A kind of particle image velocimetry is with electronic target and method of application thereof
(1) technical field
The present invention relates to a kind of particle image velocimetry and use electronic target, belong to the velocity measuring technique field of flowing.
(2) background technology
Particle image velocimetry (Particle Image Velocimetry is called for short PIV) is a kind of modern laser velocimeter technology, mainly applies to flow field velocity and measures.Obtain the flow field velocity field through following the trail of the motion of trace particle in the flow field.Traditional P IV technology uses a thickness to illuminate the particle in the flow field at the laser light sheet below 1 millimeter; Through single camera the position of particle in very short time followed the trail of, realize the two-dimension speed field measurement (representing with 2D2C usually) in the two dimensional surface.The PIV technology all has in fields such as Aero-Space, the energy, chemical industry and medical science very widely to be used.
A crucial experiment link being arranged demarcating in the PIV technology, mainly is to concern one to one in order to set up in physical measurement zone and the imaging plane, promptly obtains mapping function.Timing signal is positioned over the laser light sheet irradiation area with target, and target surface is complete and laser light sheet is overlapping.Realize demarcation then through the location of pixels on the imaging plane of punctuate on the record by imaging target, and through physical location and the relation between the location of pixels of analyzing punctuate to the physical measurement zone.Here target flat board normally be provided with the consistent punctuate battle array of size shape of geometry arrangement in target plane, and punctuate can be circular, square or criss-cross pattern.
PIV uses common target to be the metal target at present, is after handle on the metal plate surface, the punctuate dot matrix to be printed on target surface, perhaps suppresses the punctuate battle array of a depression at target surface.The use of this type of target has more limitation.At first, the dot matrix of target can not change with the requirement of different experiments operating mode, has influenced its applicability.After changing the viewing field of camera size, can change over the magnification of picture.Like this size of the punctuate on the target and punctuate spacing are just had different requirement, and the metal target of customization can only use in certain usable range, can not arbitrarily change the dot matrix of target.Secondly, the imaging of target is restricted.Because metal target itself is not a light emitting source, imaging the time must rely on add light source reflect to form clearly as, this practicality to target has caused certain restriction, the image quality of target also depends on intensity and the angle that adds light source simultaneously.For example the punctuate of compacting generation is forming the identification that shade is unfavorable for punctuate under the extraneous illumination sometimes near the punctuate imaging.This phenomenon has at camera under the situation at visual angle and seems more outstanding.The 3rd, the imaging precision of punctuate cannot say for sure to demonstrate,prove on the target.Because the restriction of machining precision, generally the machining precision of target often lags behind the resolution of camera imaging.For example common PIV experiment, the resolution of camera imaging is at several microns or tens microns, and in the manufacturing of target, the shape of punctuate and yardstick all are difficult to reach this precision.If add bad that light source is provided with, the precision of demarcation more cannot say for sure to have demonstrate,proved.The present invention just is being based on above some consideration, has proposed a kind of particle image velocimetry and has used electronic target.
(3) summary of the invention
The purpose of this invention is to provide a kind of particle image velocimetry and use electronic target; The user can realize having difformity through the operation setting target lattice parameter of electronic target TFT touch-screen, the target dot matrix of size and spacing, to satisfy the PIV experiment demand of different operating modes.
A kind of particle image velocimetry of the present invention is used electronic target; It comprises hardware system and software systems two parts; Hardware system comprises Software Development Platform and electronic target main body two parts again; Wherein Software Development Platform comprises microcomputer 1 and emulator 2, and the electronic target main body comprises development board 3 and display screen 4.This microcomputer 1 is general microcomputer, adopts the OPTIPLEX of Dell 960 desktop computers, and win764 position system, basic configuration are Intel Core2 central processing unit, 6GB internal memory, 1TB hard disk, ATI Radeon HD 4670 independent video cards; This emulator 2 adopts the general 20 pin jtag interface emulators of ARM, version 8.0; This development board 3 is selected the STM32 development board in Divine Land for use, supports general 2.4/2.8 cun LCD liquid crystal touch screen; This display screen 4 adopts common 2.8 cun TFT touching display screens.Wherein, microcomputer 1 is connected with the data line of emulator 2 through jtag interface; Adopt 20 faller gill lines to connect between emulator 2 and the development board 3; Display screen 4 is fixed on the development board 3, connects through 32 general core LCD interfaces.Development board 3 and the display screen 4 common electronic target main bodys of forming can work independently after breaking away from development environment, and required power supply is that separate configurations or link to each other with microcomputer 1 through the USB interface on the development board 3 obtains.
Its development environment of these software systems adopts software uVision IDE V4.10, and software J-linkARM V4.20 is adopted in the emulation of development board 3.Configuring simulator 2 and development board 3 in software uVision make uVision discern development boards 3 through emulator 2.The boot of compiling electronic target generates the HEX file, and the firmware import tool that carries through uVision is loaded into the flash memory (flash) on the development board 3 with this HEX, and so each startup electronic target can both move this program automatically.Electronic target after the installation boot can be through the prompting on the display screen 4, and touch display screen 4 comes the operating and setting dot matrix.
A kind of particle image velocimetry of the present invention is with the method for application of electronic target, and its step is following:
(1) connect the electronic target power supply, electronic target is opened automatically and is shown start-up picture.
(2) operation interface that dot matrix is provided with occurs after start-up picture finishes, touch successively and select to be provided with option, select to be provided with until accomplishing last, electronic target generates the punctuate dot matrix automatically.It is following successively that each is provided with the interface:
A) select the punctuate shape, promptly circular, square, cruciform or User Defined punctuate etc.If selected the User Defined punctuate, that parameter is provided with carries out the setting of punctuate spacing d with directly jumping to step e.
B) select punctuate size dimension c, i.e. 3,5,7 and 9 pixel sizes;
C) select punctuate brightness type, promptly wait bright and Gaussian distribution;
D) select the punctuate color, i.e. white, green, red and blue;
E) select punctuate spacing d, i.e. 7,9,11 and 13 pixels;
(3) after the completion lattice parameter was provided with, boot showed the electronic target dot matrix according to each parameter automatically.
(4) if the user wants to change the setting of dot matrix, the parameter that just can turn back to behind the start-up picture by return key on the touch-screen is provided with the interface.Parameter setting in the repeating step (2) can change the dot matrix on the electronic target.
The electronic target boot has been reserved open programmable interface function U DM, i.e. User Defined Mark (user definition punctuate).This interface provides fixing function structure, and the user is according to the parameters such as shape, color and size of the self-defined single punctuate of structure of function.It is empty that this UDM function requires input parameter, and rreturn value is the two-dimensional matrix (being the punctuate color matrix) of unsigned 16-bit integer, and translation and compiling environment adopts the uVision development platform equally.Import user-defined UDM function and compile whole boot through the uVision development platform, the HEX file that generates is imported the flash memory (being flash) on the development board 3, the user just can realize the target dot matrix of self-defined punctuate.
A kind of particle image velocimetry of the present invention is with the effect and the advantage of electronic target and method of application thereof:
(1) electronic target possesses the calibrating function of traditional PI V measurement with the plane target, and more traditional plane target has wider applicability simultaneously, can change the form of dot matrix in the target according to different requirement of experiment, like punctuate shape, size, spacing etc.And traditional PI V just can't change the form of its dot matrix after one-shot forming with the plane target.
(2) dot matrix of electronic target with rule arranged, and precision is high.High-quality LCDs has very high resolution, and at present available LCDs can reach the resolution greater than 300ppi, is applicable to the demarcation needs that PIV measures fully.And electronic target can guarantee that when forming punctuate each punctuate geometric configuration, size are consistent with spacing; And precision can reach the resolution of PIV experiment digital camera imaging, has reduced the error that punctuate shape, size and spacing that traditional PI V causes when the machining with the plane target differ greatly.
(3) electronic target belongs to luminophor, the luminous intensity and the color of ability free adjustment punctuate, and this is the characteristic that common PIV target does not possess.Adopt the electronic target timing signal, experiment will not need that external light source is auxiliary to be carried out to picture, and this has strengthened the applicability of electronic target greatly.According to different experiment conditions,, change the color and the inner Luminance Distribution of single punctuate of punctuate, the precision that can effectively improve punctuate identification and demarcate to the difference of punctuate recognizer in the calibration process.
(4) electronic target has designed the open DLL expanded and makes the user to call for bootstrap program module according to the special target punctuate function of own needs exploitation, realizes user-defined electronic target.
(4) description of drawings
Fig. 1 is an electronic target development platform synoptic diagram;
Fig. 2 is an electronic target dot matrix synoptic diagram;
Fig. 3 is that the electronic target parameter is provided with block diagram;
Fig. 4 is circular punctuate centroid algorithm synoptic diagram;
Fig. 5 is the setting and the imaging synoptic diagram of square punctuate gray scale Gaussian distribution;
Symbol among the figure:
The 1-microcomputer; The 2-emulator; The 3-development board;
The 4-display screen;
The a-direction reference line; The b-punctuate; C-punctuate size dimension;
D-punctuate spacing;
(5) practical implementation method
A kind of particle image velocimetry of the present invention is used electronic target, and the user can realize having difformity through the operation setting target lattice parameter of electronic target TFT touch-screen, the target dot matrix of size and spacing, to satisfy the PIV experiment demand of different operating modes.
As shown in Figure 1, electronic target main body of the present invention is made up of development board 3 and display screen 4.Wherein said development board 3 is selected the STM32 development board in Divine Land for use, supports general 2.4/2.8 cun LCD liquid crystal touch screen.Described display screen 4 adopts common 2.8 cun TFT touching display screens.Display screen 4 is fixed on the development board 3, connects through 32 general core LCD interfaces.Electronic target is when working alone, and required power supply is provided by microcomputer 1, and promptly linking to each other with microcomputer 1 usefulness usb data line through the USB interface on the development board 3 obtains.
The software systems of electronic target, its Software Development Platform comprise two hardware componenies: microcomputer 1 and emulator 2.Wherein said microcomputer 1 is general microcomputer, adopts the OPTIPLEX of Dell 960 desktop computers, and win764 position system, basic configuration are Intel Core2 central processing unit, 6GB internal memory, 1TB hard disk, ATI Radeon HD 4670 independent video cards.Emulator 2 adopts the general 20 pin jtag interface emulators of ARM, version 8.0.The connected mode of development platform is: microcomputer 1 is connected with the data line of emulator 2 through jtag interface; Adopt 20 faller gill lines to connect between emulator 2 and the development board 3.
Software uVision IDE V4.10 is adopted in the exploitation of electronic target software systems, and software J-link ARM V4.20 is adopted in the emulation of development board 3.Configuring simulator 2 and development board 3 in software uVision make uVision discern development boards 3 through emulator 2.The boot of compiling electronic target generates the HEX file, and the firmware import tool that carries through uVision is loaded into the flash memory (flash) on the development board 3 with this HEX, and so each startup electronic target can both move this program automatically.
The standard target dot matrix that electronic target showed is as shown in Figure 2, adopts the equidistant structurized dot matrix of punctuate to arrange.Wherein a is the direction reference line of target, is used to point out the direction of target placement and the flow direction in experiment measuring flow field.B is a punctuate, promptly forms the fundamental element of target dot matrix, and the punctuate that shows in the diagram is square punctuate, has circle commonly used and cruciform punctuate to supply the user to select during practical application in addition.C is defined as the punctuate size dimension, and square punctuate is the length of side, and circular punctuate is a diameter, and the cruciform punctuate is the cross curve line length.D is the punctuate spacing, i.e. distance between two adjacent punctuates.
A kind of particle image velocimetry of the present invention is accomplished through touch operation display screen 4 with the use of electronic target; The parameter of electronic target dot matrix is set and generates satisfactory target dot matrix according to the information on the display screen 4 during operation, the step of its method of application is (as shown in Figure 3) as follows:
(1) connect the electronic target power supply, promptly connect the USB interface of development board 3 and the USB interface of microcomputer 1 through the usb data line, electronic target is opened automatically and is shown start-up picture.
(2) operation interface that dot matrix is provided with occurs after start-up picture finishes, touch successively and select to be provided with option, select to be provided with until accomplishing last, electronic target generates the punctuate dot matrix automatically.It is following successively that each is provided with the interface:
A) select the punctuate shape, promptly circular, square, cruciform or User Defined punctuate etc.If selected the User Defined punctuate, that parameter is provided with carries out the setting of punctuate spacing d with directly jumping to step e.
B) select punctuate size dimension c, i.e. 3,5,7 and 9 pixel sizes etc.
C) select punctuate brightness type, promptly wait bright and Gaussian distribution etc.
D) select the punctuate color, i.e. white, green, redness and blueness etc.;
E) select punctuate spacing d, i.e. 7,9,11 and 13 pixels etc.;
(3) after the completion lattice parameter was provided with, boot showed the electronic target dot matrix according to each parameter automatically;
(4) if the user wants to change the setting of dot matrix, the parameter that just can turn back to behind the start-up picture by return key on the touch-screen is provided with the interface.Parameter setting in the repeating step (2) changes the dot matrix on the electronic target.
Be provided with in the step in the target parameter, the Luminance Distribution type of each pixel in the described punctuate brightness of step (2c) the type index point is specially to design according to the demand of discerning the punctuate CENTER ALGORITHM in the PIV experimental calibration process.Each pixel is luminous for equal strength under the selected color in its medium bright index point.Experiment test result as shown in Figure 4 (for the synoptic diagram display effect needs, the effect of negative film has been adopted in the target imaging), what the left figure of its Fig. 4 showed is the imaging of circular dot matrix, target has adopted bright patterns such as punctuate.Therefore see from imaging that the punctuate imaging is clear, the sharp apparition of punctuate edge brightness.Shown in the punctuate profile identification figure of the right figure of Fig. 4, adopt the method for setting gray threshold can be very easy to and the profile that obtains punctuate accurately.The display mode that this punctuate etc. are bright is applicable to the coordinate that obtains punctuate center sub-pixel precision through the geometric center of gravity algorithm of punctuate imaging region.
Another kind of Gaussian distribution is that the colour brightness of index point distributes that outside gradual change weakens from the punctuate center according to the standard Gaussian distribution in the punctuate brightness type.As shown in Figure 5, the brightness of target setting is the standard Gaussian distribution of a square punctuate, and the normalization of brightness size is handled.Luminance Distribution and the Luminance Distribution of setting of this punctuate after imaging has extraordinary similarity.Especially outstanding is that effect is, adopts the punctuate of Gauss's Luminance Distribution, because there is the punctuate geometric center to be brightness peak, therefore imaging back Luminance Distribution also has a very significantly peak value.This imaging effect is highly profitable to the peak value method of identification of discerning the punctuate center in the PIV experimental calibration link, and promptly the regional peak value according to punctuate imaging gray scale obtains the punctuate centre coordinate.This shows that it is that the difference of punctuate recognizer specially is provided with in demarcating to PIV that electronic target adopts different punctuate brightness types, than traditional PI V target very outstanding advantage is arranged.
The electronic target boot has been reserved open programmable interface function U DM, i.e. User Defined Mark (user definition punctuate).This interface provides fixing function structure, and the user can be according to the parameters such as shape, color and size of the self-defined single punctuate of structure of function.It is empty that this UDM function requires input parameter, and rreturn value is the two-dimensional matrix (being the punctuate color matrix) of unsigned 16-bit integer, and translation and compiling environment adopts the uVision development platform equally.Import user-defined UDM function and compile whole boot through the uVision development platform, the HEX file that generates is imported the flash memory (flash) on the development board 3, the user just can realize the target dot matrix of self-defined punctuate.