Vibration Suppression in Flexible Structures using Hybrid Active and Semi-active Control PDF
Preview Vibration Suppression in Flexible Structures using Hybrid Active and Semi-active Control
Vibration Suppression in Flexible Structures using Hybrid Active and Semi-active Control Irfan Ullah Khan Supervisor: Prof. D. Wagg and Prof. N. D. Sims Department of Mechanical Engineering University of Sheffield This dissertation is submitted for the degree of Doctor of Philosophy June 2017 Iwouldliketodedicatethisworktomyparents. Declaration I hereby declare that all the work presented in this thesis is original unless otherwise stated or referred and has not been submitted anywhere else to attain a degree. The thesis meets the university requirements and has less than 80,000 words including appendices, references, footnotes, equations, tables. The work presented here is my ownworkandhasnotbeendoneincollaborationwithanyinstituteorgroup. IrfanUllahKhan June2017 Acknowledgements Firstofall, Iwouldliketo thank myparentsandfamilyfor theirsupportandbeliefin me. Without their support, it would not be feasible for me to reach up to this stage. I wouldliketoexpressmydeepgratitudetomysupervisorsProf. DavidWaggandProf. Neil Sims for their guidance and help. Weekly discussions with my supervisors and theircontinuous feedback helpedmea lotineverystep ofmyresearch. I acknowledge and appreciate Prof. David Wagg, who has provided me with various opportunities topresentmyworkindifferentconferences. HehasassociatedmewithEngineering Nonlinearity (ENL) group as well, where I have presented my work in the form of postersandpresentations. Thisplatformhasalsogivenmeanopportunitytointeract with people linked with academia and industry. I also want to thank everyone from the Dynamic Research Group (DRG) for their support. I would like to acknowledge Mr. Les Morton help during redesigning of rig in the lab and Mr. Richard Kay, who provided his expertise along with the Oddy hydraulics people for fault identification inthehydraulicsystem. Iamthankfultoallmyfriendswhosupported,toleratedand encouraged me throughout this journey. Last but not the least, a special gratitude to MelanieFitzgeraldandNumairaKhanforthesupportandhelpwiththeproofread. Abstract This thesispresents a new hybrid active and semi-active controlmethod for vibration suppression in flexible structures. The method uses a combination of a semi-active device and an active control actuator situated elsewhere in the structure to suppress vibrations. The key novelty is to use the hybrid controller to enable the semi-active device to achieve a performance as close to a fully active device as possible. This is accomplishedbyensuringthattheactiveactuatorcanassistthesemi-activedeviceinthe regionswhereenergyisrequired. Also,thehybridactiveandsemi-activecontrolleris designedtominimisetheswitchingofthesemi-activecontroller. Thecontrolframework usedistheimmersionandinvariancecontroltechniqueincombinationwithasliding modecontrol. Atwodegree-of-freedomsystemwithlightlydampedresonancesisused asanexamplesystem. Bothnumericalandexperimentalresultsaregeneratedforthis systemandthencomparedaspartofavalidationstudy. The experimental system uses hardware-in-the-loop simulation to simulate the effectofboththedegrees-of-freedom. Theresultsshowthattheconceptisviableboth numerically and experimentally, and improved vibration suppression results can be obtainedforthesemi-activedevicethatapproachestheperformanceofanactivedevice. To illustrate the effectiveness of the proposed hybrid controller, it is implemented to keepthecontactforceconstantinthepantograph-catenarysystemofhigh-speedtrains. Adetailedderivationisgivenafterwhichthesimulationresultsarepresented. Then a method to design a reduced order observer using an invariant manifold approachisproposed. Themainadvantageofthisapproachisthatitenablesasystematic design approach, and (unlike most nonlinear observer design methods), it can be generalisedoveralargerclassofnonlinearsystems. Themethodusesspecificmapping x functions in a way that minimises the error dynamics close to zero. Another important aspectistherobustnesspropertywhichisduetothemanifoldattractivity: animportant featurewhenanobserverisusedinaclosedloopcontrolsystem. Theobserverdesign is validated using both numerical simulations and hardware-in-the-loop testing. The proposedobserveristhencomparedwithaverywellknownnonlinearobserverbasedon theoff-linesolutionoftheRiccatiequationforsystemswithLipschitztypenonlinearity. Inallcases,theperformanceoftheproposedobserverisshowntobeexcellent.
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