A biologically-inspired sensor fusion approach to tracking a wind-borne odor in three dimensions

An autonomous vehicle that can track a wind-borne odor plume to its source could locate lost pets and people, pipeline breaks, illegal drug labs, or improvised explosive devices (IEDs). This work explores moth-inspired strategies for tracking a wind-borne odor plume with an aerial vehicle. When tracking an odor, moths counter-turn horizontally back and forth across the wind while generally progressing upwind. Previous studies suggest that moths maintain their altitude at the mean altitude of the odor plume and that the timing of their turns is controlled by an internal mechanism.; The ability of moths to stabilize their altitude while tracking an odor plume was examined in a laboratory wind tunnel. It was hypothesized that an enriched visual environment in the lateral visual field would allow moths to stabilize their altitude. The moths did not maintain their altitude fixed at the mean altitude of the odor plume. Instead, they used a combination of horizontal and vertical undulations to search for odor in a plane normal to the wind direction while making upwind progress.; The three dimensional observations of moth odor tracking inspired the design of strategies that direct an agent to control its turn rate in the wind-normal plane, and upwind speed, as independent functions of the measured odor concentration. The aerial agent estimates its egomotion, altitude, the wind velocity, and the ground structure using a new technique that fuses visual and mechanosensory input. Two odor tracking strategies---Spiraling and Spiraling5---were developed and tested in simulation on an odor tracking software platform called OdorTracker. The behavior of the Spiraling strategy was dependent on the odor concentration while the Spiraling5 strategy was dependent on the time derivative of odor concentration. Using either strategy, the simulated agent approached the odor source with moth-like undulations in the vertical and horizontal directions without internal counter-turn timers; however, the Spirarling5 algorithm sometimes became unstable. Not only did the odor tracking strategies allow the tracking agent to reach the odor source, they also allowed the tracking agent to remain in the vicinity of the odor source for several seconds, which also agrees with moth behavior.