Avoiding obstacles while intercepting a moving target: A miniature fly's solution

The miniature robber fly Holcocephala fusca intercepts its targets using a
system whose behaviour is approximated by the proportional navigation
guidance law. During predatory trials, we challenged Holcocephala's
interception performance by placing a large object in its potential flight
path. In response, Holcocephala deviated from the path predicted by
pure-proportional navigation, but in many cases still eventually contacted
the target. We show that such flight deviations can be explained as the
output of two competing navigational systems; pure-proportional navigation
and a simple obstacle avoidance algorithm. Obstacle avoidance by
Holcocephala is here described by a simple feedback loop that uses the
visual expansion of the approaching obstacle to mediate the magnitude of
the turning-away response. We name the integration of this this steering
law with pro-nav "Combined Guidance". The results demonstrate
that predatory intent does not operate a monopoly on the fly's
steering when attacking a target, and that simple guidance combinations
can explain obstacle avoidance during interceptive tasks.