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Traversing from Point-to-Point along a straight line with a ballbot
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. (Robotics and Control Lab)
2010 (English)In: 8th IFAC Symposium on Nonlinear Control Systems, 2010Conference paper (Refereed)
Place, publisher, year, edition, pages
URN: urn:nbn:se:umu:diva-39715OAI: diva2:395227
Available from: 2011-02-04 Created: 2011-02-04 Last updated: 2011-02-08Bibliographically approved
In thesis
1. Underactuated mechanical systems: Contributions to trajectory planning, analysis, and control
Open this publication in new window or tab >>Underactuated mechanical systems: Contributions to trajectory planning, analysis, and control
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Nature and its variety of motion forms have inspired new robot designs with inherentunderactuated dynamics. The fundamental characteristic of these controlled mechanicalsystems, called underactuated, is to have the number of actuators less than the number ofdegrees of freedom. The absence of full actuation brings challenges to planning feasibletrajectories and designing controllers. This is in contrast to classical fully-actuated robots.A particular problem that arises upon study of such systems is that of generating periodicmotions, which can be seen in various natural actions such as walking, running,hopping, dribbling a ball, etc. It is assumed that dynamics can be modeled by a classicalset of second-order nonlinear differential equations with impulse effects describing possibleinstantaneous impacts, such as the collision of the foot with the ground at heel strikein a walking gait. Hence, we arrive at creating periodic solutions in underactuated Euler-Lagrange systems with or without impulse effects. However, in the qualitative theory ofnonlinear dynamical systems, the problem of verifying existence of periodic trajectoriesis a rather nontrivial subject.The aim of this work is to propose systematic procedures to plan such motions and ananalytical technique to design orbitally stabilizing feedback controllers. We analyze andexemplify both cases, when the robotmodel is described just by continuous dynamics, andwhen continuous dynamics is interrupted from time to time by state-dependent updates.For trajectory planning, systems with one or two passive links are considered, forwhich conditions are derived to achieve periodicmotions by encoding synchronizedmovementsof all the degrees of freedom. For controller design we use an explicit form tolinearize dynamics transverse to the motion. This computation is valid for an arbitrarydegree of under-actuation. The linear system obtained, called transverse linearization, isused to analyze local properties in a vicinity of the motion, and also to design feedbackcontrollers. The theoretical background of these methods is presented, and developedin detail for some particular examples. They include the generation of oscillations forinverted pendulums, the analysis of human movements by captured motion data, and asystematic gait synthesis approach for a three-link biped walker with one actuator.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, Institutionen för tillämpad fysik och elektronik, 2011. 64 p.
Robotics and control lab, ISSN 1654-5419 ; 5
Underactuated mechanical systems, mechanical systems with impacts, trajectory planning, periodic trajectories, orbital stabilization, walking robots, virtual holonomic constraints, transverse linearization
National Category
Control Engineering
Research subject
Automatic Control
urn:nbn:se:umu:diva-39719 (URN)978-91-7459-149-1 (ISBN)
Public defence
2011-03-01, KBC-huset , KB3A9, Umeå Universitet, Umeå, 09:00 (English)
Available from: 2011-02-08 Created: 2011-02-04 Last updated: 2011-03-01Bibliographically approved

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La Hera, Pedro
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