Info

10 20 30

0 10 20 30

Batch number

Figure 6.41. Quality variables measured at the end-of-batches for the reference set (listed in Table 6.7).

erence set. The score plots provide a summary of process performance from one batch to the next. The control limits for new independent t scores under the assumption of normality at significance level a at any time interval k is given by [214]

where n and sref are the number of observations and the estimated standard deviation of the t-score sample at a given time interval k (mean is always 0) and in—1,0/2 is the critical value of the Studentized variable with n — 1 degrees of freedom at significance level a/2 [435]. The axis lengths of the confidence ellipsoids in the direction of ath principal component are given by [262]

0 200 400 600 800 0 200 400 600 800

Figure 6.42. Unequal/unsynchronized raw batch trajectories of the reference set.

0 200 400 600 800 0 200 400 600 800

Figure 6.42. Unequal/unsynchronized raw batch trajectories of the reference set.

Table 6.8. Faulty batch information and data sets

Variable name

Fault definition

Introduction time

Agitator power input (Variable 2) Data: Xi(750 x 14) Glucose feed rate (Variable 3) Data: X2(761 x 14) Glucose feed rate (Variable 3) Data: X3(764 x 14)

10% step decrease Small downward drift Large downward drift

70 - 90 hrs (140th and 180th samples)

Beginning of fed-batch operation

Beginning of fed-batch operation

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