【作者】 毕鲲；

【导师】 耿涛；

【作者基本信息】 哈尔滨工程大学 ， 光学工程， 2008， 硕士

【摘要】 激光多普勒测速系统以其非接触测量、线性特性、较高分辨率和快速动态响应等技术优势,被广泛应用于科研和工业领域。但多普勒信号具有噪声干扰大、频率变化范围大、信号不连续等特点,对它的分析处理直接关系到整个激光多普勒测速系统性能的好坏,因而有效去除噪声,提高测量精度成为激光多普勒测速方面不可忽视的问题。本文针对多普勒信号的特性,引入相应的信号处理方法。首先为降低噪声干扰的影响,引入了自适应滤波算法,在最小均方LMS算法的基础上,提出一种新的变步长LMS算法,该算法使用的变步长因子,兼顾了测量噪声方差和误差信号的具体变化过程,而且求变步长因子时计算量较小,使该算法具有更好的收敛性能和滤波效果。其次针对激光多普勒信号是一种密集型频谱的特性,研究了一种能根据频带带宽自适应地选择细化倍数的重采样算法,改进了传统的复调制Zoom-FFT算法,该算法对感兴趣的任意频带自适应地选择细化倍数,然后通过频谱校正算法进一步逼近真实频率,较好地解决制约传统复调制细化分析的计算速度问题,达到提高频率分辨率,快速细化的目的。通过仿真试验,精确地测得多普勒频率,验证了上述算法的高效性及鲁棒性。更多还原

【Abstract】 The Laser Doppler Velocimeter (LDV) is widely used in the science research and industry fields due to its many technological advantages, such as non-contact measurement, linearity, high resolution and rapid dynamic response, etc. But the Doppler signal possess the characteristics of heavy noise interference, broad frequency change and discontinuous signal, its analysis and processing affects directly whether the whole system is better or not. Thus, removing the noise effectively and improving the measurement accuracy become a significant question for the LDV system.A corresponding signal processing method is proposed in this paper according to the characteristics of Doppler signal. At first, in order to decrease the noise interference, a self-adapted filtering algorithm is introduced. On the basis of LMS algorithm, a novel LMS with varying step distance is presented. This vary step distance factor not only measures the detailed changing process of the noise variance and the error signal, but also needs relatively less computation, allows this improved algorithm to have better convergence property and filter effect. In addition, since the signal has a kind of dense spectrum, a re-sampled algorithm that can chose zooming multiple self-adapted according to frequency band is researched, is an improvement of traditional Zoom-FFT. For the frequency band of interest, after choosing the zooming multiple, is approached real frequency. This algorithm solves the problem of the traditional compound modulating that constrains the computing velocity, increases the high-frequency resolution and satisfies the demand of quickly zooming. Through the simulation, the frequency can be obtained accurately, and the high efficiency and robustness of proposed algorithm can be validated.更多还原