crown princess vessel dynamics. overview ship dynamics under ins 2 nd officer’s manual inputs two...
TRANSCRIPT
Crown PrincessCrown Princess
Vessel Dynamics
Overview
• Ship dynamics under INS
• 2nd officer’s manual inputs
• Two opposing heeling responses
• Lag between wheel input and rudder/ship response
• Motion cues
Primary Motion
• Yaw Axis
– Heading– Turn rate– Turn acceleration
• Roll Axis
– Heel angle– Heel rate– Heel acceleration
Recorded Motion
15:05:00 15:10:00 15:15:00 15:20:00 15:25:00 15:30:0030
25
20
15
10
5
0
-5
-10
-15
-20
-25
-30
Starboard
PortT
urn
Ra
te (
de
g/m
in)
Local Time (hr:min:sec)
Turn rate
Manual Steering Begins
15:05:00 15:10:00 15:15:00 15:20:00 15:25:00 15:30:0030
25
20
15
10
5
0
-5
-10
-15
-20
-25
-30
40
30
20
10
0
-10
-20
-30
-40
Starboard
Tu
rn R
ate
(d
eg
/min
)
Local Time (hr:min:sec)
Turn rate
Port
Ru
dd
er
& H
ee
l An
gle
(d
eg
)
Heel angle
Port
Starboard
Manual Steering Begins
15:05:00 15:10:00 15:15:00 15:20:00 15:25:00 15:30:0030
25
20
15
10
5
0
-5
-10
-15
-20
-25
-30
40
30
20
10
0
-10
-20
-30
-40
Starboard
Tu
rn R
ate
(d
eg
/min
)
Local Time (hr:min:sec)
Turn rate
Port
Ru
dd
er
& H
ee
l An
gle
(d
eg
)
Heel angle Rudder command
Port
Starboard
Manual Steering Begins
Turning a ship
• Wheel command to rudder
Rudder force
Rudder force
Rudder force
Rudder force
Ship’s Response to Rudder
Direct Rudder Heeling Moment
Direct Rudder Heeling Moment
Response Lag
• Direct rudder effect
– Immediate heel response to rudder
• Sideslip effect
– Ship must first yaw in response to rudder
– Takes longer– Much stronger
Saturated Rudder
15:24:00 15:24:15 15:24:30 15:24:45 15:25:00 15:25:1530
20
10
0
-10
-20
-30
-40
-50
Starboard
Rud
der
(de
g)
Time (hr:min:sec)
Rudder command Rudder response
Port
42 sec
Manual Steering
Motion Cues
• Positive correlation with:
– Heel angular acceleration– Heel rate
Summary
• The 2nd officer’s commanded rudder changes faster than the rudder could respond
– During a 30 deg starboard rudder command the rudder actually port
Summary (cont.)
• Two effects of rudder on heel
– Short term direct response in direction of rudder input
– Longer term more powerful sideslip effect in opposite direction
Summary (cont.)
• Rudder commands modulated heel rate (while turn rate continued to increase)
– Port rudder initially slowed starboard heel rate
– But at longer term expense of increased starboard sideslip
• Starboard sideslip overwhelmed direct rudder effect producing starboard heel
Summary (cont.)
• Opposing long term and short term effects complicate the 2nd officer’s efforts to control the heel