This application is intended to help investigate the possibility of effective coordination of physical movements between remotely separated users. Using this application it is possible to "shake hands" across the network. The result of this investigation is being used in other applications to provide support for haptic collaboration.

Capabilities & Requirements

This application slaves together two or haptics devices such as the SensAble Technologies Phantom. The application operates as a collection of peers. Each peer periodically reports the current 3D location of the haptics device. Each peer uses the reports received from other users to produce a "centering" force that tends to draw the local device to the location of the remote user.

The traffic between peers consists of udp packets containing 50 bytes of position and timing information. At a rate of 100 packets per second the user can detect a coarseness in the device corresponding to the discrete changes in force as each new position packet arrives. Low velocity movements minimize this sensation. The sensation also decreases as the packet send rate increases. Latency in the network is perceived as a viscous drag on the devices. The application is tolerant of minor packet loss and out-of-order packets which tend to reduce the fidelity of the path.

The application has been tested between various locations in the US (Stanford, La Crosse, Los Angeles, Chicago and Besthda) as well as between La Crosse and Canberra Australia. While large network latencies present a significant viscous force to the user, users are still able to easily coordinate simple movements.

Operation

In the simplest form of this application (1) two haptics devices to be slaved together by periodically exchanging position information. The application is integrated into the Information Channels framework so that the initial peer announces the availability of a "handshake" channel. A second peer can be launched through the web page listing active "handshake" partners.

In addition to the "handshake" peer we have implemented a couple of server applications that can take the place of a remote peer in different scenarios. The Reflection server (2) simply returns to the sender all the position reports it receives. This means that the Handshake Peer is slaved to itself with a time delay determined by the roundtrip time of the intervening network. The user feels a viscous damping force corresponding to the latency of the network.

The Auto-Handshake server (3) provides an automated peer to take the place of a remote partner. The server monitors the movements of a remote user. When the user completes a closed loop path (returns to the starting point) the server begins to repeat the path until the user breaks off by forcing the haptics device to remain stationary for a few seconds. This server allows a user to test the ability to coordinate movements without requiring a remote partner to be present. The Auto-Handshake server also produces a diagnostic channel that can be used to visualize the current positions of both the Auto-Handshake server and the connected peer.

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Last Modified: 6-Apr-03, Server Contact: senger@csfac.uwlax.edu
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