Autonomous mapping and spectroscopic analysis of distributed radiation fields using aerial robots

This paper presents a strategy for field estimation and informative path planning towards autonomous mapping and radiological characterization of distributed gamma radiation fields within confined GPS-denied environments using aerial robots. First, an online distributed radiation field estimation and spectroscopic analysis framework is presented which combines sequentially acquired measurements to estimate both the field intensity and gradient and propagate the belief over the initially unknown map, while simultaneously classifying each map region with respect to its dominating isotope. As such a process depends on the quality of the acquired measurements and given the limited endurance of small flying robots, we further contribute an informative path planner responsible for iteratively guiding the robot towards the next-best radiation measurement location such that high estimation confidence is achieved in short time. A divided global and local planning architecture is proposed enabling the robot to guide itself towards the radiologically most interesting areas quickly and acquire sufficient measurements within those. We further develop a tailor-made collision-tolerant micro flying robot that is equipped with a lightweight scintillator and silicon photomultiplier combination, alongside GPS-denied localization and mapping capabilities. A set of experimental studies are presented involving the autonomous characterization of distributed radiation fields containing live uranium ore and radium sources within GPS-denied industrial settings.