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

Chapter 9 / Performance
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863 m/s. Increasing the guidance bandwidth so that the missile can respond
rapidly to target manoeuvres is detrimental in the non-manoeuvring case.
Clearly the choice of gain is dependent on manoeuvring levels and hence the
up-linked IMM filter probabilities.
PN performance and gain selection against weaving targets is fundamentally
different. Target compensation induced LOS rates as guidance tries to
establish the a non-existent constant velocity geometry, were so severe the
compensation was switched off until the missile achieved Mach 2 at
(launch + 2 s). Baseline performance with a gain of 4 and no acceleration
compensation (PN10 - blue) is compared with (PN11 - green) no target
compensation, and (PN14 - red) delayed target compensation in Figure 9-17
to Figure 9-20. There is little difference in the performance without target
acceleration. Target compensation against weaving targets is clearly
detrimental with excessive LOS rate oscillations throughout the flight.
Care is required when quoting miss distance and impact speed against
weaving targets. The weave phase, and to a lesser extent the target lateral
acceleration, must be treated as stochastic variables in a Monte Carlo
analysis for definitive results. This deficiency was highlighted in the
discussion on targets in §2. The results here are sufficient to demonstrate
the fundamental difference in approach between constant velocity and
weaving targets. The performance using different gains PN12 (gain := 2:
green), PN14 (gain := 4: blue) and PN16 (gains := 6: red) is compared in
Figure 9-21 to Figure 9-24. The trends are similar to previous results with
the higher bandwidth inducing larger oscillations at the expense of a 50 m/s
reduction in impact speed. These results show the importance of weave
detection, as distinct from lateral manoeuvre detection. Ideally the target
acceleration compensation must be removed and the gain reduced as the
target weaves. Low bandwidth is preferable against weaving targets so as to
track the underlying trajectory until close to impact. Close to the target the
bandwidth must be increased to remove the heading error dependent on the
phase of the target relative to its fundamental trajectory.
T3_TPN000.MTB
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TIME [seconds]