ThreeDimensional Posture Control ofMono-wheel RobotwithRollRotatable Torso

Thispaperpresents three dimensional stabilization ofa monowheel robotthathasa rollaxisjoint atthewaist partoftherobotanda wheel. Therobotisunderactuated system. Therobotinsagittal planeapproximates a pendulum ona cart. Therobotinlateral planeapproximates a double pendulum whosefirst axis isunderactuated. Thisrobot hasonly twoactuators andissupposed tobetheminimumstructure of themobile robot. Inthis paper, themotion equation ofthesystem isderived. Then,stabilizing controllers forsagittal andlateral motion arepresented. Through thethree dimensional simulation wherewholethreedimensional dynamics isconsidered, the validity ofthecontroller isverified. Moreover, incombination ofsagittal andlateral controller, turning motionaroundyaw axisisrealized inspite oflackofayawaxisactuator. I.INTRODUCTION Recent years, manystudies forwheel-type mobile robots havebeenreported. Mostofthemhavetwoactuated wheels andsomepassive wheels. Whentherobot turnsquickly, it receives thecornering centrifugal force. Letthemassofthe robot beM,thelinear velocity oftherobot bev,theangular velocity around theyawaxis bew.Thenthecentrifugal force isrepresented byF = Mv. Inthecaseofatwo-wheel robot, itislimited within acertain value depending onthestructure oftherobot. Thecondition isgiven bylFlsidered, thevalidity ofthecontroller isverified. Moreover, in combination ofsagittal andlateral controller, turning motion around yawaxisisrealized inspite oflackofayawaxis actuator. Therestofthepaperisorganized asfollows. InSection II,amodelofamonowheel robot isintroduced wherethe lateral andsagittal motionisrepresented. Thedesign of stabilizing controller forbothlateral andsagittal motion is explained intheSection III, Thethree dimensional numerical simulation ofthemonowheel robot isprovided inSection IV, andintroduction ofanexperimental setupisintroduced in Section V.Conclusions areoutlined intheSection VI.