ESTIMATING THE DEGREE OF COMPACTION OF ASPHALT USING PROPRIOCEPTIVE SENSORS AND DYNAMIC MODEL Arnaud Delclos 1, Pierre-Olivier Vandanjon 1, François Peyre 1, Maxime Gauier 2, Michel Froumenin 3 1 Sie Roboics Subdivision, Laboraoire Cenral des Pons e Chaussées, BP 129, 31, Bouguenais, France 2 IRCcYN, 1 rue de la Noë, 31 Nanes Cédex, France 3 Cenre d Expérimenaions Rouières, chemin de la poudrière, BP25,6121, Grand Quevilly, France Absrac: The paper is abou a new mehod, aiming a esimaing in real ime he compacion degree reached by an asphal compacor This mehod was developed a LCPC in he frame of a European projec called OSYRIS (Open SYsem for Road Informaion Suppor) This mehod is based upon various measuremens using propriocepive sensors and a dynamic model of he machine, necessary o exrac he desired informaion from he measured one This informaion is foreseen o be profiable o he new inelligen compacing sysem developed in he frame of he OSYRIS projec Firs is inroduced he mehodology for esablishing he model, based upon a well-known indusrial robos modeling mehod, and he model iself Then is presened he principle of he mehod of esimaion, based upon he correlaion beween he resising force of he fresh maerial and is degree of compacion Finally is described how he mehod was validaed hanks o fullscale experimens, carried ou wih a real compacor, on real ho maerials, in Sepember 2000 The paper ends wih he pracical quesions raised by he indusrial implemenaion of he mehod Keywords: dynamic model, asphal compacion, auomaion, resisive effor 1 INTRODUCTION This aricle focuses on he compacion of he base course, he binding course and he wearing course of road made wih asphal The goals of he compacion are o improve he mechanical performance of he maerials, o decrease he ariion, o decrease he permeabiliy Therefore, he compacion of he asphal is an essenial sep in he road consrucion So, he compaciy required has o be reached and, in order o reduce he coss, wih he minimum number of passes The measuremens of he compaciy are difficul o carry ou, expensive and, more resricive, i can only be made a he end of he process Several mehods have been proposed o ensure he final objecive of he compaciy by conrolling he compacion during he process iself We propose here a new sysem of conrol In France, he curren way o specify he number of passes is o use an official guide of he compacion process esablished by some French expers, knowing he ype of he layer, he naure of he maerial, he weaher condiion, he hickness or he kind of compacor Some oher organisaions propose a sysem of conrol of he compacion which uses some acceleromeers mouned on he drums of he machinery In he case of a vibraing compacor, he signal given by he acceleromeers can be correlaed wih he siffness of he soil and herefore wih he compaciy of he soil In he new mehod presened here, on conrary o he classical mehod, we do no measure he reacion of he soil wih an acceleromeer bu we measure he effor needed by he compacor o advance: he resisive effor This principle of measure is illusraed by Figure 1 Reacion of he soil Asphal moion Figure 1: llusraion of our new principle Resisive effor 1
The main advanage of his principle is ha we measure a surface effor whereas he classical principle measures he reacion of he road which includes he reacion of he sublayers under he layer considered This remark means ha even when hin layers are compaced, he mehod we propose can provide relevan informaion whereas mehods based on he acceleraion of he equipmen provide informaion coming mainly from he under layers Our new mehod of conrol supposes o know he relaionship beween he compaciy (measured afer he process) and he resisive effor (calculaed during he process) I was one of he goals of our sudy o quanify his relaionship We carried ou a specific experimen on a real case of compacion process o find he relaionship, o know is accuracy and is domain of validiy This aricle presens he essenial seps, resuls and conclusions of his sudy abou our new mehod We begin by a brief descripion of he modelling needed o calculae he resisive effor Then we described he full scale experimen A daa analysis is given in he following par This documen ends wih he final resuls abou he relaionship which summarises he daa analysis A conclusion shows he drawbacks and he possibiliies of our new mehod 2 MODELLING Our modelling of mobile machines is based on he Denavi Harenberg parameerisaion which is widely used in he roboics field The compacor used in he experimens is an ALBARET VA12DV shown on Figure 2 The model of his compacor was fully solved by EGuillo and al ( [1], [2]) In his secion, we jus give he essenial resuls required for he undersanding of he aricle : he equaions of he resisive effor and he idenificaion of he parameers We call 'racive effor' he effor produced by he compacor o move and 'resisive effor' he effor, due o he ground, ha brakes he moion In he case of a compacor moving along a sraigh line, he racive effors F and F and he resisive effor Fr are given by he nex 3 equaions: F F F r 1 = r c 1 = r c = Mr ( u ( u c + u θ + F θ + F θ Mg sin( dc) F + u 0 0 - ZZ - ZZ v v x θ + F θ + F F x s s sign( θ ) ) sign( θ ) ) where, -i= : fron drum; i= : rear drum -M is he oal mass of he compacor, -ZZ i is he ineria of he drum Ci, -F νi and F si are he viscous and sricion fricion parameers for he drums i -u 0i is an offse on he moor orque ui, -d c, is he longiudinal slope (decliviy) of he rolling plan, -r ci is he radius of he drum Ci, The radius of he drums is a daa given by he consrucor, he decliviy has o be measured for each rajecory, he roaions θ i and he moor orques u i have o be measured during he compacion bu all he oher values are no direcly available The mass, he ineria, he viscous and sricion fricion parameers and he offses of he moor orques are no daa given by he consrucor and so have o be calculaed The process used o calculae hese parameers is he idenificaion The principles of he parameer s idenificaion, he descripion of is pracical implemenaion and he applicaion of hem o he compacor is described in [3] We give in Table 1 he resuls of he idenificaion made on he ALBARET VA12DV Xs is he calculaed value, σ xs is sandard deviaion and σ r =σ xs / Xs Parameers Unis Xs σ xs σ r (%) M Kg 10216 656 06 ZZ Kgm 2 6381 1 06 F ν Nms 633 5 89 F s Nm 122 5 613 U 0 Nm -2535 38 19 ZZ Kgm 2 661 31 0 F ν Nms 2102 8 231 F s Nm 02 9 1126 U 0 Nm -3916 2 106 Table 1 : Idenified parameers Figure 2: The Albare VA12DV compacor 2
3 EXPERIMENTS A full scale experimen was made in CETE of Rouen in Sepember 2000 The goals of his experimen were: (i) o obain all he variables needed o calculae he resisive effor and, (ii) o measure he real compaciy, in order o evaluae he relaionship beween hese wo values The experimen consised in racks of asphal (rack 2, rack, rack 8, rack 16) idenically prepared bu compaced 2,,8 and 16 imes so ha he differences of compacion can be compared A se of poins were measured wih a heodolie saion ( Sokkia Ne2 ) Track 8 was chosen o have a complee se of opographical measuremens On each rack, he asphal was laid on 25m lengh and m widh The asphal is a base course asphal 0/1 We performed gyraory shear compacing press ess o deermine he capabiliy of his maerial o be compaced The ess show ha he minimum voids conen are abou 5%, ie, he maximum of compaciy for he maerial used is abou 95% This resul means ha over his value, he evoluion of he compaciy can no be linked o he number of passes Noe : resuls of gyraory shear compacing press ess are represened by a graph showing he compaciy versus he number of gyraions, generally here is a logarihmic law beween hese wo parameers in he domain 5-95% compaciy rae and here is no more relaion ou of his domain DATA ANALYSIS 1 Decliviy (longiudinal slope) An inclinomeer was embedded on he roof of he compacor o measure he decliviy Signal processing showed ha he signal of he inclinomeers is oo much perurbed by he vibraions induced by he sysem Afer filering he signal can no give beer han he mean of he decliviy on he oal lengh of he rack (25m) We compued oo he decliviy using he coordinaes of he compacor given by he GPS measuremens The resuls fi quie well he 'real' slope evaluaed wih he help of he opographical measuremens done on rack 8 The resuls are quie beer wih he GPS measuremens han wih he inclinomeer 2 Compaciy We measured he compaciies every 2 meers of each axis, (ie 10 compaciies per axe) Measuremens of compaciy have been done wih a Variable-deph Poin Gammadensiomeer Figure 3 shows he evoluion of he mean of he compaciies obained on each axis of he racks represened wih is sandard deviaion, he X axis is logarihmic scale in order o be coheren wih he represenaion associaed o he gyraory shear compacing press es The arge hickness was abou 13cm jus afer laying for an expeced hickness afer he process of compacing abou 10cm The emperaure of he asphal was conrolled during he laying and sayed consan a abou 135 C Track afer rack, he compacion was immediaely made afer he laying Each rack was divided in wo bands of 10m widh (size of he drums) wih a 0cm widh overlap band The driver began he compacion on he righ band and drove he compacor 'here and back' for he 2 bands This process was repeaed unil he expeced number of passes was reached The parameers of he compacor correspond o he NFP 98 36 classificaion (French sandard): - linear mass : 29 kg/cm - Ampliudes : 086mm - Frequency : 38 Hz - Speed : 5km/h Figure 3: Evoluion of he compaciy As expeced, he compaciy increases wih he number of passes Furhermore, he compaciy on he middle axis is above he compaciy on he lef and righ axis which is logical since here was an overlap band in he middle of he racks We noice ha he compaciy on he righ axis is always above he compaciy on he lef axis; we do 3
no have a clear explanaion for ha bu we assume his resul can be linked o he fac ha we began he compacion on he righ axis Generally he relaionship beween he number of passes and he compaciy is a logarihmic law Acually, he number of passes represens he energy of compacion as in he gyraory shear compacing press es he number of gyraions represens he energy of compacion However we can noice on Figure ha he relaion does no seem o be linear any more above 8 passes We assume ha around 9% of compaciy, he law is no more logarihmic bu is an inermediae law beween logarihmic law and sauraion 3 Resisive effor We calculaed he average resisive effor on each rack, for each pass and each axis The resuls are represened on Figure, wih a logarihmic scale for he x-axis Figure : Average resisive effor The evoluion of he resisance is no linear, so, ha i has no a logarihmic law As expeced, he resisive effor is decreasing wih he number of passes For rack 8, here is no more evoluion of he resisive effor from he h pass The case of rack 16 is discussed laer We observe, for boh lef and righ axis, ha he values of resisive effor are very closed for passes 1 and 2, only passes for which he comparison of he resuls is possible for all racks From he h pass we observe an increase of he dispersion of he resuls On Figure we observe for rack 16, an imporan dispersion (abou 1200Nm) beween even and uneven passes (ie forwards and backwards) We ried o explain his fac helping wih wo observaions made during he compacion of rack 16: (i) he driver and he people around he rack could feel he vibraions, (ii) he wind was sronger We propose an analysis of he influence of hese wo phenomena ha he modelling used o compue he resisive effor does no ake ino accoun and finally we propose an oher way o esimae i Influence of he vibraions 2 acceleromeers were embedded on he fron frame and drums, o record he x and z vibraions So we made a frequency analysis on he signal of hese acceleromeers o sudy he evoluion of he vibraions of he compacor on rack 16 Using he Fas Fourier Transform we calculaed he frequencies and heir ampliudes The fundamenal of he signals corresponds o he frequency of he vibraion equipmen (abou 38Hz) The evoluion of he raio of he ampliudes of he firs harmonic on he fundamenal can be observed on Figure This raio increases wih he number of passes and reaches a sauraion a 10 passes, excep for he 8 h pass (problem of acquisiion) We can assume a change in he response of he soil a he 10 h pass Before his 10 h pass, he soil absorbs he vibraion and afer, he soil forwards he vibraion o he compacors and excies oher modes of i So, he impac of he vibraion on he movemen of he compacors becomes more imporan Acually we suppose he vibraions have a privileged direcion ha suppors he moion in a way and brakes he moion in he oher way Of course, his explanaion is only our inerpreaion : we do no have enough daa o confirm i Currenly our model does no ake ino accoun he vibraions However, i is possible o include his effec via a more complicaed model, more expensive sensors and more expensive experimens in order o idenify he parameers of he vibraions Influence of he wind In he case of he exisence of wind, he compacor is subjeced o an addiive racive or resisive effor We evaluae his effor by his formula: R wind = ρsv where, ρ, is he volumeric mass of he air, S, is he surface of he compacor exposed o he wind, a recangle of 2m widh and 3m high V= V compacor + V wind, is he relaive speed V compacor =5km/h, V wind =20km/h 2
We esimae ha during he compacion of rack 16 he compacor was subjeced o a racive or resisive effor abou 380N The influence of he wind does no explain alone he dispersion beween even and uneven passes bu, i can be a par of i 'There and back soluion' In order o remove he influence of he privileged direcion due o he vibraions and he wind, we compued he resisive effor for he 'here and back' rajecory Figure 5 shows he resisive effor for each here and back of he compacor, wih a logarihmic x-axis We can see ha he resisive effor is decreasing unil he 3 rd here and back, say consan unil he h and seems o increased afer respecively 09996 and 0995 on he righ and lef axis ; he slopes of hese relaions are very closed from each oher The poins corresponding o he rack 16 have no been used o make he regression In he secion 62 we noiced ha for he las passes on he rack 16 he resisive effor was increasing In he secion 5 we made an oher observaion: afer 95% of compaciy he behaviour of he asphal is changing, ie, he asphal is no more in is logarihmic law of compacion These wo remarks can be linked because he compaciy measured on he rack 16 is 95% We deduce from hese remarks ha he change in he evoluion of he resisive effor is linked wih a change in he law of compacion For his asphal and in he condiions of he experimen previously described, he relaionship Compaciy / Resisive Effor : - is linear unil he compaciy rae of 9% (which is equivalen o 8 passes), (i corresponds for he gyraory shear compacing press es o he domain where he asphal is compaced in is logarihmic law) - can no be defined afer 9% of compacion (i corresponds, for he gyraory shear compacing press es, o he domain where he asphal is no longer compaced in is logarihmic law) Figure 5: Average resisive effor calculaed on 'here and back' The compuaion of he resisive effor on 'here and back' has he advanage o eliminae he influence of he graviy 5 RELATIONSHIP COMPACITY/RESISTIVE EFFORT Previous secion presened he compaciy and he resisive effor resuls Figure 6 (nex page) represens he compaciies of each rack versus he resisive effor calculaed for he las here and back rajecory on his rack The compaciy is represened wih is sandard deviaion I was obvious ha he relaionship beween compaciy and resisive effor for boh lef and righ axis is linear for he firs hree racks so we draw he regression lines beween 2 and 8 passes The correlaion coefficiens of he regressions are Thanks o Figure 6, we can define a precision on he resisive effor assuming ha he resisive effors have o be he same when he compaciies are he same For rack 2 and, o a smaller exend for rack 8, he compaciies can be compared on he lef and righ axis, we noice a deviaion beween he resisive effors of less han 50N For rack, he compaciies are no equals and we have a difference beween he resisive effors Associaed o he sandard deviaion of abou 50Nm on he resisive effor, we have a precision on he esimaion of he compaciy of abou 01% So, if we assume ha he accuracy on he esimaion is given by wice he sandard deviaion, he accuracy on he measuremen of compaciy by he resisive effor is +/- 02% 6 CONCLUSIONS AND PERSPECTIVES We proposed in his aricle a new mehod of conrol of he compacion rae during he process This mehod consiss in he calculaion of he resisive effor, due o he asphal, by using propriocepives sensors embedded on he compacor 5
The evoluion of he compacing rae is linked wih he evoluion of he resisive effor We could make his sudy helping wih he modelling of he compacor moving along a sraigh line and wih a full scale experimen, presened in he beginning The daa analysis presened leads o he sudy of he relaionship compaciy/ resisive effor This sudy shows ha, in he condiions of he experimen: for a compacing rae beween 89% and 9%, he calculaion of he resisive effor makes possible he esimaion of he compaciy wih an accuracy of +/- 02% Figure 6: Relaionship compaciy/resisive effor Having developed he compuaions ools, he esimaion of he compacing rae is possible in 'real ime' wih a few equipmen This minimum equipmen required is represened Figure 2 pressure sensors o calculae he moors orques, 2 encoders, one for each drum, o calculae he roaions speed, An onboard compuer o record he daa and o compue he resisive effor Encoder GPS sysem In he case of a calculaion only on he 'here and back' rajecories i has o be noice ha he decliviy does no have o be calculaed Then he GPS sysem which is an expensive equipmen is no required The idenificaion is an essenial sep o compue he resisive effor This sep can be made wih he same equipmen embedded on he compacor o esimae he compacing rae The idenificaion requires : o move he compacor on a 'here and back' rajecory, o pu he compacor on suppor Some mehods ha permi o idenify he parameers more direcly and more simply may be invesigaed o reduce he cos Even if we obain good resuls, we are no able ye o propose a global ool o esimae he compacing rae for all he maerials I would be of ineres o make oher experimens o have a bigger se of resuls We can imagine o change he hickness of he asphal, he iniial emperaure, he decliviy or he weaher condiions Obviously, i would be of higher ineres o sudy differen kinds of asphal Bu he cos of each experimen is very high because i requires many people and he laying of he asphal is expensive An idea is o use a compacor fully equipped and o use i o make measuremens on real roads sies in order o build a daa base REFERENCES [1] Guillo E, Gauier M, Vandanjon PO 'Observer for vehicle-errain ineracion using he dynamic model of vehicles : applicaion o he compacor' IARP 2000 [2] Guillo E 'Modélisaion e idenificaion dynamique des engins mobiles de consrucions de roues' Thesis of he Universiy of Nanes Jan 2000 Pressure sensor Rear Frame Cabin PC Fron Frame [3] Guillo E and Gauier M 'Dynamic modelling and idenificaion of earhmoving engines wihou kinemaic consrains: applicaion o he compacor' Proceedings of IEEE Inern Conf on Roboics and Auomaion San Francisco, California 2000 Rear Drum Fron Drum Figure : Minimum equipmen required 6