CN107238432A - One kind vibration Deformation Observation method, device and recording method - Google Patents

Abstract

The invention provides a vibration deformation observation method, device and recording method. The vibration frequency of the observed vibration target is measured, and the measurement result is recorded as f, and then a square wave signal with a frequency of f-δ is synthesized, and δ is preset Frequency difference, according to this square wave signal, the light source is controlled to flicker at a frequency of f-δ, and the deformation state of the object is elongated in time to show the deformation of the object when it vibrates, and it is elongated to f/δ times the original vibration process of the object; vibration deformation observation The device includes a transducer, a signal conditioner, a frequency analysis module, a frequency synthesizer and a light source. The present invention utilizes the method of accumulating phase difference by frequency difference to ingeniously realize the observation of the deformation of high-speed vibrating objects with the naked eye, and at the same time, use ordinary cameras to record the deformation of high-speed vibrating objects, and provide a low-cost vibration deformation observation device , suitable for popularization and use, and has important market value.

Description

A vibration deformation observation method, device and recording method

technical field

The invention belongs to the technical field of vibration deformation measurement, and more specifically relates to a vibration deformation observation method, device and recording method.

Background technique

It is very important to study the deformation of an object when it vibrates. It can analyze the force of the object when it vibrates, and provide basic data reference for structural design. In addition, the study of animal motion (such as the vibration of insect wings) is also a work of observing the deformation of vibrating objects. When studying acoustics, the vibration and deformation of objects are also analyzed. Usually the vibration frequency of these objects is relatively fast, generally from tens of hertz to thousands of hertz. At this time, the naked eye cannot directly observe the deformation of the object when it vibrates. The usual method is to record it with a high-speed camera (thousands to tens of thousands of frames per second) ), and then playback at the normal playback speed (about 25 frames per second), the vibration deformation can be observed. But high-speed cameras are very expensive and require high-power lighting to shoot properly.

Contents of the invention

Aiming at the defects of the prior art, the invention proposes a low-cost vibration deformation observation, device and recording method.

The technical solution of the present invention proposes a vibration deformation observation method. First, measure the vibration frequency of the observed vibration target, record the measurement result as f, and then synthesize a square wave signal with a frequency of f-δ, where δ is the preset frequency difference According to this square wave signal, the light source is controlled to flicker at a frequency of f-δ, and the time is elongated to show the deformation of the object when it vibrates, and the elongation is f/δ times of the original vibration process of vibrating the object.

Furthermore, the frequency difference δ takes a value between 0.1 and 2 Hz.

Also, the duty cycle at which the light source is turned on is 10%.

The present invention correspondingly provides a vibration deformation observation device, including a transducer 1, a signal conditioner 2, a frequency analysis module 3, a frequency synthesizer 4 and a light source 5, the transducer 1, a signal conditioner 2, a frequency analysis module 3, The frequency synthesizer 4 and the light source 5 are connected in sequence,

The transducer 1 is used to collect the vibration signal of the observed vibration target, convert it into an electrical signal, and transmit it to the signal conditioner 2;

The signal conditioner 2 is used to amplify and filter the electrical signal input by the transducer 1, and transmit it to the frequency analysis module 3;

The frequency analysis module 3 is used to extract the vibration frequency f of the observed vibration target and transmit it to the frequency synthesizer 4;

The frequency synthesizer 4 is used to synthesize a square wave signal with a frequency of f-δ, where δ is a preset frequency difference and transmits it to the light source 5;

The light source 5 is used to flicker at a frequency of f-δ to elongate in time to show the deformation of the object when vibrating, and the elongation is f/δ times the original vibration process of vibrating the object.

Furthermore, the frequency difference δ takes a value between 0.1 and 2 Hz.

Also, the duty cycle at which the light source is turned on is 10%.

Also, the transducer 1 employs a vibration sensor or a microphone.

The present invention correspondingly provides a vibration deformation recording method. First, the vibration frequency of the observed vibration target is measured, and the measurement result is recorded as f, and then a square wave signal with a frequency of f-δ is synthesized, and δ is a preset frequency difference. According to this square wave signal, the light source is controlled to flicker at a frequency of f-δ, and the deformation state of the object is elongated in time to show the deformation of the object when it vibrates, and the elongation is f/δ times the original vibration process of the object; the camera is used to shoot and record The deformation of a time-elongated object as it vibrates.

Also, make the shutter exposure time longer than the flickering period of the light source.

Alternatively, use the light source control signal to control the camera shutter.

The present invention utilizes the method of accumulating phase difference by frequency difference to ingeniously realize the observation of the deformation of high-speed vibrating objects with the naked eye, and at the same time, use ordinary cameras to record the deformation of high-speed vibrating objects, and provide a low-cost vibration deformation observation device , suitable for popularization and use, and has important market value.

Description of drawings

FIG. 1 is a schematic diagram of the relationship between the vibration frequency of an object, the flickering frequency of a light source and the observed vibration frequency according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of the principle structure of an embodiment of the present invention.

FIG. 3 is a schematic diagram of a circuit structure of an embodiment of the present invention.

FIG. 4 is a schematic diagram of a frequency analysis and synthesis circuit according to an embodiment of the present invention.

detailed description

The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments.

The vibration frequency of a vibrating object is generally tens to thousands of hertz, and its vibration frequency is mainly determined by the material, shape, and size, so its vibration frequency is relatively stable, and the process of each vibration is basically the same. Therefore, the present invention proposes to illuminate it with a light source with a flash frequency close to its vibration frequency (for example, 1 Hz lower than the vibration frequency), and because of the frequency difference between each vibration and illumination, the phase difference between the moment of illumination and the vibration position is It can be changed sequentially within one cycle, and the changing frequency is exactly the difference between the vibration frequency and the flickering frequency of the light source. In this way, the state of different phases of the vibrating object in one cycle can be captured sequentially, and the connection is exactly the continuous deformation of the vibrating object. Although the vibration frequency of the object has not changed, the observed visual vibration frequency is the difference between the vibration frequency and the flash frequency (for example, 1 Hz). At this time, the deformation of each position when the object vibrates can be clearly observed, and an ordinary camera can also be used Recording, but because the light source is flickering, the camera may cause black bars and flickering phenomena. The present invention further proposes: on the one hand, it can be improved by adjusting the exposure time. On the other hand, if the camera supports shutter control, the control of the light source can be controlled The signal controls the shutter of the camera directly or after frequency division to achieve complete synchronization and ensure the camera effect.

First, use a transducer (vibration sensor or microphone) to measure the vibration frequency of the observed vibration target, record the measurement result as f, and then synthesize a signal with a frequency of f-δ, and the frequency difference δ is preferably 0.1 to 2 Hertz, and use this signal to control the flickering of the light source, that is, the light source flickers at a frequency f-δ. The duty cycle of its lighting is preferably controlled at about 10%, that is, in each cycle, the light source lighting time accounts for 10% of the total time. The temperature is 10 milliseconds, the light source is on for 1 millisecond and off for 9 milliseconds. If the duty cycle is too low, the brightness of the target is not enough, making it difficult to observe. If the duty cycle is too high, the observed target will be blurred.

Let the vibration equation of any particle of the object be:

A＝a×cos(t×f×2×π+ω) Formula 1

Where A is the position of the particle, a is the amplitude, t is the time, f is the vibration frequency, and ω is the initial phase. The initial phase of each particle is different.

Then the flickering equation of the light source is: (for simplified representation, it is represented by a sine wave, which is actually a square wave, and the light source is bright when it is at a high level)

L=b×cos(t×(f－δ)×2×π) Formula 2

Where L is the state of the light source, b is the amplitude, since the light source is controlled by a square wave, b=1 in practice.

The actual design is a square wave with adjustable duty ratio, so that the light source is bright when the level is high. To simplify the analysis, it is considered that the light source is bright when L=1. Then when the light source is on, the conditions to be satisfied are:

t×(f－δ)×2×π=2×n×π, n=0,1,2,3... Formula 3

where n is the number of cycles.

but:

t=n/2(f－δ), n=0,1,2,3... Formula 4

The observed state of any particle of a vibrating object is:

S=a×cos((n/2(f－δ))×f×2×π+ω), n=0,1,2,3... Formula 5

Assume that the time 1/f of one period of vibration of the object is divided into f-δ equal parts on average, and the length of each period is 1/(f×(f-δ)), if the object is observed at each equal time, then it can be observed to the vibration state of the object, and the observed state is:

S'=a×cos((n/2(f－δ))×2×π+ω), n=0,1,2,3... Formula 6

S-S'=-2×a×sin(n×π×f/(f-δ))×sin(n×π×(f-1)/(f-δ)), n=0,1, 2,3... Formula 7

Let D be the distance difference between the position of a particle at a certain moment in a vibration cycle and the actually observed position, then:

D=sin(n×π×f/(f-δ))×sin(n×π×(f-1)/(f-δ)), n=0,1,2,3... Formula 8

Since the value of δ is very small (the preferred value is between 0.1 and 2), the value of f is generally between tens and one kilohertz, so the three values of f-δ, f, and f-1 are very close. Therefore, f The values of /(f-δ) and (f-1)/(f-δ) are both close to 1, so the value of D is close to sin(n×π)×sin(n×π), and n is an integer, Therefore D is close to 0, even when f=50 Hz, δ=2 Hz, the value of D is not greater than 0.01. It can be considered that the observed vibration state S of the object is very close to its actual vibration state S', and the observed vibration frequency of the object's visual effect is δ. Since the vibration frequency of the original particle is f, and the actually observed vibration frequency is δ, the value of f is generally tens to hundreds of Hz, and the value of δ is generally 0.1-2 Hz, so it is equivalent to the original vibration process It is elongated by f/δ times, almost tens to thousands of times.

Therefore, an embodiment of the present invention provides a vibration deformation observation method. First, the vibration frequency of the observed vibration target is measured, and the measurement result is recorded as f, and then a square wave signal with a frequency of f-δ is synthesized, and δ is a preset The frequency difference value controls the light source to flicker at the frequency f-δ according to the square wave signal, and elongates in time to show the deformation of the object when it vibrates, which is f/δ times the original vibration process of the object.

The present invention proposes through experiments that the preferred value of δ is between 0.1 and 2 Hz, which can achieve a relatively comfortable observation effect. When the vibration frequency of the object is high, the value of δ can be appropriately increased, but generally it should not exceed 5 Hz, otherwise The observation effect is not good. In particular, when δ=1 Hz, D=0.

Therefore, through the method of the present invention, the deformation state of the object when it vibrates is clearly and accurately observed, and can be recorded with an ordinary camera.

In Fig. 1, the vibration frequency of the object is drawn as 10 Hz (a solid line with an amplitude of 1), ie f=10. The flickering frequency of the light source is 9 Hz (dashed line with an amplitude of 0.2), that is, δ=1, the abscissa is time, and the ordinate is amplitude. The circle on the horizontal axis represents the moment when the light source is flickering, which corresponds to L=1 in formula 2. The symbol 'X' represents the state of vibration of the object at the moment when the light source is on, and the symbol '口' represents the vibration state of the object In one cycle, the time is divided into 9 parts, and the vibration state at the beginning of each time, it can be seen that each 'X' symbol has a corresponding '口' symbol, and the dotted line connected by the 'X' symbols is equivalent to Because the vibration state of the object is elongated in time, that is, the vibration is felt to be slowed down visually, which can be observed with the naked eye. Its visual frequency is exactly 1 Hz, which is the difference frequency δ between the vibration frequency of the object and the flash frequency.

Fig. 2 shows the realization principle, the transducer 1, the signal conditioning module 2, the frequency analysis module 3, the frequency synthesizer 4 and the light source 5 are connected in sequence. The transducer 1 collects the vibration signal of the vibrating target, converts it into an electrical signal, and transmits it to the signal conditioning module 2, where the signal is amplified and filtered and then transmitted to the frequency analysis module 3 to extract the instantaneous frequency f of the vibration of the object, and thus The frequency determines the signal frequency f-δ synthesized by the frequency synthesizer 4, and δ is the frequency difference. The signal is a square wave signal with an adjustable duty cycle, which is used to control the light source 5 to produce flickering lighting. When the level is high, the light source 5 is turned on, and the light source 5 is turned off when the level is low. The cost of implementing the frequency synthesizer 4 using a single-chip microcomputer is relatively low, and it is easy to implement. In addition, it can also be implemented with an FPGA or a VCO (voltage-controlled oscillator). The frequency analysis module 3 and the frequency synthesizer 4 can be integrated and realized as a frequency analysis and synthesis module, which can be realized by using a phase-locked loop and a voltage-controlled oscillator, or by using a single-chip microcomputer. The transducer 1 can be a vibration sensor or a microphone. The transmission of the output of the frequency synthesizer 4 to the light source 5 can be realized by using a switch component. The light source 5 can be an ordinary white LED lighting source. The signal conditioning module 2 may use an existing signal conditioner.

In addition, the power supply can also be set to provide operating voltage for the required components. Further, a control panel may be provided for users to set up by themselves.

As shown in FIG. 3 , the embodiment is realized with a vibration sensor 11 , a signal conditioner 12 , a frequency analysis and synthesis module 13 , a switch assembly 14 , a white LED lighting source 15 , a power supply 16 and a control panel 17 . Vibration sensor 11, signal conditioner 12, frequency analysis and synthesis module 13, switch assembly 14 and white LED lighting source 15 are connected sequentially, control panel 17 is connected to frequency analysis and synthesis module 13, power supply 16 is respectively connected to signal conditioner 12, frequency analysis and synthesis module 13. Switch assembly 14.

For the accessible observation target, the vibration sensor 11 contacts the observation target to detect its vibration frequency. For observation targets that are difficult to contact (such as the vibrating wings of insects), the transducer can also use a microphone to collect the sound of the target's vibration to detect its vibration frequency.

The signal conditioner 12 is composed of LM324 operational amplifier, and the function realized is to amplify and filter the weak signal collected by the vibration sensor 11. Generally speaking, only the signal below 1000 Hz is reserved, because the frequency of most vibrating objects is here within range.

When the frequency analysis and synthesis module 13 adopts a single-chip microcomputer, the performance requirement is not high, but it is preferably provided with a timer to realize frequency analysis. The ATMEGA328 of ATMEL is selected here.

The functions preferably provided by the control panel 17 are firstly to control the amplification factor and filter cut-off frequency of the signal conditioner 12, and secondly to control the preset frequency difference δ and the brightness of the light source. The setting of control panel 17 can be input to single-chip microcomputer, is controlled by single-chip microcomputer.

The signal processed by the signal conditioner 12 is sent to the single-chip microcomputer, and the single-chip microcomputer counts its frequency to obtain its frequency f, and then subtracts the frequency difference δ preset by the control panel 17 from f to obtain the flickering frequency f-δ of the light source, and according to This value controls the timer (timer) that single-chip microcomputer itself possesses, makes the frequency of the output signal of timer be f-δ, also sets the duty ratio of timer timer output signal according to the brightness setting of control panel 17 simultaneously.

The switch assembly 14 is composed of a field effect transistor IFR540. The signal output by the timer of the single-chip microcomputer controls the switch assembly 14. When the output signal is at a high level, the switch assembly 14 is turned on to control the white LED lighting source 15 to emit light. When the output signal is low When it is flat, the switch assembly 14 is cut off, and the white LED lighting source 15 is turned off. The white LED illumination light source 15 should shine on the object to be observed.

According to such a design, the flickering frequency of the white LED lighting source 15 can be δ higher than the vibration frequency of the observation target. When δ is between 0.1 and 2, the vibration deformation can be clearly observed by the naked eye, and can be detected with an ordinary video camera or The camera performs image recording.

The frequency analysis and synthesis module 13 can also be realized by using a phase-locked loop and a voltage-controlled oscillator, as shown in FIG. The frequency converter 103, the reference frequency source 101 and the mixer 103 are respectively connected to the phase-locked loop 102, the phase-locked loop 102 is connected to the voltage-controlled oscillator 104, and the output of the voltage-controlled oscillator 104 is connected to the mixer 103 and the switch assembly 14. Both the signal from the signal conditioner 12 and the output signal from the voltage-controlled oscillator 104 are sent to the mixer 103 for frequency mixing to obtain a difference frequency signal. The output signal of the voltage-controlled oscillator 104 is simultaneously sent to the switch assembly 14 to control the light source. The difference frequency signal obtained by the reference frequency source 101 and the mixer 103 is sent to the phase locked loop 102 for comparison.

First, the reference frequency source 101 is set to δ, and the mixer 103 mixes the signal from the signal conditioner 12 and the signal of the voltage-controlled oscillator 104 to obtain a difference frequency signal, and the difference frequency signal and the signal from the reference frequency source 101 are sent into The phase-locked loop 102 performs the comparison and uses the comparison result to control the voltage-controlled oscillator 104. Under the control of the phase-locked loop 102, the frequency difference between the signal synthesized by the voltage-controlled oscillator 104 and the signal from the signal conditioner 12 is δ. At this time, the output signal of the voltage-controlled oscillator 104 and the signal from the signal conditioner 12 always maintain a difference frequency δ.

During specific implementation, the reference frequency source (REF Clock), phase-locked loop (PLL), mixer (VCO) and voltage-controlled oscillator (MIXER) can use existing components and parts. A relatively low-cost implementation is to use LM567, which integrates PLL and VCO. The reference frequency source is generated by frequency division of a general-purpose crystal oscillator.

The embodiment of the present invention also provides a vibration deformation recording method correspondingly. First, the vibration frequency of the observed vibration target is measured, and the measurement result is recorded as f, and then a square wave signal with a frequency of f-δ is synthesized, and δ is a preset Frequency difference, according to the square wave signal to control the light source to flicker at the frequency f-δ, to elongate in time to show the deformation of the object when it vibrates, and to elongate to f/δ times the original vibration process of vibrating the object; Filming, recording the deformation of an object elongated in time as it vibrates.

When you need to take pictures, you need to pay attention. Since the light source is flickering, human eyes can produce the illusion of continuous movement of objects through the persistence of vision effect, but the shutter of the camera is opened instantly, so flickering and black bars may occur. The present invention further proposes to solve this problem in two optional ways:

1. If the shutter of the camera cannot be controlled by an external trigger, the shutter exposure time can be extended appropriately. Specifically, the exposure time of the shutter should be longer than the flickering period of the light source. For example, if the flickering frequency of the light source is 100 Hz, its flickering period is

1/100 = 0.01 second

As long as the shutter exposure time of the camera is equal to 0.01 second, it is guaranteed to capture a light source illumination during each exposure. Further, if the shutter exposure time of the camera is equal to 0.02 second, it can be guaranteed that two light source illuminations are captured for each exposure time. This ensures that the camera results are free from flickering and black bars.

2. If the camera supports external triggering of the shutter, the camera shutter can be controlled by the light source control signal. Since the frame rate of a general camera is about 24-30fps, which is lower than the flickering frequency of the light source, the shutter cannot be triggered every time the light source lights up, but this can make the light source illuminate every time the shutter is exposed, and make the frame frequency as high as possible.

The specific embodiments described herein are intended to be illustrative of the invention only. Any skilled person familiar with the technology can easily obtain its changes or replacements within the technical scope disclosed in the present invention, so the protection scope of the present invention should be covered within the protection scope defined by the claims.

Claims (10)

1. A vibration deformation observation method is characterized in that: firstly, the vibration frequency measurement is carried out to the vibration target to be observed, and the measurement result is f, and then a synthesized frequency is a square wave signal of f-δ, and δ is a preset frequency The difference value, according to this square wave signal, controls the light source to flicker at a frequency of f-δ, elongates in time to show the deformation of the object when vibrating, and elongates to f/δ times the original vibration process of vibrating the object. 2. The vibration deformation observation method according to claim 1, characterized in that the frequency difference δ is between 0.1 and 2 Hz. 3. The vibration deformation observation method according to claim 1, characterized in that: the duty cycle of the light source being on is 10%. 4. A vibration deformation observation device is characterized in that: comprise transducer (1), signal conditioner (2), frequency analysis module (3), frequency synthesizer (4) and light source (5), transducer (1), signal conditioner (2), frequency analysis module (3), frequency synthesizer (4) and light source (5) are connected sequentially, The transducer (1) is used to collect the vibration signal of the observed vibration target, convert it into an electrical signal, and transmit it to the signal conditioner (2); The signal conditioner (2) is used to amplify and filter the electrical signal input by the transducer (1), and transmit it to the frequency analysis module (3); the frequency analysis module (3) is used to extract the observed The vibration frequency f of the vibration target is transmitted to the frequency synthesizer (4); the frequency synthesizer (4) is used to synthesize a square wave signal with a frequency of f-δ, and δ is a preset frequency difference, and transmitted to the light source (5); The light source (5) is used to flicker at a frequency of f-δ to elongate in time to show the deformation of the object when vibrating, and the elongation is f/δ times the original vibration process of vibrating the object. 5. The vibration deformation observation device according to claim 4, characterized in that the frequency difference δ is between 0.1 and 2 Hz. 6 . The vibration deformation observation device according to claim 4 , wherein the duty cycle of the light source is 10%. 7. The vibration deformation observation device according to claim 4, 5 or 6, characterized in that: the transducer (1) adopts a vibration sensor or a microphone. 8. A vibration deformation recording method is characterized in that: firstly, the vibration frequency measurement is carried out to the observed vibration target, and the measurement result is recorded as f, and then a frequency is synthesized as a square wave signal of f-δ, and δ is a preset frequency The difference value, according to the square wave signal, controls the light source to flicker at the frequency f-δ, and shows the deformation of the object when it vibrates in time, which is f/δ times the original vibration process of vibrating the object; the camera is used to shoot , recording the deformation of a time elongated object as it vibrates. 9. The vibration deformation recording method according to claim 8, characterized in that: the exposure time of the shutter is longer than the flickering period of the light source. 10. The vibration deformation recording method according to claim 8, characterized in that: the camera shutter is controlled by a light source control signal.