基于多重反馈自混合干涉的振动测量技术研究

发布时间：2018-10-04 20:41

【摘要】：当自混合干涉(SMI)发生在一个非准直激光器外腔时,反射光将在激光器和外部物体之间发生多次反射,然后再返回激光内腔与发出光耦合形成自混合干涉效应,这现象被称为多重反馈自混合干涉效应(MSMI)。与自混合干涉相比,它可以在不增加复杂算法和设备的前提下,成倍提高测量仪器的分辨率。这对于提高仪器的测量精度具有非常重要的意义。许多科研人员已经开展了多重反馈自混合干涉现象和产生机理的研究。然而,目前还缺少多重反馈自混合干涉振动测量技术和多重反馈次数的判定等相关问题的研究。本课题利用多重反馈自混合干涉的分辨率高,光路简单、能判别方向、自准直、结构紧凑、成本低等特点,开展多重反馈自混合干涉振动测量技术的研究,旨在解决自混合干涉振动测量中存在的测量误差大、实时性差、抗干扰能力弱、通用性不强等问题,力求提高振动测量准确性和通用性。本文主要研究对象是低频微纳米级的振动测量。在低频范围内,振动强度与位移成正比,所以本文通过振动位移表征振动强度和形变。本文的主要研究内容如下:首先,针对多重反馈自混合干涉振动测量时,缺少相应振动测量理论支持的问题,以自混合干涉三镜腔(F-P)模型理论为基础,建立了多重反馈自混合干涉通用的相位方程、功率方程和位移方程,并对测量分辨率进行了分析。为多重反馈自混合干涉振动测量技术研究奠定了理论基础,并通过实验方法研究外腔长和倾斜角度对多重反馈自混合干涉的影响。其次,针对相位解卷算法中跳变点检测阈值判断的问题,提出一种不需要判断阈值的改进跳变点检测算法。该算法利用干涉信号经过微分处理后,有效条纹趋势波动大,而无效条纹趋势波动小的特点,通过获取识别方波判别有效干涉条纹,根据有效干涉条纹确定峰谷值点位置,进而确定相位解卷算法中重构振动位移的关键参数,提高了干涉条纹检测的准确率,并把该算法应用于多重反馈自混合干涉的振动重构中。实验结果表明,多重反馈自混合干涉的重构误差比自混合干涉减少了38%。再次,针对基于相位解卷方法中需要对光反馈因子和线性展宽因子进行联合估计的问题,提出基于功率谱分析的多重反馈自混合干涉振动快速解调算法。该算法利用多重反馈自混合干涉信号功率谱中的极大值与第一类贝塞尔函数极大值对应的特点,建立功率谱极大值与外部物体振幅的对应关系及功率谱主频的判断规则,进而能快速计算出外部物体振动频率和振幅。该方法不需对光反馈因子和线性展宽因子进行联合估计,在获取外部物体振动频率及幅度的过程中只提取干涉信号功率谱的基频及主频所对应的频率,其他干扰信息均被屏蔽,提高了算法的抗干扰能力和解调速度。实验结果表明,当外部物体振幅小于5μm时,振幅解调的最大误差是75nm,比自混合干涉的降低了53%。同时,本章提出了多重反馈自混合干涉反馈次数的判定规则,解决了多重反馈自混合干涉反馈次数无法区分的问题,并通过实验进行了验证。然后,针对多重反馈自混合干涉振动位移重构误差大,无法进行高精度测量的问题,提出正弦相位调制的振动位移重构方法,该方法用电光相位调制器(EOM)对干涉信号进行正弦相位调制,建立调制信号频谱的一次谐波和二次谐波与第一类贝塞尔函数第一阶和第二阶的对应关系,提取频谱的一次谐波和二次谐波进行实时相位计算,根据实时相位重构外部物体的振动位移。实验结果表明,对于振幅小于5μm的低频振动,重构误差小于5nm。因为重构振动位移时只用到了调制信号频谱一次、二次谐波,其它成分均被屏蔽,所以该方法具有很好的抗干扰性能。最后,为了验证基于正弦相位调制的多重反馈自混合干涉振动测量技术的性能,从不同振幅、不同频率两方面与多普勒测振仪(LDV)进行对比。实验结果表明,该技术重构的速度在不同振幅、不同频率两方面与LDV有较好的一致性。将多重反馈自混合干涉用于管道泄漏检测上,提出了管道泄漏检测单点定位方法。在管道的一端同一检测点安装两个多重反馈自混合干涉传感器,一个用于测量管道横向振动,另一个用于测量管道纵向振动,利用管道壁内横波和纵波传播速度不同,通过二者的时间差测量泄漏点到检测点的距离,同时利用干涉条纹倾斜方向来判断声源方向。实验结果表明,所设计的单点泄漏定位传感器能在管道一端正确测量泄漏位置,定位误差小于5%。
[Abstract]:When a self-mixing interference (smi) occurs in an outer cavity of a non-collimated laser, the reflected light will be reflected multiple times between the laser and the external object and then return to the laser cavity to form a self-mixing interference effect with the emitted light, This phenomenon is referred to as multiple feedback self-mixing interference effect (MSMI). Compared with the self-mixing interference, it can multiply the resolution of the measuring instrument under the premise of not adding complex algorithm and equipment. This is of great importance to improve the measuring accuracy of the instrument. Many researchers have conducted multiple feedback self-mixing interference phenomena and mechanism research. However, there is a lack of research on the related problems of multi-feedback self-mixing interference vibration measurement technology and multiple feedback times. This paper makes use of the characteristics of high resolution, simple optical path, direction, self-collimation, compact structure and low cost of multiple feedback self-mixing interference, and carries out the research on multi-feedback self-mixing interference vibration measurement technology. aiming at solving the problems of large measurement error, poor real-time performance, weak anti-interference capability, strong universality and the like existing in the self-mixing interference vibration measurement, and aims to improve the accuracy and the universality of vibration measurement. The main research object is the low-frequency micro-scale vibration measurement. In the low frequency range, the vibration intensity is proportional to the displacement, so the vibration intensity and deformation are characterized by vibration displacement. The main contents of this paper are as follows: Firstly, based on the theory of hybrid interference three-mirror cavity (F-P) model, a general phase equation of multiple feedback self-mixing interference is established based on the theory of hybrid interference three-mirror cavity (F-P) model. The power equation and displacement equation are analyzed and the measurement resolution is analyzed. This paper establishes a theoretical basis for multi-feedback self-mixing interference vibration measurement technology, and studies the influence of external cavity length and tilt angle on multi-feedback self-mixing interference through experimental methods. Secondly, an improved hop-point detection algorithm which does not need to judge the threshold is proposed for the problem of threshold judgment of the jump point detection in the phase deconvolution algorithm. According to the algorithm, after the interference signal is subjected to differential processing, the effective fringe trend fluctuation is large, and the characteristic that the fluctuation of the invalid stripe trend is small, the peak valley value point position is determined according to the effective interference fringe by acquiring the identification square wave judging effective interference fringe, Furthermore, the key parameters of the reconstruction vibration displacement in the phase deconvolution algorithm are determined, the accuracy of the interference fringe detection is improved, and the algorithm is applied to the vibration reconstruction of multiple feedback self-mixing interference. The experimental results show that the reconstruction error of multiple feedback self-mixing interference is reduced by 38% compared with the self-mixing interference. Thirdly, a multi-feedback self-mixing interference vibration fast demodulation algorithm based on power spectrum analysis is proposed for the problem of combining the optical feedback factor and the linear broadening factor in the phase-based deconvolution method. The algorithm uses the characteristic of the maximum value in the power spectrum of the multi-feedback self-mixing interference signal and the maximum value of the first class Bezier function to establish a judgment rule of the corresponding relation between the power spectrum maximum value and the amplitude of the external object and the dominant frequency of the power spectrum, in addition, that vibration frequency and the amplitude of the external object can be rapidly calculated. The method does not need to jointly estimate the optical feedback factor and the linear broadening factor, extracts only the frequency corresponding to the fundamental frequency and the dominant frequency of the interference signal power spectrum in the process of acquiring the vibration frequency and amplitude of the external object, and the other interference information is shielded, and the anti-jamming capability and the demodulation speed of the algorithm are improved. The experimental results show that when the amplitude of external object is less than 5. m, the maximum error of amplitude demodulation is 75nm, which is 53% lower than that of self-mixing interference. At the same time, this chapter puts forward the decision rule of multiple feedback self-mixing interference feedback times, solves the problem that multiple feedback self-mixing interference feedback times cannot be distinguished, and verifies by experiment. then, aiming at the problem that the multi-feedback self-mixing interference vibration displacement reconstruction error is large and the high-precision measurement cannot be carried out, a sinusoidal phase modulation vibration displacement reconstruction method is proposed, and the method uses an electro-optical phase modulator (EOM) to carry out sine phase modulation on the interference signal, establishing a corresponding relation between the primary harmonic and the second harmonic of the frequency spectrum of the modulated signal and the first order and the second order of the first class of bezier functions, extracting the primary harmonic and the second harmonic of the frequency spectrum for real-time phase calculation, and reconstructing the vibration displacement of the external object according to the real-time phase. The experimental results show that the reconstruction error is less than 5nm for low frequency vibration with amplitude less than 5. m the method has good anti-interference performance because only one time, the second harmonic and the other components of the modulation signal are shielded when the vibration displacement is reconstructed. Finally, in order to verify the performance of multi-feedback self-mixing interference vibration measurement technology based on sinusoidal phase modulation, it is compared with the Doppler vibrometer (LDV) from different amplitudes and different frequencies. The experimental results show that the speed of the technique is consistent with LDV at different amplitudes and different frequencies. Multi-feedback self-mixing interference is used for pipeline leakage detection, and a single point positioning method for pipeline leakage detection is proposed. two multiple feedback self-mixing interference sensors are arranged at the same detection point at one end of the pipeline, one is used for measuring the transverse vibration of the pipeline, the other is used for measuring the longitudinal vibration of the pipeline, and the transverse wave and the longitudinal wave propagation speed in the pipeline wall are different, the distance between the leakage point and the detection point is measured by the time difference of the two, and the direction of the sound source is judged by the oblique direction of the interference fringe. The experimental results show that the designed single-point leak positioning sensor can measure the leakage position correctly at one end of the pipeline, and the positioning error is less than 5%.
【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TH744.5

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