User`s guide

Section 1 — An Operator’s Quick Tour of Profit Optimizer Displays
1.2 Control Concepts You Need to Understand
1/00 Profit Optimizer User's Guide 5
Honeywell Inc.
How Profit
Optimizer
Computes
Control Moves
These are the calculations Profit Optimizer uses to formulate its output:
• Prediction Calculations These calculations track the disturbance variables in
the process as well as the results of previous control moves to predict where
the process is going.
• Control Calculations From where the prediction calculations estimate the
process is going, the control calculations formulate adjustments to the process
to meet the control objectives. The Profit Controllers calculate the control
moves
These adjustments are then output as control moves, increasing temperature,
reducing flow, the like. The influence of these control moves is then tracked
by the prediction calculations, which then again estimate where the process is
going.
• Optimization Calculations These calculations push a process according to
economic considerations after the control objectives are met. Profit Optimizer
(DQP) calculates the optimal for all Profit Controllers. The Profit Controllers
perform the control calculations.
Controller
Execution
Intervals
How frequently Profit Optimizer executes is user defined, and is generally
determined by some combination of the following:
1. How critical (volatile) the process is
2. How tight the optmization needs to be
3. The dead time, or lag, and
4. The reaction time – how fast the process is (in Control Engineering terms, the
length of the major time constants).
Experience with the process or similar processes, and information gathered at the
step tests during identification usually give Control Engineers a good indication
of an appropriate execution interval.