| With the rapid development of modern engineering and technology, especially in the area of aviation, spaceflight and manufacture, it is necessary to measure the speed with high accuracy. In the navigation system, the existing speed measuring methods (accelerometer, global positioning system and so on) have the disadvantages of error accumulation and slow dynamic response. As a result, they cannot meet the requirement of the development of the navigation system any more. Laser Doppler technique has many advantages such as high accuracy, good spatial resolution, rapid dynamic response, large measuring range, and non-contact, so it represents the developing direction of speed measurement. This dissertation starts from the practical application, does some theoretical and experimental studies in terms of laser Doppler measurement, signal detecting, processing and analysis to broaden the application areas of this technology.The dissertation points out the defects of the existing speed measuring methods in the navigation system and compares and analyzes the characteristics of several ordinary optical and noncontact speed measurement methods. As a result, the idea of using laser Doppler velocimeter (LDV) to offer velocity for the vehicle navigation system is proposed. The feasibility of measuring the speed of certain solid surface using LDV is discussed after reviewing the development history and current status of the laser Doppler technology.The Doppler effects with different relative motion between a source and a detector are analyzed systematically and the measurement principle for vehicle's velocity is expatiated. The superiority of optical heterodyne method for detecting the Doppler frequency is demonstrated based on the comparison of the features and the conditions between using direct light spectrum and optical heterodyne technique.The advantages and disadvantages of three optical model: dual-beam, reference beam and self-mixing, are discussed and analyzed. 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 and a multipoint layer-type LDV is designed. In order to reduce the effects of sway and toss of a vehicle on the measurement accuracy, Janus configuration used in millimeter wave and acoustic wave logs is proposed for reference beam model and reference beam LDV based on Janus configuration is designed. Especially, acousto-optic modulator is used for two kinds of LDVs to realize the direction discrimination and low speed measurement.The essence of laser Doppler signal, produced by the motion of solid surface that is superposed between two relevant speckle fields, is explained according to the order of the speckle field intensity variation. The expression of the solid-state scattering signal intensity of the laser Doppler is derived based on the speckle theory combined with the stochastic process. In addition, the relationship among light spot size on objects to be measured, the signal intensity and the signal-to-noise ratio is analyzed.A mathematic model of LDV, which is based on a theoretical model of fringes and the principle of light scattering, is developed for solid-state surface for analyzing the formation of the Doppler signal. The relationship among the characteristics of the solid-state surface, the signal intensity and the measurement accuracy is given by numerical simulations. By studying the distribution of the optical field, the expression and simulation results of heterodyne efficiency are given on the conditions of both exact match and mismatch. The results are of great importance to the design of the optical structure and the optimization of the optical parameters of the measurement system.A tracking filter is designed using frequency feedback technique to track the Doppler signal and to eliminate the noises of 50Hz, Gaussian basement, and other frequency interference (for example acousto-optic modulator) based on the characteristics of the Doppler signal. In order to extract Doppler frequency more exactly from the weak signal, the digital correlation technique is used to suppress the noise after filtering so that the signal-to-noise ratio is improved greatly.A high precision signal processing technology is introduced into LDV owing to the shortages of the real-time fast Fourier transform (FFT) algorithm such as limited data and low measurement precision. Firstly, using FFT algorithm to obtain the frequency spectrum of the Doppler signal and searching its peak value frequency; secondly, making zooming analysis using Goertzel algorithm; finally, using ratio correction algorithm to obtain a precise Doppler frequency. This technology combines three kinds of algorithms and makes good use of their advantages. The simulation results show that the precision of the frequency estimation is better than 0.004%. Moreover, a new method which combines frequency domain threshold and acceleration threshold is put forward to distinguish whether the Doppler signal is valid or not. The lost velocity information is compensated by the method of least square polynomial fitting.Measurement error of the LDV is analyzed systematically and methods to reduce the error in various situations are put forward. In order to clarify the potential of improving the measurement accuracy, the estimation of parameters and their Cramer-Rao Lower Bounds (CRLBs) of the Doppler signal with Gaussian envelope are investigated based on the introduction of the acceleration.Experimental systems of the LDV are built to do some research on speed measurement of solid-state surface. Firstly, a differential laser Doppler system is set up for measuring the tangential velocity of a certain point on the chopper. The mean relative accuracy of the laser Doppler system is 0.47% compared with the optics counting method. Secondly, a reference beam laser Doppler system is built to measure the rotating speed of a rotary table and the relative measurement accuracy is better than 0.35%. Finally, a multipoint layer-type LDV and a LDV based on Janus configuration are designed respectively for measuring the speed of a pushcart, which verified the feasibility of using LDV for the vehicle self-contained navigation systems.
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