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Locating a signal source



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US patent and EP patent n°06291133.4 filed on July 7th, 2006 and entitled “Method and system for locating a source of particle, molecule, or fragment of molecule using their reception rate”



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Exclusive or non-exclusive licenses and collaborative research


Laboratoire Génétique in silico – CNRS URA 2171



Animals like insects or birds look for food and other animals by locating odorous sources. Semiconductor sensor detect substances and evaluate their concentration, however such task must take into account the environment like air flow which impact the diffusion characteristics. Chemotactic strategies are based on gradient of concentration measurement but mixing in a flowing medium breaks up regions of high concentration into random and disconnected patches and average concentration may decay rapidly with distance from the source. So a macroscopic searcher must devise a strategy of movement based on sporadic cues and partial information.


The present invention proposes a search algorithm, which we call ‘infotaxis’, designed to locate the source of a signal. The idea is that the rate of acquisition of information on source location, can play the same role as local concentration in bacterial chemotaxis; the expected local rate of information gain and the resulting trajectories feature zigzagging and casting paths similar to those observed in flights of moths and birds. When signal is an odour a lattice is designed in search space after having determined the diffusion parameters of the desired particles in said space. The sensor measures the presence/or absence of molecule and the system determines the probability of presence on each node of the space. Then the sensor moves to another node depending on the entropy of the computed probabilities.
Said particles may be biological molecules or proteins or dust or fragments thereof or pathogens. The method also applies to the localization of two or more sources of signal.
The general idea of infotaxis can be applied more broadly in the context of searching with sparse information and provides a framework for quantitative understanding of the balance between the competing exploration and exploitation behaviors in learning processes.


  • Reduced time of search
  • Easy to implement on any robot type
  • Sensor independent  (gas or drug molecule…)
  • Adapted to fluid (gas or liquid) environment
  • Distance of localization much higher than with chemotaxis


  • Civilian security and defense : research of explosive, mines, drugs, chemical or gas leaks, fire detection …
  • Industrial security : chemical or gas leaks, fire detection …
  • Luggage inspection

Computer validation and test with robots have shown that the search time is reduced
Search on a 10 m scale is possible which chemotaxis does not allowed

For further information, please contact us (Ref 01034-01)

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