GPS World, January 2014

INNOVATION Algorithms Methods readings provide the vehicles speed in the forward direction FIGURE 2 VKRZV D JHQHUDO YLHZ RI WKH 566 FRQ JXUDWLRQ EORFN GLDJUDP RI WKH WLJKWO FRXSOHG 36 566 XVHG LQ RXU ZRUN LV VKRZQ LQ FIGURE 3 W WKLV VWDJH WKH V VWHP XVHV 36 SVHXGRUDQJHV WRJHWKHU ZLWK WKH 566 REVHUYDEOHV WR FRPSXWH DQ LQWHJUDWHG QDYLJDWLRQ VROXWLRQ Q WKLV WKUHH GLPHQVLRQDO version of RISS the system has a total of nine states These states DUH WKH ODWLWXGH ORQJLWXGH DQG DOWLWXGH HUURUV the east QRUWK DQG XS YHORFLW HUURUV WKH D LPXWK HUURU WKH HUURU DVVRFLDWHG ZLWK RGRPHWHU GULYHQ DFFHOHUDWLRQ and the gyroscope error 7KH QLQH VWDWH HUURU YHFWRU x k at time t k is expressed as Cycle Slip Detection and Correction FOH VOLS KDQGOLQJ XVXDOO KDSSHQV LQ WZR GLVFUHWH VWHSV GHWHFWLRQ DQG LQJ RU FRUUHFWLRQ Q WKH UVW VWHS XVLQJ VRPH WHVWLQJ TXDQWLW WKH ORFDWLRQ RU WLPH RI WKH VOLS LV IRXQG XULQJ the second step the size of the slip is determined which is needed DORQJ ZLWK LWV ORFDWLRQ WR WKH F FOH VOLS 9DULRXV WHFKQLTXHV KDYH EHHQ LQWURGXFHG E UHVHDUFKHUV WR DGGUHVV WKH SUREOHP RI F FOH VOLS GHWHFWLRQ DQG FRUUHFWLRQ LIIHUHQW PHDVXUHPHQWV DQG WKHLU FRPELQDWLRQV DUH XVHG LQFOXGLQJ FDUULHU SKDVH PLQXV FRGH XVLQJ RU PHDVXUHPHQWV FDUULHU SKDVH RQ PLQXV FDUULHU SKDVH RQ RSSOHU RQ RU DQG WLPH GLIIHUHQFHG SKDVHV XVLQJ RU Q 36 16 LQWHJUDWLRQ V VWHPV WKH 16 LV XVHG WR SUHGLFW WKH UHTXLUHG YDULDEOH WR WHVW IRU D F FOH VOLS ZKLFK LV XVXDOO WKH WUXH UHFHLYHU WR VDWHOOLWH UDQJH LQ GRXEOH GLIIHUHQFH PRGH GLIIHUHQFLQJ PHDVXUHPHQWV EHWZHHQ D UHIHUHQFH receiver and the roving receiver and between satellites In this DUWLFOH ZH LQWURGXFH D WLJKWO FRXSOHG 36 566 DSSURDFK IRU F FOH VOLS GHWHFWLRQ DQG FRUUHFWLRQ SULQFLSDOO IRU ODQG YHKLFOH QDYLJDWLRQ XVLQJ D UHODWLYH SRVLWLRQLQJ WHFKQLTXH Principle of the Algorithm The proposed algorithm compares FDUULHU SKDVH PHDVXUHPHQWV ZLWK HVWLPDWHG YDOXHV GHULYHG IURP WKH RXWSXW RI WKH 36 566 V VWHP Q WKH FDVH RI D F FOH VOLS WKH PHDVXUHPHQWV DUH FRUUHFWHG ZLWK WKH FDOFXODWHG difference A general overview of the system is given in FIGURE 4 7KH QXPEHU RI VOLSSHG F FOHV is given by where LV WKH FDUULHU SKDVH PHDVXUHPHQW LQ F FOHV LV HVWLPDWHG FDUULHU SKDVH YDOXH LQ F FOHV LV FRPSDUHG WR D SUH GH QHG WKUHVKROG If the threshold is H FHHGHG LW LQGLFDWHV WKDW WKHUH LV D F FOH VOLS LQ WKH FDUULHU SKDVH PHDVXUHPHQWV 7KHRUHWLFDOO ZRXOG EH DQ LQWHJHU EXW EHFDXVH RI WKH HUURUV LQ WKH PHDVXUHG FDUULHU SKDVH DV ZHOO DV HUURUV LQ WKH HVWLPDWLRQV FRPLQJ IURP WKH 16 V VWHP will EH D UHDO RU ÀRDWLQJ SRLQW QXPEHU 7KH HVWLPDWHG FDUULHU SKDVH WHUP LQ TXDWLRQ LV REWDLQHG as follows x 108 0 500 1000 1500 135 130 125 120 115 110 105 Epoch number Cycles FIGURE 5 Measured carrier phase at the rover where LV WKH ZDYHOHQJWK RI WKH VLJQDO FDUULHU LQ PHWHUV PRN 9 PRN 12 PRN 14 PRN 15 PRN 18 PRN 19 PRN 21 PRN 22 PRN 25 PRN 27 are the estimated ranges from the rover to satellites i and j UHVSHFWLYHO LQ PHWHUV are known ranges from the base to satellites i and j UHVSHFWLYHO LQ PHWHUV KDW ZH QHHG WR JHW IURP WKH LQWHJUDWHG 36 566 V VWHP is the estimated range vector from the receiver to each available satellite QRZLQJ RXU EHVW SRVLWLRQ HVWLPDWH ZH FDQ FDOFXODWH UDQJHV IURP WKH UHFHLYHU WR DOO DYDLODEOH VDWHOOLWHV WKURXJK where LV WKH FDOFXODWHG UDQJH IURP WKH UHFHLYHU WR WKH mth satellite LV WKH UHFHLYHU SRVLWLRQ REWDLQHG IURP 36 566 DOPDQ OWHU VROXWLRQ is the position of the mth satellite M LV WKH QXPEHU RI DYDLODEOH VDWHOOLWHV 7KHQ WKH HVWLPDWHG FDUULHU SKDVH WHUP LQ TXDWLRQ FDQ EH FDOFXODWHG DQG WKH IROORZLQJ WHVW TXDQWLW LQ TXDWLRQ FDQ be applied I D F FOH VOLS RFFXUUHG LQ WKH iWK FDUULHU SKDVH VHW WKH corresponding set is instantly corrected for that slip by where s LV WKH FDUULHU SKDVH VHW QXPEHU LQ ZKLFK WKH F FOH VOLS KDV RFFXUUHG Experimental Work The performance of the proposed algorithm was examined on WKH GDWD FROOHFWHG IURP VHYHUDO UHDO ODQG YHKLFOH WUDMHFWRULHV KLJK HQG WDFWLFDO JUDGH 08 ZDV LQWHJUDWHG ZLWK D VXUYH JUDGH 36 UHFHLYHU WR SURYLGH WKH UHIHUHQFH VROXWLRQ 7KLV 08 XVHV WKUHH ULQJ ODVHU J URVFRSHV DQG WKUHH DFFHOHURPHWHUV PRXQWHG RUWKRJRQDOO WR PHDVXUH DQJXODU UDWH DQG OLQHDU DFFHOHUDWLRQ 7KH 36 UHFHLYHU DQG WKH 08 ZHUH LQWHJUDWHG LQ D FRPPHUFLDO SDFNDJH RU WKH 36 566 VROXWLRQ WKH VDPH 36 UHFHLYHU GPS World January 2014 www gpsworld com 66