维的速度参数，结合多点分层差动技术和分光再利用参考光技术设计了三维激光多普勒测速系统；考虑到加速度会引起多普勒信号频谱的增宽，为了给系统的参数估计提供准确的评价标准，在引入加速度分量的基础上，根据数理统计的理论，利用费希尔信息矩阵深入研究了高斯包络型多普勒信号参数估计方差的 CRLB。最后，在研究分析激光测速光路结构、信号处理方案、误差项及控制措施的基础上，研制出了车载激光多普勒测速仪工程样机。为评价所研制激光测速仪的性能，进行了实验室内的高精度转台实验。实验结果表明：所研制激光测速仪测量精度优于0.08%；测量线性度优于0.082%。进行了普通柏油路、泥泞草地、大石子路上等不同路况下的车载速度测量实验以及与惯性测量单元的组合导航实验，得到了较好的结果。