Locating underground chemical sources by tracking chemical gradients in 3 dimensions

This paper describes current progress in a project to develop a robot for locating underground chemical sources. There are important economic, environmental and humanitarian applications for systems that can find the source of an odor or volatile chemical located beneath the ground. These applications cover the spectrum from harvesting truffles, to finding the location of leaking gas pipes and land mines. In previous work the feasibility of detecting vapor percolating through the ground was demonstrated. An algorithm was then developed to control a robot enabling it to gather information about the location of the source and to guide the robot towards it. This algorithm was limited to searching in two dimensions (depth was held constant). In this paper the original algorithm is extended to 3-dimensions allowing variations in depth to be included. The 3-dimensional search algorithm involves following a path through the ground that corresponds to the edges of closely packed dodecahedra. Simulations and physical experiments both confirm the capabilities of this search algorithm.