Networked haptic cooperation with remote dynamic proxies




Li, Zhi

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Networked haptic cooperation entails direct interactions among the networked users in addition to joint manipulations of shared virtual objects. For example, therapists may want to feel and guide the motions of their remote patients directly rather than via an intervening virtual object during tele-rehabilitation sessions. To support direct user-to-user haptic interaction over a network, this dissertation introduces the concept of remote dynamic proxies and integrates it into two distributed control architectures. The remote dynamic proxies are avatars of users at the sites of their distant peers. They have second order dynamics and their motion is coordinated to the remote user whom they represent either via virtual coupling or via wave-based control. The remote dynamic proxies render smooth motion of the distant peers regardless of the infrequent and delayed information received over the network. Therefore, the integration of remote dynamic proxies into distributed networked haptic cooperation allows stiffer contacts to be rendered to users and improves position coherency in the presence of longer constant network delays. The thesis investigates the advantages and limitations of the remote dynamic proxies for two distributed haptic architectures. These architectures coordinate the peer users and their virtual environments via: - virtual coupling control. For virtual coupling-based networked haptics with remote dynamic proxies, stability is analyzed within a multi-rate state space framework and the analysis is validated through experiments involving both cooperative manipulations and direct user-to-user interactions. The results show that the remote dynamic proxies maintain high coherency between the distributed virtual environments and enable users to see and feel their peers moving smoothly. They also increase the stiffness of direct user-to-user contact in the presence of larger constant network delay. However, the remote dynamic proxies do not lessen users' perception of a predominantly viscous virtual environment in the presence of network delay. - wave-based control. To enable users to feel other dynamics in addition to viscosity during networked haptic cooperation, this dissertation further develops a wave-based distributed coordination approach for the remote dynamic proxies. The performance of the proposed approach is investigated via experiments involving both cooperative manipulations and direct user-to-user interactions. The results demonstrate that the remote dynamic proxies mitigate the poor coherency typical to wave-based coordination architectures and enable users to touch their peers. Furthermore, the remote dynamic proxies improve users' perception of inertia in the presence of network delay.



Networked haptics, Remote dynamic proxies, Constant time varying Delay, Control