Time-Domain Passivity Control for

Stable Haptic Enabled Systems


Professor Blake Hannaford


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.

1500 EECS