  We develop an effective computer model to simulate sensing environments that
consist of natural trees. The simulated environments are random and contain
full geometry of the tree foliage. While this simulated model can be used as a
general platform for studying the sensing mechanism of different flying
species, our ultimate goal is to build bat-inspired Quad-rotor UAVs- UAVs that
can recreate bat's flying behavior (e.g., obstacle avoidance, path planning) in
dense vegetation. To this end, we also introduce an foliage echo simulator that
can produce simulated echoes by mimicking bat's biosonar. In our current model,
a few realistic model choices or assumptions are made. First, in order to
create natural looking trees, the branching structures of trees are modeled by
L-systems, whereas the detailed geometry of branches, sub-branches and leaves
is created by randomizing a reference tree in a CAD object file. Additionally,
the foliage echo simulator is simplified so that no shading effect is
considered. We demonstrate our developed model by simulating real-world
scenarios with multiple trees and compute the corresponding impulse responses
along a Quad-rotor trajectory.
