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COORDINATED CONTROL BLOCK (CC)
An Advanced Control Block in the MANTRA Process Control System
The Coordinated Control Block (CC) controls a single process variable by
manipulating as many as three different controller outputs. As an option, any of the three controller outputs can be used as an input to create feedforward
action in the controller.
For example, temperature control in a chemical reactor may use low-cost
low BTU steam, higher-cost higher-BTU steam, and chiller water. The control problem is to keep costs down by using the low-cost steam most of
the time and using the high-cost steam and the chiller water only when needed. The Coordinated Control Block can maintain tight control of the process while fulfilling the
secondary goal of decreasing costs.
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How:
The goal of the CC Block is two-fold: reject any disturbances to the
process and optimize the three controller outputs (CO) during long-term steady state control.
The CC Block performs these goals by utilizing two independent lists
named Active and Target.
The Active List tells the CC Block which controller output device is
the strongest and most effective.
When the process variable (PV) is not at the setpoint, the most
active controller output is used first.
When the most active controller output saturates, then the second
most active controller output is used, and finally the third most active is used.
The Target List is used by the CC Block to control the long-term
steady state value of each controller output. As the process variable reaches the desired setpoint, the CC Block will start to drive each of
the controller outputs to their target values without upsetting the process.
In this way the CC Block can optimize the short-term control
requirements and minimize the long-term economic costs.
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Use Examples:
Cooling Skids
Process Variable Temperature
Controller Output 1 River or Lake Water
Controller Output 2 Chiller Water
Controller Output 3 Steam
Chemical Reactor
Process Variable Temperature
Controller Output 1 Plant Steam
Controller Output 2 Purchased Steam
Controller Output 3 Chiller Water
Extruder Control
Process Variable Zone 2 Temperature
Controller Output 1 Zone 1 Heater
Controller Output 2 Zone 2 Heater
Controller Output 3 Zone 3 Heater
Dissolved Oxygen Control
Process Variable Dissolved O2
Controller Output 1 Agitator RPM
Controller Output 2 Air Flow
Controller Output 3 Pressure Control
Features:
- Self-Tuning
- Bumpless Transfer from Auto/Manual
- Individual Auto/Manual Controls for each CO
- Full Alarming
- Online changing of the Target List
- Online changing of CO Target Values
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Key Parameters:
Process Control Parameters
Setpoint (SP)
Process Variable (PV)
Controller Output for CO1, CO2, & CO3
Manual CO Value for CO1, CO2, & CO3
Auto-Manual for CO1, CO2, & CO3
Active List for CO1, CO2, & CO3
Target List for CO1, CO2, & CO3
Target Value for CO1, CO2, & CO3
Limits and Alarms
Positive Dev HiHi Alarm
Positive Dev Hi Alarm
Negative Dev Hi Alarm
Negative Dev HiHi Alarm
Minimum CO Value for CO1, CO2, & CO3
Maximum CO Value for CO1, CO2, & CO3
Rate Limit Pos for CO1, CO2, & CO3
Rate Limit Neg for CO1, CO2, & CO3
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Model Based Parameters
Model Gain for CO1, CO2, & CO3
Model Time Constant for CO1, CO2, & CO3
Model Dead Time for CO1, CO2, & CO3
Filter Time Constant for CO1, CO2, & CO3
Other Parameters
CO Direction for CO1, CO2, & CO3
Controller Speed for CO1, CO2, & CO3
Noise Level
PV Tuning Limit
Tuning Step Size for CO1, CO2, & CO3
Start Tuning for CO1, CO2, & CO3
Tuning Status for CO1, CO2, & CO3
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