Laser interference normal / angular vibration synchronous measurement device and decoupling method

Abstract

The invention discloses a laser interference normal / angular vibration synchronous measurement device and a decoupling method, and belongs to the field of laser interference measurement. The linear / angular vibration synchronous measurement device comprises an optical system, a precise adjustment support, a controller, a data acquisition system, linear / angular vibration comprehensive calibration software and an integrated connection cable. And the optical system is used for emitting three beams of measuring light, focusing the three beams of measuring light on the surface of the vibrator, receiving light energy returned from the surface of the vibrator and converting the light energy into photoelectric signals. And the precise adjusting bracket is used for precisely adjusting the measurement attitude of the optical system. And the linear / angular vibration upper computer is used for decoupling the acquired signals, respectively acquiring linear vibration and angular vibration parameters, realizing real-time tracking display of a time-frequency domain curve, and automatically fitting and quickly displaying a space operation vector trajectory of a moving target. According to the invention, a three-beam symmetric differential Mach-Zehnder heterodyne interference method is adopted, linear vibration and angular vibration parameters of a measured target can be synchronously obtained, and comprehensive calibration of a calibrated sensor is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of laser interference measurement, and relates to a laser interference normal / angular vibration synchronous measurement device and a decoupling method. Background Art

[0002] Patents CN221649712U and CN105547454.A mainly focus on improving the measurement accuracy and measurement range of linear vibration by improving the optical path design and signal processing algorithm. Although the patents have achieved certain results in linear vibration measurement, they do not involve the measurement of angular vibration.

[0003] Patent CN200610152126.6 mainly focuses on the measurement and analysis of the angular vibration of the rotating table. By collimating the laser incident on the grating and using the laser Doppler principle, the angular vibration of the rotor is demodulated.

[0004] This limitation is particularly prominent in aerospace, precision machinery, earthquake monitoring and other fields, because these fields often require synchronous analysis of linear vibration and angular vibration in complex vibration environments to accurately evaluate the dynamic performance of the system. Summary of the invention

[0005] The purpose of the present invention is to provide a laser interference normal / angular vibration synchronous measurement device and decoupling method, which adopts a three-beam symmetrical differential Mach-Zehnder heterodyne interference method to synchronously obtain the linear vibration and angular vibration parameters of the measured target and realize comprehensive calibration of the calibrated sensor.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] The invention discloses a laser interferometer normal / angular vibration synchronous measurement device, comprising an optical system, a precision adjustment bracket, a controller, a data acquisition system, a linear / angular vibration comprehensive calibration software installed on a host computer, and an integrated connection cable;

[0008] The optical system is used to emit three beams of measuring light and focus them on the surface of the oscillator, and at the same time receive the light energy reflected from the surface of the oscillator and convert it into a photoelectric signal.

[0009] The precision adjustment bracket is used to accurately adjust the measurement posture of the optical system so that the incident light is accurately aimed at the surface of the cylindrical grating to be measured.

[0010] The controller is used to control the power supply of the optical system, the drive of the acousto-optic modulator, and the preprocessing of the original photoelectric signal, and transmit the preprocessed three-way original photoelectric signal and the acousto-optic modulator drive signal to the data acquisition system in the form of analog signals.

[0011] The data acquisition system is used to collect the signals output by the controller.

[0012] Linear / angular vibration host computer is used to decouple the collected signals and obtain the linear vibration and angular vibration parameters respectively, realize the real-time tracking and display of time-frequency domain curves, and automatically fit and quickly display the spatial operation vector trajectory of the moving target;

[0013] The integrated connecting cable is used for power supply and signal transmission between the optical system and the controller. The signal transmission includes the transmission of high-frequency signals, low-frequency signals, DC signals and control signals. The cable shielding structure is used to isolate the crosstalk between the signals.

[0014] The optical system emits three beams of measurement light and focuses them on the surface of the vibrator. At the same time, it receives the light energy reflected from the surface of the vibrator, converts it into a photoelectric signal and transmits it to the controller. The controller is used to control the power supply of the optical system, the drive of the acousto-optic modulator, and the preprocessing of the original photoelectric signal. The preprocessed three-way original photoelectric signal and the acousto-optic modulator drive signal (reference signal) are transmitted to the data acquisition system in the form of analog signals (BNC cable). The linear / angular vibration comprehensive calibration software installed on the host computer is used to realize the decoupling and separate acquisition of linear vibration and angular vibration parameters, that is, to realize the real-time tracking and display of the time-frequency domain curves of linear vibration and angular vibration parameters. At the same time, it further automatically fits and quickly displays the spatial running vector trajectory of the moving target. The data acquisition system also synchronously collects the output of the calibrated sensor, takes the measurement result of the optical system as the reference value, and realizes the linear / angular vibration comprehensive calibration of the calibrated sensor by comparing it with the linear / angular vibration value obtained by the optical system, that is, to realize the separate calibration of the linear vibration value and the angular vibration value simultaneously, and then realizes the calibration of the comprehensive running trajectory.

[0015] The optical system adopts a single helium-neon laser as a light source; the laser light emitted by the laser is collimated by a collimating lens group and a λ / 2 wave plate, and then is divided into three beams by a beam splitter prism: one beam is used as a linear vibration measurement beam-center, which is directly incident on a spherical cat's eye reflector located at the center of the angular vibration worktable; the other two beams are used as an angular vibration measurement beam-left and an angular vibration measurement beam-right, which are respectively incident on the lateral cylindrical surface of the angular vibration worktable from symmetrical positions on both sides, and the cylindrical surface is processed with a cylindrical grating; by controlling the incident angle of the measurement beam-center, the first-order diffracted light is overlapped with the incident beam, so as to realize the precise alignment of the measurement beam-center; the measurement beam-center is reflected back in the original direction through the spherical cat's eye reflector, passes through the wave plate, and is reflected by the beam splitter prism, and the reference light is reflected by the right side of the beam splitter prism, transmitted by the beam splitter prism, and then passed through the straight The light from the angle reflection prism, the two beams converge and interfere at the beam splitter prism, and after passing through the wave plate, are received by the photodetector; the measuring beam carries an acousto-optic modulator to apply a carrier, so as to form a heterodyne interference signal of the carrier after interference; the left angular vibration measurement light is incident on the cylindrical grating surface of the lateral cylinder, and by controlling its incident angle to be 1 / 2 of the initial diffraction angle, the first-order diffraction light coincides with the incident beam, that is, it returns in the original direction, and converges and interferes with the light reflected by the beam splitter prism, the beam splitter prism and the right-angle reflection prism at the beam splitter prism, and is finally received by the photodetector to obtain the original photoelectric signal and output it; similarly, the right angular vibration measurement light converges and interferes with the light reflected by the beam splitter prism, the beam splitter prism and the right-angle reflection prism at the beam splitter prism, and is finally received by the photodetector to obtain the original photoelectric signal and output it.

[0016] The controller comprises an optical head power supply module, an acousto-optic modulator driving module, a photoelectric signal energy display module, a signal preprocessing module and a function expansion module.

[0017] The optical head power supply module provides power drive for the optical devices and electronic devices in the optical head and controller.

[0018] The AOM driver module provides a high-power drive signal for the AOM in the optical head and outputs a synchronous reference signal to the data acquisition system.

[0019] The photoelectric signal energy display module, based on the logarithmic amplifier detection function, obtains and displays the current photoelectric signal amplitude in real time.

[0020] The signal preprocessing module includes functions such as adaptive amplitude modulation of the photoelectric signal, adjustable signal gain and phase-locked amplification, which are used to improve the signal quality and the accuracy of the demodulation process.

[0021] Function expansion module: reserve a position for installing the function expansion module.

[0022] The invention discloses a laser interferometer normal line / angular vibration synchronous measurement and decoupling method, which is implemented based on the laser interferometer normal line / angular vibration synchronous measurement device. The invention discloses a laser interferometer normal line / angular vibration synchronous measurement and decoupling method, which comprises the following steps:

[0023] Step 1: Decouple the normal / angular vibration. The laser measurement system emits three beams of measurement light, which are defined as measurement beam-left, measurement beam-center, and measurement beam-right. The measurement beam-center is directly incident on the spherical cat's eye reflector located at the center of rotation. The measurement beam-left and measurement beam-right are incident on the lateral cylinder of the angular vibration worktable from symmetrical positions on both sides. By controlling the incident angle of the measurement beam, the first-order diffracted light is made to coincide with the incident beam.

[0024] For the measurement of linear vibration, since there is only linear vibration but no angular vibration at the center of the angular vibration table, the measurement beam directly measures the center position of the table. The measurement target mirror uses a spherical cat's eye reflector to avoid the measurement beam deflection caused by the table rotation and large amplitude vibration process, and keep the direction of the reflected beam stable during the angular vibration process, thereby ensuring the quality of the measurement signal. Linear vibration measurement is based on the same principle as traditional heterodyne laser vibrometer, and the target speed is measured through the proportional relationship between the Doppler frequency shift and the measured speed.

[0025] For the measurement of angular vibration, during the vibration process, the measurement beam-left measurement point is the linear vibration velocity ν(t) and the angular vibration velocity v 左 (t), in order to achieve the decoupling of the angular vibration value, the measurement beam -left and the reflected light in the measurement beam -are interfered (i.e., subtracted) to obtain the photoelectric signal -left, and the interference is subtraction. Since the reflected light of the measurement beam -left contains the linear vibration velocity ν(t) and the angular vibration velocity v 左 (t), the reflected light in the measuring beam - contains only the linear vibration velocity ν(t) information, so the photoelectric signal - obtained after the interference beat frequency between the two contains only v 左 (t) information, that is, to achieve the decoupling of angular vibration and linear vibration.

[0026] Similarly, it is also possible to achieve ν 右 (t) acquisition, v 左 (t) and ν 右 (t) are the two linear velocity values ​​at the symmetrical positions of the table center, which should be equal when the radius is consistent. In order to improve the measurement accuracy of the angular vibration value, v 左 (t) and ν 右 (t) The final angular vibration measurement result is obtained by taking the average. The laser vibrometer measures the displacement change at the equivalent radius R of the rotation axis of the angular vibration worktable, which is the displacement amplitude.

[0027] According to the laser Doppler formula:

[0028] v 左 (t) = g × Δf 左 (t)

[0029]

[0030] Similarly, we get

[0031]

[0032] Where: v 左 (t) is the angular vibration velocity of the measuring beam-left measuring point, g is λ / 2, Δf 左 (t) is the Doppler frequency of the measurement beam-left measurement point, ω 左 (t) is the rotation speed of the measuring beam-left measuring point. ω 右 (t)Same.

[0033] The angular velocity value can be calculated by using the known grating constant and the radius of the table measuring point, as well as the Doppler frequency shift measured by the optical system.

[0034] For the same vibration table, the measuring points have the same radius and the angular velocity at any position on the surface is equal. In order to improve the accuracy of angular velocity measurement, the average angular velocity value is obtained by taking the average value of symmetrical measurement.

[0035]

[0036] Step 2: The decoupled linear / angular vibration laser interference signal is transmitted to the host computer. By demodulating the amplitude and phase of the signal output, the displacement, velocity or acceleration peak value can be analyzed. The sinusoidal approximation demodulation method is used to analyze the displacement, velocity or acceleration peak value. The two photoelectric signals are A / D converted, and the two continuous signals are converted into two discrete sequences u1(t i ) and u2(t i ). Divide the two signals and then perform an inverse tangent operation on the quotient to obtain the sequence

[0037]

[0038] Where:

[0039]

[0040] Since the inverse tangent function is a multi-valued and discontinuous function, in order to obtain a certain value, a phase expansion algorithm is used to process it so that the obtained phase value is continuous. After phase expansion and appropriate calculation, a discrete sequence of continuous phase values ​​can be obtained.

[0041]

[0042] Where: k i are the values ​​obtained through the phase expansion algorithm, ω is the angular velocity, φ0 is the initial phase, and l0 is a constant.

[0043] By calculating the discrete sequence, the waveform of the vibration signal to be measured can be reproduced, thereby obtaining the amplitude and initial phase. However, the obtained amplitude and phase are not accurate. In order to improve the measurement accuracy, The sine fitting algorithm is used for further processing. Written as follows:

[0044]

[0045] Where:

[0046] i=1, 2, ..., n;

[0047]

[0048] Through the data series Fitting with a sine function with a DC component and using the least squares method to calculate A, B, and C in the above formula, we know that the vibration displacement d and initial phase φ0 are as follows:

[0049]

[0050] The displacement data is differentiated once and twice to obtain the velocity and acceleration of the object being measured. The differential equation of the differentiator is:

[0051]

[0052] In the formula, u i (t) is the input signal of the differentiator; u o (t) is the output signal of the differentiator.

[0053] When the noise bandwidth is greater than the signal bandwidth, the signal-to-noise ratio after differentiation will deteriorate. Differentiation operations must take into account the impact of noise on the operation results. The data before processing requires limiting the signal and noise bandwidths, and low-pass filtering must be performed after processing.

[0054] Step 3: In the actual measurement process, factors such as stage jitter, large amplitude vibration guidance error, cat's eye reflector installation deviation and processing quality will inevitably cause the original photoelectric signal to have amplitude modulation related to the vibration phase. Although this phenomenon can be reduced through high-precision structural design, optical system optimization and photoelectric signal preprocessing circuit, it cannot be completely eliminated. In order to further improve the accuracy of the measurement system and reduce the uncertainty of the device, in the process of photoelectric signal demodulation, a correlation algorithm is used to perform adaptive optimization modulation on the non-stationary photoelectric signal to improve the signal-to-noise ratio of the original photoelectric signal. The specific implementation method is as follows:

[0055] The key problem of adaptive optimization modulation of non-stationary optoelectronic signals is the estimation accuracy of frequency and initial phase. Frequency and initial phase estimation methods are easily affected by low signal-to-noise ratio and poor signal quality, resulting in large errors. Therefore, it is necessary to optimize and improve the frequency and initial phase estimation methods.

[0056] In the improved method of frequency estimation, the autocorrelation detection method is used to reduce the signal-to-noise ratio. By assuming that there is no correlation between the signal and the noise, an autocorrelation function with the same frequency as the original signal is calculated, and then FFT frequency estimation is performed on the autocorrelation function.

[0057] In the improved method of initial phase estimation, the independence of signal and noise is utilized, and the cross-correlation function is combined with the least squares parameter estimation method. A group of parameter estimation equations is established when the sum of squares of errors between the estimated value and the true value is minimized. By solving the group of equations, a high-precision estimate of the phase is obtained.

[0058] The noisy Doppler signal is processed into a smooth Doppler signal. Common processing methods include low-pass filtering, neighborhood smoothing filtering, and wavelet filtering. Among the three methods, low-pass filtering causes the greatest distortion to the Doppler signal, and the filtering effect is worse than the other two methods, so it is not adopted. The processing effects of neighborhood smoothing filtering and wavelet filtering are equivalent, among which the advantage of wavelet filtering is that the distortion caused to the Doppler signal is minimal; the advantage of neighborhood smoothing filtering is that it can process Doppler signals modulated in any frequency band by flexibly changing the smoothing coefficient, while wavelet filtering needs to adjust its wavelet basis function, decomposition scale and threshold processing method according to different types of Doppler signals to achieve the best effect. Since the present invention is a real-time signal demodulation solution, in order to be more in line with the characteristics of real-time, the neighborhood smoothing filtering method is adopted for processing.

[0059] ①Autocorrelation detection frequency estimation method

[0060] The autocorrelation detection method utilizes the uncorrelated characteristics between signal and noise to perform autocorrelation analysis on the input signal in order to improve the signal-to-noise ratio.

[0061] The single-frequency real sinusoidal signal mixed with Gaussian white noise is

[0062]

[0063] Where z(n) is white noise.

[0064] By sampling the signal, N samples are obtained.

[0065]

[0066] The time-averaged correlation function is defined as

[0067]

[0068] Where τ is the delay.

[0069] Then the autocorrelation function R of the signal x(n) is xy (τ) is

[0070] R XX (τ) = R SS (τ)+R SZ (τ)+R ZS (τ)+R ZZ (τ)

[0071] Among them, R ss (τ) and R zz (τ) are the autocorrelation functions of the sinusoidal signal s(n) and white noise z(n), R sz (τ) and R zs (τ) are the cross-correlation functions of the sinusoidal signal s(n) and the noise z(n). The white noise z(n) is random and has no correlation with the sinusoidal signal s(n). Therefore, R sz (τ) and R zs The (τ) terms all approach zero.

[0072] The autocorrelation function of Gaussian white noise is expected to be 0 at all locations except the zero point, that is,

[0073] R ZZ (τ)=σ 2 δ(τ)

[0074] Where δ(τ) is the unit sampling signal.

[0075] When the sample value N is large enough, the autocorrelation function R of the sinusoidal signal s(n) SS (τ) is

[0076]

[0077] When N is large enough, the autocorrelation function of the sinusoidal signal is a sinusoidal signal with the same frequency as the sinusoidal signal. Autocorrelation preprocessing of the input signal can reduce noise, thereby improving the accuracy of the frequency estimation algorithm for sinusoidal signal frequency estimation.

[0078] ② Cross-correlation combined with least squares parameter estimation algorithm

[0079] Least squares estimation is essentially parameter estimation, that is, establishing a set of equations about parameters and solving the parameters by solving the set of equations.

[0080] The observed signal mixed with Gaussian white noise is

[0081]

[0082] Where s(n) is a real sinusoidal signal and z(n) is Gaussian white noise.

[0083] Φ is the parameter estimation value of the amplitude and phase of the sinusoidal signal, and the sum of square errors between the parameter estimation value and the true value are examined.

[0084]

[0085] When the signal-to-noise ratio is high, the least squares solution can be used to obtain the parameter estimate. However, when the signal-to-noise ratio is low, the accuracy of the parameter estimate obtained by using the least squares solution is not high, or even no parameter estimate can be obtained.

[0086] In order to establish the validity of the parameter estimation equations, it is necessary to remove the interference of the noise term. This paper uses the irrelevance between the signal s(n)=cos(ω0n) and the noise z(n) to reduce the noise interference, and adopts the method of cross-correlation combined with the minimum quadratic parameter estimation to establish the parameter estimation equations.

[0087] Known cross-correlation function

[0088]

[0089] z(n)=x(n)-[a1 cos(w0n)-a2 cos(w0t)]

[0090] The amplitude component

[0091] When the sum of squares of the error between the parameter estimate and the true value is minimized, according to the irrelevance between the signal s(n) = cos(ω0n) and the noise z(n), the above formula can be expressed as

[0092]

[0093] The following formula is established

[0094]

[0095] Expand to obtain the parameter estimation equation system

[0096]

[0097] Solve the equations to get a1, a2, and then get the estimated values ​​of the amplitude and initial phase

[0098]

[0099] The initial phase estimation result obtained is more reliable and stable than directly using the least squares estimation method, thereby realizing automatic acquisition of the initial phase of the reference signal and realizing real-time signal resolution of the photoelectric signal.

[0100] Beneficial effects:

[0101] 1. The present invention discloses a laser interference normal / angular vibration synchronous measurement device and decoupling method, which emits three beams of measurement light (respectively, measurement beam-left, measurement beam-middle, and measurement beam-right), wherein the measurement beam-middle is directly incident on the spherical cat's eye reflector located at the center of rotation, and the measurement beam-left and measurement beam-right are respectively incident on the lateral cylinder of the angular vibration worktable from symmetrical positions on both sides. By controlling the incident angle, the first-order diffracted light coincides with the incident beam and returns in the original direction, and merges and interferes with the light reflected by the dichroic prism, and the original photoelectric signal is received and output by the photoelectric detector. Since the three measurement channels are all based on the same laser light source and the same reference clock, the time synchronization of the linear vibration and angular vibration measurements can be guaranteed, thereby improving the accuracy of the laser interference normal / angular vibration synchronous measurement. Compared with the method of using two independent systems to obtain angular velocity and linear velocity respectively, the measurement device and method used in this patent can quickly, synchronously, and accurately obtain linear / angular velocity.

[0102] 2. The present invention discloses a laser interference normal / angular vibration synchronous measurement device and decoupling method, which subtracts the reflected light from the measuring beam -left from the measuring beam -to obtain the photoelectric signal -left. Since the reflected light from the measuring beam -left contains v 左 (t) and v(t), the reflected light in the measuring beam - contains only v(t) information, so the photoelectric signal - obtained after the interference beat frequency between the two contains only v 左 (t) information, that is, the decoupling of angular vibration and linear vibration is achieved. Similarly, v 右 (t) is obtained. 左 (t) and ν 右 (t) are the two linear velocities at the symmetrical positions of the table center, which are equal when the radius is the same. 左 (t) and ν右 (t) The final angular vibration measurement result is obtained by averaging, which improves the measurement accuracy of the angular vibration value. Through this method, the linear vibration and angular vibration can be decoupled, so that high-precision linear velocity and angular velocity can be obtained synchronously in subsequent signal processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0103] Figure 1 Laser interferometer normal / angular vibration comprehensive measurement system

[0104] Figure 2 is a schematic diagram of the optical system;

[0105] Among them, 1 is a helium-neon laser, 2 is a collimating lens group, 3-1 is a wave plate, 3-2 is a wave plate, 3-3 is a wave plate, 4-1 is a right-angle reflecting prism, 4-2 is a right-angle reflecting prism, 4-3 is a right-angle reflecting prism, 5-1 is a beam splitter, 5-3 is a beam splitter, 5-4 is a beam splitter, 5-5 is a beam splitter, 5-6 is a beam splitter, 5-7 is a beam splitter, 5-8 is a beam splitter, 6 is an acousto-optic modulator, 7-1 is a measuring beam - left, 7-2 is a measuring beam - middle, 7-3 is a measuring beam - right, 8-1 is a photoelectric detector, 8-2 is a photoelectric detector, 8-3 is a photoelectric detector, 13 is a spherical cat's eye reflector, 14 is an angular vibration worktable, and 15 is a lateral cylinder;

[0106] Figure 3 is a schematic diagram of an embedded reflector;

[0107] Figure 4 Schematic diagram of a cylindrical grating with a lateral cylindrical surface

[0108] Figure 5 This is the principle structure diagram of the controller based on the serial bus;

[0109] Figure 6 This is a typical circuit schematic diagram of a logarithmic amplifier;

[0110] Figure 7 This is a schematic diagram of the LED array energy bar (controller front panel);

[0111] Figure 8 It is a block diagram of the components of the amplification and conditioning part;

[0112] Fig. 9 Schematic diagram of linear / angular vibration decoupling;

[0113] Fig.10 It is a flowchart of the orthogonal phase solution based on inverse tangent;

[0114] Fig.11 This is the data processing block diagram of the sine approximation method. DETAILED DESCRIPTION

[0115] In order to better illustrate the purpose and advantages of the present invention, the invention is further described below with reference to the accompanying drawings and examples.

[0116] Embodiment 1:

[0117] like Figure 1 As shown, a laser interferometer normal / angular vibration synchronous measurement device disclosed in this embodiment includes an optical system, a precision adjustment bracket, a controller, a data acquisition system, a linear / angular vibration comprehensive calibration software installed on a host computer, and an integrated connection cable;

[0118] The optical system is used to emit three beams of measuring light and focus them on the surface of the oscillator, and at the same time receive the light energy reflected from the surface of the oscillator and convert it into a photoelectric signal.

[0119] The precision adjustment bracket is used to accurately adjust the measurement posture of the optical system so that the incident light is accurately aimed at the surface of the cylindrical grating to be measured.

[0120] The controller is used to control the power supply of the optical system, the drive of the acousto-optic modulator, and the preprocessing of the original photoelectric signal, and transmit the preprocessed three-way original photoelectric signal and the acousto-optic modulator drive signal to the data acquisition system in the form of analog signals.

[0121] The data acquisition system is used to collect the signals output by the controller.

[0122] Linear / angular vibration host computer is used to decouple the collected signals and obtain the linear vibration and angular vibration parameters respectively, realize the real-time tracking and display of time-frequency domain curves, and automatically fit and quickly display the spatial operation vector trajectory of the moving target;

[0123] The integrated connecting cable is used for power supply and signal transmission between the optical system and the controller. The signal transmission includes the transmission of high-frequency signals, low-frequency signals, DC signals and control signals. The cable shielding structure is used to isolate the crosstalk between the signals.

[0124] The optical system emits three beams of measurement light and focuses them on the surface of the vibrator. At the same time, it receives the light energy reflected from the surface of the vibrator, converts it into a photoelectric signal and transmits it to the controller. The controller is used to control the power supply of the optical system, the drive of the acousto-optic modulator, and the preprocessing of the original photoelectric signal. The preprocessed three-way original photoelectric signal and the acousto-optic modulator drive signal (reference signal) are transmitted to the data acquisition system in the form of analog signals (BNC cable). The linear / angular vibration comprehensive calibration software installed on the host computer is used to realize the decoupling and separate acquisition of linear vibration and angular vibration parameters, that is, to realize the real-time tracking and display of the time-frequency domain curves of linear vibration and angular vibration parameters. At the same time, it further automatically fits and quickly displays the spatial running vector trajectory of the moving target. The data acquisition system also synchronously collects the output of the calibrated sensor, takes the measurement result of the optical system as the reference value, and realizes the linear / angular vibration comprehensive calibration of the calibrated sensor by comparing it with the linear / angular vibration value obtained by the optical system, that is, to realize the separate calibration of the linear vibration value and the angular vibration value simultaneously, and then realizes the calibration of the comprehensive running trajectory.

[0125] The optical system uses a single helium-neon laser 1 as a light source, with a wavelength of 632.8nm and a peak power of 3.3mW. The laser emitted by the laser 1 is collimated by the collimating lens group 2 and the λ / 2 wave plate 3-1, and then divided into three beams by the beam splitter prism 5-1: one beam is used as the linear vibration measurement beam-center 7-2, which is directly incident on the spherical cat's eye reflector 13 located at the center of the angular vibration workbench 14; the other two beams are used as the angular vibration measurement beam-left 7-1 and the angular vibration measurement beam-right 7-3, which are respectively incident on the lateral cylindrical surface 15 of the angular vibration workbench 14 from symmetrical positions on both sides, and the cylindrical surface is processed with a 1200L / mm cylindrical grating. By controlling the incident angle of the measurement beam-center 7-2, the first-order diffracted light is overlapped with the incident beam, so as to achieve precise alignment of the measurement beam-center 7-2. The measuring light beam 7-2 is reflected in the original direction through the spherical cat's eye reflector 13, passes through the wave plate 3-2, and is reflected by the dichroic prism 5-8. The reference light is the light reflected by the right side of the dichroic prism 5-1, transmitted by the dichroic prism 5-1, and then passes through the right-angle reflecting prism 4-2. The two light beams converge and interfere at the dichroic prism 5-5, pass through the wave plate 3-3, and are received by the photodetector 8-2. The measuring light beam 7-2 carries a 40MHz carrier applied by the acousto-optic modulator 6, thereby forming a heterodyne interference signal of a 40MHz carrier after interference; the left angular vibration measuring light 7-1 is incident on the surface of the cylindrical grating 15 of the lateral cylinder, and by controlling its incident angle to be 1 / 2 of the initial diffraction angle, the first-order diffracted light can be coincident with the incident light beam, that is, it returns in the original direction, and merges and interferes with the light reflected by the diffraction prism 5-8, the diffraction prism 5-3 and the right-angle reflection prism 4-4 at the diffraction prism 5-7, and is finally received by the photodetector 8-1, and the original photoelectric signal is obtained and output; similarly, the right angular vibration measuring light 7-3 merges and interferes with the light reflected by the diffraction prism 5-8, the diffraction prism 5-4 and the right-angle reflection prism 4-3 at the diffraction prism 5-6, and is finally received by the photodetector 8-3, and the original photoelectric signal is obtained and output.

[0126] The controller comprises an optical head power supply module, an acousto-optic modulator driving module, a photoelectric signal energy display module, a signal preprocessing module and a function expansion module.

[0127] The optical head power supply module provides power drive for the optical devices and electronic devices in the optical head and controller.

[0128] The AOM driver module provides a high-power drive signal for the AOM in the optical head and outputs a synchronous reference signal to the data acquisition system.

[0129] The photoelectric signal energy display module, based on the logarithmic amplifier detection function, obtains and displays the current photoelectric signal amplitude in real time.

[0130] The signal preprocessing module includes functions such as adaptive amplitude modulation of the photoelectric signal, adjustable signal gain and phase-locked amplification, which are used to improve the signal quality and the accuracy of the demodulation process.

[0131] Function expansion module: reserve a position for installing the function expansion module.

[0132] The present embodiment discloses a laser interferometer normal / angular vibration synchronous measurement and decoupling method, which is implemented based on the laser interferometer normal / angular vibration synchronous measurement device. The present invention discloses a laser interferometer normal / angular vibration synchronous measurement and decoupling method, which includes the following steps:

[0133] Step 1: Decouple the normal / angular vibration. The laser measurement system emits three beams of measurement light, which are defined as measurement beam-left, measurement beam-center, and measurement beam-right. The measurement beam-center is directly incident on the spherical cat's eye reflector located at the center of rotation. The measurement beam-left and measurement beam-right are incident on the lateral cylinder of the angular vibration worktable from symmetrical positions on both sides. By controlling the incident angle of the measurement beam, the first-order diffracted light is made to coincide with the incident beam.

[0134] For the measurement of linear vibration, since there is only linear vibration but no angular vibration at the center of the angular vibration table, the measurement beam directly measures the center position of the table. The measurement target mirror uses a spherical cat's eye reflector to avoid the measurement beam deflection caused by the table rotation and large amplitude vibration process, and keep the direction of the reflected beam stable during the angular vibration process, thereby ensuring the quality of the measurement signal. Linear vibration measurement is based on the same principle as traditional heterodyne laser vibrometer, and the target speed is measured through the proportional relationship between the Doppler frequency shift and the measured speed.

[0135] For the measurement of angular vibration, during the vibration process, the measurement beam-left measurement point is the linear vibration velocity ν(t) and the angular vibration velocity v 左 (t), in order to achieve the decoupling of the angular vibration value, the measurement beam -left and the reflected light in the measurement beam -are interfered (i.e., subtracted) to obtain the photoelectric signal -left, and the interference is subtraction. Since the reflected light of the measurement beam -left contains the linear vibration velocity v(t) and the angular vibration velocity v 左 (t), the reflected light in the measuring beam - contains only the linear vibration velocity v(t) information, so the photoelectric signal - obtained after the interference beat frequency between the two contains only v 左 (t) information, that is, the decoupling of angular vibration and linear vibration is achieved. Similarly, ν 右 (t) acquisition, v 左 (t) and v 右 (t) are the two linear velocity values ​​at the symmetrical positions of the table center, which should be equal when the radius is consistent. In order to improve the measurement accuracy of the angular vibration value, v 左(t) and ν 右 (t) The final angular vibration measurement result is obtained by taking the average. The laser vibrometer measures the displacement change at the equivalent radius R of the rotation axis of the angular vibration worktable, which is the displacement amplitude.

[0136] According to the laser Doppler formula:

[0137] v 左 (t) = g × Δf 左 (t)

[0138]

[0139] Similarly, we get

[0140]

[0141] Where: v 左 (t) is the angular vibration velocity of the measuring beam-left measuring point, g is λ / 2, Δf 左 (t) is the Doppler frequency of the measurement beam-left measurement point, ω 左 (t) is the rotation speed of the measuring beam-left measuring point. ω 右 (t)Same.

[0142] The angular velocity value can be calculated by using the known grating constant and the radius of the table measuring point, as well as the Doppler frequency shift measured by the optical system.

[0143] For the same vibration table, the measuring points have the same radius and the angular velocity at any position on the surface is equal. In order to improve the accuracy of angular velocity measurement, the average angular velocity value is obtained by taking the average value of symmetrical measurement.

[0144]

[0145] Step 2: The decoupled linear / angular vibration laser interference signal is transmitted to the host computer. By demodulating the amplitude and phase of the signal output, the displacement, velocity or acceleration peak value can be analyzed. The sinusoidal approximation demodulation method is used to analyze the displacement, velocity or acceleration peak value. The two photoelectric signals are A / D converted, and the two continuous signals are converted into two discrete sequences u1(t i ) and u2(t i ). Divide the two signals and then perform an inverse tangent operation on the quotient to obtain the sequence

[0146]

[0147] Where:

[0148]

[0149] Since the inverse tangent function is a multi-valued and discontinuous function, in order to obtain a certain value, a phase expansion algorithm is used to process it so that the obtained phase value is continuous. After phase expansion and appropriate calculation, a discrete sequence of continuous phase values ​​can be obtained.

[0150]

[0151] Where: k i are the values ​​obtained through the phase expansion algorithm, ω is the angular velocity, φ0 is the initial phase, and l0 is a constant.

[0152] By calculating the discrete sequence, the waveform of the vibration signal to be measured can be reproduced, thereby obtaining the amplitude and initial phase. However, the obtained amplitude and phase are not accurate. In order to improve the measurement accuracy, The sine fitting algorithm is used for further processing. Written as follows:

[0153]

[0154] Where:

[0155] i=1, 2, ..., n;

[0156]

[0157] Through the data series Fitting with a sine function with a DC component and using the least squares method to calculate A, B, and C in the above formula, we know that the vibration displacement d and initial phase φ0 are as follows:

[0158]

[0159] The displacement data is differentiated once and twice to obtain the velocity and acceleration of the object being measured. The differential equation of the differentiator is:

[0160]

[0161] In the formula, u i (t) is the input signal of the differentiator; u o (t) is the output signal of the differentiator.

[0162] When the noise bandwidth is greater than the signal bandwidth, the signal-to-noise ratio after differentiation will deteriorate. Differentiation operations must take into account the impact of noise on the operation results. The data before processing requires limiting the signal and noise bandwidths, and low-pass filtering must be performed after processing.

[0163] Step 3: In the actual measurement process, factors such as stage jitter, large amplitude vibration guidance error, cat's eye reflector installation deviation and processing quality will inevitably cause the original photoelectric signal to have amplitude modulation related to the vibration phase. Although this phenomenon can be reduced through high-precision structural design, optical system optimization and photoelectric signal preprocessing circuit, it cannot be completely eliminated. In order to further improve the accuracy of the measurement system and reduce the uncertainty of the device, in the process of photoelectric signal demodulation, a correlation algorithm is used to perform adaptive optimization modulation on the non-stationary photoelectric signal to improve the signal-to-noise ratio of the original photoelectric signal. The specific implementation method is as follows:

[0164] The key problem of adaptive optimization modulation of non-stationary optoelectronic signals is the estimation accuracy of frequency and initial phase. Frequency and initial phase estimation methods are easily affected by low signal-to-noise ratio and poor signal quality, resulting in large errors. Therefore, it is necessary to optimize and improve the frequency and initial phase estimation methods.

[0165] In the improved method of frequency estimation, the autocorrelation detection method is used to reduce the signal-to-noise ratio. By assuming that there is no correlation between the signal and the noise, an autocorrelation function with the same frequency as the original signal is calculated, and then FFT frequency estimation is performed on the autocorrelation function.

[0166] In the improved method of initial phase estimation, the independence of signal and noise is utilized, and the cross-correlation function is combined with the least squares parameter estimation method. A group of parameter estimation equations is established when the sum of squares of errors between the estimated value and the true value is minimized. By solving the group of equations, a high-precision estimate of the phase is obtained.

[0167] The noisy Doppler signal is processed into a smooth Doppler signal. Common processing methods include low-pass filtering, neighborhood smoothing filtering, and wavelet filtering. Among the three methods, low-pass filtering causes the greatest distortion to the Doppler signal, and the filtering effect is worse than the other two methods, so it is not adopted. The processing effects of neighborhood smoothing filtering and wavelet filtering are equivalent, among which the advantage of wavelet filtering is that the distortion caused to the Doppler signal is minimal; the advantage of neighborhood smoothing filtering is that it can process Doppler signals modulated in any frequency band by flexibly changing the smoothing coefficient, while wavelet filtering needs to adjust its wavelet basis function, decomposition scale and threshold processing method according to different types of Doppler signals to achieve the best effect. Since the present invention is a real-time signal demodulation solution, in order to be more in line with the characteristics of real-time, the neighborhood smoothing filtering method is adopted for processing.

[0168] ①Autocorrelation detection frequency estimation method

[0169] The autocorrelation detection method utilizes the uncorrelated characteristics between signal and noise to perform autocorrelation analysis on the input signal in order to improve the signal-to-noise ratio.

[0170] The single-frequency real sinusoidal signal mixed with Gaussian white noise is

[0171]

[0172] Where z(n) is white noise.

[0173] By sampling the signal, N samples are obtained.

[0174]

[0175] The time-averaged correlation function is defined as

[0176]

[0177] Where τ is the delay.

[0178] Then the autocorrelation function R of the signal x(n) is xy (τ) is

[0179] R XX (τ) = R SS (τ)+R SZ (τ)+R ZS (τ)+R ZZ (τ)

[0180] Among them, R ss (τ) and R zz (τ) are the autocorrelation functions of the sinusoidal signal s(n) and white noise z(n), R sz (τ) and R zs (τ) are the cross-correlation functions of the sinusoidal signal s(n) and the noise z(n). The white noise z(n) is random and has no correlation with the sinusoidal signal s(n). Therefore, R sz (τ) and R zs The (τ) terms all approach zero.

[0181] The autocorrelation function of Gaussian white noise is expected to be 0 at all locations except the zero point, that is,

[0182] R ZZ (τ)=σ 2 δ(τ)

[0183] Where δ(τ) is the unit sampling signal.

[0184] When the sample value N is large enough, the autocorrelation function R of the sinusoidal signal s(n) SS (τ) is

[0185]

[0186] When N is large enough, the autocorrelation function of the sinusoidal signal is a sinusoidal signal with the same frequency as the sinusoidal signal. Autocorrelation preprocessing of the input signal can reduce noise, thereby improving the accuracy of the frequency estimation algorithm for sinusoidal signal frequency estimation.

[0187] ② Cross-correlation combined with least squares parameter estimation algorithm

[0188] Least squares estimation is essentially parameter estimation, that is, establishing a set of equations about parameters and solving the parameters by solving the set of equations.

[0189] The observed signal mixed with Gaussian white noise is

[0190]

[0191] Where s(n) is a real sinusoidal signal and z(n) is Gaussian white noise.

[0192] Φ is the parameter estimation value of the amplitude and phase of the sinusoidal signal, and the sum of square errors between the parameter estimation value and the true value are examined.

[0193]

[0194] When the signal-to-noise ratio is high, the least squares solution can be used to obtain the parameter estimate. However, when the signal-to-noise ratio is low, the accuracy of the parameter estimate obtained by using the least squares solution is not high, or even no parameter estimate can be obtained.

[0195] In order to establish the validity of the parameter estimation equations, it is necessary to remove the interference of the noise term. This paper uses the irrelevance between the signal s(n)=cos(ω0n) and the noise z(n) to reduce the noise interference, and adopts the method of cross-correlation combined with the minimum quadratic parameter estimation to establish the parameter estimation equations.

[0196] Known cross-correlation function

[0197]

[0198] z(n)=x(n)-[a1 cos(w0n)-a2 cos(w0t)]

[0199] The amplitude component

[0200] When the sum of squares of the error between the parameter estimate and the true value is minimized, according to the irrelevance between the signal s(n) = cos(ω0n) and the noise z(n), the above formula can be expressed as

[0201]

[0202] The following formula is established

[0203]

[0204] Expand to obtain the parameter estimation equation system

[0205]

[0206] Solve the equations to get a1, a2, and then get the estimated values ​​of the amplitude and initial phase

[0207]

[0208] The initial phase estimation result obtained is more reliable and stable than directly using the least squares estimation method, thereby realizing automatic acquisition of the initial phase of the reference signal and realizing real-time signal resolution of the photoelectric signal.

[0209] The specific description above further illustrates the purpose, technical solutions and beneficial effects of the invention in detail. It should be understood that the above is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A laser interferometer normal / angular vibration synchronous measurement device, characterized in that: Includes optical system, precision adjustment bracket, controller, data acquisition system, linear / angular vibration comprehensive calibration software installed on the host computer and integrated connection cable; An optical system, used for emitting three beams of measuring light and focusing them on the surface of the vibrator, and receiving the light energy reflected from the surface of the vibrator and converting it into a photoelectric signal; Precision adjustment bracket, used to accurately adjust the measurement posture of the optical system so that the incident light can be accurately aimed at the surface of the cylindrical grating to be measured; The controller is used to control the power supply of the optical system, the drive of the acousto-optic modulator, and the preprocessing of the original photoelectric signal, and transmit the preprocessed three-way original photoelectric signal and the acousto-optic modulator drive signal to the data acquisition system in the form of analog signals; A data acquisition system, used to collect signals output by the controller; Linear / angular vibration host computer is used to decouple the collected signals and obtain the linear vibration and angular vibration parameters respectively, realize the real-time tracking and display of time-frequency domain curves, and automatically fit and quickly display the spatial operation vector trajectory of the moving target; An integrated connecting cable is used for power supply and signal transmission between an optical system and a controller. The signal transmission includes the transmission of high-frequency signals, low-frequency signals, direct current signals and control signals. The cable shielding structure is used to isolate crosstalk between signals.

2. A laser interferometer normal / angular vibration synchronous measurement device as claimed in claim 1, characterized in that: The optical system emits three beams of measuring light and focuses them on the surface of the oscillator. At the same time, it receives the light energy reflected from the surface of the oscillator, converts it into photoelectric signals and transmits it to the controller. The controller is used to control the power supply of the optical system, the drive of the acousto-optic modulator, and the preprocessing of the original photoelectric signals. The preprocessed three-way original photoelectric signal and the acousto-optic modulator drive signal are transmitted to the data acquisition system in the form of analog signals. The linear / angular vibration comprehensive calibration software installed on the host computer is used to realize the decoupling and separate acquisition of linear vibration and angular vibration parameters, that is, to realize the real-time tracking and display of the time-frequency domain curves of linear vibration and angular vibration parameters. At the same time, the spatial operation vector trajectory of the moving target is further automatically fitted and quickly displayed. The data acquisition system also synchronously collects the output of the calibrated sensor, takes the measurement result of the optical system as the reference value, and realizes the comprehensive calibration of the linear / angular vibration of the calibrated sensor by comparing it with the linear / angular vibration value obtained by the optical system, that is, to realize the separate calibration of the linear vibration value and the angular vibration value simultaneously, and then realizes the calibration of the comprehensive operation trajectory.

3. A laser interferometer normal / angular vibration synchronous measurement device according to claim 2, characterized in that: The optical system adopts a single helium-neon laser as a light source; the laser light emitted by the laser is collimated by a collimating lens group and a λ / 2 wave plate, and then is divided into three beams by a beam splitter prism: one beam is used as a linear vibration measurement beam-center, which is directly incident on a spherical cat's eye reflector located at the center of the angular vibration worktable; the other two beams are used as an angular vibration measurement beam-left and an angular vibration measurement beam-right, which are respectively incident on the lateral cylindrical surface of the angular vibration worktable from symmetrical positions on both sides, and the cylindrical surface is processed with a cylindrical grating; by controlling the incident angle of the measurement beam-center, the first-order diffracted light is overlapped with the incident beam, so as to realize the precise alignment of the measurement beam-center; the measurement beam-center is reflected back in the original direction through the spherical cat's eye reflector, passes through the wave plate, and is reflected by the beam splitter prism, and the reference light is reflected by the right side of the beam splitter prism, transmitted by the beam splitter prism, and then passed through the straight The light from the angle reflection prism, the two beams converge and interfere at the beam splitter prism, and after passing through the wave plate, are received by the photodetector; the measuring beam carries an acousto-optic modulator to apply a carrier, so as to form a heterodyne interference signal of the carrier after interference; the left angular vibration measurement light is incident on the cylindrical grating surface of the lateral cylinder, and by controlling its incident angle to be 1 / 2 of the initial diffraction angle, the first-order diffraction light coincides with the incident beam, that is, it returns in the original direction, and converges and interferes with the light reflected by the beam splitter prism, the beam splitter prism and the right-angle reflection prism at the beam splitter prism, and is finally received by the photodetector to obtain the original photoelectric signal and output it; similarly, the right angular vibration measurement light converges and interferes with the light reflected by the beam splitter prism, the beam splitter prism and the right-angle reflection prism at the beam splitter prism, and is finally received by the photodetector to obtain the original photoelectric signal and output it.

4. A laser interferometer normal / angular vibration synchronous measurement device according to claim 2, characterized in that: The controller includes an optical head power supply module, an acousto-optic modulator driving module, a photoelectric signal energy display module, a signal preprocessing module and a function expansion module; Optical head power supply module, providing power drive for optical devices and electronic devices in the optical head and controller; The AOM driver module provides a high-power drive signal for the AOM in the optical head and outputs a synchronous reference signal to the data acquisition system; The photoelectric signal energy display module acquires and displays the current photoelectric signal amplitude in real time based on the logarithmic amplifier detection function; Signal preprocessing module, including adaptive amplitude modulation of photoelectric signals, adjustable signal gain and phase-locked amplification, which is used to improve signal quality and the accuracy of demodulation process; Function expansion module: reserve a position for installing the function expansion module.

5. A laser interferometer normal / angular vibration synchronous measurement and decoupling method, based on a laser interferometer normal / angular vibration synchronous measurement device as claimed in claim 2, 3 or 4, characterized in that: The steps include: Step 1, decoupling the normal / angular vibration; the laser measurement system emits three beams of measurement light, which are respectively defined as measurement beam-left, measurement beam-center, and measurement beam-right. The measurement beam-center is directly incident on the spherical cat's eye reflector located at the rotation center, and the measurement beam-left and measurement beam-right are respectively incident on the lateral cylinder of the angular vibration worktable from bilaterally symmetrical positions. By controlling the incident angle of the measurement beam, the first-order diffracted light is made to coincide with the incident beam; For the measurement of linear vibration, since there is only linear vibration but no angular vibration at the center of the angular vibration table, the measurement beam directly measures the center position of the table; the measurement target mirror adopts a spherical cat's eye reflector to avoid the measurement beam deflection caused by the table rotation and large amplitude vibration process, and keep the direction of the reflected beam stable during the angular vibration process, thereby ensuring the quality of the measurement signal; the linear vibration measurement is based on the same principle as the traditional heterodyne laser vibrometer, and the target speed is measured through the proportional relationship between the Doppler frequency shift and the measured speed; For the measurement of angular vibration, during the vibration process, the measurement beam-left measurement point is the linear vibration velocity ν(t) and the angular vibration velocity v 左 (t), in order to achieve the decoupling of the angular vibration value, the measurement beam -left is interfered with the reflected light in the measurement beam -, and the photoelectric signal -left is obtained. The interference is subtraction; since the reflected light of the measurement beam -left contains the linear vibration velocity ν(t) and the angular vibration velocity v 左 (t), the reflected light in the measuring beam - contains only the linear vibration velocity ν(t) information, so the photoelectric signal - obtained after the interference beat frequency between the two contains only v 左 (t) information, that is, to achieve the decoupling of angular vibration and linear vibration; Similarly, to achieve ν 右 (t) acquisition, v 左 (t) and ν 右 (t) are the two linear velocity values ​​at the symmetrical positions of the table center, which should be equal when the radius is consistent. In order to improve the measurement accuracy of the angular vibration value, v 左 (t) and ν 右 (t) The final angular vibration measurement result is obtained by averaging; the laser vibrometer measures the displacement change at the equivalent radius R of the rotation axis of the angular vibration worktable, and the displacement change is the displacement amplitude; According to the laser Doppler formula: v 左 (t)=g×Δf 左 (t) Similarly, we get Where: v 左 (t) is the angular vibration velocity of the measuring beam-left measuring point, g is λ / 2, Δf 左 (t) is the Doppler frequency of the measurement beam-left measurement point, ω 左 (t) is the rotation speed of the measuring beam-left measuring point; ω 右 (t) similarly determined; The angular velocity value can be calculated by using the known grating constant and the radius of the table measuring point, as well as the Doppler frequency shift measured by the optical system. For the same vibration table surface with the same radius of measurement points, the angular velocity at any position on its surface is equal. In order to improve the accuracy of angular velocity measurement, the average angular velocity value is obtained by taking the average value of symmetrical measurement. Step 2: The decoupled linear / angular vibration laser interference signal is transmitted to the host computer; the amplitude and phase of the signal output are demodulated to realize the analysis of the displacement, velocity or acceleration peak value; the sinusoidal approximation demodulation method is used to realize the analysis of the displacement, velocity or acceleration peak value; the two-way photoelectric signal is A / D converted, and the two-way continuous signal is converted into two-way discrete sequence u1(t i ) and u2(t i ) ; perform division operation on the two signals, and then perform arc tangent operation on the quotient to obtain the sequence Where: Since the inverse tangent function is a multi-valued and discontinuous function, in order to obtain a certain value, the phase expansion algorithm is used to process it so that the obtained phase value is continuous; After phase expansion and appropriate calculation, a discrete sequence of continuous phase values ​​can be obtained. Where k i are the values ​​obtained by the phase expansion algorithm, ω is the angular velocity, φ0 is the initial phase, and l0 is a constant; By calculating the discrete sequence, the waveform of the vibration signal to be measured can be reproduced, thereby obtaining the amplitude and initial phase; however, the obtained amplitude and phase are not accurate. In order to improve the measurement accuracy, The sine fitting algorithm is used for further processing; the sine fitting method is to Written as follows: Where: i=1,2,...,n; Through the data series Fitting with a sine function with a DC component and using the least squares method to calculate A, B, and C in the above formula, we know that the vibration displacement d and initial phase φ0 are as follows: The displacement data is differentiated once and twice to obtain the velocity and acceleration of the object being measured; the differential equation of the differentiator is: In the formula, u i (t) is the input signal of the differentiator; u o (t) is the output signal of the differentiator; When the noise bandwidth is larger than the signal bandwidth, the signal-to-noise ratio after differentiation will deteriorate; the differential operation must take into account the impact of noise on the operation results, the data before processing requires limiting the signal and noise bandwidth, and low-pass filtering must be performed after processing; Step 3: In the process of photoelectric signal demodulation, a correlation algorithm is used to perform adaptive optimization modulation on the non-stationary photoelectric signal to improve the signal-to-noise ratio of the original photoelectric signal. The specific implementation method is as follows: In the improved method of frequency estimation, the autocorrelation detection method is used to reduce the signal-to-noise ratio. By assuming that there is no correlation between the signal and the noise, an autocorrelation function with the same frequency as the original signal is calculated, and then the FFT frequency estimation is performed on the autocorrelation function. In the improved method of initial phase estimation, the mutual independence of signal and noise is utilized, and the cross-correlation function is combined with the least squares parameter estimation method. When the sum of square errors between the estimated value and the true value is minimized, a parameter estimation equation group is established, and a high-precision estimation value of the phase is obtained by solving the equation group. The noisy Doppler signal is processed into a smooth Doppler signal by using a neighborhood smoothing filter method; ①Autocorrelation detection frequency estimation method The autocorrelation detection method uses the uncorrelated characteristics between signal and noise to perform autocorrelation analysis on the input signal to achieve the purpose of improving the signal-to-noise ratio. The single-frequency real sinusoidal signal mixed with Gaussian white noise is Where z(n) is white noise; By sampling the signal, N samples are obtained. The time-averaged correlation function is defined as Where τ is the delay; Then the autocorrelation function R of the signal x(n) is xy (τ) is R XX (τ)=R SS (t)+R SZ (t)+R ZS (t)+R ZZ (t) Among them, R ss (τ) and R zz (τ) are the autocorrelation functions of the sinusoidal signal s(n) and white noise z(n), R sz (τ) and R zs (τ) are the cross-correlation functions of the sinusoidal signal s(n) and the noise z(n), respectively. The white noise z(n) is random and has no correlation with the sinusoidal signal s(n). Therefore, R sz (τ) and R zs The (τ) terms all approach zero; The autocorrelation function of Gaussian white noise is expected to be 0 at all locations except the zero point, that is, R ZZ (t)=s 2 d(t) Where δ(τ) is the unit sampling signal; When the sample value N is large enough, the autocorrelation function R of the sinusoidal signal s(n) SS (τ) is When N is large enough, the autocorrelation function of the sinusoidal signal is a sinusoidal signal with the same frequency as the sinusoidal signal. Autocorrelation preprocessing of the input signal can reduce noise, thereby improving the accuracy of the frequency estimation algorithm for sinusoidal signal frequency estimation. ② Cross-correlation combined with least squares parameter estimation algorithm The essence of least squares estimation is parameter estimation, that is, to establish a system of equations about parameters and solve the parameters by solving the system of equations; The observed signal mixed with Gaussian white noise is Where s(n) is a real sinusoidal signal and z(n) is Gaussian white noise; Φ is the parameter estimation value of the amplitude and phase of the sinusoidal signal, and the sum of square errors between the parameter estimation value and the true value are examined. When the signal-to-noise ratio is high, the least squares solution is directly used to obtain the parameter estimate for the above formula; however, when the signal-to-noise ratio is low, the accuracy of the parameter estimate obtained by directly using the least squares solution for the above formula is not high, or even the parameter estimate cannot be obtained; The noise interference is reduced by using the uncorrelation between the signal s(n)=cos(ω0n) and the noise z(n), and the parameter estimation equations are established by using the cross-correlation combined with the minimum quadratic parameter estimation method. Known cross-correlation function z(n)=x(n)-[a1 cos(w0n)-a2 cos(w0t)] The amplitude component When the sum of squares of the error between the parameter estimate and the true value is minimized, according to the irrelevance between the signal s(n) = cos(ω0n) and the noise z(n), the above formula can be expressed as The following formula is established Expand to obtain the parameter estimation equation system Solve the equations to get a1, a2, and then get the estimated values ​​of the amplitude and initial phase This can automatically obtain the initial phase of the reference signal, thereby realizing real-time signal resolution of the photoelectric signal.

Images