| Length is one of the seven basic physical quantities stipulated by the General Conference of Weights & Measures.The length can be used to synthesize information such as topography and coordinates,and play a key role in the fields of aerospace,equipment manufacturing,and micro-nano detection.As a powerful length measurement tool,laser has been widely used in precision measurement.In recent years,the femtosecond laser frequency comb ranging technology has attracted widespread attention due to its large range,high accuracy,and online traceability.At present,the research is still in the stage of principle verification,and mainly focuses on static target measurement.A few absolute distance measurements for dynamic targets are also limited to the measurement of larger motion amplitudes and simple motion states.At the same time,scenarios such as satellite formation measurement and industrial vibration monitoring put forward requirements for precise measurement of dynamic targets,especially small amplitude motions and micro vibrations.In this thesis,researches based on the free-running dual-comb absolute distance measurement technology are carried out.Firstly,Singular Spectrum Analysis(SSA)is applied to femtosecond laser absolute distance measurement since the insensitivity to the motion model of SSA.The measurements from distance measurement system are decomposed by SSA and classified as trend,oscillation or noise according their characteristics.Therefore,motion can be separated from noise,and implement measurement precision improvement.Secondly,as the estimation accuracy of traditional adaptive filtering is limited by the accurate acquisition of prior information,SSA is used to improve the adaptive filter,which eliminates the dependence of adaptive filtering on prior information.The first algorithm uses the reconstructed signal obtained by SSA as the expected response of the Wiener filter to construct an improved Wiener filter.The second algorithm is based on Kalman filter,using SSA to decompose the input noise signal to obtain the motion trajectory instead of Kalman filter’s equation of state to predict the position of the dynamic target.Finally,in accordance with the requirements of the 863 project "High-precision real-time measurement and control technology for formation satellite systems",a real-time absolute distance measurement system based on FPGA technology and a miniaturized positioning camera based on photogrammetry technology are designed.Three-dimensional position information can be measured precisely by the design. |
