Powered parafoil aerial vehicles (PAV) represent a very unique class of aircraft which have thus far seen limited use beyond recreational flight. Their slow flight and large payload characteristics make them a practical platform for applications such as aerial spraying and surveillance. One of the more interesting characteristics that distinguish PAV from conventional aircraft is the pendulum stability which is a consequence of suspending the majority of the aircraft weight so far from the wing surface and which introduces an appreciable amount of lag into the system. The Parafoil - Payload system undergoes both aerodynamic and kinematic motions and thus, the dynamic disturbances associated with such forms of motion most often employ a 6 or 9 DOF representation with the canopy modeled as a rigid body during flight. It is postulated that, as a result of such a combinational movement, a relative motion occurs in the elements between the load and the canopy, assuming both to be rigid. Generally, any such arrangement is assumed to be stiff and therefore the interaction between interdependent motion of canopy and payload (i.e. the kinematics) and aerodynamic flight reactions are nullified and thus, resulting in loss of a number of degree of freedoms. A 9 degree-of-freedom model is developed that helps to accurately model relative pitching and yawing motion of a payload with respect to a para foil. Two approaches are used for the estimation of relative motion. The first approach will be mathematical modeling and simulation whereas the second one will be done using a upward facing camera on the payload to identify the relative motion of the para foil and payload. Comparison between the mathematical modeling results and results from the camera output will be examined for consecutive results.
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