An Autonomous Blimp for the Wall Following Control.

Transcription

1 An Auonomous Blimp for he Wall Following Conrol. Seung-Yong Oh *,**, Chi- Won Roh *, Sung- Chul Kang *, Eun-ai Kim ** * Inelligen Roboics Research Cener, Korea Insiue of Science an echnology, Seoul, Korea (el : ; osy0804@kis.re.kr) Inelligen Roboics Research Cener, Korea Insiue of Science an echnology, Seoul, Korea (el : ; cwroh@kis.re.kr) Inelligen Roboics Research Cener, Korea Insiue of Science an echnology, Seoul, Korea (el : ; kasch@kis.re.kr) ** School of elecrical an elecronic engineering, Yonsei Universiy, Seoul, Korea (el : ; ekim@yonsei.ac.kr) Absrac: his paper presens he wall following conrol of a small inoor airship (blimp). he purpose of he wall following conrol is ha a blimp mainains is posiion an pose an flies along he wall. A blimp has grea ineria an i is affece by emperaure, amospheric pressure, isurbance an air flow aroun blimp. In orer o fly inoors, a volume of blimp shoul be small. he volume of a blimp becomes small hen he buoyancy of a blimp shoul be smaller. herefore, i is ifficul o aach aiional equipmens on he blimp which are necessary o conrol blimp. For hese reasons, i is ifficul o conrol he pose an posiion of he blimp uring he wall following. In our research, o cope wih is efecs, we evelope new blimp. Generally, a blimp is conrolle by using ruers an elevaors, however our evelope blimp has no ruers an elevaors, an i has faser responses han general blimps. Our evelope blimp is esigne o smoohly follow he wall by using low-cos small ulra sonic sensors insea of high-cos sensors. Finally, he conroller is esigne o robusly conrol he pose an posiion of he blimp which coul conrol in spie of arbirary isurbance uring he wall following, an he effeciveness of he conroller is verifie by eperimen. Keywors: Auonomous Blimp, Wall Following, Decoupling conrol 1. INRODUCION Recenly, here are many challenges in he fiel of unmanne aerial vehicle (UAV) research. Amongs hem, a small inoor blimp airship (blimp) has unique avanage since i can pass over he errain ha may be impossible for lan-base robos o eplore. herefore we nee no consier he sae of floor. An i has an effec ha can arac aenion from observers since i flies in he air higher han he groun vehicle. An a blimp nees no energy o mainain an aliue, as i relies on is neural buoyancy o say alof. [1] However, i is very ifficul o conrol a blimp auonomously for he following reasons. Firsly, blimp s payloa is resrice. herefore, i is ifficul o insall aiional equipmens on he blimp which are necessary o conrol is pose an posiion (i.e. gyro sensor, GPS evice, on boar conroller, acuaors ec). Seconly, a blimp has grea ineria an i is grealy affece by emperaure, amosphere, air flow aroun he blimp an isurbance. In orer o resolve ifficulies on is conrol, various researches have been performe o conrol auonomously by using vision sysem [2-4], saionary posiion conrol sysem which has passive wheele mechanism [5], an navigaion sysem using ulra sonic sensors [6]. However, he blimp conrol using vision sysem is grealy affece by surrouning coniions such as illuminaion. he blimp conrol which has passive wheele mechanism can conrol only hree egrees of freeom, no all egrees of freeom. Finally, he navigaion sysem using ulra sonic sensors has comple srucure. However, our evelope blimp has avanages which coul conrol he pose an posiion of he blimp a he same ime using low-cos small ulra sonic sensors insea of high-cos sensors. I was esigne o have a simple srucure an have faser response capabiliy han he general blimp which is conrolle by ruers an elevaors. his paper eals wih he wall following conrol by using newly evelope blimp which is no affece by is surrounings. he ynamic equaion of he blimp is erive, an is conroller is esigne o robusly conrol he pose an posiion of he blimp. Finally, he effeciveness of he conroller is verifie by eperimens ha arbirary isurbances are applie o he evelope blimp uring he wall following. his paper is organize as follows Secion 2 eplains he srucure of blimp. Secion 3 presens he ynamic equaion of he blimp an is linearizaion. Secion 4 eals wih ecoupling echniques for he conroller esign. Secion 5 shows he conroller esign for self posiioning an posing of he blimp for he wall following. Secion 6 emonsraes eperimenal resuls. Finally, secion 7 conains conclusions an fuure works. 2. DESCRIPION OF SYSEM DESIGN A general inoor blimp is conrolle by elecric moors. Also he volume of he blimp shoul be enough small o fly inoors. If he volume of a blimp becomes small hen is buoyancy shoul be smaller. Because of his reason, i is ifficul o insall aiional equipmens such as he sensors, he acuaors, a baery, an he on-boar conroller. In orer o overcome hese consraine coniions, we mae he gonola which is mae of he ligh maerials. Also, low-cos small ulra sonic sensors an acuaors are insalle on he gonola Fig. 1 shows he srucure of he blimp. he lengh of blimp is 7 f an he maerial is ligh, highly elasic polyurehane an i is fille wih helium gas. he gonola is esigne is weigh o be small. he weigh of he gonola is 800gram. A general blimp is conrolle using ruers an elevaors, however our evelope blimp is no conrolle using ruers an elevaors. Our blimp has 6 ulra sonic sensors an 6 moors on he srucures in he longiuinal an he laeral irecion respecively, as shown in fig 1.

2 (a) Fron View (b) Sie View frames. One is place in he blimp s boy, a he buoyancy cenre (blimp frame {b}), an he oher in he groun plane, (he worl frame {w}). he referre frames are presene in Fig. 2. o escribe he posiion an orienaion of he blimp wih respec o he worl frame {w}, he following physical variables are use: η = η 1, η 2 ; η1 = yz,,, η2 =[ φ, θ, ψ] v = v 1, v 2 ; v1 = [ v, vy, vz], v2 = w, wy, wz τ = τ1, τ 2 ; τ1 = [ F, Fy, Fz], τ2 = N, Ny, Nz Where, (c) he gonola of he blimp Fig. 1 Auonomous blimp srucure In he laeral conrol, he ulra sonic sensor S1 an S2 measure yaw angle an he isance from he wall. Base on he measure values, he on-boar conroller calculaes yaw angle an isance beween he blimp an he wall an conrols hem hrough he moor M1 an M2. In he same way, in he aliue conrol, he ulra sonic sensor S3 an S4 measure he roll angle an he aliue of he blimp. Base on he measure values, he on-boar conroller calculaes roll angle an aliue of he blimp an conrols hem hrough he moor M3 an M4. Finally, in he longiuinal conrol, sensor S5 an S6 eec he wall or he obsacles, an he moor M5, M6 are conrol he rajecory of he blimp. 3. DYNAMICS AND KINEMAICS OF BLIMP 3.1 Nonlinear Dynamic Equaion A full si egree of freeom mahemaical moel for his blimp is erive base on [1, 7, 8]. y w z w w y b z b b Fig. 2 he placemen of reference frames. he kinemaic escripion of he vehicle is base on wo η = η, η represens he pose an posiion vecor of he 1 2 blimp wih respec o he worl frame {w}. v v v = 1, 2 escribes he velociy an angular velociy vecors in he blimp frame{b}. τ = τ, τ represens he force vecor in 1 2 he blimp frame{b}. Assuming he blimp is rigi boy, he ynamic equaion coul be erive as following wo equaions. he firs one moels he ynamic equaion wih respec o he blimp frame {b} an he secon equaion represens he kinemaic relaion beween he blimp frame {b} an he worl frame {w}. ( ) ( ) ( η ) & = (1) Mvb + C vb vb + D vb vb + g b τb J1( η2) [ 0] 3 3 [ 0] J ( η ) & η v η J η = v & = 2 Where, ( η ) v= v, vy, vz, w, wy, wz is he 6 1 mari which conains linear velociy( v, vy, vz ) vecor an angular velociy vecor ( frame{w}. w, wy, wz v ) wih respec o he worl M = MRB + MA is he 6 6 mass mari conaining all masses an inerias of he rigi boy ( M RB ) an he ae mass an he ineria erms ( M A ). Assuming ha he blimp is symmery an non-eformable, cross-coupling inerial erms in M RB can be neglece. An ( g, yg, z g ) represens he locaion of he cener of he mass wih respec o he origin of he blimp frame {b}. An hen we can erive he equaion ha escribes he rigi boy mari, where: 0 -zg yg mi ms M 33 RB =, S = zg 0 -g ms Ib yg g 0 M A = iag a11, a22, a33, a44, a55, a66 C = CRB( vb ) + CA( vb ) is he 6 1 ynamic force mari. Where, CRB( v b), CA( vb) conain he Coriolis force an he

3 cenrifugal erm of he ynamic moel. Assuming he blimp moves slowly hen C ( v ) becomes zero. RB b D( vb ) is he aeroynamic amping mari. Assuming he blimp moves slowly, nonlinear amping erms coul be erase. Consequenly, only linear amping erms eis. g ( ηb ) is he resoring force vecor, which epresses he influence of he graviy an buoyancy forces in he ynamic behavior. Assuming he blimp is symmeric, he pich angle of blimp becomes zero. τ b conains he isurbance, he acuaion forces an he orque vecor & M D M G & u = 2 J [ 0] [ 0 ] y ψ y = (3) vy wz 4.2 Aliue Moe he perurbe sae variables for he aliue moe are () = [ z() φ() v () w (). he moe is escribe by z ] he sae space moel in equaion (4) 3.2 Linearize Equaion For he purpose of simplifying he analysis of ynamic characerisic an he conroller esign process, equaion (1) coul be linearize. Assuming he blimp moion o be consraine o small perurbaion abou some equilibrium coniions, a consierably simplifie linear moel can be obaine. In orer o obain he linearize moel of he blimp, i is necessary o efine equilibrium values for velociy an pose. hese are efine as: [ ] & M D M G & u = + J [ 0] [ 0] z φ y = vz w 4.3 Longiuinal Moe η0() = 0(), y0(), z0(), φ0(), θ0(), ψ 0() he perurbe sae variables for he longiuinal moe v0() = v0(), vy0(), vz0(), w0(), wy0(), wz0() are () = () v (). he moe is escribe by he sae space moel in equaion (5) herefore he linearize ynamic equaion becomes he following equaion: & M D M G 1 + M & B 1 1 u & 1 M ( C() + D() ) M G() = 2 0 J 2 0 = + u & 2 J () y = [ 1 0] (2) v ( 5) (4) Where: Cv () Dv () gv () C () = ; D () = ; G () = v0() v0() η0() J () = J( η0 ()) 1 = v () v0(), 2 = η() η0(), 5. CONROLLER DESIGN his secion eals wih conrollers which are esigne for he wall following conrol of he blimp. Our sraegy uses eperimenally une PD-conrollers for each conrollable egree of freeom. 5.1 Laeral Moe Conroller 4. DECOUPLING FOR CONROLLER DESIGN In secion 3, he ynamic equaions were erive an linearize. In orer o easily analyze an conrol he fligh of he blimp, he equaion (2) coul be ecouple ino hree moes, i.e., he laeral moe, he aliue moel an he longiuinal moe. 4.1 Laeral Moe he perurbe sae variables for he laeral moe are () = y() () v () () ψ y wz. he moe is escribe by he sae space moel in equaion (3) he esigne conrollers for he laeral moe are as follows. l() = kpe() + k e() + k pea() + k ea() r() = kpe() + k e() k pea() k ea() he seay sae error of yaw angle ( e () ) an posiion ( ea () ) are calculae wih sensor S1, sensor S2 as shown in F ig. 1. k p, k are he PD gains o conrol he isance beween he blimp an he wall. An k p, k are he PD gains o conrol he pose of he blimp. he oupu l (), r () are eermine by he PD conroller. Where, () is he hrus l

4 of he moor M1 an r () is he hrus of he moor M Aliue Moe Conroller wall an he blimp is 95 (cm), an he flying isance is 10(m) as shown in able 1. he esigne conrollers for he aliue moe are as follows. () % () % l = k pe % + k e % () + k pe % a() + k e % a() () % () % r = k pe % + k e % () k pe % a() k e % a() he seay sae error of roll angle ( e% a( ) ) an posiion ( e % ( ) ) are calculae wih sensor S3, sensor S4 as shown in Fig. 1. k % p blimp. An k p,, k % are he PD gains o conrol he aliue of k are he PD gains o conrol he pose of he blimp. he oupu l (), r () are eermine by he PD conroller. Where, l () is he hrus of he moor M3 an r () is he hrus of he moor M Longiuinal Moe Conroller he esigne conroller for he longiuinal moe is as follow. () = k$ () $ pe $ + k e $ () he seay sae error of posiion ( e $ ()) are calculae wih sensor S5, sensor S6 as shown in Fig. 2. k $ p, k $ are he PD gains o conrol he longiuinal moe of blimp. he oupu, () are eermine by he PD conroller. Where, () is he oupu of moor M5 an moor M6. he longiuinal moe conroller is esigne o make a roun rip hrough consan isance. However, he range of ulra sonic sensor is 2.5 meer. So if he blimp becomes ou of he sensor s range, i is programme so ha flies wih consan velociy owar he longiuinal irecion unil i reaches wihin he sensor s range. hen he longiuinal conroller on he blimp correcs course of he blimp o fly he preeermine rajecory of he blimp. By repeaing hese proceures, he blimp follows he wall wih sable behavior. Fig. 3 Eperimenal seup Fig. 4(a) presens he seay sae error of yaw angle uring he wall following. Fig. 4(b) shows he isance beween he wall an he blimp. Fig. 4(c) is he seay sae error of roll angle uring he wall following. Fig. 4() epresses he aliue of blimp. Fig. 4(e) presens he longiuinal isance when i flies owar an backwar. he isurbances are applie o he blimp wo imes; 5(sec) an 14(sec). he eperimen resuls show ha he posiion an pose of he blimp coul be sabilize wihin 4(sec) in spie of he isurbances uring he wall following as shown in Figure 4. (a) he laeral moe conrol ( yaw angle error) 6. EXPERIMENS We conuce e perimens ha he blimp flies an reurns consan isance as shown in Figure 3. An he arbirary isurbances are applie o he blimp o es performance of he esigne conroller. he coniions of eperimens are as follows: able 1 he Coniions of Eperimens. he aliue 85 (cm) Disance beween he wall an he blimp 95 (cm) he flying isance 10 (m) (b) he laeral moe conrol (isance from he wall) he aliue of he blimp is 85 (cm), he isance beween he

5 Roll angle (egree) Disurbance ime (sec) (c) he aliue moe conrol (roll angle error) () he aliue moe conrol (he aliue) A forwar 100 movemen A backwar movemen ime (sec) posiion wihin a shor perio espie of he arbirary isurbance. If our blimp wih he averisemens flies in crowe places, i makes people o concenrae on he averisemens. herefore, our blimp woul be useful o ransfer he informaion in public places an is applicaions coul be eene in he fiel of averisemen. REFERENCES [1] Keiko Mooyama, Hienori Kawamura, Masahio Yamamoo, an Azuma Ohuchi, Developmen of auonomous blimp robo wih inelligen conrol, Enerainmen Compuing echnologies an Applicaions, Kluwer Acaemic Publishers, pp , [2] Jose Sanos-Vicor, Sjoer van er Zwaan, Aleanre Bernarino, Vision base saion keeping an ocking for an aerial blimp, IEEE/RSJ Inernaional Conference on Inelligen Robos an Sysems, pp , 2000 [3] akanori Fukao, Kazushi Fujiani, an akeo Kanae, An auonomous blimp for surveillance sysem, Proc. Of he 2003 IEEE/RSJ Inl. Conference on Inelligen Robos an Sysems, Vol. 2, pp , [4] Hong Zang an James P. Osrowski, Visual servoing wih ynamics: Conrol of unmmane blimp, Proc. of IEEE Conference of Roboics an Auomaion, pp , [5] Sungchul Kang, Mihee Nam, Bongsuk Kim, akashi subouchi, Shinichi Yua, A novel esign an conrol of roboic wheele blimp for ele-guiance, Proc IEEE Inernaional Symposium on Compuaional Inelligence in Roboics an Auomaion, pp 67-72, [6] Goron Wyeh an Ivan Barron, An auonomous blimp, Proc IEEE In Conf. on Fiel an Service Roboics, pp , [7] Sergio. B. V. Gomes an Josue Jr G. Ramos, Airship ynamic moeling for auonomous operaion, Proc. IEEE In. Conf. on Roboics an Auomaion, vol.4, pp , [8] Gabriel A. Khoury an J. Davi Gille, Airship echnology, Cambrige Universiy Press, 1999 (e) he longiuinal moe conrol Fig. 4 Eperimenal resuls 7. CONCLUSIONS In his paper, he wall following conrol of he blimp is presene. We evelope he new blimp which has no ruers an elevaors. he propose blimp was esigne o have simple srucure an consise of he small low-cos ulra sonic sensors an moors. However, he response of he propose blimp has faser han general blimps which are conrolle by ruers an elevaors. he conroller was esigne o conrol he blimp auonomously an i coul mainain he sable pose an posiion of he blimp in spie of arbirary isurbance uring he wall following. he effeciveness of he conroller was verifie by eperimens ha he blimp coul reurn he original pose an