6.5 Evaluation
When using the ARX simulation in Matlab, a linear approximation could not be
made on the maneuvers which were not centered around trim. Therefore, not only are
maneuvers around trim desired for a linear approximation, but they are also necessary
in order for the simulation to be done.
It is particularly difficult to find maneuvers to use for a linear approximation for
this specific vehicle due to the fact that it is very hard to trim. Therefore, before most
maneuvers there is an indication in the data that there are some oscillations about the
roll axis. Similarly, the data indicates that several seconds after a maneuver has been
initiated, a component of yaw rate begins to develop.
The build up of yaw rate after a morphing maneuver has been initiated can be
attributed to the fact that the shape of the wing is being altered. The wings on this
vehicle are being curled underneath, one at a time resulting in an asymmetric morphing
actuation. This leads to nonlinearities in the flight characteristics of the vehicle which
can explain the oscillations and the build up of yaw seconds after a maneuver has been
initiated.
The modeling is a linear approximation of coefficients, and when considering
nonlinear behavior it might not provide data that can be trusted. The 24 in MAV is
morphed by twisting the wings symmetrically, which can be approximated as a linear
behavior. However, the 12 in MAV is being morphed asymmetrically, and therefore
requires further studies to obtain a better approximation of the model.