arXiv subjects

Michael J. Coleman

Publications and source records attributed to Michael J. Coleman.

2 recordsLinked to original sources

arXiv2001

Prediction of stable walking for a toy that cannot stand

Previous experiments [M. J. Coleman and A. Ruina, Phys. Rev. Lett. 80, 3658 (1998)] showed that a gravity-powered toy with no control and which has no statically stable near-standing configurations can walk stably. We show here that a simple rigid-body statically-unstable mathematical model based loosely on the physical toy can predict stable limit-cycle walking motions. These calculations add to the repertoire of rigid-body mechanism behaviors as well as further implicating passive-dynamics as a possible contributor to stability of animal motions.

physics.class-ph↗

arXiv1997

An Uncontrolled Toy That Can Walk But Cannot Stand Still

We built a simple two-leg toy that can walk stably with no control system. It walks downhill powered only by gravity. It seems to be the first McGeer-like passive-dynamic walker that is statically unstable in all standing positions, yet is stable in motion. It is one of few known mechanical devices that are stable near a statically unstable configuration but do not depend on spinning parts. Its design is loosely based on simulations which do not predict its observed stability. Its motion highlights the possible role of uncontrolled nonholonomic mechanics in balance.

physics.class-ph↗