Human-guided management of collaborating unmanned vehicles in degraded communication environments

Abstract

Unmanned Aerial Systems (UASs) currently fulfill important roles in modern military operations. Present commitments to research and development efforts for future UASs indicate that their ubiquity and the scope of their applications will only continue to increase. For sophisticated UASs characterized by coordination of multiple vehicles, it is a formidable challenge to maintain an understanding of the complexities arising from the interaction of human supervisory control, automated planning, and network communication. This research investigates the robustness of UAS performance under degraded communication conditions through simulation with a particular futuristic UAS, the On-board Planning System for UxVs in Support of Expeditionary Reconnaissance and Surveillance (OPS-USERS) system. The availability of reliable communications is vital to the success of current UASs.

This dependence is not likely to be diminished in future systems where increased inter-vehicle collaboration may actually increase reliance on communications. Characterizing the effects of communications availability on the performance of a simulated UAS provides crucial insight into the response of UASs to communication failure modes which may be encountered in real-world implementations. Additionally, defining a minimum tolerable level of communication availability which will allow a UAS to operate with acceptable performance represents the groundwork for designing engineering specifications for communications systems, as well as for defining conditions under which such a system could be expected to operate effectively. Experiments are designed and executed to investigate the impact of degraded communication conditions on the performance of UASs by sampling the performance of a simulated UAS under a variety of degraded communication conditions.

These experimental conditions are based on a similar previous experiment, which utilized the same simulation testbed and investigated the impact of operator workload on system performance in experiments with human participants. However, this research seeks to collect data over a wider range of communication conditions than experimentation with human participants practically allows. Therefore, a human model is also developed to emulate the interaction of an average human operator with the system. After initial experiments validated that the human model produced results that were statistically indistinguishable from the results of the experimental data on which the model was based, it was employed in repeated simulations to collect data across a large number of experimental conditions.

Communication availability was modulated by imposing various network connectivity topologies on the agents in the UAS, as well as by introducing artificial delays into message transmissions between agents. Analysis of the simulation results suggests that the various functions of the system exhibit two main modes of sensitivity to communication failures. In one mode, exhibited in searching the environment and discovering targets, performance gains associated with a high level of communication availability are relatively small. Performance did not continue to drop with the introduction of further communication failures, indicating a robustness to communication failures. The other mode, observed in target tracking and hostile destruction performance, exhibits a negative correlation with increasing communication delays.

The magnitude of the effect of communication delays is also significantly impacted by the connectivity of the network topology, with lower connectivity topologies amplifying the negative correlation. Data collected through this experiment provided insight into the characteristics of an ideal minimum level of communication. In addition, the trade-offs between performance in different aspects of the system as well as the optimal allocation of communication resources were considered. This work also investigated the potential for the operator to mitigate performance losses incurred due to communication degradation through more frequent replanning. However, no evidence was found which supported this possibility. Although these results represent preliminary research into the effect of degraded communication on a complex autonomous system, they provide valuable principals to consider when designing future UASs.