Valuing Attrition in a Fleet of Robots Used as Path-Based Sensors for Gathering Information in a Communications Restricted Environment

In this paper we propose a new algorithm for robots searching a hazardous, communications-denied area to gather information using a robot fleet that has a limited number of agents. The centralized algorithm uses robot survival along search paths as a sensor event for a distributed sensor network. As agents are lost to hazards, the search behavior adjusts to prioritize agent longevity in order to maximize information gain. In the past, related work solving this problem has assumed an infinite number of agents. In contrast, we assume that the number of agents is finite. We use Bayesian inference to update target and hazard belief maps of an area using data from the probability of survival of prior agents’ paths as well as sensor readings from the agents along those paths. Using those belief maps, the algorithm can construct paths that maximize information gain, in expectation, while taking into account the predicted decrease in future information collected when losing an agent. This behavior increases the likelihood that agents survive longer, allowing them to collect more data.Using simulations with various fleet sizes and probabilities for hazards disabling agents, we compare our algorithm to work that does not account for attrition. The results show an increase in the longevity of the fleet when hazards are more effective at disabling agents. In nearly all cases, this contributes to an increased rate in information gain when the fleet size is small. Small sized fleets, in our case 10 or less agents, do not meet a threshold of collected information necessary to direct agents away from hazards. Large fleets, over 200 agents in our scenario, collect most of the information before Our algorithm causes a noticeable change in agent behavior (as compared to existing techniques). We find that the proposed method provides the greatest advantage for mid-sized fleets, between 20 and 100 agents, and when hazards have an increased probability of immobilizing agents.