Thesis - Leigh Moody.pdf - Bad Request - Cranfield University

Chapter 3 / Sensors / Fins
_ _
3.10 Missile Fin Position Transducers
3.10.1 Review
Fin positions and IMU measurements provide the missile autopilot with data
it needs to generate the guidance demands and compensate for gravity. The
autopilot rolls the missile into the manoeuvring plane, desensitising it to
pitch-yaw cross coupling, body flexure, body incidence, mass property and
aerodynamic load variations with speed and height. For GPS and radar
altimeters it is important that the missile roll is controlled to ensure that their
FoV restrictions are not violated. For missile state observers, fin positions
are part of the force and moment balance used in the filter dynamic model in
conjunction with quasi-static aerodynamic data.
3.10.2 Description
Guidance demands are converted into individual fin demands (A/PδD) subject
to flight dependent limitations as described in §6.8.
AP
δ
D
≡
( ) T
ξ , ζ , η
3.10-1
D
D
D
Equation 3.10-1
The convention adopted for fin displacement is that positive demands cause
positive angular rotations about the FRD Missile Body axes according the
right hand screw rule, as shown in Figure 3-56.
LOOKING ALONG
MISSILE X-AXIS
U
L
R
E E
D
R
R
S
L
U
S
S
D
R
S
LOOKING ALONG
MISSILE X-AXIS
Figure 3-56 : Aileron, Rudder and Elevator Deflections
A positive fin deflection is a clockwise rotation about its hinge line when
looking outwards from the missile. The individual fin demands are,