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Foundations of Robotics
Seminar, May 22, 2006
Time
and Place | Seminar Abstract | Speaker
Biography | Presentation Slides | Speaker
Appointments
Computing stable
equilibrium stances of a legged robot in frictional environments
Yizhar Or
Smith Hall 100
Refreshments 3:45 pm
Talk 4:00 pm
Multi-legged robots that perform quasistatic
locomotion are becoming progressively more sophisticated. Quasistatic multi-legged
locomotion can be characterized as a sequence of postures where the mechanism
supports itself against gravity while moving free limbs to new foothold
positions. Autonomous planning of these motions requires tools for selecting
postures that can stably support the mechanism against gravity while allowing
motion of its free limbs to new positions. In this talk I focus on identifying
and computing the stable equilibrium postures of multi-legged mechanisms
supported by frictional contacts in a two-dimensional and three-dimensional
gravitational field. As a first step, the complex kinematic structure of the
mechanism is lumped into a single rigid body having the same contacts with the
environment and a variable center of mass. Since free limbs of the mechanism
must move during locomotion, inertial forces generated by the moving parts are
lumped into a neighborhood of disturbance wrenches (i.e. forces and torques)
centered at the nominal gravitational wrench. The identification of the
feasible postures associated with a given set of contacts is reduced to the
identification of center-of-mass locations at which the contacts can stably
resist the entire set of disturbance wrenches while satisfying the frictional
constraints.
First, I will provide analytical and
graphical characterization of frictional equilibrium stances in 2D, and extend
to robust stances, which can resist a bounded set of disturbance wrenches.
Considering the dynamic response involving frictional contacts, I will
demonstrate the dynamic ambiguity phenomena, present the application of Strong
Stability to computation of robust and non-ambiguous equilibrium stances, and
discuss the application of the classical notion of dynamic stability under
bounded position-and-velocity perturbations. Finally, I will present recent
results on exact and approximate computation of frictional equilibrium stances
in 3D.
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Bio |
Yizhar Or is a Ph.D. Student in the Dept. of
Mechanical Engineering at the Technion - Israel Institute of Technology, under the
supervision of Professor Elon Rimon. On 2001 he graduated two B.Sc. degrees
Suma Cum Laude, in Mechanical Engineering and in Education in Computer Science,
both at the Technion. Currently he is studying in the direct doctoral track
towards Ph.D. degree, and works on his thesis about "Motion Planning and
Control of a Quasi-Static Multi-Limbed Robot in Gravitational Field" in
the Laboratory of Robot Motion. He is supposed to complete his Ph.D. degree by
the end of summer 2006. Yizhar's areas of interest are robotics, geometric
methods in nonlinear control, and control of mechanical systems with
intermittent frictional contacts.
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Speaker Appointments |
For appointments, please contact Howie
Choset (choset@cs.cmu.edu)
The Robotics Institute is part of the School of Computer Science, Carnegie Mellon University.