Chemical Plume Tracking Behavior in Animals and Mobile Robots

Mark A. Willis

Abstract:	Locating important resources by tracking fluidborne chemicals is routine behavior for many animals. This can be the most challenging feat of navigation these animals perform. As air or water flows past an important resource its molecules dissolve into the downstream flow and form a patchy turbulent distribution known as a plume. Most animals that follow flow-borne plumes require intermittent odor stimulation to exhibit tracking behavior, and this is provided by the patchy structure of plumes. For most animals larger than 1mm, two pieces of information are necessary to successfully track a plume; (1) the presences or absence of odor, and (2) the direction of the flow carrying the odor. By steering into the flow and moving upstream while in contact with odor, in most cases, a plume tracker should successfully locate the odor’s source. Plume trackers are thought to maintain contact with an odor plume using one of two possible fundamental mechanisms; (1) simultaneous comparison of odor concentration at two points in space using two bilaterally symmetrical sensors, or spatial sampling, and (2) comparison of odor concentration between two sequentially sampled points in time, or temporal sampling. Spatial trackers typically move slowly through their odor environment (e.g., walking and crawling) and maintain contact with plumes by steering toward the sensor experiencing the higher concentration. Temporal trackers typically move through their odor environment much faster (e.g., flying or swimming) and often maintain plume contact by incorporating an odor activated, but not odor-guided, internal program of turns. Whether plume trackers using these two strategies can adapt in response to changing odor environments is largely unknown. How plume trackers sample for odor information and other important biological questions may be addressed using computer simulations or mobile robots as models of the biological trackers. These approaches can also result in the development of control algorithms for autonomous man-made plume tracking systems.
Published in:	Proceedings of the 63rd Annual Meeting of The Institute of Navigation (2007) April 23 - 25, 2007 Royal Sonesta Hotel Cambridge, MA
Pages:	15 - 24
Cite this article:	Updated citation: Published in NAVIGATION: Journal of the Institute of Navigation
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