Home

meas_syst_report

1. UNPIPSALA UNIVERSITET TVE12041 Examensarbete 15 hp Maj 2012 Measurement system with image analysis Detecting signal disturbances in the Head up display of the JAS 39 Gripen Jenny Eriksson Matilda Dahlqvist Lars Svensson UNIVERSITET Teknisk naturvetenskaplig fakultet UTH enheten Bes ksadress ngstr mlaboratoriet L gerhyddsv gen 1 Hus 4 Plan O Postadress Box 536 751 21 Uppsala Telefon 018 471 30 03 Telefax 018 471 30 00 Hemsida http www teknat uu se student Abstract Measurement system with image analysis Jenny Eriksson Matilda Dahlqvist Lars Svensson A measurement system has been developed to detect errors in the head up display of JAS 39 Gripen Errors have been identified by continuously capturing images of the display and comparing it to a reference image Signal acquisition has been made concurrently with a Data Acquisition device and the data has been processed and analyzed in LabVIEW a visual programming tool The resulting measurement system functioned as intended There was an uncertainty in the time stamp of the logged error with a standard deviation of 15 1 ms Handledare Per Nilstad Mikael Lindeman Amnesgranskare Ken Welch Examinator Martin Sj din ISSN 1401 5757 TVE12041 Popul rvetenskaplig sammanfattning Ett m tsystem har tagits fram med syftet att detektera orsaker till fel i siktlinjesindikatorn det vill s ga siktesanordningen p JAS 39 Gr
2. and facilitate use of the measurement system the DAQ device and the voltage divider was mounted and enclosed in an aluminum electronics box The box was fitted with cable glands for the outgoing USB cable and for the signal cable connected to the HUD via a 96 pole DIN 41612 connector 10 4 1 6 Notebook computer The computer used was a Dell Latitude E4300 with an Intel Core 2 Duo P9400 2 40GHz 4 Gb RAM and an SSD storage drive The dual core pro cessor can manage two separate strings of code simultaneously provided the program is adapted for this feature 4 2 Software Image analysis signal saving and presentation of data were accomplished using LabVIEW Two different VIs were created one for the acquisition and analysis and one for the presentation They were called Measurement VI and Presentation VI 4 2 1 Programming tools The software used that was compatible with both the camera and the DAQ device was LabVIEW LabVIEW is very user friendly while working with image and signal processing One option was to acquire the signals in Lab VIEW and then do the analysis in MATLAB however trouble with com patibility was expected It would be a more expensive solution since some licenses for extra modules for LabVIEW already existed at SAAB The licenses to the vision modules existing at SAAB were however earlier versions so they were not compatible with the latest version of LabVIEW LabVIEW 2011 The option was either to purcha
3. LAB gives greater scope to accurately shape the program s functionality but it is often more time consuming to build and less user friendly A visual programming tool generally makes the development process quick and the code easy to understand This is because it works with blocks of pre written code called Virtual Instruments VIs presented as icons instead The update rate is confidential of rows of text commands It was decided to use the visual programming tool LabVIEW which is frequently used in various types of data acquisition The LabVIEW user interface is divided into two parts one for the code and one for execution 3 5 Signal Conditioning Signal conditioning is necessary if the signals to be measured do not fit the acquisition device For example a noisy signal may have to be filtered to be able to extract relevant information from it If a signal has higher voltage levels than the analog inputs of the DAQ device are specified for it has to be conditioned There is a variety of methods to lower the voltage without losing relevant information from the signal Voltage division is a method to linearly lower voltage levels of signals Un Li out Z2 Figure 2 Scheme of a voltage divider The layout of a voltage divider is illustrated in figure 2 In this case the outgoing voltage is given by equation 1 where U and U are voltages and Z and Zo are resistances La Uout S LED U 1 4 Method d
4. am plitude in DAQ assistant The signal data were loaded into queues as wave packets sampled at a rate of 2 kHz each signal was loaded into a specific queue A wave packet had 2000 samples and represented one second so in this case the queues were designed to include 13 elements The queues were filled in a while loop which included the wait function to control the iteration time The signal acquisition and image analysis was run thus in the same VI in parallel loops When the trigger in the image analysis went on a loud sound was announced from the notebook computer Then acquisition of images and signal data for three more seconds was triggered to get data of a total of 13 seconds An empty AVI file was created in a designated folder This AVI file was then filled with the images released from the queue one by one The signal data were in the same way saved to file with the function VI Write To Measurement File The VI was designed so another AVI file or Mea surement file could not be created within 13 s after the last one This was to prevent the same data being saved several times in the case of flickering 13 on the HUD The signal and image data were presented to the user by a graphical user interface GUI in LabVIEW The measurement VI had a graphical user in terface where the user could control test parameters and observe an ongoing test A graph of each signal was shown in real time in the user interface There were input o
5. as auto scaled to present unpredictable changes in amplitude A screenshot of the GUI is presented in figure 13 19 Time of error 12012 05 04 14 27 14 734 Group 0 Additional graphs Instructions for zoom and cursor ZOOM i Cursors 3 x al 5 Right cick the cur a 14 45 22 742 6 Drag the cursor to the specified time of failure see current Figure 13 The Graphical user interface used to present the signal data from saved files When the VI ran the user could select which file to retrieve and analyze The files were named after which HUD unit was tested and which time the files were saved The time when the error occurred was shown in the GUI With tools implemented in the GUI the user could add a red line cursor in the graphs to mark where the error occurred To look at a close up of the error zoom tools were implemented Instructions of how to use the tools were available 5 3 Testing and time stamp The tests were very useful for the development of the measurement system See section 4 4 for descriptions of the tests The stress test running Hyper Pi at the same time did not halt the pro gram However there were some delays in the loop times Problems with RAM memory and how the signals were acquired were discovered and solved with help of the long time tests The test that detected most VI complications was the short time test When 20 the VI was restarted repeatedly the image ac
6. asurement accuracy and stability If the measurement system is going to be used as a long term solution a more professional set of hardware is required Changing the USB DAQ device for a PCI express or PXI device will greatly improve stability timing and accuracy of the system Equipping the system with a real time operating system will further increase timing capabilities Hardware of this stature demands a considerable investment so the cheaper prototype device must prove to be useful before such an upgrade is considered 6 5 4 Trigger on a signal error Another development that might contribute to a better analysis of the signals is to trigger the saving of images and signals on an alternation in the signal instead of on the display This can be done on a few signals that are detected to be the ones causing the problem or on all signals To be able to do the triggering on a signal you need to know what its waveform look like The detection of an irregularity could then be done by continuously measuring for example the amplitude and frequency or by doing a Fourier analysis of the wave 6 5 5 Replacing the camera with a light sensor To improve timing precision beyond 10 ms in the measuring system the camera frame rate must increase High speed cameras are expensive and have data transfer interfaces that are problematic to connect to a notebook computer Since the image analysis only measures average intensity it may be possible to replace
7. can simulate a system failure of this kind in a stationary test rig However they currently have no equipment to accurately correlate the system failiure to a certain set of input signals To detect abnormal input signals or loose wiring a custom designed measurement system is needed 2 Objective The project s main objective was to design a measurement system to aid the technicians analyzing the signal package going in the head up display seconds before and after the disturbance occurs The specifications of the system are e Errors should be identified by analyzing images of the HUD captured by a camera e Signal and video data were to be saved from ten seconds before to three seconds after an error occurred e The system should be mobile e The uncertainty in the time stamp should not exceed ten milliseconds e The system should be able to acquire video data and 16 signals from the HUD e The system should be able to run for up to five hours e The system must be able to measure signals from the HUD ranging from 100 to 100 volts e The software interface should be designed in a user friendly manner e An audio alarm should sound when an error has occurred 3 Theory 3 1 Image Acquisition The displayed image of the HUD is drawn line by line on the collimating glas with a certain update rate To film a continuously updated display with a digital video camera has complications A digital video consists of a sequence of images ca
8. e acquisition speed 22 was still a heavy load for the notebook processor Under normal testing con ditions the processor load was around 70 giving little room for additional activities during tests The stress test did not halt the program but loop times increased and the measurement accuracy was severely impaired During the development process memory leak problems were encountered and quickly halted the program due to the high data rate of the image ac quisition part The problems were identified and fixed and during final tests memory leak was a few megabytes over hours of testing and considered neg ligible In the final testing process a few bugs remained unsolved These problems occurred in approximately 1 run out of 20 and was tracked to the pre programmed express Vls for visual and data acquisition The so called express VIs of LabVIEW are high level user friendly tools that enables the programmer to quickly develop programs at the price of certain elements of control in advanced programs More experienced graphical programmers would use the lower level functionality of LabVIEW to make the same pro gram and prevent the express VIs from interfering with the main program Since the more persistent bugs were rare and solved by a simple program restart they did not significantly affect the practicality of the program 6 5 Suggested further development 6 5 1 Exporting a standalone application Software development licenses represent a co
9. e measurement system are described in sec tion 4 1 The complete system is shown in figure 7 and the specific hardware for signal acquisition is shown in figure 8 Figure 8 Signal acquisition hardware 16 The measurement system with the head up display is shown in figure 9 Figure 9 The measurement system 5 2 Software The two graphical user interfaces were built as user friendly as possible To simplify a user manual was written The finished versions of the GUls are described and shown in figures in this section 5 2 1 Measurement VI GUI The interface shown to the user during a test displayed both image and signal data A three step method had to be followed consisting of the steps calibration Accept reference image and Image and signal display In the first step calibration real time images from the camera were shown The calibration step was used to put the camera in a fixed position and adjust settings on the camera When the calibration was done there was a continue button to go to the next step see figure 10 17 Step 1 Calibration Calibration Figure 10 Step 1 in the measurement system GUI Enter unit identity number 123 Press CONTINUE when camera is in a fixed some In step 2 a proposal of a reference image was shown A pop up window appeared and the user could confirm the frame as the reference image by pressing ok or choose to select a new frame as refe
10. ed Several factors added up to a difference between the actual time of error and the logged time of error The largest factor contributing is our non deterministic operating system Windows XP Professional 32 bit that cannot be more accurate than within 100 ms with NI SignalExpress The DAQ device itself can acquire accurate samples however the time stamp for the initial value is not logged until it reaches the operating system and therefore it is the software that determines how accurate the timing is One solution to the problem would be to use a real time operating system which is deterministic instead of a regular operating system Another one would be to purchase a high speed digitizer which uses hardware time stamps 21 The operating system also affected the accuracy in the Get Date Time in Seconds Function used in the program Even though the function displays the time in milliseconds it only updates every 16 milliseconds The last factor noticeably affecting the time precision was the frame rate of the camera Since an image was taken only every 10 millisecond an uncer tainty of equal magnitude existed A solution to lowering this number would be to buy a camera with a higher frame rate A better strategy than using the logged time of error would be to analyze the acquired signal Master Blank which goes high as soon as the HUD goes black However this method cannot be used when it is Master Blank that is malfuncti
11. eues can keep a set number of elements of any type The Lossy en queue element VI removes element from the front of the queue when it has to add an element to a queue that is full The queue holding the images was designed to keep 1300 elements equivalent to 13 seconds of data at 100 fps The comparison of the last recorded image with the golden picture was ex ecuted with VIs included in the extra modules IMAQ Light Meter Rect angle VI computes a mean value of the intensity in all pixels in the image The difference between the mean intensity in the golden picture and mean intensity in the latest captured image was calculated and compared to the parameter Maximum match score Maximum match score was set auto matically in the beginning of a run but could also be altered by the user If the difference was higher than this parameter for 50 frames in a row the images were classified as inaccurate The 50 frames were to compensate for the flickering in the captured video caused by the update rate of the HUD see section 3 1 The saving of data could have been triggered based on analysis of only one image but since some frames were not fully updated the 50 frames were chosen to not classify the flickering as an error The signals were acquired by the DAQ device and transferred to Labview with a function called DAQ assistant The signals which were conditioned in the voltage divider were scaled in amplitude to their initial voltage
12. evelopment 4 1 Hardware To troubleshoot the head up display a customized signal measurement instru ment with image analysis was created The measurement system consisted of three parts image acquisition and analysis signal acquisition and pre sentation of the data Hardware used in the image analysis was a digital camera and a DAQ device for signal acquisition The measurement system should be a mobile solution and hardware used for presentation of data and analysis was therefore a notebook PC A schematic overview of the system is displayed in figure 3 Vision acquisition gt c gt IEEE 1394b D expansion card Notebook computer Signal data acquisition gt ou gt e gt Figure 3 Graphical illustration of measurement system components 4 1 1 Camera For the image analysis a camera with the right characteristics was needed particularly a high frame rate The most cost efficient camera that was found had a rate of 120 fps frames per second Cameras with a higher frame rate were available but they saved the data internally for later exportation For this application real time data transfer of every frame was needed The captured frames were transferred for analysis in the software Since the camera had to be compatible with the software the best alternatives for transferring the images with was USB GigE or IEEE1394B 2 There was a demand on the amount of data transferred each second A USB interface is limi
13. image with reference image Play sound If results differ trigger saving Store i e dsofvisual reference es rames in queue containing 13 seconds of visua image ata information in memory Signal acquisition loop Sample 15 analog signals on the DAQ device Store samples in queues containing 13 seconds of signal data Figure 5 Structure of the Measuring VI The VI started with showing a real time video used to calibrate the camera position When the calibration was finished the camera continued capturing frames frame number 60 was set to be the reference image golden picture if the user accepted it Otherwise it would take a new frame for the user to approve The delay of 59 frames was set so the reference image was taken after the camera had made its auto adjustments The final chosen reference image was sent to a while loop in which it was compared to the latest recorded image in each loop iteration The camera frame rate was lowered to 100 fps to secure a stable loop time To ensure that the loop time was kept a wait function was added called Wait Until next ms Multiple Function The image subroutine saved a film clip of the display when the image on the HUD disappeared The film clip contained frames from ten seconds be fore to three seconds after the triggering Since the computer could not keep 12 five hours of data in its memory the solution was to introduce queues in the VI Qu
14. ipen Fel har identifierats genom att filma displayen kontinuerligt och j mf ra bilderna med en referensbild Samtidigt har signaldata fr n siktlinjesindikatorn insamlats med hj lp av ett Data Acquisition kort Dessa data har sparats p fil n r den nytagna bilden fr n en kamera skiljt sig fr n referensbilden Databehandlingen och analysen har gjorts i LabVIEW som r ett grafiskt programmeringsverktyg Det resulterande systemet fungerade som planerat Det hade en m tos kerhet i tiden f r ett intr ffat fel Det visade sig att 95 procent av de uppm tta tiderna skiljde sig med upp till 30 2 millisekunder fr n den egentliga tiden Table of contents 1 Background Ll SAMBA Sa ie sd ro o a A Bg 1 2 Head Up Display 2d 238044244514 225 54428 54 1 3 Problem description Siac sas css rss A 2 Objective 3 Theory 3 1 Image Acquisition sosse A A ss see es 3 2 Image Analysis og Speak eho esse ser A sho inp as Se de Boia es 3 3 Signal Acquisition s s sa Ke Ae ee a A 3 4 Software for analysis and acquisition 3 5 Signal Conditioning e iy a ae PES CPE SS 4 Method development 471 Hardware svinet ae mov msk eS ane eT ee eth bok es eth hg AND Camera i IEC ee Gd a BO A 4 1 2 Expresscard adapter oo ooo oe eae Se ES 4 1 3 Camera attachment solution AL DAQ deVICE uss ra mode ed Bea lala do dd 4 1 5 Signal conditioning ARA A AA ve 4 1 6 Notebook computer rca pa A ot A NR 4 2 1 Program
15. it with a photo resistor sampled by the DAQ device In this case the sample rate could increase from 100 samples per second to maximally 250 000 samples per second making this uncertainty small compared to others 24 7 Conclusion A measurement system for signal acquisition for the head up display in the JAS 93 Gripen was constructed To fulfill the objective of creating a system that saves signal data when an unexpected shutdown occurred in the head up display a VI in LabVIEW was created The VI acquired signals from the Head up display with a DAQ device The VI was programmed to save signal data for a period of time ten seconds before and three seconds after the shutdown and to detect the shutdown using recorded frames of the head up display from a camera A laptop was used to get a mobile system for use in an industrial environment To provide the signal data in analyzable form for the technicians another VI in LabVIEW was created which could present saved signal data during a shutdown The data was presented with accuracy in time of 15 1 ms with 68 percent confidence References 1 What is Data Acquisition available at http www ni com dataacquisition whatis 22 03 12 2 NI Vision acquisition software available at http sine ni com nips cds view p lang en nid 12892 26 03 12 3 Hyper Pi available at http files extremeoverclocking com file php f 211 10 05 12 4 Gripen Cockpit available at http royaluniteds
16. ming tools A RR 4 2 2 Measurement VI 42 3 Presentation VI ees sa meii e or a eee a Aa UNS a 12 a a a es BS a a a A ee a BT a a a ke AA TES E E o E a li a o Rn 5 Results Od HardWare Ci A A A A DA Ss DEA OOMWArE A A A e igre 5 2 1 Measurement VIGUI 5 2 2 Presentation VI GUI usos Das al or 3 3 Testing and time Stallone ew ae or 6 Discussion 6 1 Effects of downgrading LabVIEW 6 2 Measurement accuracy 2 0 aoe Get a ss doo do 6 3 Processor bottleneck o o 15 16 17 17 19 20 6 4 Software Robustness 0 000004 22 6 5 Suggested further development 0 23 6 5 1 Exporting a standalone application 23 6 5 2 Acquire more signals aleja as to oa A 8 OO Be 23 6 5 3 Increase measurement accuracy and stability 24 6 5 4 Trigger on a signal A 24 6 5 5 Replacing the camera with a light sensor 24 7 Conclusion 1 Background 1 1 SAAB AB SAAB AB is an aerospace and defence company that has provided the Swedish Airforce with military aircraft since it was founded in Trollh ttan 1937 The company consists of the five major divisions Support and Services Security and Defence Solutions Aeronautics Dynamics and Electronic De fence Systems Aeronautics develop the JAS 39 Gripen system Dynamics produce ground combat weapons and Electronic Defence Systems develop radar systems Security and Defence Soution
17. nsiderable investment for a com pany To motivate the investment of our LabVIEW license SAAB wants to utilize it for more projects For the computer to be able to run the program without the license the program must be exported as an executable a exe file in windows Exporting programs from LabVIEW utilizes the LabVIEW Application Builder which is not as user friendly in our version LabVIEW 8 6 as it is in the later versions Initial attempts to export the software resulted in compatibility errors and missing files Since this desire appeared late in the time plan and seemed to consume more time than could be spared a decision was made to have the technicians test and feedback on the pro gram under the LabVIEW license for a few weeks Later the project group will return to SAAB to finalize and export the executable program 6 5 2 Acquire more signals One thing that the client mentioned as a desired development in the mea surement system was to acquire all 96 signals from the HUD Ideally one 23 would like to measure and analyze all of them but the budget limited the number to the 16 most important channels The quickest way of measuring more signals would be to add another USB DAQ device for instance the 80 channel NI USB 6225 and use the rest of the existing hardware This expansion will maintain the mobility of the system but it will not improve timing issues or stability due to the limitations of the USB bus 6 5 3 Increase me
18. oning 6 3 Processor bottleneck Initially the conceptual idea of the image analysis was to compare the color spectrum of a reference image with the color spectrum of a real time video The signal saving is triggered when the average pixel color shifted from green to black Since the amount of data to be acquired and analyzed was con siderable the processor had trouble keeping the acquisition speed up One hundred frames per second is equivalent to a cycle time of ten milliseconds The spectrum matching image processing had a cycle time of 20 ms For this reason another less time consuming method had to be implemented Re search implied that intensity analysis is less computationally intensive than color spectrum analysis and it provided a cycle time less than 10 ms To further optimize the software for the hardware LabVIEWs tools for parallel programming were used The computer SAAB provided was equipped with an Intel dual core pro cessor LabVIEW offers powerful and user friendly methods to utilize multi core processors The compiler recognizes separated while loops and handles them as two separate threads This was very useful for the application since we could dedicate one core to the signal acquisition and one to the visual acquisition and fully utilize all available processing power 6 4 Software Robustness Intensity measurement of a monochrome image proved to be an effective way to conduct the image analysis However the high imag
19. ptured by a sensor Normal acquisition rate is 25 30 frames per second but faster cameras are available If the shutter of the camera is open for a shorter time than the time it takes for the HUD to draw one display cycle the frame is delivered incomplete In cases when the camera frame rate is an even multiple of the display update rate the drawing operation appears in the same finished or unfinished state in every frame This problem may cause the captured video to fade in and out for second long periods 3 2 Image Analysis Image analysis can be made in several ways and the choice of method depends on the accuracy demands Each pixel of an image contains information about color and intensity To compare two images and decide if they are similar one can extract and compare data pixel by pixel 3 3 Signal Acquisition Data acquisition DAQ is a process that samples analog signals and convert them to digital values for processing in a computer and it is done with a DAQ device There are different models of DAQ devices adapted for different measurement situations For example how many and what type of signals to acquire the sampling rate and the hardware interface 1 3 4 Software for analysis and acquisition When combining image analysis and signal acquisition it is convenient to handle them in the same programming tool One can either use a text based or a visual programming language A text based programming environment for example MAT
20. quisition part of the VI some times failed this problem occured in approximately 1 run out of 20 Restart ing LabVIEW solved this problem By simulating several HUD input errors a mean value of the accuracy in the time stamp could be determined This mean value was adjusted for in the registered time of error The standard deviation was 15 1 ms This value was slightly greater than desired preferably it should be below 10 ms 6 Discussion 6 1 Effects of downgrading LabVIEW As presented in section 4 2 1 the programming software used for the project were versions from 2008 Software modules from this version existed at SAAB but were not compatible with LabVIEW 2011 The most cost efficient solution was to downgrade the LabVIEW license The downgrade caused us some trouble and was a bit time consuming Since there were many com ponents both software and hardware that had to be compatible with each other we had to investigate whether we could downgrade at all While wait ing for ordered hardware other components were used temporarily and some of them were not compatible with the old version of LabVIEW This resulted in a couple of weeks when we could not perform real tests Also most of the code was written in evaluation versions which were the latest updates so they had to be adjusted to function with the 2008 versions 6 2 Measurement accuracy As described in section 5 3 the desired accuracy in the measurements was not achiev
21. rence image by pressing cancel This procedure was repeated until the reference image was ideal see figure 11 Step 1 Calibration Step 2 Accept reference image Calibration Reference image Enter unit identity number gt Prompt User for Input 123 Step 2 Do you accept this reference image Press CONTINUE when camera is in a fixed position CONTINUE Figure 11 Step 2 in the measurement system GUI In step 3 the acquired frames from the camera were shown in a film clip and the acquired signal data was shown in real time graphs see figure 12 The y axis represented the amplitude of the voltage of the signals 18 Step 3 Image and Signal display Real time video Output Input Maximum mat tch score Tolerance Default 90 22 1207 goo Current match score 0 678 Number of registered failures o 3 HV SHUTDOWN AV Figure 12 Step 3 in the measurement system GUI A number of inputs and outputs were shown in the interface such as number of registered failures There were two outputs Maximum match score and Current Match score and one input value Tolerance The user can set Tolerance to change Maximum match score When Current match score raised above Maximum match score a failure was registrated 5 2 2 Presentation VI GUI This graphical user interface showed fifteen graphs one for each signal The y axis presented the voltage It w
22. s deals with training and sim ulation and Support and Services provide maintenance field facilities and testing equipment for customers This bachelor thesis work was performed at the Department Test Solutions under Support and Services at Saab in Ar boga The department mainly deals with development of testing equipment and repairs of electronic components for the systems in the JAS 39 Cripen 1 2 Head Up Display The head up display HUD is a transparent display located in front of the pilot see figure 1 The system consists of a cathode ray tube emitting a light beam reflected by a system of mirrors and collected by a lens which only transmitts a narrow frequency band in the green frequency range The result is that the pilot sees a hologram of the transmitted image focused about 20 meters in front of the plane This feature gives the pilot the ability to focus on both crosshairs and target at the same time and the possibility of altering the aiming device for different weapon systems Figure 1 Position of the Head Up Display in the cockpit of JAS 39 Gripen 1 3 Problem description The Department of Test Solutions performs repairs of head up displays that have shown problems during operation A problem occurring in several units is unexpected shutdown during operation making the entire display go black This is probably caused by abnormalities in one or more of the system s input signals In the testing facility in Arboga technicians
23. same time that LabVIEW was running to investigate robustness Hy per Pi calculates decimals of pi and is developed for benchmarking processors 14 Since the measurement system was developed for tests executing for up to five hours A long time test was done a number of times In addition several short time tests were performed to detect errors in the start up of the program By simulating several errors it was possible to determine how accurate the time stamp usually was The actual time of error could be determined by analyzing a specific signal This signal goes high as soon as the HUD goes black so by identifying the time the signal alters one could find the differ ence between the logged time and the actual time of error Unfortunately it was not possible to try the system on a HUD with a specific malfunction Therefore failures had to be induced in various ways First off the display was unlit by turning a regulator causing a disruption in one of the signals Since there was an uncertainty when the signal responded to the regulator another method was desired The solution was to ground a sig nal from the HUD causing display failure and alterations to several signals simultaneously Figure 6 The test rig 5 Results The system functioned as desired and it was both mobile and user friendly However there was an uncurtainty in the logged time of error see section 5 3 15 5 1 Hardware The hardware components in th
24. se licenses for the latest versions of the modules or to downgrade LabVIEW To upgrade the extra modules would be an additional investment and therefore it was decided to downgrade LabVIEW with the risk of losing some useful functions in the latest version A result of the downgrade was that the operating system had to be downgraded as well from Windows 7 to Windows XP The software used for the image analysis was NI LabVIEW 8 6 NI Vision Ac quisition 8 6 which enabled acquisition of images and NI Vision Development Module 8 6 which enabled analysis of the acquired images 4 2 2 Measurement VI The Measurement VI created in LabVIEW was based on the idea of com paring the recorded images to an initial reference shot The intensity from each frame in the video was compared to the intensity of the reference im age If the difference between the intensity in the frames was below a certain 11 value saving of acquired signal data was initiated The saved signal data ranged from ten seconds before to three seconds after the error occurred on the head up display The structure of the VI is shown in figure 5 Preparations Running test Saving triggered Calibrate Image acquisition and analysis loop Save image data to camera avi video file Acquire images from camera at 100 fps Save signal data to Prompt user to measurement file accept reference Analyze intensity of every frame and compare results
25. tatesairforce wetpaint com 26 05 18 25
26. ted when it comes to high speed data transfer Since GigE is a more expensive solution than IEEE1394B IEEE1394B was used Since slow auto adjustments in low budget cameras were considered a risk for the image analysis it was decided to choose a high quality camera The chosen camera was Basler scout IEEE1394B Area scan camera scA640 120fc It had the frame rate needed the interface IEEE1394B and also it was rec ommended by National Instruments the producer of LabVIEW 4 1 2 Expresscard adapter The specified camera frame rate demanded a transfer speed of 800 1000 Mbit s in the interface between the camera and the notebook computer IEEE1394B also called Firewire 800 was chosen The notebook computer did not have an internal IEEE1394B port so to connect the Basler Scout camera an IEEE1394B Expresscard adapter was used The Expresscard slot on modern notebook computers can handle speeds of up to 2500 Mbit s so the IEEE1394B interface could be utilized at full speed Since the express card slot cannot deliver power to the camera a separate 12V power supply was utilized 4 1 3 Camera attachment solution While the camera recorded images from the head up display it had to be in a fixed but adjustable position The solution was to construct a device with appearance similar to an already existing attachment solution to the head up display The measurements of the camera were handed over to a prototype workshop which constructed the attachment sol
27. ution 4 1 4 DAQ device For acquiring the signals from the Head Up display a DAQ device was used The DAQ device was ordered from National Instrument and was of the model NI USB 6210 The interface selected was USB which in this case it did not limit the data transfer This model was used to sample 16 channels at a voltage range of 10 V 4 1 5 Signal conditioning The signals acquired by the DAQ device had different voltages ranging up to 100 V To comply with the specifications for the DAQ device a voltage divider was required for certain channels to lower the voltage levels The signals that were conditioned had voltage levels of 100V 30V and 28V re spectively The layout of the voltage divider is displayed in figure 4 To be sure not to overload and effect the HUD system with excessive current levels two resistors in the kQ range was chosen The following resistors were used Divider 1 for Ul in 28V Z 68kQ Z 13k0Q Divider 2 for U2_in 30V Z 68kQ Z2 138k Divider 3 for U3_in 100V Z 68kQ Z 4 4kQ GROUND U1_in U2_in U3_in 68kQ 68kQ HN 68kQ 13kQ 13kQ 4 4k0 Le a U1_out U2_out U3_out Figure 4 Layout of the voltage divider The resistors were soldered to a lab card along with connector cables A control measurement of the ratios was conducted to compensate for imper fections of the resistors and inner impedance of the DAQ device To ensure durability
28. utput parameters like number of failures and the com paring score in the image analysis 4 2 3 Presentation VI This GUI presented the signal data that was saved when an error occurred By selecting one of the saved files the user could analyze the signals and detect which of them caused the disturbance in the image Both a video clip and a file of signal data were saved and named after the time the error occurred and which specific HUD was tested to connect the data to the right video The GUI for signal analysis consisted of fifteen graphs presenting each signal ten seconds before and three seconds after the error occurred 4 3 Signals The technicians defined the 15 most important signals to be acquired by the measurement system The signals were both analog and digital There were five digital signals sampled One signal had an independent ground and therefore a 16th signal had to be sampled There were ten analog signals to be acquired Nine of them were DC signals while one was AC all connected to the same ground Even though there were both analog and digital signals they were all sampled as analog 4 4 Testing Four different tests were performed to see whether the system fulfilled the specifications They were stress tests long time tests short time tests and tests for examining the accuracy in the time stamp The test rig is shown in figure 6 The stress test was performed by running a program called Hyper Pi 3 at the

Download Pdf Manuals

Related Search

meas_syst_report

meas_syst_report

Contents

Download Pdf Manuals

Related Search

Related Contents