CN108489596B - Continuous scanning laser quick vibration measuring method and system thereof - Google Patents
Continuous scanning laser quick vibration measuring method and system thereof Download PDFInfo
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Abstract
The invention discloses a continuous scanning laser rapid vibration measurement method and a system thereof, wherein the method comprises the following steps: step S1: driving a pair of high-speed scanning lenses by using a continuous sinusoidal signal to guide measuring laser to continuously scan a closed curve on the surface of a measured object; step S2: and synchronously obtaining a vibration signal of the measuring laser and a lens position signal of the high-speed scanning lens so as to obtain the vibration frequency of a plurality of measuring points on the closed curve path. The system comprises a laser source, a high-speed X-Y scanning lens, a controller and a processor, wherein the high-speed X-Y scanning lens is used for guiding measuring laser to continuously scan a closed curve on the surface of a measured object under the driving of a continuous sinusoidal signal. The problem of can not measure the whole vibration response on object surface in the short time among the prior art is solved.
Description
Technical Field
The invention relates to the technical field of vibration detection, in particular to a rapid vibration measurement technology combining a laser Doppler vibration meter and a high-speed scanning galvanometer.
Background
Vibration information of a machine is often used to assess the operating state of the machine, diagnose operating faults of the machine, or correct a computer simulation model of the machine. Therefore, it is important to accurately measure the vibration information of the mechanical device. The measurement of vibration can be divided into contact and non-contact. The contact measurement method needs to attach the vibration sensor to the surface of the object to be measured, but the added mass often damages the original vibration state of the object to be measured, and affects the measurement accuracy. Therefore, the contact measurement method is not suitable for measuring vibration of a thin-walled, lightweight object. In addition, when a large-surface object is measured by using the contact type measuring method, a sensor array needs to be installed, and the hardware cost and the installation cost are greatly increased.
In the noncontact vibration measurement, a laser doppler vibrometer is a noncontact measuring device which has been used in recent years in many cases, and has high measurement accuracy without being limited by the size, temperature, vibration frequency, and the like of a measured object. The control signal drives a pair of guide lenses (a high-speed response scanning lens, a galvonometer Scanner, Cambridge Technology, model 6240HM40A), and even the laser can be guided to scan on the measured object point by point in sequence, so that the vibration measurement of the whole object surface is realized, the hardware and installation cost of the contact sensor is saved, and the vibration testing time is greatly reduced. The novel infrared laser Doppler vibration meter has high signal-to-noise ratio, and greatly reduces the requirement on the optical characteristics of the surface of an object. For example, the far infrared laser Doppler vibration meter can be used for measuring the vibration of a static wind energy engine blade in hundreds of meters, so that the test cost is greatly reduced. Compared with the traditional contact sensor, the vibration measurement method of scanning point by point sequentially has great advantages, but still has certain limitations. For example, for a wind powered engine blade under wind excitation, or a vehicle body surface under impact, the full vibrational response of the object surface needs to be measured in a short period of time because the excitation is of short duration and cannot be repeated. There is a disadvantage in that the entire vibration response of the surface of the object cannot be measured in a short time.
Disclosure of Invention
In view of this, embodiments of the present invention provide a method and a system for continuously scanning laser fast vibration measurement, which solve the problem that the whole vibration response of the surface of an object cannot be measured in a short time.
In a first aspect, an embodiment of the present invention provides a continuous scanning laser rapid vibration measurement method, including:
step S1: driving a pair of high-speed scanning lenses by using a continuous sinusoidal signal to guide measuring laser to continuously scan a closed curve on the surface of a measured object;
step S2: and synchronously obtaining a vibration signal of the measuring laser and a lens position signal of the high-speed scanning lens so as to obtain the vibration frequency of a plurality of measuring points on the closed curve path.
According to a specific implementation manner of the embodiment of the present invention, the step S2 specifically includes:
step S21: synchronously obtaining a laser vibration signal of the measuring laser and a lens position signal of the high-speed scanning lens;
step S22: resampling the laser vibration signal to ensure that an integral number of measuring points are arranged on a scanning path in the same laser scanning period; resampling the lens position signal by adopting a sampling frequency which is the same as the sampling frequency of the laser vibration signal so as to ensure that the vibration information of the measuring point is consistent with the position of the measuring point, thereby obtaining the vibration information of the measuring point;
step S23: carrying out Fourier transform on the vibration information of the measuring points so as to obtain amplitude, frequency and phase information in the vibration information of the measuring points;
step S24: and carrying out distortion restoration on frequency and phase information in the vibration information of the measuring point obtained after Fourier transform.
According to a specific implementation manner of the embodiment of the present invention, the resampling the laser vibration signal and the resampling the lens position signal in step S22 adopt an interpolation algorithm in the time domain or zero-padding in the frequency domain.
According to a specific implementation manner of the embodiment of the present invention, the performing distortion restoration on the frequency information in the vibration information of the measurement point in step S24 specifically includes:
and reversely solving the frequency information in the vibration information of the measuring points obtained after Fourier transform in the step S23 in the folding process.
According to a specific implementation manner of the embodiment of the present invention, the folding process specifically includes:
firstly: omeganTo be provided with
Is an axis of symmetry, folded to obtain omegan1；
Then: due to omegan1＜0,ωn1With 0 as the symmetry axis, folding to obtain omegan2；
And finally: due to the fact that
ωn2To be provided with
Is an axis of symmetry, folded to obtain omegan3；
Wherein: omeganIs the nth order natural vibration frequency, ωsFor measuring the scanning frequency of the laser。
According to a specific implementation manner of the embodiment of the present invention, the performing distortion restoration on the phase information in the vibration information of the measurement point in step S24 specifically includes:
and measuring the time delay of two adjacent measuring points, and moving the phase of the next measuring point forward according to the measured delay time.
According to a specific implementation manner of the embodiment of the present invention, before the step S21, the method further includes: and measuring the surface of the measured object through a laser single point to obtain an accurate natural frequency range of the measured object.
According to a specific implementation manner of the embodiment of the invention, in the step S1, the scanning frequency of the high-speed scanning mirror does not exceed 200 hz.
According to a specific implementation manner of the embodiment of the invention, the scanning angle of the high-speed scanning lens is less than +/-5 degrees.
In a second aspect, an embodiment of the present invention provides a continuous scanning laser rapid vibration measurement system, including:
the laser source emits measuring laser to the high-speed X-Y scanning lens;
high speed X-Y scanning mirror: under the drive of continuous sinusoidal signals, guiding the measuring laser to continuously scan a closed curve on the surface of the measured object;
a controller: sending a continuous sinusoidal signal to drive a high-speed X-Y scanning lens and receiving a vibration signal of a laser source so as to obtain a vibration signal of the measuring laser and a lens position signal of the high-speed scanning lens;
a processor: and processing the vibration signal of the measuring laser and the lens position signal of the high-speed scanning lens acquired by the controller to obtain the vibration frequencies of a plurality of measuring points.
Compared with the prior art, the device and the method of the invention have the following obvious advantages:
1. the high-speed scanning lens is driven by adopting continuous signals to continuously scan on the surface of an object to be measured at a high speed, hundreds of virtual vibration sensors can be constructed on a laser scanning path through signal processing, so that the vibration information on the laser scanning path can be measured simultaneously, the time requirement of vibration testing is met, and the whole vibration response of the surface of the object is measured in a short time.
2. The scanning frequency of the high-speed scanning lens is limited below 200Hz, and the influence of the nonlinear response of the lens on the measurement accuracy is reduced.
3. The scanning angle of the high-speed scanning lens is controlled to be less than +/-5 degrees, so that the closed curve can cover part or all of the surface of the measured object.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a flow chart of a method for continuous scanning laser rapid vibration measurement according to an embodiment of the present invention;
fig. 2 is a flowchart of acquiring vibration frequencies of a plurality of measurement points on the closed curve path by the continuous scanning laser rapid vibration measurement method according to the embodiment of the present invention;
FIG. 3 is a schematic diagram of a measurement result obtained by a continuous scanning laser rapid vibration measurement method according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of frequency folding in frequency distortion recovery according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of a continuous scanning laser rapid vibration measurement system according to an embodiment of the present invention;
fig. 6 is an enlarged schematic structural diagram of an X-Y scanning lens of a continuous scanning laser rapid vibration measurement system according to an embodiment of the present invention.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
It should be understood that the described embodiments are only some embodiments of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, an embodiment of the present invention provides a continuous scanning laser rapid vibration measurement method, which is characterized by including:
step S1: driving a pair of high-speed scanning lenses by using a continuous sinusoidal signal to guide measuring laser to continuously scan a closed curve on the surface of a measured object;
step S2: and synchronously obtaining a vibration signal of the measuring laser and a lens position signal of the high-speed scanning lens so as to obtain the vibration frequency of a plurality of measuring points on the closed curve path.
The high-speed scanning lens adopts an X-Y scanning lens, the frequency ratio of the driving signals of the X-Y scanning lens must be an integer to ensure that a laser scanning path is a closed curve, and the smaller value of the frequency of laser scanning (namely the frequency of scanning the complete closed curve by laser per second) is the same as the smaller value of the frequency in the driving signals of the X-Y scanning lens. Based on the aforementioned condition, the vibration information on the laser scanning path can be repeatedly scanned by the laser, and the vibration information of all points on the laser scanning path can be acquired through a specific signal processing module by combining the output position signals of the X-Y scanning lens.
As an optional implementation manner, as shown in fig. 2, step S2 specifically includes:
step S21: synchronously obtaining a laser vibration signal of the measuring laser and a lens position signal of the high-speed scanning lens;
because the frequency ratio of the driving signals of the X-Y scan mirror is an integer, the scan path of the laser is a closed curve (e.g., an ellipse in fig. 3), and the laser must pass through the same measurement point (e.g., point a in fig. 3) on the scan path many times.
Step S22: resampling the laser vibration signal to ensure that an integral number of measuring points are arranged on a scanning path in the same laser scanning period; resampling the lens position signal by adopting a sampling frequency which is the same as the sampling frequency of the laser vibration signal to ensure that the vibration information of the measuring point is consistent with the position of the measuring point, thereby obtaining the vibration information of the measuring point;
because the ratio of the sampling frequency to the laser scanning frequency is not necessarily an integer multiple when the laser vibration signal is measured, the laser vibration signal needs to be resampled to ensure that there are an integer number of measurement points (such as several measurement points on the elliptical path shown in fig. 3) on the scanning path in the same laser scanning period, and the lens position signal should be resampled with the same sampling frequency to ensure that the vibration information of the measurement points is consistent with the position thereof. The method of resampling the lens position signal and the laser vibration signal may be interpolation in the time domain or zero-padding in the frequency domain. After sampling, an integer number of measurement points can be obtained in each laser scanning period (which is equivalent to installing a plurality of virtual sensors on a laser scanning path, wherein each measurement point is a virtual sensor). Since the time when the laser passes through these measurement points is known (such as the lens signal time t21, t22, t23, … in fig. 3), the vibration information at these time points, i.e. the vibration information at the measurement points measured by the virtual sensor, can be obtained from the continuous laser vibration signal.
Step S23: carrying out Fourier transform on the vibration information of the measuring point so as to obtain amplitude, frequency and phase information in the vibration information of the measuring point; and converting the time domain signal into a frequency domain signal, and performing signal analysis. At each measurement point, the vibration sampling frequency at each measurement point is equal to the laser scanning frequency because the laser passes once per scanning cycle.
Step S24: and carrying out distortion restoration on frequency and phase information in the vibration information of the measuring point obtained after Fourier transform.
The specifically performing distortion restoration on the frequency information in the vibration information of the measurement point is as follows: to obtain vibration information of all measurement points on the laser scanning path at each same time, wherein the vibration information of each measurement point comprises three parameters of amplitude, frequency and phase, the amplitude of the vibration can be accurately measured directly through Fourier transform, but the vibration information of each measurement pointThe vibration sampling frequency may not satisfy the aroma theorem condition (i.e. the signal sampling frequency should be greater than or equal to twice the highest natural frequency of the object to be measured), so that frequency distortion may exist, and the vibration frequency distortion of the measuring point must be repaired. The frequency distortion repair process is as follows: if the laser scanning frequency is omegasSince each measurement point is measured only once per scanning period, the vibration sampling frequency of each measurement point is the laser scanning frequency ωs. According to the fragrance concentration sampling theorem, all the natural vibration frequency information of the tested object can be folded to 1/2 sampling frequency range
As shown in fig. 4, the nth order natural vibration frequency ωnIs folded to omegan3 
The specific folding process is as follows, the first step, ωnTo be provided with
For the axis of symmetry, the frequency is folded to ωn1. Second step, due to ωn1＜0,ωn1With 0 as the axis of symmetry, fold to ωn2. The third step is due to
ωn2To be provided with
Is a symmetry axis, is folded to omegan3. And omegan3Can be obtained from the frequency domain signal in a fourier transform. Therefore, on the premise that the accurate natural frequency range of the measured object is known, the real vibration frequency of the measured point of the measured object can be recovered by reversely solving the folding process, and the frequency can be repaired.
In addition, since the measurement sequence is that each measurement point is measured sequentially along the scanning path, and there is a fixed measurement time difference between two adjacent measurement points, in order to obtain the vibration information of all measurement points on the laser scanning path at the same time, the vibration phase distortion of the measurement points must be repaired. In step S24, the specifically performing distortion restoration on the phase information in the vibration information of the measurement point is:
because the time interval of the laser passing through two adjacent measuring points is known and fixed (namely the sampling period when the laser vibration signal is measured), the phase repairing can directly use the time delay of the laser measuring two adjacent measuring points to move the phase of the next measuring point forward until the phase of all the measuring points is adjusted to be consistent, which is equivalent to that the virtual sensor simultaneously measures the vibration of the measured object, namely completing the phase repairing.
After the processing of the frequency and phase repairing module, signals of hundreds of (even more) virtual vibration sensors on a scanning path in the same time can be obtained in a short time, the measuring result is consistent with the measuring result of a real vibration sensor, and the installation time and cost are greatly saved.
As an optional implementation manner, step S21 is preceded by: and measuring the surface of the measured object through a laser single point to obtain an accurate natural frequency range of the measured object. After the accurate natural frequency range of the object is obtained, the laser vibration signal and the lens position signal are processed, and therefore the vibration frequency of the object to be measured is obtained.
As an alternative embodiment, in step S1, the scanning frequency of the high speed scanning mirror does not exceed 200 hz.
As an alternative embodiment, the scanning angle of the high speed scanning mirror is ± 5 ° or less.
Referring to fig. 5, an embodiment of the present invention provides a continuous scanning laser rapid vibration measurement system, including:
the laser source emits measuring laser to the high-speed X-Y scanning lens;
high speed X-Y scanning mirror: under the drive of continuous sinusoidal signals, guiding the measuring laser to continuously scan a closed curve on the surface of the measured object;
a controller: sending a continuous sinusoidal signal to drive a high-speed X-Y scanning lens and receiving a vibration signal of a laser source so as to obtain a vibration signal of the measuring laser and a lens position signal of the high-speed scanning lens;
a processor: and processing the vibration signal of the measuring laser and the lens position signal of the high-speed scanning lens acquired by the controller to obtain the vibration frequencies of a plurality of measuring points. In the technical scheme, the processor adopts a computer, and can also adopt a server or a chip with a computing function. Laser source: a laser doppler vibrometer is used.
The present invention utilizes a pair of high speed X-Y scanning optics (galvanosimeter scanner, Cambridge Technology, model 6240HM40A) to measure the vibration information on the laser scan path while directing the laser to continuously scan over the object under test. The laser doppler vibrometer may be any type and wavelength of single point doppler vibrometer such as visible laser, OFV-505 of polytec, germany, or invisible laser such as RSV-150. When the lens group is installed, the distance between the laser source and the X-Y scanning lens group is required to be reduced as much as possible, and the laser incidence direction is ensured to be vertical to the rotation axis of the first group lens (X scanning lens), the laser point is on the rotation axis of the first group lens, and the rotation axis of the first group lens is vertical to the rotation axis of the second group lens (Y scanning lens) in space. The incident direction of the laser is adjusted to ensure that the laser point falls on the rotation axis of the second group of mirrors after the laser is reflected by the first group of mirrors, as shown in fig. 6. The purpose of this mounting is to reduce laser measured surface vibration of the high speed scanning mirror. Since the closer the laser spot is to the axis of rotation, the smaller the measured lens velocity signal.
The lens is fixedly connected with the rotating shaft, the rotating shaft and the lens fixedly connected with the rotating shaft are driven to complete rotating motion through the driving signal, the driving signal is a sine signal (a DC direct current signal is regarded as a special case of the sine signal, the frequency of the signal is 0 at the moment), the amplitude of the sine signal determines the angle limit value of reciprocating swing of the rotating shaft, the larger the amplitude is, the larger the angle limit value of the swing is, the frequency of the sine signal determines the frequency of the reciprocating swing of the rotating shaft, the higher the frequency is, the higher the swing frequency is, when the frequency of the driving signal is 0 (namely, the DC signal), the lens does not rotate (namely is kept static), and the position of the lens depends. For example, if the image to be scanned is a straight line, the driving signal of the first group of lenses is a sinusoidal signal (frequency is not 0), the driving signal of the second group of lenses is a sinusoidal signal (DC direct current signal) with frequency 0, the length and the reciprocating frequency of the scanning straight line can be adjusted by adjusting the frequency and the amplitude of the driving signal of the first group of lenses, and the position of the straight line on the object to be measured can be adjusted by adjusting the amplitude of the driving signal of the second group of lenses. If the image to be scanned is an ellipse, the two groups of lens driving signals have the same frequency but different amplitudes, and the size and direction of the ellipse can be adjusted by adjusting the amplitude and phase of the driving signals so as to cover the surface of the object as much as possible. Similarly, by adjusting the ratio of the driving signal frequencies of the lenses, more complex patterns can be obtained. For example, if the frequency of the X-scan mirror is three times that of the Y-scan mirror, a clover pattern can be obtained. If the laser scanning path is a closed curve, it is necessary to ensure that the frequency ratio of the driving signals of the two mirrors is an integer (as shown in fig. 3, the frequency of the X-scanning mirror is the same as that of the Y-scanning mirror, but the amplitude is different, and the closed graph is an ellipse). If more measurements are to be taken over the scan path within the same scan time, the frequency of the drive signals for both mirrors can be adjusted simultaneously, but the ratio is maintained. However, the scanning frequency is generally controlled not to exceed 200Hz to reduce the random noise of the measurement laser and the effect of the nonlinear response of the lens on the measurement accuracy.
The content in the method embodiment of the present invention corresponds to the content in the device embodiment described above, and is not described herein again.
Compared with the prior art, the device and the method of the invention have the following obvious advantages:
1. since the purpose of capturing real-time images of the blades in operation by the high-speed camera is only to capture the position of the blades, the requirements on the photographing frequency and the resolution of the photographs are greatly reduced.
2. The blade in motion is guided to be tracked by the laser by utilizing the position information captured by the camera, the position of a laser scanning point is accurate, a laser source is not required to be placed on the axis of the rotation center of the blade, and the operability of the measuring method is greatly improved (especially for the measurement of the blade of the wind driven generator with high height).
3. The blade edge position in two continuous frames of pictures of the high-speed camera can be compared, the swing speed of the blade in the rotating plane can be calculated, the swing speed of the blade can be used for compensating a lens control signal, so that the influence of the swing of the blade in the rotating plane on the tracking precision can be counteracted, and the vibration measurement precision is further improved.
It is to be noted that, in this document, relational terms such as first and second, and the like are used solely to distinguish one entity or operation from another entity or operation without necessarily requiring or implying any such relationship.
There may be any such actual relationship or order between the entities or operations. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
All the embodiments in the present specification are described in a related manner, and the same and similar parts among the embodiments may be referred to each other, and each embodiment focuses on the differences from the other embodiments.
The logic and/or steps represented in the flowcharts or otherwise described herein, e.g., an ordered listing of executable instructions that can be considered to implement logical functions, can be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. For the purposes of this description, a "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of the computer-readable medium would include the following: an electrical connection (electronic device) having one or more wires, a portable computer diskette (magnetic device), a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disc read-only memory (CDROM). Additionally, the computer-readable medium could even be paper or another suitable medium upon which the program is printed, as the program can be electronically captured, via for instance optical scanning of the paper or other medium, then compiled, interpreted or otherwise processed in a suitable manner if necessary, and then stored in a computer memory.
It should be understood that portions of the present invention may be implemented in hardware, software, firmware, or a combination thereof.
In the above embodiments, the various steps or methods may be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, any one or combination of the following techniques, which are known in the art, may be used: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application specific integrated circuit having an appropriate combinational logic gate circuit, a Programmable Gate Array (PGA), a Field Programmable Gate Array (FPGA), or the like.
It is understood that the terms "a" and "an" should be interpreted as meaning that a number of one element or element is one in one embodiment, while a number of other elements is one in another embodiment, and the terms "a" and "an" should not be interpreted as limiting the number.
While ordinal numbers such as "first," "second," etc., will be used to describe various components, those components are not limited herein. The term is used only to distinguish one element from another. For example, a first component could be termed a second component, and, similarly, a second component could be termed a first component, without departing from the teachings of the inventive concepts. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
The terminology used herein is for the purpose of describing various embodiments only and is not intended to be limiting. As used herein, the singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, numbers, steps, operations, components, elements, or combinations thereof, but do not preclude the presence or addition of one or more other features, numbers, steps, operations, components, elements, or groups thereof.
Terms used herein, including technical and scientific terms, have the same meaning as terms commonly understood by one of ordinary skill in the art, unless otherwise defined. It will be understood that terms defined in commonly used dictionaries have meanings that are consistent with their meanings in the prior art.
The above description is only for the specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (5)
1. A continuous scanning laser rapid vibration measurement method is characterized by comprising the following steps:
step S1: driving a pair of high-speed scanning lenses by using a continuous sinusoidal signal to guide measuring laser to continuously scan a closed curve on the surface of a measured object;
step S2: synchronously obtaining a vibration signal of the measuring laser and a lens position signal of the high-speed scanning lens so as to obtain vibration frequencies of a plurality of measuring points on the closed curve path;
the step S2 specifically includes:
step S21: synchronously obtaining a laser vibration signal of the measuring laser and a lens position signal of the high-speed scanning lens;
step S22: resampling the laser vibration signal to ensure that an integral number of measuring points are arranged on a scanning path in the same laser scanning period; resampling the lens position signal by adopting a sampling frequency which is the same as the sampling frequency of the laser vibration signal so as to ensure that the vibration information of the measuring point is consistent with the position of the measuring point, thereby obtaining the vibration information of the measuring point;
step S23: carrying out Fourier transform on the vibration information of the measuring points so as to obtain amplitude, frequency and phase information in the vibration information of the measuring points;
step S24: carrying out distortion restoration on frequency and phase information in the vibration information of the measuring point obtained after Fourier transform;
the resampling of the laser vibration signal and the resampling of the lens position signal in the step S22 adopt an interpolation algorithm in the time domain, or zero-padding in the frequency domain;
the performing distortion restoration on the frequency information in the vibration information of the measurement point in step S24 specifically includes:
reversely solving the frequency information in the vibration information of the measuring point obtained after Fourier transform in the step S23 in the folding process;
the folding process specifically comprises the following steps:
firstly: omeganTo be provided with
Is an axis of symmetry, folded to obtain omegan1；
Then: due to omegan1＜0，ωn1Taking 0 as a symmetry axis, and folding to obtainOmegan2；
And finally: due to the fact that
ωn2To be provided with
Is an axis of symmetry, folded to obtain omegan3；
Wherein: omeganIs the nth order natural vibration frequency, ωsTo measure the scanning frequency of the laser.
2. The vibration measuring method according to claim 1,
the step S24 of performing distortion restoration on the phase information in the vibration information of the measurement point specifically includes:
and measuring the time delay of two adjacent measuring points, and moving the phase of the next measuring point forward according to the measured delay time.
3. The vibration measuring method according to claim 1, characterized in that: before the step S21, the method further includes: and measuring the surface of the measured object through a laser single point to obtain an accurate natural frequency range of the measured object.
4. The vibration measuring method according to claim 1, characterized in that: in step S1, the scanning frequency of the high speed scanning mirror does not exceed 200 hz.
5. The vibration measuring method according to claim 1 or 4, characterized in that: the scanning angle of the high-speed scanning lens is less than +/-5 degrees.
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Denomination of invention: Continuous scanning laser rapid vibration measurement method and system Effective date of registration: 20220311 Granted publication date: 20200421 Pledgee: Bank of Hangzhou Limited by Share Ltd. Nanjing branch Pledgor: NANJING CHAOS DATA TECHNOLOGY Co.,Ltd. Registration number: Y2022980002395 |
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