Fault Detection and Diagnostics for Rooftop Air Conditioners

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Step i Do FDD on fault i . After steps 1,2,
L , i − 1 have been done, either x = 0 or
l = 0 ( for k < i ) is guarantied.
ik
sign _ stat(
zi)
z
i
= li
1x1
+ li2x2+
, L , + liixi
= liixi
⇒ xi,
sign
=
sign(
l )
If it exists, fix fault i if it is severe enough, or otherwise modify the infected
features.
ii
k
M
M
Step n Do FDD on fault n . After steps 1,2,
L , n −1
have been done, either x = 0 or
l = 0 ( for k < n) is guarantied.
nk
sign _ stat(
z
z
n
= ln1x1
+ li2x2
+ , L , + lnnxn
= lnnxn
⇒ xn,
sign
=
sign(
l )
Fix fault n , if it exists and is severe enough.
nn
n
)
k
1.2 Strategy for Decoupling Rooftop Unit System
The approach proposed in the previous section is based on decoupled features.
Mathematically, there exists an infinite number of decoupled features, but for HVAC
systems only those with intuitive physical meaning and those that are readily available
(low-cost) are practical. This section develops a methodology or guidelines to find these
kinds of features.
Philosophically, any
problem could be approached microscopically or
macroscopically or both to obtain required results with different details. A macroscopic
approach uses external and overall information to interpret the observed phenomenon or
predict a coming phenomenon, while a microscopic approach uses internal and
component information to interpret or predict the phenomenon. In some situations, a
macroscopic approach is preferred and unnecessary details are often ignored to simplify a
complicated problem to be a manageable one at the cost of losing some information. For
example, statistical thermodynamics considers physical models at the level of particles
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