rtRR.31. lYYf3 5: 4“(7-TI 5L1FLNCE RRIWROD NO. >y~ 1-’.1313 m TI-113PATNFINDERIVWSIONmhf.ms tbas@iweofMarostthetime the d F ; Iandar completed sun-finding and identifi 3 the cliraetion of mrirtiannorth on 90! 1. Int$ 4 Autonomous Navigation and the madkfe wqqmints (ss needed) were also de- tined by the driver if them was a preferent$l : Sojourner Microrover path toward the fml dcstindors (such ss a 7 . route to avoid obvious hazsrds along t$e 8 path). If the rover was not slreody faoing e 9 J. Matijevic next waypoinL it was carunandsd to 10 toward tbe god until it facd the destination+ 11 These oommnds (W30to Waypointfl tuqs, 12 and a command to update the position of e TtM Mars ex@xation program has as an ing, the rover used teobniques for aukmo- rover in the x and y coordinate tie) w e i: ovmamhingtheme tho mamh for md under- mous control which were (among sewed sent to tho rovor as part of a single c d stnnding of life, climate, and resou.moson technologies)tkst damonstrate$in flight on sequence. 4 15 16 this fascinating planet. The abfiity to move this mission. One such technique for Upon exeoution of tha “Go to Waypo”mt” 17 aboutthe surfiiof Mars is key to makb autonomow navigation and hszad avoidance cunmand the rover drove an appmxirrde 18 measuremcmtsand the gathuirtg of tha straight lina, ac@9& - its ps data which address this therm (J). In Oc- when it datacted drifi off ils co c ;: tober 1992, the NASA Office of Spaea or enoountoreda tid condili 21 Access and kbno]o~ fdod an ex- king cxooutionof a “Go to Wai - 22 periment to d~nsti~ the mobile vti- point” eomrnsnd,the rover updstdd 23 ck technologiesneeded for a Msrs surl%oc its position relntive to the lander {o 24 mission (2), lllat exporimlmh the Micro- dexarmine(at a mioirnurn) if it ~d rover Flight Expmimcnt (MJ?EX) or reaohed the objeotivc of the trsy- : “So@mer;’ flew on tbe Mars Pathfinder erse. This position relative to the 27 (MPFl mission, which began no 4 July lander was kept in tho same x and 28 1997and eaded 26 &@xnber 1997. y coordinate syntmn as the OOr/L- 29 IM.tsgthe 83sols(l sol= lmartims mands developed by the row# day “ 24 hours, 40 rein) of the Mars driver bsok on Earth. ‘Iheupdate to :; PMMindcrmiP9iQ the MFEX rover was position was performed by ~ f 32 released from the Mars Pdh.tMer lander of dead reokoning. Enooder coun* 33 and performad its srtkmion to cxxtduct wem aceumula~ on each of technology~SS S* as de~n- wheel actuators,where a s@e - :: ing the interaction betwasn martian soil * COt&ttWas t8gistOrOd0S3 36 and the SOVH whtxzd$navigating, travers- time tbe motor shaft of the aotuat 37 ing, and avoiding hauds; and gnthoring completed a revolution. TIMaocT- 38 data on the engineering oapsbii~ of the mulated counts on each of the .s$ vehiole(thrzrnsl control, power generation WbCdS WCfS awTa&d to deterrnh.e % perfom.ante, conununication, and SO the number of motor revulutio~ 41 forth),In addition, tha mvor carried an al- exeotstsdlGiventhe gearing ratio of pha proton x-ray spectrometer (APXS), 2000:1, encodercounts were 42 * 43 whioh allowed roseamhers to determine into wheel revolutions and th 44 tie eontpositionof soil ~d rook. Lastly,e- distnncetrsveled. During tuma, tbT rovrsrmoaswed the .Chnqgein o~- % taiswUm images of the lander taken ~ ontation by intagratmg the o~ 47 the rov8r~*otslarly holptld in fiwn an onboard rate gyro. DSi 48 assessing status of the mission and dam- tance am-angle were then used ~ 49 ageto Comt)onentac is bsieflv&sorii below [3. 4. S). -pute an x andy location. \ - ma Ml%x Sr)ve$(Fig. 1) activititi Wcxe ‘l%e%o to Waypoint”’&* was the The Iovnr oould eutonornously idan’ : directadby an OPQ’?Sti0518M&n OXI%&. ThiS * implernenhttion of autonomous sewed typs of hazards, Among Iheso w? 52 team, waxking under the mnstraints of lim- nsmgation on the $AFEXrover. llsis com- proxirn@4eteoted rooks, &opffi, slopesr ited hnder power and rmfxiotedantenna oov- msndwas issuadty thernsmber of the op- excaaive tilt of the vehicle, a triggered con- ii era$oatEarthcould (OIICC pcf S01) command ezstions warn oalled the “rova diver,” The tact sensor. or a eornbination thereof. If@ 5s the rovor to drive, taka pioturos, *orm ox- driver used rovm or4meraimoges, Ian* ste- rover detwtad a proximityhazard, the vehiclf S6 #rnants, and ookot and transmit dats to reo earnem imagm taken of the rover in the turned in place in irsorementa,until the ba~ 57 the lander. The ro= WM requiwd to winy tsmaim and portions of a stereoterrain pano- ml wss no longer detectable.Th~ tie vehsi out dtese tnska safely without intervention rama to ideati@ the roves location and the cle drove fosw-ardone-half vohiclo Ion $’% :! fi-omthe operations town until tha next com- site of intmst (thegoal loodion of tbc “00 to a~er which it resumed norrnsl traverse op 60 mand opp’tunity on the next sol, In so d~ Waypoint”Cmrnaod).Through 8 gra~c emtions, hrading back toward the god loca+ 61 Oveday Symeru used with the s.tomo images, tion. Al this pint, h rover maintained 62 %e ●ulhor h ●l Iho JOI Prepu1810nLaborelory, the driver speoified the x andy coordinatesof memory of tho hazard that it had jus 63 Osll(omlsIrrsllluteof Tschnologv,4S00 Oek CUnve the rovcxIocotionand the new tar et. ‘llese avoided. j Drlv@, Pa.edoM, CA 91100, USA. E-mall: 64 coordinatesware in a oOordinata/!amo (tlw protity hazard detection WS9 perform [email protected]~,gov ~ 65 “stice-fixed frame”) that beornne fixed to with tie fhtwrd caroera$ and five laser stri~ SCIENCE● VOL.276•31Marm1998● tnqx//ww.Ioimwmsg.or~ l! rlf2R 31 ’98 15:33 2E12 7E19 5316 PFIGE. @3 ..---i--- m-s. Every 7 cm of traveme, tie rover the angle to the localgravityvector.h angle not always lead the row to the rnpmted stoppd and uxeoutoda aonsing qwle. The measurementbeyonda threshold (not greater nation.However,the hazard detectionsysh rover coptured an irnago both with and thm a 30” slope) represented on exeessive workedwc~ sueocssfidly keeping the v&L without a Mer aotk. Selected away from nontrnwable hrmud seats lines from each image wero Althotsgh some of the Obsert diffesonczd10loate the lnser spot difficulties were clearly due in the aocnc.(Fig, 2 shows the in: limitations in the implerrmtati thrad Iaswstripe,m seenbythe Oeautonomousnavigation on born rovar during nurt%cc opcrntions) If the vehicle, the JwfOsamce c the terrain is flat and lmrel 88 raf- also be atbibumd to the caution eremcdfiosn thorowr, the laser the operation team in enabling t spot wus visible in a kDOWSSposi- rover’s Ml suite of hazud avoi tion alongthe scan line. Deviations ante foatums during specific u-s from flat and ICVCIground woutd 8ss4s. ‘his caution was unch cause the larse.rspot 10 slide aloruz I J standable, given tit each ro~ traversa inhorontlypu~thc vehicle at risk of prematureend of the mission. k fbtwo planned rover missions, such the Mfu9 !ltweyor Progmm 2001 missic the operations taasrrwill not be able to rnt the mission objectives while mstintining cautious approach to autonomous novigatio In thoso missions, the rover will be requin to traverse approximately 100 m.kol in ord to reach sites of soientifiointerest and oolk Samplesfor eventual rehlrts to Earth. This equivalent to performing all of the travcrs of the MF33Xrover during the dire Pat t.lndcrsurthce mission in a single sol. SW lon@istanc4 travame4will squire a sigd osnt inorease in autonomous capability, U\ der consideration for this future mission a onbosrd teohniquss for terrain f~ture trncl ing, creation of obstacle maps, and vim ~okittg to targets which may aid rnissic performance through improvements 1 autormmousnavigation. amngad so thatobstacles could-be &- teotedto the sides of the rover traverse di- the attemptsto achiovman unrea;hstie goal. ReMmcaa and Notaa reotionat sufficientrange so that the entire -g on the parameter settings in the 1. Pa sequesm, any remaining traverse D. Shlrtey and J. Matifevio,Mm Rowm.’ rover’sturning circle (a circle 70 cm in di- commends RDsent @ Fulufs, IWtoelon Spew Swrlk amata.r)was 6’00of hazlrds. ‘MS allowed were skipped (because the rover was not lnetJlula201h tilwaarv Conkwenca,Prfnoeto the rovesto turn around in pleoe and drive whexeit MS oxpeoted)or the rover smntinued NJ, hhy 10, 1SS7(Publhhqr,Io@lon, llW7)[J&f3 2. J, MSIW gnd D. Shlrlay, ControlEw. Pmctb forwardto avoid an obstacl~ If the density onto the next speeifiedlocation & 927 (1W7S, Ofhezlrds inthetamain waatoo highto ‘Me autonomous navigation porfonnanco S. E’.Oat.-R. Did, R. Mav J. Loch, D. Miller, H permit the vehiob to maintain a clear of the rovoron Mars generallyequaledor srx- Tmla Robsos Aubrn. h4]lo, 4M (1W4). eoededthe pdormanoe obwrved during tests 4. R, B@m, KEE J, R0Luc4 AutLm R&2, Yin turning oirole, a “thread the needle” ap (lQIMMDW. pros@ could be enabled. This technique an Earth Beoaueeof the nearly ob$aok%ee 6, D, wkOK D, Shnnofy, A h$8h)dII,Pm.z SP/ 100?, mw tie rover 10 shivs betwoo13ob. nature of the tarrain in the itnmediaw vicinity XXX[JM6] 10SS, of the lander, initial rover tmvsrrsoswere 6. Thh work wc owried 0~ bytheJd Pro@ak staoles that were apart at least one vehi- L.@wrelory,CelNornlalnstiluloof Tschnolngyund cle’swidth If enobled,the rover would at- comrnnndedthrou@t low-kvd moves, with ● oonlrnotwkh NASA tempt to driw in a straight line along the no “(30to Wa int” commandsused By aol peqmndiouhr bisector between the two 1A ORCOtheTasorkamma hwrard dotoction Digital madbox: obstaoles.It would oontinuedriving until it _ ~$ oaliiated (an example of a ww%v.aciencernrig.org/drnoil.cgi?53621 found a clearing large enough to turn measurement is shown in Fig.