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Motion planning for humanoid robots based on virtual constraints extracted from recorded human movements
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
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2008 (English)In: Intelligent Service Robotics, ISSN 1861-2776, Vol. 1, no 4, 289-301 p.Article in journal (Refereed) Published
Abstract [en]

In the field of robotics there is a great interest in developing strategies and algorithms to reproduce human-like behavior. In this paper, we consider motion planning for humanoid robots based on the concept of virtual holonomic constraints. At first, recorded kinematic data of particular human motions are analyzed in order to extract consistent geometric relations among various joint angles defining the instantaneous postures. Second, a simplified human body representation leads to dynamics of an underactuated mechanical system with parameters based on anthropometric data. Motion planning for humanoid robots of similar structure can be carried out by considering solutions of reduced dynamics obtained by imposing the virtual holonomic constraints that are found in human movements. The relevance of such a reduced mathematical model in accordance with the real human motions under study is shown. Since the virtual constraints must be imposed on the robot dynamics by feedback control, the design procedure for a suitable controller is briefly discussed.

Place, publisher, year, edition, pages
Springer-Verlag , 2008. Vol. 1, no 4, 289-301 p.
Keyword [en]
Motion planning, Humanoid robots, Virtual holonomic constraints, Underactuated mechanical systems
Identifiers
URN: urn:nbn:se:umu:diva-26261DOI: 10.1007/s11370-008-0027-2OAI: oai:DiVA.org:umu-26261DiVA: diva2:241257
Available from: 2009-10-01 Created: 2009-10-01 Last updated: 2011-02-08Bibliographically approved
In thesis
1. Principles for planning and analyzing motions of underactuated mechanical systems and redundant manipulators
Open this publication in new window or tab >>Principles for planning and analyzing motions of underactuated mechanical systems and redundant manipulators
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Metoder för rörelseplanering och analys av underaktuerade mekaniska system och redundanta manipulatorer
Abstract [en]

Motion planning and control synthesis are challenging problems for underactuated mechanical systems due to the presence of passive (non-actuated) degrees of freedom. For those systems that are additionally not feedback linearizable and with unstable internal dynamics there are no generic methods for planning trajectories and their feedback stabilization. For fully actuated mechanical systems, on the other hand, there are standard tools that provide a tractable solution. Still, the problem of generating efficient and optimal trajectories is nontrivial due to actuator limitations and motion-dependent velocity and acceleration constraints that are typically present. It is especially challenging for manipulators with kinematic redundancy.

A generic approach for solving the above-mentioned problems is described in this work. We explicitly use the geometry of the state space of the mechanical system so that a synchronization of the generalized coordinates can be found in terms of geometric relations along the target motion with respect to a path coordinate. Hence, the time evolution of the state variables that corresponds to the target motion is determined by the system dynamics constrained to these geometrical relations, known as virtual holonomic constraints. Following such a reduction for underactuated mechanical systems, we arrive at integrable second-order dynamics associated with the passive degrees of freedom. Solutions of this reduced dynamics, together with the geometric relations, can be interpreted as a motion generator for the full system. For fully actuated mechanical systems the virtually constrained dynamics provides a tractable way of shaping admissible trajectories.

Once a feasible target motion is found and the corresponding virtual holonomic constraints are known, we can describe dynamics transversal to the orbit in the state space and analytically compute a transverse linearization. This results in a linear time-varying control system that allows us to use linear control theory for achieving orbital stabilization of the nonlinear mechanical system as well as to conduct system analysis in the vicinity of the motion. The approach is applicable to continuous-time and impulsive mechanical systems irrespective of the degree of underactuation. The main contributions of this thesis are analysis of human movement regarding a nominal behavior for repetitive tasks, gait synthesis and stabilization for dynamic walking robots, and description of a numerical procedure for generating and stabilizing efficient trajectories for kinematically redundant manipulators.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, Institutionen för tillämpad fysik och elektronik, 2009. 88 + 8 papers p.
Series
Robotics and control lab, ISSN 1654-5419 ; 4
Keyword
Motion Planning, Underactuated Mechanical Systems, Redundant Manipulators, Virtual Holonomic Constraints, Orbital Stabilization, Human Movement, Walking Robots, Hydraulic Manipulators
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Automatic Control
Identifiers
urn:nbn:se:umu:diva-30024 (URN)978-91-7264-914-9 (ISBN)
Public defence
2010-02-05, Naturvetarhuset, N200, Umeå universitet, Umeå, 09:00 (English)
Opponent
Supervisors
Available from: 2009-12-15 Created: 2009-11-30 Last updated: 2011-02-09Bibliographically approved
2. 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.
Series
Robotics and control lab, ISSN 1654-5419 ; 5
Keyword
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
Identifiers
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)
Opponent
Supervisors
Available from: 2011-02-08 Created: 2011-02-04 Last updated: 2011-03-01Bibliographically approved

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Mettin, UweLa Hera, Pedro M.Freidovich, LeonidShiriaev, Anton

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