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Table 10.1
MSI (sea
sickness index), simulation
results of the Mamdani
Fuzzy-PID controller
SSN
U (knots)
Without
With
controller
control
4
20
0.10
0,09
4
30
0.03
0.02
4
40
0.07
0.07
5
20
0.31
0.30
5
30
0.38
0.36
5
40
0.49
0.46
6
20
0.42
0.40
6
30
0.53
0.51
6
40
0.63
0.61
Simulation results with this controller predicted an improvement over the 47%
for SSN 4, up to 37% for SSN 5, and 19% of the pitch decrement for SSN 6. The
real time experiments with the replica, as it will be presented in the next section,
reached even greater reduction of the acceleration for those sea states in some cases.
10.4.2 Experimental Results
Real experiments have been carried out in a basin 152m long, 30m wide, and 5m
deep (CEHIPAR
2013
), with both regular waves (1.7-15m length) and long and
short-crested irregular waves with a maximum directional angle of 60
◦
. A scaled-
down replica 1/25 (4.5m long) of the TF-120 ferry was used (Fig.
10.8
). Sensors were
applied at several places of the ship to measure the heave, pitch, height of incident
waves, drag forces, and vertical accelerations. A T-foil near the bow (
15
◦
) and
two transom flaps (15
◦
) have been added (Fig.
10.9
). The speed of these actuators is
13
◦
/s (López et al.
2002
).
The results of applying the Fuzzy PID-Sugeno control described in Sect.
10.3
are summarized in Table
10.2
, where the MSI (motion sickness incidence) has been
defined as a function of the average WVA (Worst Vertical Acceleration) and the
encounter frequency. It has been proved that the fixed actuators alone are extremely
effective in attenuating the WVA (
◦
/s
2
). Moving the fins with a control systemmakes
this reduction greater. In fact, as the simulation results did not take into account the
proper action of the shape of the ferry, particularly at stern where the flap is placed,
the real results are better than the simulation ones in some cases (see Table
10.1
).
The controller was tested at different speeds for irregular waves, heading sea, and
different sea states (Santos et al.
2005a
). The improvement was greater than when
applying other types of controllers.
The improvement is clear, particularly at high speed and strong sea state. It seems
that the higher the speed, the more effective the actuators.
+
15/
−
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