Abstract
This paper describes a novel autonomous ground vehicle that is designed for exploring unknown environments which contain sources of ionising radiation, such as might be found in a nuclear disaster site or a legacy nuclear facility. While exploring the environment, it is important that the robot avoids radiation hot spots to minimise breakdowns. Broken down robots present a real problem: they not only cause the mission to fail but they can block access routes for future missions. Until now, such robots have had no autonomous gamma radiation avoidance capabilities. New software algorithms are presented that allow radiation measurements to be converted into a format in which they can be integrated into the robot’s navigation system so that it can actively avoid receiving a high radiation dose during a mission. An unmanned ground vehicle was fitted with a gamma radiation detector and an autonomous navigation package that included the new radiation avoidance software. The full system was evaluated experimentally in a complex semi-structured environment that contained two radiation sources. In the experiment, the robot successfully identified both sources and avoided areas that were found to have high levels of radiation while navigating between user defined waypoints. This advancement in the state-of-the-art has the potential to deliver real benefit to the nuclear industry, in terms of both increased chance of mission success and reduction of the reliance on human operatives to perform tasks in dangerous radiation environments.
Highlights
In nuclear facilities, there is often a need to explore and characterise an environment that has constrained access due to the risk posed by extreme levels of radiation exposure
Using the new combined costmap, the robot was given the added functionality of being able to navigate around and actively remove itself from areas of high radiation that were detected during the mission
The full system was validated in two unknown environments on a real robot using safe radiation sources
Summary
There is often a need to explore and characterise an environment that has constrained access due to the risk posed by extreme levels of radiation exposure. The robot detects regions of high radiation as it passes through them and avoids these regions for the rest of the mission, reducing the overall dose that the robot receives The reason that this was selected as the most appropriate solution is because there is an inherent latency in gamma radiation detectors due to the stochastic nature of radioactive decay and the subsequent requirement for there to be an integration time for a dose rate to be calculated. Experimental verification that CSIRO’s Navigation Pack and accompanying experimental navigation stack can navigate obstacles and topography in varied and complex environments In the literature, both ground and aerial robots have been used to produce location tagged nuclear radiation data, with varying levels of sophistication in terms of autonomy and radiation mapping ability. In [20], an energy requirement costmap was generated for a UAV and used to increase flight times
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