Experimental Study of Problem of Estrangement of AR. Drone Four Rotor Helicopter Velocity Parameter Calculated by the Internal IMU Hideki Toda

Transcription

1 Intrnational Journal of Enginring Rsarch & Scinc (IJOER) ISSN: [ ] [Vol-3, Issu-8, August- 2017] Exprimntal Study of Problm of Estrangmnt of AR. Dron Four Rotor Hlicoptr Vlocity Paramtr Calculatd by th Intrnal IMU Hidki Toda Dpartmnt of Elctric and Elctronic Enginring, Univrsity of Toyama, 3190 Gofuku, Toyama, , Japan Abstract For four rotor hlicoptr systm, th vlocity paramtr is important for stabl ral-tim control, and th vlocity is calculatd by th IMU (Intrnal Masurmnt Unit) from th thr-axis acclration and gyro snsors. Sinc th IMU unit dvlopd and dsignd for multi-purpos us, high-frquncy rang of th acclration/gyro snsors information was usd for stimating th vlocity and it is afraid to do ovrstimation of th vlocity spcially whn th dron collision against th wall (vn with a slight contact) and th impact du to blasts. Th rsult shows that th IMU unit calculatd vlocity was divrgnt 20 tims from th ral vlocity masurd from th camra on th ciling vn whn low spd contact with a wall (25 cm/sc spd). Whn th stimatd vlocity paramtr would b usd for th position control and stabilizing of AR. Dron hlicoptr, it will b ncssary to considr th problm of th strangmnt of th vlocity to dvlop th dron systm for inspction at infrastructur quipmnt such as th bridg or tunnl. Kywords Four rotor hlicoptr, AR. Dron 1.0, Vlocity stimation, IMU, Invstigation of bridg or tunnls. I. INTRODUCTION In this papr, th vlocity paramtr obtaind from th IMU (Intrnal Masurmnt Unit) in AR. Dron four rotor hlicoptr 1.0 was masurd and analyzd, and it was found that th vlocity paramtr was calculatd as an strangmnt fashion whn th dron touch against a wall with a slight impact. Th IMU is on of th standard quipmnt of th dron systm, sinc th information of acclration and gyro snsors is indispnsabl for ral-tim stabl postur controlling [1-7]. In addition, th vlocity paramtr is also stimating at th sam tim in th IMU, and it was typically usd for th "spac position" controlling and stabilizing procss for dron controlling [1,8-16]. Sinc th IMU is dvlopd and dsignd for multi-purpos us, high-frquncy rang of th acclration and gyro snsors information was usd for stimating th vlocity paramtr and it is afraid to do ovrstimation of th vlocity spcially whn th dron collids against objct such as wall or tr branchs (Fig.1).Also, impacts from wind flow blasts would b afraid to do ovrstimation of th vlocity. Th main objct of this papr is to compar th ral vlocity valu masurd from th camra on th ciling with th IMU output stimatd vlocity paramtr in th x yspac in th room (Fig.2) to confirm th ffct of th ovrstimation of th vlocity paramtr by th IMU. FIG.1. IMPACTED BY BLASTS AND SLIGHT COLLISION TO OBJECT WOULD OCCURS FREQUENTLY WHILE INSPECTING BRIDGE OR TUNNEL BY USING A DRONE SYSTEM. Twnty prcnt of currntly 730,000 bridgs ar undr construction for mor than 50 yars in Japan [8].Many businss oprations of priodic inspction of th undr bridg, insid tunnls and buildings ar bginning to b trid [17-19]. Evn if Pag 123

2 Intrnational Journal of Enginring Rsarch & Scinc (IJOER) ISSN: [ ] [Vol-3, Issu-8, August- 2017] th dron would b controlld by a human bing, th flight by visual confirmation of man is difficult in th ovr 10 m long distanc flight [2,3,8-10,20-23].In many cass, th priodic inspction of a bridg is ncssary to oprat in a plac 200 m away, and it is impossibl to rmov th influnc of contact and blasts around th four rotor machin that cannot b visually obsrvd [1, 14, 17,18]. II. PREVIOUS STUDY AND THE MATHEMATICAL BACKGROUND Four rotor hlicoptr systm would not b includd autonomous position controlling way as itslf, and th positioning control is ncssary for th spac using InfraRd 3D camras [3,12] or GPS snsor systm [14, 18] to control th dron position [3, 13-15, 24-27].In th InfraRd 3D camra, th prcision of th position masurmnt is 1 mm ordr. Howvr, th ara of th using this mthod is within 10 m and th indoor situation only [2].On th othr hand, if th dron would b controlld in th outdoor situation, th GPS signal can b usd that thr is no obstacls uppr dirction (sky) and movmnt dirction. Howvr, to us th dron for th priodic inspction of undr th bridg or insid tunnls, th two approachs cannot b adoptd sinc th instability of th GPS signal undr ths sits [17]. Also, in such situations of th long distanc priodic inspction (such a cas 200 m distanc from th bas), camra imag fdback control (or by visual confirmation of man from th bas point) is ncssary. To raliz stabl flight control at th long-distanc situation (ovr 10 m), th camra imag fdback control would bcom important, on th othr hand, autonomous flight stabilizing procss using th IMU information would b mor indispnsabl sinc slight touching to thin tr branchs and impacts from wind flow blasts could not corrctly confirm from th bas point visually [3].To supprss th dviation of trajctory du to th disturbancs such as wind flow, on of th main factors of th fdback control is vlocity paramtr v. Equation of motion of th dron whil floating was dscribd as (not includd four rotors dpnd on complx dynamics, simpl on-mass quation of motion). ma = F = kv + f (1) whr m is a mass, a is th acclration, v is th vlocity, k is friction cofficint by air and fis th xtrnal control input. In Eq.1, th trm kv has movmnt vibration supprssion influnc as th friction, and it can stabiliz th dron movmnt, but th ffct is limitd small sinc th k is vry small and unstabl. To raliz th stabilization, th ffct of th D (diffrntial) gain is typically usd as blow, f = k d v (2) whr k d is constant fdback diffrntial gain paramtr, v is stimatd vlocity calculatd by th IMU. Gnrally, th ral vlocity v and th stimatd vlocity v (calculatd valu by th IMU) tak sam valu undr normal flight situation, and th trm k d v affcts th movmnt vibration supprssion. Th ffct is typically larg comparing with th air friction k. On th othr hand, to calculat th stimatd vlocityv, th IMU hav to stimatv by using two snsor outputs - th intrnal acclration and gyro snsor. Sinc th IMU is dvlopd and dsignd for multi-purpos us, high-frquncy rang of th acclration and gyro snsors information is usd for prcis stimating ofv. Espcially, th high-frquncy (fw hundrd hrtz) information is indispnsabl to stimat it. But whn th dron would collid with som slight touching to thin tr branchs or impacts from blasts in th outdoor inspction works, thr is a possibility that an unprdictabl highfrquncy chang of th acclration and gyro snsors would distort thv. As a rsult, it is afraid to shift th vlocity valu spcially whn th dron collids against som objct or would b impactd by blasts. III. METHOD In this xprimnt, AR. Dron 1.0 quad rotor modl hlicoptr dvlopd by Parrot Co. [28] was usd. In Fig. 2, th aircraft is positiond at th cntr of th room (5 6 m squar room, hight is 2.4 m) and it flows automatically with th hight of 0.6 m from th ground. To control th movmnt of th aircraft, AR. Dron library for Procssing namd ARDronForP5 as dvlopd by Y.Shigo [28] was usd and it was connctd to a PC with Wi-Fi ntwork. Th basic priod of movmnt command transmission btwn th aircraft and th PC was about 99.6 msc (18.4 msc standard dviation S.D.). Th stimatd vlocity v can b masurd from th intrnal IMU of th dron via th control library ARDronForP5 with about 10 Hz spd. Pag 124

3 Intrnational Journal of Enginring Rsarch & Scinc (IJOER) ISSN: [ ] [Vol-3, Issu-8, August- 2017] FIG.2. SIDE VIEW OF THE EXPERIMENTAL SETUP. AR.DRONE WAS CONTROLLED TO A CONSTANT VELOCITY MOVEMENT, AND COLLIDED WITH A WALL AT THE CONSTANT VELOCITY. THE REAL DRONE MOVEMENT VELOCITY WAS MEASURED BY A WEB CAMERA AT THE CEILING. Fig.3 shows a top viw of th xprimntal stup. Th ral dron position in th x y spac (Fig.3) was masurd by a wb camra (BSW20KM11, , 60 fps, 130 dg visual angl, ibuffalo Co.) attachd to th ciling of th room. Th position discrimination was about 2 mm. To rduc masurmnt nois of th ral vlocity, a low pass filtr was applid to th ral vlocity valu calculatd from th position data obtaind at 60 Hz. Tim constant was dfind about 100 msc (10 Hz).From th rsult of th dron position, th ral vlocity v can b calculatd. FIG.3. SETUP OF AR. DRONE COLLIDING EXPERIMENT TO A WALL WITH A CONSTANT VELOCITY v (TOP VIEW). To compar th two vlocity valus whil th collision, y axis valus of th vlocity v and v wr usd in Fig.3. It wr r p dnotd as v y and v y rspctivly. Th dron's movmnt roll and pitch spd commands V command = xaxis, V command =yaxis s and th yaw (spin) control command V command ar dtrmind. r = 0 V command p V command V command = γ p s = 0 (3) Pag 125

4 Intrnational Journal of Enginring Rsarch & Scinc (IJOER) ISSN: [ ] [Vol-3, Issu-8, August- 2017] Whr γ p is constant valu [2, 10, 20-22]. IV. EXPERIMENT Thr ar two phass of th movmnt control in th xprimnt. (1) Tak off and 5 sc fixd point floating phas: Th γ p st as 0 bfor th dron tak off. Aftr th tak-off, 5 sc normal flight (without any control of th dron) is implmntd to stabiliz th postur. Sinc th phas (1) was totally within 10 sc, thr is slight yaw chang (< 0.5 dg) and slight movmnt (< 15 cm) by th dron implmntd postur control systm. From th rason, w do not snd any control commands to th dron whil phas (1). (2) Constant vlocity and backward (slowdown) control phas: Firstly, thγ p st as 30 or 100 (max 100 in th ARDronForP5 library) as constant vlocity movmnt (+y axis dirction) aftr th phas (1). Nxt, whn th dron is crossd th position of th camra on th ciling, th constant vlocity paramtr γ p is changd to -100, and th dron was trid to backward movmnt ( y axis dirction) with th inrtial motion continud. Sinc th positiv vlocity v y of th dron is continuously rducing whil th backward control phas, th v y would pass through 0 and tak ngativ valu. In this phas (2), th dron would collid with th wall at a collision vlocity, and th collision vlocity v y c mainly dpnds on th firstly st γ p valu (30 or 100%). V. RESULT Figur 4 rprsnts th rsult of comparison btwn th ral vlocity v y of yaxis in Fig.3 and th stimatd vlocityv y of y axis obtaind from th AR.Dron's IMU. Horizontal axis mans lapsd tim t [sc].in this xprimnt, th standard dviation (S.D.) of th ral position of x was masurd as 6.7 cm whil 2.3 m flight, and it mans that thr was littl movmnt of xaxis whil th movmnt. Filld Squar mark mans th ral vlocity v y masurd from th camra on th ciling, and th whit squar mark is th stimatd vlocity v y obtaind from th AR.Dron's IMU in ach tim priod [sc]. Two vlocity transitions vary in coincidnc, and th dviation (S.D. of v y v y ) was calculatd as 23.4 cm/sc. FIG.4. COMPARISON BETWEEN THE REAL VELOCITY v y OF y AXIS AND THE ESTIMATED VELOCITY v y OBTAINED FROM THE AR.DRONE'S IMU. THERE IS NO COLLISION CASE WITH THE WALL. HORIZONTAL AXIS REPRESENTS TIME [sc] Figur 5 rprsnts th rsult of comparison btwn th ral vlocity v y of y axis and th stimatd vlocity v y of y axis obtaind from th AR.Dron's IMU whn thr is a slight collision with a wall. Evn in this xprimnt, th two vlocity transitions vary in coincidnc, but in th timing of vrtical dottd lin (collision timing), th stimatd vlocity v y suddnly transitiond to a high positiv valu (205 cm/sc) and it was dcrasing and approaching to ral vlocity valu v y with a larg dlay. Immdiatly aftr th collision, th ral vlocity was v y =-10.0 cm/sc.in th timing of th collision, th ral vlocity v y taks about 25 cm/sc, and this vlocity strangmnt phnomnon was obsrvd in almost all collisions. Thr is an ovr 20 tims diffrnc btwn th v y and v y whn th collisions (v y v y = 205 cm /sc 10.0 cm /sc = 20.5). Pag 126

5 Intrnational Journal of Enginring Rsarch & Scinc (IJOER) ISSN: [ ] [Vol-3, Issu-8, August- 2017] FIG.5. COMPARISON BETWEEN THE REAL VELOCITY v y OF y AXIS AND THE ESTIMATED VELOCITY v y OBTAINED FROM THE AR.DRONE'S IMU WHEN THE DRONE COLLIDES WITH THE WALL SOFTLY (ABOUTv y c =25 CM/SEC) Figur 6 rprsnts th rsult of comparison btwn th ral vlocity v y and th stimatd vlocity v y whn th dron was collidd to a wall with a high vlocity (about v yc =60 cm/sc). Th two vlocity transitions vary in coincidnc basically until th collision timing (vrtical dottd lin), th stimatd vlocity v y suddnly transitiond to a positiv high valu (maximum 425 cm/sc) and it was dcrasing and approaching to ral vlocity valu v y with a larg dlay. Th ral vlocity was masurd as -5 cm/sc in th abov timing. In th timing of th collision, th ral vlocityv y taks about 60 cm/sc. FIG.6COMPARISON BETWEEN THE REAL VELOCITY v y OF y AXIS AND THE ESTIMATED VELOCITY v y OBTAINED FROM THE AR.DRONE'S IMU WHEN THE DRONE COLLIDES WITH THE WALL HARDLY (ABOUTv y c =60 CM/SEC) From abov thr xprimnts, th stimatd vlocity v y was strangd from th ral vlocity v y aftr th collision timing with th wall. Mayb multipl causs ar considrabl to xplain th phnomnon, howvr, if th dron us th v y to stabiliz th position movmnt that was discussd in sction 2, th strangmnt of th vlocity would affct incorrct D gain fdback as dnotd by Eq.2. VI. DISCUSSION Th rason for th strangmnt of th stimation vlocity v y would b inducd by th vlocity stimating algorithm implmntd in th IMU. Sinc IMU is gnrally dvlopd and dsignd for multi-purpos us, it would us high-frquncy Pag 127

6 Intrnational Journal of Enginring Rsarch & Scinc (IJOER) ISSN: [ ] [Vol-3, Issu-8, August- 2017] rang of th acclration and gyro snsors information to stimat th vlocity, and thr is a problm that th influnc of high-frquncy information affcting to th vlocity stimation would b unstabl spcially whn th IMU is impactd by small tr branchs collision or blasts to four rotors systm. If th IMU dos not us th high-frquncy information, th prcision of th stimatd vlocity would b rducd, and imprcision in th vlocity stimation would mak control of th spatial position of th four rotors systm inaccurat (s Eq.2). To improv th accuracy of th spatial position control, high prcision vlocity stimation is ncssary, th two factors ar in a trad-off rlationship and it would b difficult to analyz this trad-off problm. Th strangmnt of th stimation vlocity is ncssary to tak car whn th subjct uss th stimation vlocity factor to stabiliz th AR. Dron 1.0 hlicoptr at last. VII. CONCLUSION In this papr, th vlocity paramtr obtaind from th IMU (Intrnal Masurmnt Unit) in AR. Dron four rotor hlicoptr 1.0 was masurd and analyzd, and it was found that th vlocity paramtr was calculatd as an ovrstimatd fashion whn th dron touch against th wall with a slight impact. For four rotors hlicoptr systm, th vlocity paramtr is important for stabl ral-tim control, and th vlocity is gnrally calculatd by th IMU (Intrnal Masurmnt Unit) from th thr-axis acclration and gyro snsors. Th rsult shows that th IMU stimating vlocity v y was divrgnt 20 tims from th ral vlocity v y masurd from th camra on th ciling vn whn low spd contact with a wall (25 cm/sc spd). Whn th stimatd vlocity paramtr would b usd for th position control and stabilizing of AR. Dron hlicoptr, it will b ncssary to considr th problm of th strangmnt of th vlocity to dvlop th dron systm for inspction at infrastructur quipmnt such as th bridg or tunnl. ACKNOWLEDGEMENTS This work was supportd by JSPS KAKENHI Grant Numbr JP15K REFERENCES [1] K. Nonami, F. Kndoul, S. Suzuki andw. Wang, D. Nakazawa, Autonomous flying robots: unmannd arial vhicls and micro arial vhicls, Springr Japan, [2] H. Takano andh. Toda, Roll movmnt ralizd by yaw and roll command combination mthod of AR Dron 4 rotor hlicoptr for improving stability of automatic position stop, Intrnational Confrnc on Advancd Mchatronics (ICAM 2015), Wasda Univrsity, Tokyo, Japan, Dc.5-8, 2015, p.53. [3] S. Azrad, F. Kndoul andk. Nonami, Visual Srvoing of Quadrotor Micro-Air Vhicl Using Color-Basd Tracking Algorithm, Journal of Systm Dsign and Dynamics (JSME), Vol. 4, No. 2, 2010,pp [4] T. K. Roy, M. Garratt, H. R. Pota andm. K. Samal, Robust altitud control for a small hlicoptr by considring th ground ffct compnsation", Intllignt Control and Automation (WCICA), 10th World Congrss, DOI: /WCICA , 2010, pp [5] A. C. Satici, H. Poonawala andm. W. Spong, Robust Optimal Control of Quadrotor UAVs, IEEE Accss, Vol. 1, DOI: /ACCESS , 2013, pp [6] J. Toldo, L. Acosta, M. Sigut, J. Flip, Stability Analisys of a Four Rotor Hlicoptr, Automation Congrss, WAC '06. World, 2006, pp [7] P. Castillo, A. Dzul, R. Lozano, Ral-tim stabilization and tracking of a four-rotor mini rotorcraft, IEEE Transactions on Control Systms Tchnology, Vol.12,Issu: 4, DOI: /TCST , 2004, pp [8] E. Altug, J. P. Ostrowski, C. J. Taylor, Control of a quadrotor hlicoptr using dual camra visual fdback, Intrnational Journal of Robotics Rsarch, Vol.24, No.5, 2005, pp [9] B. Ludington, E. Johnson, G. Vachtsrvanos, Augmnting UAV autonomy: vision-basd navigation and targt tracking for unmannd arial vhicls, IEEE Robotics and Automation Magazin, Vol.13, No.3, 2006, pp [10] H. Toda, H. Takano, Effct of Discrt Yaw Dirction Stting for 4 Rotr Hlicoptr Control: Computr Simulation and AR. Dron Modl Implmntation, Intrnational Journal of Innovativ Rsarch in Advancd Enginring, Vol. 3, Issu 7, Papr ID JYAE10086, doi: /cj8f3v6csr.1, [11] J. Engl, J. Sturm, D. Crmrs, Camra-basd navigation of a low-cost quadrocoptr, IEEE/RSJ Intrnational Confrnc on Intllignt Robots and Systms (IROS), DOI: /IROS , [12] O. Andrisani, E. T. Kim, J. Schirman, F. P. Kuhl, A nonlinar hlicoptr trackr using attitud masurmnts, IEEE Transactions on Arospac and Elctronic Systms, Vol. 27, Issu 1, DOI: / , 1991, pp [13] L. Garcia-Dlgado, A. Dzul, V. Santib, M. Llama, Quad-rotors formation basd on potntial functions with obstacl avoidanc, Control Thory and Applications, Vol. 6, Issu. 12, DOI: /it-cta , 2012, pp Pag 128

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