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Mathematical Problems in Engineering
Volume 2012 (2012), Article ID 792057, 19 pages
Research Article

A New Method for Bilateral Teleoperation Passivity under Varying Time Delays

1Control Engineering Department, Faculty of Electrical and Computer Engineering, University of Tabriz, Tabriz 51664, Iran
2Department of Electrical and Computer Engineering, University of Alberta, Edmonton, AB, Canada T6G 2V4

Received 23 December 2011; Revised 5 April 2012; Accepted 20 April 2012

Academic Editor: Alexander Pogromsky

Copyright © 2012 Farzad Hashemzadeh et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


A new framework is proposed to mitigate the adverse effect of time-varying time delays on the passivity of a teleoperation system. To this end, the communication channel with time-varying delays is modeled as a constant-delay channel along with additive output disturbances. Then, disturbance estimator blocks are added in each of the feedforward and feedback paths to estimate these disturbances and to compensate for them. In the disturbance estimator block, there is a need for a virtual time-varying delay block such that the overall communication channel can be seen as one with a constant delay. We also propose a method for determining this virtual delay. Two PHANToM haptic devices connected through a communication channel with time-varying delays are considered for a case study. Simulation and experimental results confirm the efficiency of the proposed method in terms of passivating the teleoperation system in the presence of time-varying delays.