The ability to autonomously track a fluid-borne odor has numerous engineering applications and natural occurrences. Engineering systems can use odor-guided navigation in tasks ranging from search and rescue to locating dangerous chemicals. Animals use odors to locate food and mates. For animals in strong unsteady turbulent flow environments where the wind is intermittent and occasionally vanishes, there is an ecological benefit to maintaining wind-driven tracking behavior. This has been shown in experiments performed using moths and cockroaches, where animals that began tracking odor in wind maintained their wind driven tracking behavior and eventually located the source after the wind was shut off during their tracking behavior. Here, we use RoboMoth, a previously developed 3D odor-tracking robot, to replicate these experiments. Our results can aid biologists in understanding how animals track odors in dynamic environments. In engineering, this study provides a first step in a hardware system towards linking odor tracking in strong wind environments to tracking in zero/low flow environments by studying the transition between the two regimes. This can help further engineers' efforts to design odor-tracking systems capable of negotiating diverse and dynamic environments. Our study of the transition from using the wind as a primary directional cue to relying on odor and an established tracking direction appears to be novel in an engineering context and unique to our work.

An approach to odor source localization with an aerial vehicle using the fusion of odor sensors, visual sensors, and airspeed sensors is presented. The motion of the tracking vehicle is decomposed into two components - a component normal to the wind direction and a component tangential to the wind direction. The tangential component is controlled with a strategy that moves upwind when odor is detected and moves gradually downwind when odor is lost. The normal component of velocity is controlled by two different algorithms. The first algorithm controls the rate of turning in the plane normal to the wind direction as a function of concentration. The second algorithm controls the rate of turning and the magnitude of the normal component of velocity as a function of the time derivative of concentration. Both algorithms display the potential to declare the location of an odor source in a three-dimensional space.

A new strategy is developed for tracking an odor plume in an environment where wind is present. The strategy is inspired by the mechanisms that animals use to orient to stimuli. A male moth counter-turns horizontally and vertically across the wind while tracking a pheromone plume. The inter-turn duration, or the amount of time between turns, is about 500 milliseconds on average in both directions. This observation has lead to the development of odor tracking algorithms that use inter-turn timers to control when to turn in both directions. The algorithm presented in this work takes a different approach. The new algorithm controls the rate of turning of the tracking vehicle in a plane normal to the wind direction. Simulation results demonstrate that counter-turning can be achieved in both directions without the use of inter-turn timers. Also, the estimated odor source location approaches the true source location as time progresses

Two simple three-dimensional moth inspired odor tracking algorithms, Counter-turner and Modified counter-turner, were tested on a robotic platform. The Counter-turner uses the plume edge to modify the timing of the crosswind movements, while the Modified counter-turner uses the plume centerline. Both algorithms shows some success in tracking the plume to it’s source. In addition, flight tracks show promise in mimicking the flight tracks observed in biological experiments with the moth Manduca. Sexta.

A mobile autonomous robot capable of tracking an odor plume to its source can be used to locate hazardous material spills or leaks. To test plume tracking strategies in a laboratory environment, a robotic platform consisting of a linear Cartesian robotic gantry mounted inside a wind tunnel with a mobile floor has been designed. A plume of ionized air is created by an ion detector installed in the wind tunnel. A two-dimensional plume tracking strategy based on the behavior of the tobacco hornworm moth Manduca sexta is implemented and tested. It is discovered that a plume tracking algorithm can be implemented with the robotic platform almost as easily as in simulation.