Specifications

3 Designing Controllers Using the Design Tool GUI
3-26
Improved Setpoint Tracking for CSTR Temperature
On the other hand, the reactant concentration, C
A
, exhibits a larger deviation from its
setpoint, which is being held constant at zero (compare to Plant Outputs for T Setpoint
Scenario with Added Data Markers, where the final deviation is about a factor of 4
smaller).
This behavior reflects an unavoidable trade-off. The controller has only one adjustment
at its disposal: the coolant temperature. Therefore, it can't satisfy setpoints on both
outputs.
Output Weights
The output weights let you dictate the accuracy with which each output must track
its setpoint. Specifically, the controller predicts deviations for each output over the
prediction horizon. It multiplies each deviation by the output's weight value, and then
computes the weighted sum of squared deviations, S
y
(k), as follows
S k w r k i y k i
y
y
j j j
j
n
i
P y
( ) [ ( ) ( )]= + - +
{ }
==
ÂÂ
2
11
where k is the current sampling interval, k + i is a future sampling interval (within the
prediction horizon), P is the number of control intervals in the prediction horizon, n
y
is