Olfactory sensory system for odour-plume tracking and localization

Autonomous search of odour sources is a problem that once solved can bring large improvements to tasks like: humanitarian demining, airport patrolling, and hazardous chemical leaks detection. The main obstacles to the research in this area are the properties of current gas sensors (slow, weakly selective and poorly sensitive) and the difficulty to estimate the physical characteristics of natural odour plumes due to the "disturbances" caused by turbulence, namely meandering and intermittence. This paper presents an active olfactory sensing system that intends to be applicable to search for odour sources in outdoor environments. Three modular intelligent modules compose this olfactory system: two gas sensing nostrils and a directional thermal anemometer. The information coming from the sensing modules is fused with the spatio-temporal localization of a mobile robot in order to estimate the localization of a specific odour source. The mobile robot is controlled by a state-based odour-searching algorithm. Each sensing module self-adjust its characteristics (sensibility, selectivity and time-response) in order to optimise the information perceived during each searching state. The paper describes the sensing modules and presents results gathered with them. A special emphasis is given to the wavelet-based signal processing, implemented for the fast identification of odour puffs.