an embedded data logger based vehicle

8/14/2019 An Embedded Data Logger Based Vehicle

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An Embedded Data Logger Based VehicleTrajectory Monitoring System

S. Sakhi, A. Khettat, M. HanksPolytechnic Military College, Algiers , Algeria

M. BelhocineDevelopment Center of the Advanced TechnologiesAlgiers , Algeria

A. Elouardi, S. BouazizInstitute of Fundamental ElectronicsParis Sud University91405 Orsay, [email protected]

III. ADOPTED ARCHITECTUREA distributed architecture is the most appropriatearchitecture for our system. Sensors and actuators are directlyconnected to the common bus. Connections are considerablyreduced as all components are linked to the same bus (Fig 3)[3].

B. SecondstepIn the second step, a HIL (Hardware In the Loop) techniqueis used. This method [15] consists in establishing connections,in the same loop, between the hardware and software parts inorder to reproduce the experimental conditions of thedynamical system. The software part generates pseudo-realdata from a modeled system by dynamic simulation. Theconnection between the two parts is achieved by adequateinterface boards, which make it possible to enlarge the number

of solutions and allow the test and validation.

DataLogger

capitalizeknowledgeby data

--

DataLogger

110 Interface

>collectdata

Fig. I. First step of protot yping

Real system

Fig. 2. Second step of prototyping

, .. . . pseudo-real" dataModel of

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Abstract-This paper describes a design of a Data Logger basedsystem dedicated to vehicle trajectory monitoring. The systemevaluation is based on prototyping an embedded application. Theadopted architecture allows tests and applications and results areobtained with a set of constraints. In this multisensorsarchitecture, a GPS receiver is used for the absolute localization.In order to int egr at e the GPS module in the Data Logger, anarchitecture study is carried out. The correspondingmeasurement results are presented and analyzed. In a secondstep, a calibration procedure is applied to the implemented AIDdata converter. Results are provided and give an over view of thefuture development.

I. INTRODUCTIONThe aim of thi s work is to design an embedded system inorder to collect motion data and determine a behavioral model

using a sensor data inversion algorithm [I].The main characteristic of this system belongs in the realtime processing. The architecture adopted for this system is adistributed architecture which involves a COTS (Componenton the Shelf) model [2].

Keywords-Embedded Systems, Sensors, COTS, GPS,DistributedArchitecture, Prototyping,Hardware in the Loop

II. DESIGNING METHODDesign of embedded systems faces several difficulties dueto the large number of involved parameters (architecturemodel , real-time and mobility constraints, multi levelspecification ... etc) [3]. In order to manage this complexity, amethodology based on prototyping embedded systems is used.It is based on the principle of hierarchical organ ization whichmakes it possible to describe the whole system as a set of lowlevel subsystems [4]. The use of preconceived (COTS)components makes it possible to considerably reducedevelopment time and benefit from existing skills.The prototyping method is developed in two steps:

A. First stepThis step requires the design of an experimental platformaccording to the adopted architecture which is used to collectsensors data (accelerometers, gyrometers, GPS ...) [5].

The distributed architecture is often a complex architectureto be implemented in software level [7] . All the difficultyconsists in efficiently managing multiplexed data incomingfrom sensors and processors; so that the time constraints ofeach signal are lifted. Our distributed system integrates several

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sensors from different technologies (Inertial Measurement Unit- IMU - , GPS receiver and other sensors .. . etc .) [9] whichincrease development time. In order to overcome thisdifficulty, the use of COTS (Components On The Shelf) is anappropriate solution [2][8]. But in certain cases, the user ofthese components needs additional adaptation mechanisms tointegrate them into the system.

Precision) and possibly recorded drifts during a displacementon a determined trajectory.The standard geodetic reference used is the WGS84(World Geodetic System 1984), consequently, the raised pointsare expressed in this geocentric system, where the GTRS80ellipsoid is its reference surface.

IV. PERFORMANCE ASSESSMENTOF THE ET312GPS RECEIVER

Recording GPS dataET312GPS receiverCard

Wor ld Geo de tic Syste m World Geodetic S ystem Geocentric reference LocalWGss.i 14-4 WGSS4 14-4 North Sahara 59llipso ida l coo rdinate s Cart esia n coordi nate s Cartesian coordinates(


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TAB LE I. AVAILABILlTY EVALUATION IN THE STATIC CASE T AB LE III. EVALUATION OF OUTDOOR STATIC PRECISION

4,8811I6,1311I6,2811I7,27 11I3,7711I6,5411I

1,14 III1,5111I1,36 11I1,8111I0.9511I1,39 11I

0,9511I1.27 11I1,12 III1.52 III0,8511I I;1,14 III II

Sesson

Bias 3Da2Da 3D

Bias 2D

Error RMSCEP (50%)

Time Period

Fig. 6. Variation s of X and Y errors compared to the PositionalDilution of Precision (POOP)

(1)

(3)(4)

(2)

+-[f ( X - error ;2+ Y _ error ;2)J1=1

Nbias2D =-.!.." JX err or;2+Y error;2N L J V - -

N. 1 " 1 2 2 2btaSjf)=:i L J _errol[ +Y _errol[ +h;~

RMS error

Session I Date ITim e Period Weather Ava ila bilityconditions1st session 24" dec: 2/1117 18/11211116s Sunny time 100%2" session 21" Dec. 2/11J7 23/123111 13s Covered time 76,10 %3" session fro m 23 1024 23ft 49111 28s Covered time 99,68 %February } ()()84th session from 2610 27 24 /lOIrs Sunny time 99,99 %February }()()8s" session {rom 27-fJ2 to Of 3 days Sunny time 99,94 %Alllreh 2(}{)81st session 26' I January 24 /lOIrs Sunny time 100%2/11/82M session From 271029 3 days Sunny time 100%Jan uary }()(J83" session from os t /1 7 days Sunny time 100%January }(J(JR

(5)

N is the number of valid positions,X_error is the longitude difference [m] between the"real" and the measured position,y _error is the latitude difference [m] between the"real" and the measured position.

Statistics on the precision in static mode are shown in tablesII and III. These statistics are calculated from eight recordingsessions involving both indoor and outdoor measurements. .! - - - - - + - - T - - - - - - c - - - - ' - 7 - - - - - - ! - - - + - - ~ c _ _ - _ _ + - _ Fig. 7. Dispersion of the raised points

TA B LE II. EVALUATIONOF INDOORSTATICPRECISIONI Indoor I

Session IBias 2D I IBias 3D I I 5,8611I 21,4611I 6,3911I 6,6211I 6,40 IIIcr2D I I 5,5611I 38,85 11I 6,2611I 6,9811I 6,0611Icr3D I I 7,15 II I 52,2811I 8,0711I 8,8711I 7,88 11I

CEP (50'X,) I I 3,7711I 7,36 11I 3,9611I 4,0811I 4,0911IR ~ l S r n I I 5,5911I 38,88 II I 6,29 II I 7,01 III 6, / / III

B. Dynamic performanceThe dynamic performance evaluation is restricted to thedynamic precision which is related to the number of pointsinside a specific area limited by a polygon. The percentage is

determined from all points located in a 2m wide bandwidth,extending Im on each side of the polygonal contour. Inaddition two other parameters are quantified; DOP (Dilution ofprecision) and SNR. The tests are carried out on site, inside ourcollege, using a vehicle with an antenna. The vehicle toured thesite twice along the path shown on Figure8. The percentage ofpoints found inside the 2m bandwidth of the referencetrajectory is equal to 99.78% and the measured SNR is 42.3dB. The 2D-plot trajectory of Figure 9 shows a goodconcordance of the recording points with the reference points.This validates the performance of our receiver.



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: ~ T .. l ..., . . . . 1 d _ k ..... o 1015 102 1025 10 "'1 l OA 10 45Tne(sec)-,.__..... , I' j

t : .... .." :" .. " " ; ..:"" :"T: a!,AL,T";,"",iT"""101 5 10 2 10 25 10 3 1035 ID A 10 A5Tne (sec

Fig. 8. Satellite image of the test site (by Google Earth) Fig. IO.Variations of the different precisions POOP, HOOP andVOOP,"" ,------ ----,- - ----,- - ---,-- - --,-- - - -,--- - - .--- -----,

, ..: :80J f:. ' : ~ ~ . s. - j.

! , ,>..,i......t;?../ .: . 'AOO ;";;";":' i ",:::": , ..\ .: , ,. . to . . . . . 0

! ! _ : , ! .0J .,IT

V. LPC2129 AID CONVERTER CALIBRATIONAn estimation of the AID converter parameters for thedifferent LPC2129 microcontroller channels ismade in order toget a better evaluation of the global acquisition error. Atechnique called HIL (Hardware In the Loop) is implementedusing the dSPACE Board (DS1102) under Simulink toestablish the connection between hardware and software(Figure I I). From the dSPACE board, three signals aregenerated: Enable, clock, and reference Signal. The acquisitionof an analog signal on input is also needed in order to recoverthe reference signal which is injected into the LPC2129 ADC.Each board output has a precise function:-Enable: When I, authorizes the ADC to start conversion.

Fig. II . Calibration process diagramcollected.

(LPC2129 ofPhi l ip. )

ISABus

3 analogoutput s

The Simulink part is illustrated by the Fig 12and Fig 13:

-Clock: A square signal which defines the conversion timeby its rising edge.-Signal: An analog signal injected into the ADC input

selected. It can take any shape.It is necessary that these three signals have voltage levelsranging between 0 and 3.3V, which is the supply voltage of theLPC2129 microcontroller [13]. For the output "Signal", wehave chosen a 10Hz sinusoidal signal, the signal "Clock" is a100 Hz square signal and the third signal "Enable" is a I Hzimpulse. Theoretically, in the activation window of 1 second(by the signal "Enable"), 1000 samples should be

' - 1 input lranalog JJ ~ f a ( >

X(m)Fig. 9. 20 plot of trajectory test and the reference points

Figure 10 shows that the temporal variation of theparameters quantifying the geometrical configuration of thesatellites along the trial period is acceptable. The most commonDOPs are summarized as follows [6]:Precision of2D horizontal positioning:HDOP = ~ O ' ~ + O ' (6)

Precision of vertical positioning:VDOP=g (7)

Precision of 3D Position:PDQP = ~ O ' ~ + O ' + 0'; (8)

Where (j 2 tp , (j2 A, ()'2h represent longitude, latitude andaltitude variations respectively.The static performance results presented are satisfactory,except for the dispersion of the measured positions whichincreases over a long period of time. This is due to the changeof the satellite geometrical configuration. We also note that thedynamic performance is acceptable; on the other hand, we areconsidering compensation of GPS data errors by the insertionof an inertial measurement unit (IMU) and the study ofGPS/INS (inertial navigation system) hybridisation.



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Scope 1AnCNADClnAD e nAlICN4

SubS ys1em

DSIGNtu. DACNl Scope- DACN2

HORlOGE f-- DACM3DAC.II4"------

ENABLE DS1102DAC1

,

DS1102ADCFig. 12. Description of the global diagram Fig. 15. Zoom on the generated signals

Interruption program

InterruptonAdilillia..of theADC irteJ11.llX!n

lnila1izaI!Dnf1at:Oi :{) , Buffi.r(lOCO ]

INoYo>

The AID conversion algorithm IS implemented on theLPC2129 depicted below:

> - ~ ENABLEGain

1-- - - - -1>( 1SIGNAL

PulseGenerator

Fig. 13. Description of sub-system signals generation

f J i M l l - - - - - - - - - - - - -HORLOGE

The generated signals are illustrated in Figure 14 andFigure 15.Principalprogram

1 ~ : ~ e10 02 0 4 06 08 1 1 2 14"'- "" ,!'j03 j .......... :: :::1 :::::0 02 0 4 06 08 1 1 2 14

: -----------.. --------------1 ;1'- - - - ------------- j" j + j ...+ ...... .... . ...... 1 .o1 _. _.. . . . . . _._._..: - .. . . . . . _ . _ . _ _ . . . . . . . . . _._._.-.: . . . . . . . .. . . . : . . . . . . . .. . . . . . . . . . . ._._._._._.. _._._ .. . . . _0 02 0 4 06 08 1 1 2 14Trme js]

Fig. 16. The AID converter calibration algorithmI: dSPACE i I- L I'C 2 12 9 s; gn .. l

r\ f\ f\ f\ f\ f\ 11 f\ (/\ n---------

....... ,---- ... --- !.------ - -- ; ...----- VV V V V V lJ" '00 m m sec e m m m ,mFig. 14. lIIustration ofthe generated signals N...... t" rof , ,. .mpl . .s

Fig. 17.Acquired signal on channel IThe LPC2129 microcontroller has an AID converter withseveral programmable conversion modes of interlocking [14].We use the mode which offers a possibility to start conversionon a rising/falling edge to "Clock" signal. The "Enable" signalis configured in standard logical input whose state is testedinside the program. Experimental results are presented in thefigures 17-20. The statistical error analysis for each channel isgiven inTable IV.

In Figure 17 and 19, it may be noted that from the 500thsample the delay between the two signals becomes increasinglysignificant, and the signal acquired by the dSPACE is delayedcompared to that acquired by the AID converter. This is causedby sample drifts resulting from the divergence between thesampling time of the dSPACE board and the AID converter.One solution to face this problem is to use a common trigger toobtain the same sampling time for both of them. As for future



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Fig. 19. Signal acquired on channel 3

Fig. 20. Error between signal acquired on channel 3 and thereference signal (generated by dSPACE)

RE FERENCES[IJ John CATSOULIS Des igning Embedded Hardware 2nd editionO'Reilly May 2005.[2J Sami BEYDEDA & Volker GRUHN Testing Commercial-otT-the

ShelfComponents and Systems Springer2005.[3J Peter MARWEDEL Embedded System Design Architecture Springer2006.[4J F. Mayer-lind enbcrg Dedi cated Digit al Processors Methods inHardware/Software System Design John Wiley & Sons Ltd 2004.[5J Eric ABBOTT and David POWELL Land-Vehicle Navigat ion UsingGPS Roceedings OfThe IEEE, Vol. 87, No. I, January 1999.[6J Moham ed A. ABOUSALEM and Jam es F. McLeUan A NewTechnique for Quality Control in GPS Kinematic Positioning TheUniversity of Calgary, Calm, Canada- IEEE 1994.[7J Remy KOClK Sur l 'opt imisat ion des systemes distr ibues Temps reelernbarques : application au Prototypage rapide d'un vehicule Electriqueautonome these doctorat en inforrnatique industrielle iI l'universite deROUEN - France mars 2000.[8J Mohamed-Anouar DZIRI Modeles d' integration d'outils et de

composants logiciel /mat eriel pour la conception des syst emesheterogencs cmbarques these docteur de I'I NPG Specialite :Microelectronique -Mai 2004 .[9J Iyad ABUHADROUS Systemc ernbarque temps reel de localisation etde modelisation 3D par fusion multi capteur , these de doctorat, Ecoledes mines de PARIS. Janvier 2005.[IOJ Esmat Bekir Introduction to Modem Navigat ion Systems WorldScientific Publishing Co. Pte. Ltd. 2007.[II] Jerome TARNIEWICZ, E tude d'une methode de sondage de vapeurd'eau dans la troposphere appliquee a la correction de mesures GPS pourI 'a lt irnetrie de haute precision , these de doctora t, Ecole doctoralescience de l'environnement l'ile de France, mars 2005.[12] Damien KUBRAK Etude de l 'hybridation d'un recepteur GPS avecdes capteurs bas coats pour la navigation personnelle en milieu urbain ,these de doctorat, Ecole nationale superieur des telecommunications,

Paris, Mai 2000.[13] PHILIPS Semi-conducteur, LPC2129 User guide , Fevrier 2004.[14] Trevor MARTIN, The Insider guide to the PHILIPS ARM 7 - Basedmicrocontrollers, HiTex, Fevrier 2005.[15J lul ian MUNTEANU- Methodologie de simulation temps reelhardware-in-the loop- application aux systemes eoliens 6e ConferenceFrancophone de Modelisation et Simulation - MOSIM '06 - du 3 au 5avril2006 - Rabat- Maroc.

VI. CONCLUSIONFor absolute localisation, we have used an ET312 GPSreceiver which gives acceptable static and dynamicperformances results, except for the POOP which increasesover a long period. On the other hand, LPC2129 AID converterCalibration results show that it is necessary to use a commontrigger to obtain the same sampling time for all signals. Theobjective of the present work is to design a compact systemwhich can be embarked on any vehicle to collect the relativedata of its own movement. Once data is collected, rebuildingthe trajectory of the mobile vehicle is possible. Thecompactness and reasonable cost of this monitoring systemmay help imagine solutions to trace several vehicles. We planfor the future works to implement this system in an embeddedapplication to solve the labelling data problems and the realtime constraints.

EVALVAnON OF THECHANNELS ERROR

Fig. 18. Error between the acquired signal on channel I and thereference signal (generated by dSPACE)

A...,II A Jl i \ I. }"\. 1"'\ /vi.( l,f ! \ , .......

'00 = = = = = = = .=

.00 II... 6J

"". .1 r .......rw "1*" 'rl ,l ~ .............................

00 .............r .......... oo. '00 = = = = = = = = ,=

TABLE IV.

work, it may be interesting to carry out the same work using acommon trigger to eliminate samples drift and a LPC2294board instead of the LPC 2129 because it offers more resourcesand additional peripherals.

Signal mean (mV) a(mV)Error on channel I -22.74 155.32Error on channel 3 4.56 251.6

an embedded data logger based vehicle

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