On-lineMobile RobotPathTrackingUsing P1 Controller

This paper presents a methodforthepathtracking problemofa mobile robotusing a PIcontroller. Theproposed methodinserts an ideal relayinparallel toa conventional PI controller toidentify an equivalent FOPDT modelforthe kinematics ofthemobile robot. Theparallel connection ofthe ideal relay tothePIcontroller helpsindesigning a robust PI controller inpresenceofstatic loaddisturbances. Basedon the identified model,thePIcontroller isretuned toachieve good performance without disrupting theclosed loopcontrol. The performance oftheproposed methodisdiscussed through the simulation result toverify theeffectiveness oftheproposed method. IndexTerms-FOPDTprocess,mobilerobot, PIcontroller, phase margin,gainmargin. I. INTRODUCTION Despite theadvanced controllers, mostrobots employed in industrial applications are controlled byclassical PI/PID algorithms. Oneoftheimportant issues inthisfield isthe path-tracking (PT)problem, whichisconcerned withthe ability todrive a mobilerobotautonomously as close as possible toa previously defined reference path. Thispathis usually specified aseither a sequenceofconsecutive reference points orbya setofgeometrical primitives suchas straight lines or arcsofcircumferences. Manyapproaches havebeen tested forthePTproblem andreported intheliterature (1-4). ThePI/PID controller isdesigned based on themodelofthe kinematics of mobilerobot.But,theexternal load disturbances createproblems during thepathtracking. Therefore, an online identification ofthemodeloftherobot kinematics isrequired for asmooth pathtracking. Relaybasedidentification hasbeenactively researched for thepastdecade after theinaugural application ofAstromand Hagglund(5)relaymethodforsystemidentification. However, theapproach hasseveral practical constraints. First, itisvery sensitive todisturbance present intheprocess. Secondly, theideal relay methodisnotapplicable tocertain classes ofprocesseswhicharenotrelay stabilizable, suchas unstable processandprocesswithmore thanone integrator. Finally, theideal relay methodisan off-line identification method.