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

Chapter 9 / Performance
_ _
All the trajectories start with the target at constant velocity for the first 5 s to
allow time for the tracking filters to converge. After 5 s target manoeuvres
start, the trajectory optimiser is activated, and the launcher is steered using
target state observer data. The missile IMU is activated 5 s before launch.
The seeker powers-up at launch with its gimbals locked - once the launch
transients are over its gimbals are released and its detector activated. When
the missile is committed to launch its observer is initialised via a data link
from the target (radar) data processor to the launcher.
The missile observer then processes valid tracks and plots, characterising
the IMU prior to launch, and thereafter providing “optimal” data as the
missile passes through it various flight phases and terminal guidance. The
event sequence is controlled in the simulation by the irreversible LAUNCH
flag; the phases of flight and transition conditions are shown in Figure 9-2.
9.1.1 Flight Phase 0
Pre-launch operation starting at (t := 0) and up to missile launch, comprising
radar tracking, target state observation, launcher training and missile
initialisation and IMU characterisation.
t < t L ⇒ LAUNCH : =
9-4
0
Equation 9.1-1
Trajectory optimisation is invoked after 5 s after the target state observer has
converged. The missile IMU is activated 5 s before launch, communication
between the radar, launcher and missile is established, and the on-board
state observer is initialised. Conceptually, the trajectory optimiser is
duplicated in the launcher as part of the fire control software. When the
missile observer is initialised the boundary conditions and optimal control
sequence is loaded into the missile trajectory optimiser.
9.1.2 Flight Phase 1
Booster ignition, first motion, and constrained flight in a rotating launcher
until the missile has travelled the length of the launcher (LT).
9.1.3 Flight Phase 2
XM ( ≤ L ) ∧ ( t ≥ t ) ⇒ LAUNCH : = 1
Pm T
L
Equation 9.1-2
Missile roll control is active but no lateral acceleration demands are applied
until a stable flight speed (VS) is reached. The missile dynamics during this
phase are determined by thrust, drag and gravity induced forces alone. Tube
launched munitions often undergo an upward pitch motion resulting in a
height droop until their speed has built up.