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Section 8 Control Loop Asset Monitor (CLAM)
Sl.No
Name
16.
Auto-correlation
(ACF) ratio
17.
Setpoint Crossing
Index
18.
Cascade Tracking
Index
19.
Cascade Travel
Ratio Index
20.
Harris Performance
Index
3BUA000150-600
Table 9. Indices used in CLAM
Description
Describes how fast the auto-correlation
function (ACF) of the data decays over time. A
comparison is made between a dead time
value for the specific loop category and the
value where the ACF decreases below 30 %.
[0...1]. A value close to 0 means that the ACF
decays much slower then benchmark
(indicating sluggishness). A value close to 1
means that the ACF decays as fast as the
benchmark or faster.
Quantifies the number of setpoint crossings by
looking at the amount of zero crossings for the
control error compared to the total number of
samples in the data batch. [0-100%].
Nominal>10 %.
Simple index counting all samples that deviate
more than 3 % from the desired setpoint value
and divide this value with the total number of
samples. The result is an indication of setpoint
tracking performance. [0-100 %] Nominal<20
%.
Index comparing "travel" per hour for the
setpoint with the "travel" for the process value.
If the control is good both signals should
"travel" equally much. [0.5-Inf]. Nominal: [0.5-
1.5].
Famous performance index comparing current
variance with (theoretically) minimum
achievable variance. The result is a value in the
interval [0-1] where 1 means that minimum
achievable variance is achieved. By taking the
inverse of this index you get a factor indicating
how much the loop variance can be decreased.
Performance indices
Index class
Performance
Performance
Performance
Performance
Performance
99
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