  Safety in autonomous systems has been mostly studied from a human-centered
perspective. Besides the loads they may carry, autonomous systems are also
valuable property, and self-preservation mechanisms are needed to protect them
in the presence of external threats, including malicious robots and
antagonistic humans. We present a biologically inspired risk-based triggering
mechanism to initiate self-preservation strategies. This mechanism considers
environmental and internal system factors to measure the overall risk at any
moment in time, to decide whether behaviours such as fleeing or hiding are
necessary, or whether the system should continue on its task. We integrated our
risk-based triggering mechanism into a delivery rover that is being attacked by
a drone and evaluated its effectiveness through systematic testing in a
simulated environment in Robot Operating System (ROS) and Gazebo, with a
variety of different randomly generated conditions. We compared the use of the
triggering mechanism and different configurations of self-preservation
behaviours to not having any of these. Our results show that triggering
self-preservation increases the distance between the drone and the rover for
many of these configurations, and, in some instances, the drone does not catch
up with the rover. Our study demonstrates the benefits of embedding risk
awareness and self-preservation into autonomous systems to increase their
robustness, and the value of using bio-inspired engineering to find solutions
in this area.
