  Inverted landing is a challenging feat to perform in aerial robots,
especially without external positioning. However, it is routinely performed by
biological fliers such as bees, flies, and bats. Our previous observations of
landing behaviors in flies suggest an open-loop causal relationship between
their putative visual cues and the kinematics of the aerial maneuvers executed.
For example, the degree of rotational maneuver (the amount of body inversion
prior to touchdown) and the amount of leg-assisted body swing both depend on
the flies' initial body states while approaching the ceiling. In this work,
inspired by the inverted landing behavior of flies, we used a physics-based
simulation with experimental validation to systematically investigate how
optimized inverted landing maneuvers depend on the initial approach velocities
with varied magnitude and direction. This was done by analyzing the putative
visual cues (that can be derived from onboard measurements) during optimal
maneuvering trajectories. We identified a three-dimensional policy region, from
which a mapping to a global inverted landing policy can be developed without
the use of external positioning data. Through simulation, we also investigated
the effects of an array of landing gear designs on the optimized landing
performance and identified their advantages and disadvantages. The above
results have been partially validated using limited experimental testing and
will continue to inform and guide our future experiments, for example by
applying the calculated global policy.
