The challenge of integrating the UAV fleet into the carrier landing operational structure
with respect to navigation and control strategies is addressed. A simulation model was
developed which includes an aircraft model, an atmosphere model and an aircraft carrier
motion model. The six degree of freedom non-linear aircraft model is based on the
aerodynamic characteristics of the Mk 4a Jindivik extended to include rudder, spoiler
and thrust vectoring controls, and an undercarriage model. The atmosphere model
includes a carrier landing atmospheric disturbance model. The six degree of freedom
aircraft carrier motion model is based on the ship motion simulation program
SEAWAY.
A Navigation System was developed which conforms to current operational procedures
and future military navigation goals. This Navigation System continuously predicts the
position in space where touchdown on the carrier deck will take place, based on aircraft
position, the relative velocity between the aircraft and carrier, and the motion time
history of the carrier. A reference flight path to the predicted touchdown point is
continuously defined. The aircraft deviation from this flight path is determined and
input to the autoland control system. For the purposes of this study perfection prediction
is assumed.
Automatic flight control systems were developed to assess three control strategies for
suitability to the carrier landing task. The focus of this assessment was on vertical glide
path deviation control. Direct Lift Control was compared to conventional control and
was found to have superior performance, especially in turbulence. As UAV planforms
tend to be tailless, and therefore lateral and pitch control are generated by a common
aerodynamic surface, thrust vectoring was investigated as a means of alleviating
aerodynamic pitch control requirements in the carrier landing task.
An Adaptive Approach Speed Controller was developed as an extension of the
Navigation System. This system synchronises the time that the aircraft passes over the
stern, or ramp, of the carrier with the minimum absolute carrier pitch attitude attainable
for a given range of approach speeds. This system was shown to be an effective method
of minimising the negative effect that carrier motion has on the clearance between the
aircraft and the carrier’s ramp
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