THE MANUAL STEERING CRITERION BASED UPON PHASE MARGIN. 指導教授 : 曾 慶 耀 學 生 : 潘 維 剛. Outline. MATHEMATICAL MODEL MANUAL STEERING CRITERIA MANUAL STEERING MAP CONCLUSION. MATHEMATICAL MODEL.
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指導教授:曾 慶 耀學 生:潘 維 剛
These are concerned with the phase of total forward path transfer function when its magnitude is unity , which for a stable close loop system must be algebraically greater than
-180 deg , so that if the phase is say -120 deg , then the
close loop system will be stable . Alternatively , if the phase
is less than -180 deg , say -210 deg , then the system is un- stable .
The magnitude of the ship plus steering engine transfer function (4) may be express in logarithmic
and for an unstable system the phase can be written as
It can be seen that as long as L/U>10 , then from the
last equation , will be much small than and will not have a great effect on system .However when the reverse is true and L/U<10 , then the steering engine cause an increasing time lag which can greatly detract from the manual handlng ability of the ship.
The steady state solution of the yaw rate equation (3) is simply found by ignoring the time derivatives of r ,
so that r=
state behavior is non-linear . This may be represented
here by the inclusion of a cubic term , so that
(7) respect to r and setting the right hand side to zero ,
Then the loop width can be shown to be
, so that in this case we can eliminate
From the last expression yield