Adapting a collaborative, force-feedback, graphical user interface to best-effort networks.

摘要

Latency is an unavoidable fact of distributed systems, and an unrelenting foe of interface usability. I present methods for lessening the impact of latency on distributed haptic, graphic, and collaborative interfaces. These three interfaces are present in the distributed nanoManipulator, a shared tool for remote operation of Atomic Force Microscopes. The work is carried out in the context of the Internet, where best-effort service means that network performance is not guaranteed and that applications must function under a wide range of conditions.; The ability of a distributed control algorithm to tolerate latency is innately tied up with how data or operations in the algorithm are represented for transmission over the network. I introduce two new representations for haptics, the warped plane approximation and local environment sampling, with superior latency tolerance. I show how image-based rendering is a useful representation for transferring the output of a remote graphics engine across the network, yielding a tenfold reduction in mean response time over video-based approaches, and how optimistic concurrency control is a useful representation for transmitting the actions of a remote collaborator across the network, requiring 85% less concurrency control overhead than pessimistic approaches. All of these intermediate representations convey a meaning that is not just true at a single point space and a single point in time, but that is valid across a volume of space or across a range of times. These higher-order representations reduce both the amount of blocking necessary and the rate at which closed feedback loops must run in an algorithm.; I show how techniques used to adaptively deliver multimedia content---the User Datagram Protocol (UDP), Forward Error Correction (FEC), and Queue Monitoring (QM)---are applicable to the streams of data transmitted by force feedback teleoperators. UDP alone yields a 35% reduction in latency and a 75% reduction in jitter.; The new algorithms and adaptations for the distributed nanoManipulator's interfaces combined to make this collaborative tool feasible, leading to successful use by experimenters more than 2000 miles apart.