Robust-adaptive gait control of a 9-link biped robot

Tzafestas, SG; Krikochoritis, AE; Tzafestas, CS

dc.contributor.author	Tzafestas, SG	en
dc.contributor.author	Krikochoritis, AE	en
dc.contributor.author	Tzafestas, CS	en
dc.date.accessioned	2014-03-01T01:47:27Z
dc.date.available	2014-03-01T01:47:27Z
dc.date.issued	1998	en
dc.identifier.issn	02329298	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/25215
dc.relation.uri	http://www.scopus.com/inward/record.url?eid=2-s2.0-0031632646&partnerID=40&md5=7963f8ed938e596b92825fe0bc7b401f	en
dc.subject.other	Adaptive control systems	en
dc.subject.other	Anthropomorphic robots	en
dc.subject.other	Closed loop control systems	en
dc.subject.other	Computer simulation	en
dc.subject.other	Mathematical models	en
dc.subject.other	Nonlinear control systems	en
dc.subject.other	Parameter estimation	en
dc.subject.other	Robustness (control systems)	en
dc.subject.other	Time varying control systems	en
dc.subject.other	Adaptive gait control	en
dc.subject.other	Biped robots	en
dc.subject.other	Mobile robots	en
dc.title	Robust-adaptive gait control of a 9-link biped robot	en
heal.type	journalArticle	en
heal.publicationDate	1998	en
heal.abstract	The study and control of the locomotion of a biped robot has always been a challenging problem. The mechanical complexity of biped robots, the existence of an unpowered degree of freedom, and the peculiarity of their motion due to the repeatability of movements and a permanent change of situations during one step, synthesize a complex problem. At the same time, undesired collisions with its environment, transport of unknown loads, or simplification of some dynamic characteristics, cause uncertainty (structured or not) which makes worse the control problem since an accurate model of the biped robot is not available. In this paper a nine link planar biped model is studied. It is a biped robot that includes not only the main links: legs, thighs and trunk, but also a two segments foot. For this biped robot, the kinematic and dynamic equations which describe completely the locomotion of the robot during the different phases of walking, are defined. Furthermore, a continuous walking pattern on a flat terrain is designed and the corresponding desired trajectories of the robot joints are calculated. Then, a nonlinear robust control technique is adopted, based on the fact that the control which has to ensure the stability of the biped robot must take into account the nonlinear dynamics of the system. This requires the knowledge of an accurate model of the biped robot, a condition that is never fulfilled because of the existence of disturbances and modelling inaccuracies such as parametric uncertainty and unmodeled dynamics. Thus, for the case there is not available a priori information about the unknown parameters, the parametric uncertainty has to be gradually reduced on-line by an adaptation or estimation mechanism. Here, rapidly time-varying unknown parameters are assumed, and a kind of robust-adaptive controller is designed which achieves robustness in the face of such modelling imprecisions, while at the same time ensures that all signals in the closed-loop robot system are bounded and the tracking error is of the order of the parameter variations. Extensive simulation experiments showed the effectiveness of the proposed robust-adaptive control scheme.	en
heal.publisher	Gordon & Breach Science Publ Inc, Newark, NJ, United States	en
heal.journalName	Systems Analysis Modelling Simulation	en
dc.identifier.volume	31	en
dc.identifier.issue	4	en
dc.identifier.spage	247	en
dc.identifier.epage	304	en