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Ch19-I044963.fm Page 87 Tuesday, August 1, 2006 2:54 PM
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PLANNING OF KNOTTING MANIPULATION
Hidefumi Wakamatsu ', Tsunenori Kato ', Akira Tsumaya ', Eiji Arai', and Shinichi Hirai 2

1
Dept. of Manufacturing Science, Graduate School of Eng., Osaka University
2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
2
Dept. of Robotics, Ritsumeikan University
1-1-1 Noji Higashi, Kusatsu, Shiga 525-8577, Japan

ABSTRACT

A planning method for knotting/unknotting manipulation of deformable linear objects is proposed.
Firstly, topological states of a linear object are represented as finite sequence of crossings and two
attributes of each crossing. Secondly, transitions among the topological states are defined. Then, we
can generate possible sequences of crossing state transitions, that is, possible manipulation processes
from the initial state to the objective state. Thirdly, a method for determination of grasping points and
their moving direction is proposed to realize derived manipulation processes. Finally, criteria for
evaluation of manipulation plans are introduced to reduce the candidates of manipulation plans.

KEYWORDS

Linear Objects, Manipulation, Knotting, Unknotting, Planning

INTRODUCTION
Deformable linear objects such as tubes, cords, wires, and threads are used widely; not only for data
transmission or for object transportation but also for fixing or packing of objects including themselves.
Such manipulative tasks include knotting. On the other hand, self-entwining of linear objects should be
avoided during their manipulative processes. Therefore, it is important for linear object manipulation
to analyze knotting or entwining. There are some studies on rope tying (Inoue 1984, Hopcroft 1991,
Matsuno 2001, Morita 2003). In these studies, knotting manipulation of a linear object could be
realized by a mechanical system, but how to knot is given. To make a bowknot, for example, we
manipulate a linear object dexterously by using several fingers of both hands for bending, twisting,
holding, and/or binding. However, how to make a bowknot of us is not unique because it depends on
our physical makeup and experience. If knotting/unknotting process of a linear object can be modeled,
it is useful for design of knotting/unknotting system with mechanism unlike human arms/hands and for
planning suitable for such system. Therefore, in this paper, we propose a planning method for
knotting/unknotting of deformable linear objects.