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Date of Award

5-2009

Degree Type

Thesis

Degree Name

Master of Applied Science (MASc)

Department

Electrical and Computer Engineering

Supervisor

Shahin Sirouspour

Language

English

Abstract

Collaborative haptic simulations allow multiple users in a virtual environment to simultaneously interact with shared virtual objects. The implementation of shared virtual environments over a network removes the geographical barriers and enables users from around the globe to modify the environment and in addition feel the presence of other users. However, network issues arise in the communication of data over a network such as the Internet. Communication channel delay, jitter, packet loss and limited packet transmission rate can adversely affect the performance of collaborative haptic systems and may even cause instability.

This thesis builds upon our group's recent work in distributed networked haptics (Fotoohi et al. [31]). The proposed distributed peer-peer architecture improved the haptic simulation performance over the centralized architecture by providing local high-rate feedback to the users in a Local Area Network (LAN). Virtual spring-damper couplers synchronized the multiple copies of the virtual environment and coupled the users to the virtual objects.

Forming on the above distributed architecture, this thesis proposes methods for improving the performance and stability of shared haptic environments with a stronger emphasis on the effects of time delay in the context of Internet communication. To this end new quantitative measures are presented for quantifying the fidelity of haptic simulations in such environments. User's perceived admittance and discrepancy among local copies of virtual objects are considered in defining these measures. Furthermore, state prediction and feedforward schemes are proposed to compensate for the negative effects of the network communication delay on the transparency and stability of the haptic simulation. An optimization problem is formulated for selecting the virtual coupling gains that can enhance the performance while maintaining system stability. The solution to the this problem provides us with the set of control parameters that optimize the defined performance measures.

A three user distributed architecture is presented to show the extension of the proposed methods to haptic simulations involving more than two users. Numerical analysis and haptic interaction experiments over the Internet are carried out to demonstrate the effectiveness of the proposed approach in two-user and three-user platforms. The obtained analytical and experimental results verified improvements by the prediction and feedforward mechanisms.

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