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

9.6.2 CLOS Study
The CLOS study showed how important missile longitudinal acceleration
and body-to-beam compensation are, particularly at low speed and when
boosting. The miss distances achieved with the fully compensated guidance
law were 3 times larger than the PN equivalents. A feature of CLOS is the
increase in miss distance with range, hence the need for a seeker and a
terminal guidance phase at long-range.
Under ideal conditions the beam stiffness used allowed the missile to follow
the weaving target LOS indicating, as did PN, that range-to-go bandwidth
control is required if control effort is to be minimised.
9.6.3 Tracking Filter Tuning Study
Velocity, acceleration and Singer filter performance against idealised targets
was investigated; work is ongoing with the weave filter. System noise
levels for the VA filters were set at 1 m 2 /s 4 /Hz and 1 m 2 /s 6 /Hz respectively
to accommodate digitisation errors.
Using the low bandwidth acceleration filter, the normalised acceleration
error rapidly exceeded the expected 3σ error in response to changes in target
acceleration. This is ideal, both for IMM discrimination, and for later
manoeuvre detection. By comparison, when a new constant acceleration
regime is established the filter recovers slowly taking 2 s to 3 s. This is why
the IMM filter transition probabilities are set to inject system noise under
these circumstances.
Changing the measurement processing order made no difference to the
tracking errors using a 10 Hz data rate. Using the most accurate
measurement first, with re-linearisation, is only expected to improve
accuracy at lower data rates.
The low bandwidth Singer filter as expected provided little measurement
filtering with PVA errors of the order of 20 m, 50 m/s and 80 m/s 2 .
However, changes in the target flight regime associated with avoidance
manoeuvring are expected to be short. During such periods the velocity and
acceleration filters remained stable, if inaccurate, when tracking targets with
a different dynamic model.
9-29