Time-Domain Passivity Control for
Stable Haptic Enabled Systems
University of Washington
Biorobotics Lab
Haptic
interfaces and teleoperators which support kinesthetic feedback to the user
share the property that they create a dynamical loop between user and
environment. Like classical
control systems, this loop can be
difficult to stabilize under all conditions. The problem is characterized by highly non-linear and non-
hard to model time varying components (human operator biomechanics and
neuromotor properties). Previous
approaches have achieved stability at a large cost in performance --- measured
by haptic feedback perceptual quality.
This
talk describes experience with a new software-enabled approach which applies the
idea of passivity in real time to this stability problem. By performing an on-line realtime
measurement of energy flow from one or more system ports, adjustable damping
can be tuned to exactly constrain the system to passive behavior with
substantially less degradation of performance compared to fixed parameter
systems. With a few conservative assumptions, stability can be proven without
use of system models requiring identification.
Friday, September 13, 2002
3:30 – 4:30 p.m.