CN112378576A - Optical pressure sensitive coating pressure calibrating device based on CCD camera - Google Patents
Optical pressure sensitive coating pressure calibrating device based on CCD camera Download PDFInfo
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Abstract
The invention provides an optical pressure-sensitive paint pressure calibration device based on a CCD camera, which comprises: the device comprises an acoustic standing wave tube, a bottom cover, an optical window, a sound source, a power amplifier, a CCD camera, a lens, a light filter, an LED excitation light source, a signal generator, a dynamic pressure sensor, a direct current power supply, a signal amplifier, a data acquisition box, an optical pressure-sensitive paint calibration sheet and a computer. Has the advantages that: 1) the CCD camera-based optical pressure-sensitive paint pressure calibration device can be used for carrying out optical pressure-sensitive dynamic calibration on each wave band below 1kHz, so that the technical blank is filled; 2) dynamic calibration experiments can be continuously performed; particularly, the invention can realize the control of the LED excitation light source and the CCD camera through the two pulse signal generating units, and the structure is simple to realize; 3) the pressure calibration device for the pressure-sensitive paint has the advantages of simple structure, convenience in processing, strong anti-interference capability and low experimental cost.
Description
Technical Field
The invention belongs to the technical field of pressure-sensitive paint pressure calibration, and particularly relates to an optical pressure-sensitive paint pressure calibration device based on a CCD camera.
Background
The Pressure Sensitive Paint (PSP) technique based on computer vision and image processing technique is an important breakthrough of non-contact flow display technique. The basic principle of the optical pressure-sensitive pressure measurement technology is as follows: the pressure sensitive paint is uniformly covered on the surface of the tested model, and consists of photosensitive molecules and an oxygen permeable substrate. When excited by light of a specific wavelength, the photosensitive molecules in the paint transition from an originally stable ground state to an excited state of a high energy level. The photosensitive molecules in the unstable excited state are collided by oxygen molecules diffused from the measured surface, the energy of the excited state is lost, and the photosensitive molecules are inactivated and returned to the ground state, and the process does not generate radiant light, so that the luminous intensity is reduced, and an oxygen quenching phenomenon is formed. The greater the concentration of oxygen molecules, i.e.: the higher the pressure in the atmosphere, the stronger the quenching effect of oxygen, and the darker the coating will emit under a certain light. Therefore, under the irradiation of light, the luminous intensity of the pressure sensitive coating can reflect the pressure value on the surface of the measured model. And taking an image picture of the surface of the measured model under the light irradiation, and analyzing the image picture to obtain the pressure distribution of the surface of the measured model.
In the prior art, the optical pressure-sensitive paint pressure measurement technology mainly has the following problems:
in the detection process of the amplitude-frequency characteristic of the optical pressure-sensitive coating, in order to obtain the dynamic pressure distribution of the universe, the acquisition of images must be completed through a camera, and due to the fact that the frame rate of a CCD camera is low, when a pressure-sensitive coating fluorescence image sequence under high-frequency pulsating pressure is acquired, a large system error can be introduced, and therefore the detection accuracy of the amplitude-frequency characteristic of the optical pressure-sensitive coating is reduced.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides the optical pressure-sensitive paint pressure calibration device based on the CCD camera, which can effectively solve the problems.
The technical scheme adopted by the invention is as follows:
the invention provides an optical pressure-sensitive paint pressure calibration device based on a CCD camera, which comprises:
the device comprises an acoustic standing wave tube (1), a bottom cover (2), an optical window (3), a sound source (4), a power amplifier (5), a CCD camera (6), a lens (7), a light filter (8), an LED excitation light source (9), a signal generator (10), a dynamic pressure sensor (11), a direct current power supply (12), a signal amplifier (13), a data acquisition box (14), an optical pressure-sensitive paint calibration sheet (15) and a computer (16);
the optical pressure-sensitive paint calibration sheet (15) is fixedly installed on the inner side of the bottom cover (2) at one end of the acoustic standing wave tube (1); the section of the optical pressure-sensitive paint calibration sheet (15) is fixedly provided with the dynamic pressure sensor (11); the dynamic pressure sensor (11) is powered by the direct current power supply (12); the voltage signal output end of the dynamic pressure sensor (11) is connected to the input end of the computer (16) after passing through the signal amplifier (13) and the data acquisition box (14);
one side of the acoustic standing wave tube (1) close to the bottom cover (2) is symmetrically grooved, and two optical windows (3) are symmetrically arranged on two sides of the acoustic standing wave tube (1) respectively;
the other end of the acoustic standing wave tube (1) is fixedly provided with the sound source (4) and is opposite to the optical pressure-sensitive paint calibration sheet (15);
the 1 st channel of the signal generator (10) is connected to the sound source (4) through the power amplifier (5);
the 2 nd channel of the signal generator (10) is connected with an external trigger end of the CCD camera (6); the output end of the CCD camera (6) is connected with the computer (16); wherein the lens (7) is fixed at the front end of the CCD camera (6); the filter (8) is fixed at the front end of the lens (7);
the 3 rd channel of the signal generator (10) is connected with the external trigger end of the LED excitation light source (9);
the CCD camera (6) and the LED excitation light source (9) are respectively arranged on two sides of the acoustic standing wave tube (1) and are aligned to the optical pressure-sensitive paint calibration sheet (15) through corresponding optical windows;
the signal generator (10) comprises: the system comprises a sine electric signal generating unit, a 1 st pulse signal generating unit, a 2 nd pulse signal generating unit, a synchronous controller and a main control unit;
the main control unit is respectively connected with the synchronous controller and the sinusoidal electric signal generating unit; the synchronous controller is respectively connected with the external trigger end of the 1 st pulse signal generating unit and the external trigger end of the 2 nd pulse signal generating unit;
the sinusoidal electric signal generating unit is used for continuously outputting a sinusoidal electric signal with a period of T under the control of the main control unit, transmitting the sinusoidal electric signal to the power amplifier (5), amplifying the sinusoidal electric signal by the power amplifier (5), and transmitting the amplified sinusoidal electric signal to the sound source (4), so that the sound source (4) is controlled to emit a sinusoidal sound wave with the period of T; after the sine sound wave is acted by the acoustic standing wave tube (1), the surface of the optical pressure-sensitive paint calibration sheet (15) is subjected to stable sine pressure standing waves with the period of T;
the 1 st pulse signal generating unit is connected with an external trigger end of the CCD camera (6), the 1 st pulse signal generating unit is used for outputting a 1 st square wave pulse signal, the period of the 1 st square wave pulse signal is m × T + T/n, and the pulse width is T/n; wherein m x T + T/n is greater than the reciprocal of the maximum frame rate of the camera; n is the pulse number output after the 1 st pulse signal generating unit is triggered, and is also the phase number formed by dividing the average of the sinusoidal pressure standing waves in one period; m represents the number of camera shooting period intervals; every time the 1 st pulse signal generating unit is externally triggered once, n pulses with the pulse width of T/n are output according to the period m × T + T/n; the 1 st pulse signal generating unit is at a high level when outputting a pulse, and is at a low level when not outputting a pulse, and each time the 1 st pulse signal generating unit starts outputting a pulse, the method comprises the following steps: when the pulse is positioned at the rising edge of the pulse, the CCD camera (6) is controlled to start exposure, and every time the 1 st pulse signal generating unit finishes outputting the pulse, namely: when the pulse is positioned at the falling edge of the pulse, the CCD camera (6) is controlled to finish exposure; therefore, the 1 st pulse signal generation unit controls the CCD camera (6) to expose once every time m × T + T/n, each exposure time of the CCD camera (6) is equal to the pulse width T/n, and the CCD camera (6) exposes n times in total; when the CCD camera (6) finishes one exposure, outputting an image corresponding to the current phase; thus, when a sinusoidal pressure standing wave is divided equally into n phases, denoted in turn as phases
Phase position
Phase position
Then, the fluorescence image sequence corresponding to a complete cycle output by the CCD camera (6) is respectively as follows: and phase
Corresponding fluorescence image Q1And phase
Corresponding fluorescence image Q2…, and phase
Corresponding fluorescence image QnAnd transmitted to the computer (16);
the 2 nd pulse signal generating unit is connected with an external trigger end of the LED excitation light source (9), the 2 nd pulse signal generating unit is used for outputting a 2 nd square wave pulse signal, the pulse width of the 2 nd square wave pulse signal is n (m + T/n), the number of pulses output after each trigger is 1, wherein each time the 2 nd pulse signal generating unit is externally triggered, 1 pulse with the pulse width of n (m + T/n) is output; the 2 nd pulse signal generating unit is at a high level when outputting a pulse, and is at a low level when not outputting a pulse, and each time the 2 nd pulse signal generating unit starts outputting a pulse, the method comprises the following steps: and when the pulse is positioned at the rising edge of the pulse, controlling the LED excitation light source (9) to be switched on, enabling the LED excitation light source (9) to keep stable power and continuously emit light to irradiate the surface of the optical pressure-sensitive paint calibration sheet (15), and when the 2 nd pulse signal generation unit finishes outputting the pulse, namely: when the pulse is positioned at the falling edge of the pulse, the LED excitation light source (9) is controlled to be closed, therefore, the 2 nd pulse signal generation unit controls the on-time and the off-time of the LED excitation light source (9), and after the LED excitation light source (9) is opened, the on-time is equal to the pulse width n (m × T + T/n);
the synchronous controller is used for controlling the 1 st pulse signal generating unit and the 2 nd pulse signal generating unit to start to send out pulse signals synchronously;
the main control unit is used for: sending a synchronization start signal to a synchronization controller;
the computer (16) is configured to: receiving a fluorescent image sequence corresponding to a complete cycle output by the CCD camera (6), wherein the fluorescent image sequence is respectively as follows: and phase
Corresponding fluorescence image Q1And phase
Corresponding fluorescence image Q2…, and phase
Corresponding fluorescence image QnAnd transmitted to the computer (16); combining the pressure value collected by the dynamic pressure sensor (11) by comparing the fluorescence image Q1Fluorescence image Q2… fluorescence image QnAnd analyzing to realize pressure calibration of the pressure sensitive paint.
Preferably, the cross section of the acoustic standing wave tube (1) is a circular cross section.
Preferably, the acoustic standing wave tube (1) is made of stainless steel acoustic standing wave tube material.
Preferably, the 1 st square wave pulse signal emitted by the 1 st pulse signal generating unit has a high level of 5V and a low level of 0V; the 2 nd square wave pulse signal sent by the 2 nd pulse signal generating unit has a high level of 5V and a low level of 0V.
The optical pressure-sensitive paint pressure calibration device based on the CCD camera provided by the invention has the following advantages:
1) the CCD camera-based optical pressure-sensitive paint pressure calibration device can be used for carrying out optical pressure-sensitive dynamic calibration on each wave band below 1kHz, so that the technical blank is filled;
2) dynamic calibration experiments can be continuously performed; particularly, the invention can realize the control of the LED excitation light source and the CCD camera through the two pulse signal generating units, and the structure is simple to realize;
3) the pressure calibration device for the pressure-sensitive paint has the advantages of simple structure, convenience in processing, strong anti-interference capability and low experimental cost.
Drawings
Fig. 1 is a schematic structural diagram of an optical pressure-sensitive paint pressure calibration device based on a CCD camera provided by the present invention.
Fig. 2 is a schematic diagram of a signal generator provided by the present invention.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The invention provides a CCD camera-based optical pressure-sensitive paint pressure calibration device, which is mainly used for calibrating the dynamic pressure of a pressure-sensitive paint. The optical pressure-sensitive paint pressure calibration device based on the CCD camera provided by the invention also has the advantages of simple structure, low processing cost, strong usability and strong anti-interference capability.
The invention provides a CCD camera-based optical pressure-sensitive paint pressure calibration device, which comprises an acoustic standing wave tube 1, a bottom cover 2, an optical window 3, a sound source 4, a power amplifier 5, a CCD camera 6, a lens 7, an optical filter 8, an LED excitation light source 9, a signal generator 10, a dynamic pressure sensor 11, a direct-current power supply 12, a signal amplifier 13, a data acquisition box 14, an optical pressure-sensitive paint calibration sheet 15 and a computer 16, wherein the acoustic standing wave tube 1 is arranged on the bottom cover of the optical pressure-sensitive paint calibration device;
the cross section of the acoustic standing wave tube is a circular cross section, the design fundamental frequency of the calibration cabin is 400Hz, the overall length size is 425mm through calculation, the inner diameter is 50mm, and stainless steel with high stability and light tightness is selected as the material of the acoustic standing wave tube.
An optical pressure-sensitive paint calibration sheet 15 is fixedly arranged on the inner side of the bottom cover 2 at one end of the acoustic standing wave tube 1; the section where the optical pressure-sensitive paint calibration sheet 15 is located is fixedly provided with a dynamic pressure sensor 11; the dynamic pressure sensor 11 is used for real-time acquisition of pressure. The dynamic pressure sensor 11 is powered by a direct current power supply 12; the voltage signal output end of the dynamic pressure sensor 11 is connected to the input end of a computer 16 after passing through a signal amplifier 13 and a data acquisition box 14; therefore, the dynamic pressure sensor is powered by the direct-current power supply, the output voltage signal is amplified by the signal amplifier and input into the data acquisition box, and the data acquisition box converts the electric signal into a digital signal and transmits the digital signal to the computer to finish the display of the dynamic pressure.
One side of the acoustic standing wave tube 1, which is close to the bottom cover 2, is symmetrically grooved, and two optical windows 3 are symmetrically arranged on two sides of the acoustic standing wave tube 1 respectively;
the other end of the acoustic standing wave tube 1 is fixedly provided with a sound source 4 in a bolt mode and the like, and the sound source 4 is opposite to the optical pressure-sensitive paint calibration sheet 15;
the 1 st channel of the signal generator 10 is connected to the sound source 4 through the power amplifier 5; the sinusoidal electric signal output by the 1 st channel of the signal generator 10 is amplified by the power amplifier 5, and then the sound source is controlled to emit sound waves at a set frequency.
The 2 nd channel of the signal generator 10 is connected with the external trigger end of the CCD camera 6; the output end of the CCD camera 6 is connected with a computer 16; wherein, a lens 7 is fixed at the front end of the CCD camera 6; an optical filter 8 is fixed at the front end of the lens 7, so that the image collected by the CCD camera 6 is not interfered by an excitation light source.
The 3 rd channel of the signal generator 10 is connected with the external trigger end of the LED excitation light source 9;
the CCD camera 6 and the LED excitation light source 9 are respectively arranged at two sides of the acoustic standing wave tube 1 and are aligned with the optical pressure-sensitive paint calibration sheet 15 through corresponding optical windows; therefore, the light paths of the CCD camera and the LED excitation light source can reach the optical pressure-sensitive paint calibration sheet through the optical window.
Referring to fig. 2, the signal generator 10 includes: the system comprises a sine electric signal generating unit, a 1 st pulse signal generating unit, a 2 nd pulse signal generating unit, a synchronous controller and a main control unit;
the main control unit is respectively connected with the synchronous controller and the sine electric signal generating unit; the synchronous controller is respectively connected with the external trigger end of the 1 st pulse signal generating unit and the external trigger end of the 2 nd pulse signal generating unit;
in the invention, the external trigger end of the LED excitation light source is connected with the 2 nd pulse signal generating unit, and the brightness of the LED excitation light source is controlled by the high and low levels of the 2 nd pulse signal generating unit.
The external trigger end of the CCD camera is connected with the 1 st pulse signal generating unit, and the initial exposure and the ending exposure of the CCD camera are controlled through the high and low levels of the 1 st pulse signal generating unit.
The 1 st pulse signal generating unit and the 2 nd pulse signal generating unit realize synchronization through a synchronization controller. The main control unit controls the starting time of the 1 st pulse signal generating unit and the 2 nd pulse signal generating unit, and further the acquisition of different phases of sinusoidal pressure standing waves is achieved.
The working principle of the signal generator is described in detail as follows:
the sinusoidal electric signal generating unit is used for continuously outputting a sinusoidal electric signal with a period of T under the control of the main control unit, transmitting the sinusoidal electric signal to the power amplifier 5, amplifying the sinusoidal electric signal by the power amplifier 5, and transmitting the amplified sinusoidal electric signal to the sound source 4, so that the sound source 4 is controlled to emit a sinusoidal sound wave with the period of T; after the sinusoidal sound wave is acted by the acoustic standing wave tube 1, the surface of the optical pressure-sensitive paint calibration sheet 15 is subjected to a stable sinusoidal pressure standing wave with a period of T;
the 1 st pulse signal generating unit is connected with an external trigger end of the CCD camera 6, the 1 st pulse signal generating unit is used for outputting a 1 st square wave pulse signal, the period of the 1 st square wave pulse signal is m × T + T/n, and the pulse width is T/n; wherein m x T + T/n is greater than the reciprocal of the maximum frame rate of the camera; n is the number of pulses output after the 1 st pulse signal generating unit is triggered and is the average of the sinusoidal pressure standing wave of one periodThe number of phases formed by division; m represents the number of camera shooting period intervals; every time the 1 st pulse signal generating unit is externally triggered once, n pulses with the pulse width of T/n are output according to the period m × T + T/n; the 1 st pulse signal generating unit is at a high level when outputting a pulse, and is at a low level when not outputting a pulse, and each time the 1 st pulse signal generating unit starts outputting a pulse, the method comprises the following steps: on the rising edge of the pulse, the CCD camera 6 is controlled to start exposure, and each time the 1 st pulse signal generation unit finishes outputting the pulse, that is: when the pulse is positioned at the falling edge of the pulse, the CCD camera 6 is controlled to finish exposure; therefore, the 1 st pulse signal generation unit controls the CCD camera 6 to expose once every time m × T + T/n, the exposure time of each time of the CCD camera 6 is equal to the pulse width T/n, and the CCD camera 6 exposes n times in total; each time the CCD camera 6 finishes one exposure, outputting an image corresponding to the current phase; thus, when a sinusoidal pressure standing wave is divided equally into n phases, denoted in turn as phases
Phase position
Phase position
Then, the sequence of fluorescence images corresponding to a complete cycle output by the CCD camera 6 is: and phase
Corresponding fluorescence image Q1And phase
Corresponding fluorescence image Q2…, and phase
Corresponding fluorescence image QnAnd transmitted to the computer 16;
the 2 nd pulse signal generating unit is connected with an external trigger end of the LED excitation light source 9, the 2 nd pulse signal generating unit is used for outputting a 2 nd square wave pulse signal, the pulse width of the 2 nd square wave pulse signal is n (m + T/n), the number of pulses output after being triggered each time is 1, wherein every time the 2 nd pulse signal generating unit is externally triggered once, 1 pulse with the pulse width of n (m + T/n) is output; the 2 nd pulse signal generating unit is at a high level when outputting a pulse, and is at a low level when not outputting a pulse, and each time the 2 nd pulse signal generating unit starts outputting a pulse, the method comprises the following steps: and when the pulse is positioned at the rising edge of the pulse, controlling the LED excitation light source 9 to be switched on, enabling the LED excitation light source 9 to keep stable power and continuously emit light to irradiate the surface of the optical pressure-sensitive paint calibration sheet 15, and when the 2 nd pulse signal generating unit finishes outputting the pulse, namely: when the pulse is at the falling edge of the pulse, the LED excitation light source 9 is controlled to be turned off, so that the 2 nd pulse signal generation unit controls the on-time and the off-time of the LED excitation light source 9, and after the LED excitation light source 9 is turned on, the on-time is equal to the pulse width n (m × T + T/n);
the synchronous controller is used for controlling the 1 st pulse signal generating unit and the 2 nd pulse signal generating unit to start to send out pulse signals synchronously;
the main control unit is used for: sending a synchronization start signal to a synchronization controller;
the main control unit is specifically configured to:
1) the main control unit controls the sinusoidal electric signal generating unit to continuously output a sinusoidal electric signal with a period of T, the sinusoidal electric signal is transmitted to the power amplifier 5, and is amplified by the power amplifier 5 and then transmitted to the sound source 4, so that the sound source 4 is controlled to emit a sinusoidal sound wave with the period of T;
2) the main control unit sends an external trigger signal to the 1 st pulse signal generating unit and the 2 nd pulse signal generating unit through the synchronous controller, and then the 1 st pulse signal generating unit and the 2 nd pulse signal generating unit are started simultaneously;
3) after the 2 nd pulse signal generating unit is started, the 2 nd pulse signal generating unit outputs 1 square wave pulse signal with the pulse width of n (m × T + T/n), so that the LED excitation light source 9 is controlled to continuously emit light to irradiate the surface of the optical pressure-sensitive paint calibration sheet 15 for n (m × T + T/n);
4) after the 1 st pulse signal generating unit is started, outputting n square wave pulse signals with the period of m × T + T/n and the pulse width of T/n, and controlling the CCD camera 6 to expose once every time m × T + T/n, wherein the exposure time is T/n each time, and n times of total exposure; each time the CCD camera 6 finishes one exposure, outputting an image corresponding to the current phase;
therefore, the main control unit realizes automatic control of the CCD camera 6 and the LED excitation light source 9 through the 1 st pulse signal generating unit and the 2 nd pulse signal generating unit.
The computer 16 is used for: receiving a fluorescent image sequence corresponding to a complete cycle output by the CCD camera 6, which are respectively: and phase
Corresponding fluorescence image Q1And phase
Corresponding fluorescence image Q2…, and phase
Corresponding fluorescence image QnAnd transmitted to the computer 16; by combining the pressure values collected by the dynamic pressure sensor 11, the fluorescence image Q1Fluorescence image Q2… fluorescence image QnAnd analyzing to realize pressure calibration of the pressure sensitive paint.
Therefore, in the invention, the CCD camera performs exposure once at the time interval of m × T + T/n and outputs the fluorescence image corresponding to the corresponding phase, thereby completing the acquisition of the fluorescence image corresponding to one period phase. In addition, in practical application, the specific value of the time interval m × T + T/n can be adjusted according to the actual situation of the camera frame rate. Therefore, the invention collects the fluorescent image sequence of the pressure sensitive coating under the high-frequency pulsating pressure through the CCD camera with the low frame rate, avoids the error caused by the low frame rate of the camera, and improves the detection accuracy of the amplitude-frequency characteristic of the optical pressure sensitive coating. In addition, the image acquisition mode of the invention can avoid data storage/transmission congestion and ensure the smoothness of data storage and transmission.
The specific pressure calibration method can be as follows:
step 1.1, to the fluorescence image QjPerforming image processing to obtain sum phase
Corresponding light intensity Ij；
The step 1.1 specifically comprises the following steps:
fluorescence image QjW pixel points are provided; each pixel point corresponds to a light intensity value, therefore, w light intensity values are obtained in total, and the average value of the w light intensity values is the phase position
Corresponding light intensity Ij。
Step 1.2, obtaining a fluorescence image QjIn the acquisition process, the exposure time of the CCD camera is obtained, and then the change curve between the real pressure value and the time on the surface of the PSP sample is searched according to the exposure time of the CCD camera to obtain a fluorescence image QjCorresponding true pressure value Pj；
Step 1.3, when the sinusoidal pressure standing wave is not applied to the PSP sample, the following steps are carried out: the PSP sample is set at atmospheric pressure, and image shooting is carried out on the PSP sample, so as to obtain a reference pressure PrefAnd light intensity at a reference pressure Iref；
since j is 1, 2.., n, when j is 1, one equation for a and B is obtained; when j is 2, an equation for a and B is obtained; by analogy, when j is equal to n, one equation for a and B is obtained; thus, a total of n equations for A and B are obtained; solving n equations about A and B by adopting a least square method to obtain final values of A and B;
a and B are constants, and the values of A and B and reference pressure PrefAnd light intensity at a reference pressure IrefSubstituting the calibration equation (1) to obtain a calibration equation (2):
wherein, in the calibration equation (2), PjIs equal to the light intensity IjA corresponding calibration pressure value;
it should be noted that the main function of the calibration equation (1) is to obtain the values of a and B, so the pressure of the calibration equation (1) is the true pressure value P acquired by the dynamic pressure sensorj. After obtaining the values of a and B, further obtaining a calibration equation (2), wherein the main function of the calibration equation (2) is: the calibration pressure value of the light intensity corresponding to each fluorescence image is calculated, because the calculated calibration pressure value is the pressure value reflecting the characteristics of the coating at this time, and the real pressure value collected by the dynamic pressure sensor 4 is not adopted.
Step 4, keeping the amplitude of the sinusoidal pressure standing wave stable and unchanged, and enabling the frequency of the sinusoidal pressure standing wave to be f1Increase to f2Obtaining the corresponding amplitude A by adopting the modes of the step 2 to the step 3m(f2) (ii) a Judging the amplitude Am(f2) Whether or not to reduce to amplitude Am(f1) And if so, the amplitude Am(f2) Is the cut-off frequency of the PSP coating; if not, the frequency of the sinusoidal pressure standing wave is further increased until the current frequency f is madexAmplitude A ofm(fx) Reduced to amplitude Am(f1) Up to half the time, at this time, the current frequency fxIs the cut-off frequency of the PSP coating;
continuously increasing the frequency of the sine pressure standing wave if the current frequency fzAmplitude A ofm(fz) Decreasing to 0, the current frequency fzIs the limiting frequency of the PSP coating; therefore, the amplitude-frequency characteristic of the PSP coating is detected.
Therefore, in the invention, the sinusoidal pressure standing wave with stable frequency and amplitude is obtained through the acoustic standing wave tube; then, according to the frequency of the sinusoidal pressure standing wave, the exposure time and the frame rate of the CCD camera are controlled, and the next phase of the sinusoidal pressure standing wave corresponding to the image shot each time is ensured, so that the obtained image sequence can just form a period; in the process, the excitation light source keeps stable and continuous luminescence, and the CCD camera starts image sequence collection of different phases.
The optical pressure-sensitive paint pressure calibration device based on the CCD camera provided by the invention has the following advantages:
1) the CCD camera-based optical pressure-sensitive paint pressure calibration device can be used for carrying out optical pressure-sensitive dynamic calibration on each wave band below 1kHz, so that the technical blank is filled;
2) dynamic calibration experiments can be continuously performed; particularly, the invention can realize the control of the LED excitation light source and the CCD camera through the two pulse signal generating units, and the structure is simple to realize;
3) the pressure calibration device for the pressure-sensitive paint has the advantages of simple structure, convenience in processing, strong anti-interference capability and low experimental cost.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and improvements can be made without departing from the principle of the present invention, and such modifications and improvements should also be considered within the scope of the present invention.
Claims (4)
1. An optical pressure sensitive paint pressure calibration device based on a CCD camera is characterized by comprising: the device comprises an acoustic standing wave tube (1), a bottom cover (2), an optical window (3), a sound source (4), a power amplifier (5), a CCD camera (6), a lens (7), a light filter (8), an LED excitation light source (9), a signal generator (10), a dynamic pressure sensor (11), a direct current power supply (12), a signal amplifier (13), a data acquisition box (14), an optical pressure-sensitive paint calibration sheet (15) and a computer (16);
the optical pressure-sensitive paint calibration sheet (15) is fixedly installed on the inner side of the bottom cover (2) at one end of the acoustic standing wave tube (1); the section of the optical pressure-sensitive paint calibration sheet (15) is fixedly provided with the dynamic pressure sensor (11); the dynamic pressure sensor (11) is powered by the direct current power supply (12); the voltage signal output end of the dynamic pressure sensor (11) is connected to the input end of the computer (16) after passing through the signal amplifier (13) and the data acquisition box (14);
one side of the acoustic standing wave tube (1) close to the bottom cover (2) is symmetrically grooved, and two optical windows (3) are symmetrically arranged on two sides of the acoustic standing wave tube (1) respectively;
the other end of the acoustic standing wave tube (1) is fixedly provided with the sound source (4) and is opposite to the optical pressure-sensitive paint calibration sheet (15);
the 1 st channel of the signal generator (10) is connected to the sound source (4) through the power amplifier (5);
the 2 nd channel of the signal generator (10) is connected with an external trigger end of the CCD camera (6); the output end of the CCD camera (6) is connected with the computer (16); wherein the lens (7) is fixed at the front end of the CCD camera (6); the filter (8) is fixed at the front end of the lens (7);
the 3 rd channel of the signal generator (10) is connected with the external trigger end of the LED excitation light source (9);
the CCD camera (6) and the LED excitation light source (9) are respectively arranged on two sides of the acoustic standing wave tube (1) and are aligned to the optical pressure-sensitive paint calibration sheet (15) through corresponding optical windows;
the signal generator (10) comprises: the system comprises a sine electric signal generating unit, a 1 st pulse signal generating unit, a 2 nd pulse signal generating unit, a synchronous controller and a main control unit;
the main control unit is respectively connected with the synchronous controller and the sinusoidal electric signal generating unit; the synchronous controller is respectively connected with the external trigger end of the 1 st pulse signal generating unit and the external trigger end of the 2 nd pulse signal generating unit;
the sinusoidal electric signal generating unit is used for continuously outputting a sinusoidal electric signal with a period of T under the control of the main control unit, transmitting the sinusoidal electric signal to the power amplifier (5), amplifying the sinusoidal electric signal by the power amplifier (5), and transmitting the amplified sinusoidal electric signal to the sound source (4), so that the sound source (4) is controlled to emit a sinusoidal sound wave with the period of T; after the sine sound wave is acted by the acoustic standing wave tube (1), the surface of the optical pressure-sensitive paint calibration sheet (15) is subjected to stable sine pressure standing waves with the period of T;
the 1 st pulse signal generating unit is connected with an external trigger end of the CCD camera (6), the 1 st pulse signal generating unit is used for outputting a 1 st square wave pulse signal, the period of the 1 st square wave pulse signal is m × T + T/n, and the pulse width is T/n; wherein m x T + T/n is greater than the reciprocal of the maximum frame rate of the camera; n is the number of pulses output after the 1 st pulse signal generating unit is triggered and is also one cycleThe number of phases into which the average of the sinusoidal pressure standing wave is divided; m represents the number of camera shooting period intervals; every time the 1 st pulse signal generating unit is externally triggered once, n pulses with the pulse width of T/n are output according to the period m × T + T/n; the 1 st pulse signal generating unit is at a high level when outputting a pulse, and is at a low level when not outputting a pulse, and each time the 1 st pulse signal generating unit starts outputting a pulse, the method comprises the following steps: when the pulse is positioned at the rising edge of the pulse, the CCD camera (6) is controlled to start exposure, and every time the 1 st pulse signal generating unit finishes outputting the pulse, namely: when the pulse is positioned at the falling edge of the pulse, the CCD camera (6) is controlled to finish exposure; therefore, the 1 st pulse signal generation unit controls the CCD camera (6) to expose once every time m × T + T/n, each exposure time of the CCD camera (6) is equal to the pulse width T/n, and the CCD camera (6) exposes n times in total; when the CCD camera (6) finishes one exposure, outputting an image corresponding to the current phase; thus, when a sinusoidal pressure standing wave is divided equally into n phases, denoted in turn as phases
Phase position
…, phase
Then, the fluorescence image sequence corresponding to a complete cycle output by the CCD camera (6) is respectively as follows: and phase
Corresponding fluorescence image Q1And phase
Corresponding fluorescence image Q2…, and phase
Corresponding fluorescence image QnAnd transmitTo the computer (16);
the 2 nd pulse signal generating unit is connected with an external trigger end of the LED excitation light source (9), the 2 nd pulse signal generating unit is used for outputting a 2 nd square wave pulse signal, the pulse width of the 2 nd square wave pulse signal is n (m + T/n), the number of pulses output after each trigger is 1, wherein each time the 2 nd pulse signal generating unit is externally triggered, 1 pulse with the pulse width of n (m + T/n) is output; the 2 nd pulse signal generating unit is at a high level when outputting a pulse, and is at a low level when not outputting a pulse, and each time the 2 nd pulse signal generating unit starts outputting a pulse, the method comprises the following steps: and when the pulse is positioned at the rising edge of the pulse, controlling the LED excitation light source (9) to be switched on, enabling the LED excitation light source (9) to keep stable power and continuously emit light to irradiate the surface of the optical pressure-sensitive paint calibration sheet (15), and when the 2 nd pulse signal generation unit finishes outputting the pulse, namely: when the pulse is positioned at the falling edge of the pulse, the LED excitation light source (9) is controlled to be closed, therefore, the 2 nd pulse signal generation unit controls the on-time and the off-time of the LED excitation light source (9), and after the LED excitation light source (9) is opened, the on-time is equal to the pulse width n (m × T + T/n);
the synchronous controller is used for controlling the 1 st pulse signal generating unit and the 2 nd pulse signal generating unit to start to send out pulse signals synchronously;
the main control unit is used for: sending a synchronization start signal to a synchronization controller;
the computer (16) is configured to: receiving a fluorescent image sequence corresponding to a complete cycle output by the CCD camera (6), wherein the fluorescent image sequence is respectively as follows: and phase
Corresponding fluorescence image Q1And phase
Corresponding fluorescence image Q2…, and phase
Corresponding fluorescence image QnAnd transmitted to the computer (16); combining the pressure value collected by the dynamic pressure sensor (11) by comparing the fluorescence image Q1Fluorescence image Q2… fluorescence image QnAnd analyzing to realize pressure calibration of the pressure sensitive paint.
2. The CCD camera-based optical pressure sensitive paint pressure calibration device according to claim 1, characterized in that the cross section of the acoustic standing wave tube (1) is a circular cross section.
3. The CCD camera-based optical pressure sensitive paint pressure calibration device according to claim 1, characterized in that the acoustic standing wave tube (1) is a stainless steel acoustic standing wave tube material.
4. The CCD camera-based optical pressure sensitive paint pressure calibration device according to claim 1, wherein the 1 st pulse signal generating unit generates a 1 st square wave pulse signal having a high level of 5V and a low level of 0V; the 2 nd square wave pulse signal sent by the 2 nd pulse signal generating unit has a high level of 5V and a low level of 0V.
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