Observing Pose and Motion through Contact
Yan-Bin Jia and Michael Erdmann
Abstract
This paper investigates how to ``observe'' a planar object being pushed by a
finger. The pushing is governed by a nonlinear system that relates through contact
the object pose and motion to the finger motion. Nonlinear observability theory is
employed to show that the contact information is often sufficient for the finger to
determine not only the pose but also the motion of the object. Therefore a sensing
strategy can be realized as an observer of the nonlinear dynamical
system. Two observers are subsequently discussed. The first observer, based on the
result of Gauthier, Hammouri, and Othman (1992), has its ``gain'' determined by the
solution of a Lyapunov-like equation. The second observer, introduced in our earlier
work, solves for the initial (motionless) object pose from a few intermediate contact
points.
Simulations have been done to demonstrate the feasibility of the two observers. A
sensor has been implemented using strain gauges and mounted on an Adept robot with
which preliminary experiments have been conducted.
From a general perspective, this work presents an approach for acquiring geometric
and dynamical information about a task from a small amount of tactile data, with the
application of nonlinear observability theory.