Environmental Engineering Reference
In-Depth Information
11.3.1.2 Gain
The gain error is modeled as
S
f
ðÞ¼ð
1
þ
a
Þ
S
r
ðÞþ
v
ðÞ
ð
11
:
14
Þ
where a could be constant or time-dependent gain.
11.3.1.3 Complete Failure
The sensor could generate suddenly a constant value A that might be contaminated
with noise w
ð
t
Þ
such as
S
f
ðÞ¼
A
þ
w
ð
t
Þ
ð
11
:
15
Þ
This fault is an abrupt fault, and it might rise due to a failure in the sensor
electronics.
11.3.2 Pitch System Faults
The blade pitch system is affected by the measurements of the blade pitch angle;
however, as a system the following faults could be recognized.
11.3.2.1 Performance Degradation
The performance of the pitching system might be changing with time, which could
be seen by the change of the system response. The performance degradation is an
incipient
fault
that
could
be
introduced
by
changing
the
model
parameter,
Eq. (
11.11
), such as
b
ð
t
Þ¼
2f
ðÞ
x
n
ðÞ
b
ð
t
Þ
x
n
ðÞ
b
ð
t
Þ
b
ref
ð
t
t
d
Þ
ð
Þ
ð
11
:
16
Þ
where the damping ration f and the natural frequency x
n
are now functions of the
parameter c that is used to describe the change in system performance.
11.3.2.2 Actuator Stuck
The complete failure in the pitch actuator which will lead to loosing the ability of
pitching the blade so it sticks in its current position which will cause the rotor
imbalance. This fault is described as
