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Multiple control with Learning System Process Automation
MPS® PA Compact Workstation
&
MPS® PA Reactor Station
3/25/2010 Folie 1Jürgen Helmich, Adiro
Basic control system
A basic control system with a single process variable as:A basic control system with a single process variable, as:
• Level• Flow rate• Pressure• Temperature
can be controlled with a single controller, e.g.
• 2-point controllerP PI PID t ll• P-, PI-, PID- controller
3/25/2010 Folie 2Jürgen Helmich, Adiro
Advanced control systems
• Multiple capacity
• Cascade control
R ti t l• Ratio control
• Feed forward control
• Override controlOverride control
• Selective control
3/25/2010 Folie 3Jürgen Helmich, Adiro
Advanced control systems
• more than 1 process value
• process values are
i i - interacting,
- in dependency or
- subordinate to each othersubordinate to each other
• PID controller(s) with additional control functions
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Multiple capacitySingle capacity Multiple capacity
PV PVPV PV
PID PID
CO CO
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Multiple capacity - HardwareMPS® PA Compact Workstation with additional tank
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Cascade control
Cascade control uses the output of the primary controller to manipulate the setpoint of the secondary controller as if it were the final control element.
Reasons for cascade control:• Allow faster secondary controller to handle disturbances in
the secondary loop. • Allow secondary controller to handle non-linear valve and
other final control element problems. ll di l l d l d i• Allow operator to directly control secondary loop during
certain modes of operation (such as startup).
3/25/2010 Folie 7Jürgen Helmich, Adiro
Cascade control
Requirements for cascade control:• Secondary loop process dynamics must be at least four
times as fast as primary loop process dynamics. • Secondary loop must have influence over the primary loop. • Secondary loop must be measured and controllable.
Reasons not to use cascade:• Cost of measurement of secondary variable (assuming it is
not measured for other reasons). )• Additional complexity.
3/25/2010 Folie 8Jürgen Helmich, Adiro
Cascade control
Application Compact Workstation
PV1
PV1 process value level (primary)
PV1
SP1 setpoint level (primary) CO1 controller output setpoint flow rate
PV2 process value flow rate (secondary)SP2 setpoint flow rate (secondary)
CO1
SP2SP1
SP2 setpoint flow rate (secondary)CO2 controller output pumpCO2
PV2
3/25/2010 Folie 9Jürgen Helmich, Adiro
Cascade control - HardwareMPS® PA Compact Workstation
3/25/2010 Folie 10Jürgen Helmich, Adiro
Ratio control
Ratio control is used to ensure that two or more flows are kept at the same ratio even if the flows are changing.
Applications of ratio control:• Blending two or more flows to produce a mixture with specified
composition composition. • Blending two or more flows to produce a mixture with specified
physical properties. M i i i i d f l i b i • Maintaining correct air and fuel mixture to combustion.
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Ratio control
Application Example
3/25/2010 Folie 12Jürgen Helmich, Adiro
Ratio control – manual operation
Application Compact Workstation
PV1X1
RA1
PV1 process value flow rate 1 (wild)
X1 ratio CO1RA1 ratio value setpoint flow rate 2
CO1 manual controller output pump
PV2 l fl 2 ( ll d)SP2 PV2 process value flow rate 2 (controlled)
SP2 setpoint flow rate 2
CO2 controller output proportional valve
CO2SP2PV2
3/25/2010 Folie 13Jürgen Helmich, Adiro
Ratio control – controlled operation
Application Compact WorkstationX1
RA1
PV1 process value flow rate 1 (wild)
X1 ratio PV1 CO1SP1
RA1 ratio value setpoint flow rate 2
CO1 manual controller output pump
PV2 l fl 2 ( ll d)
PV1
SP2 PV2 process value flow rate 2 (controlled)
SP2 setpoint flow rate 2
CO2 controller output proportional valve
CO2SP2PV2
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Ratio control - HardwareMPS® PA Compact Workstation with additional pump and flow sensor
3/25/2010 Folie 15Jürgen Helmich, Adiro
Feed forward control
• feed forward controller measures the disturbance D, while it is still distant
• predicts the impact of the disturbance to the process • predicts the impact of the disturbance to the process value
• the disturbance has been identified as causing repeated and costly upsets thus justifying the expense and time
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Feed forward control
Application Example
3/25/2010 Folie 17Jürgen Helmich, Adiro
Feed forward control
heat exchanger
Application Reactor StationT T
PV1 process value temperature 1
SP1 setpoint temperature 1 SP1
T
CO1 controller output feedback
D2 disturbance value temperature 2 (load)
SP2 i 2
PV1 CO1
SP2PV2
SP1
CO
cooling unitSP2 setpoint temperature 2
CO2 controller output feed forward
CO total controller output for heater
CO2PV2
3/25/2010 Folie 18Jürgen Helmich, Adiro
CO total controller output for heater
Feed forward control - HardwareMPS® PA Reactor Station with heat exchanger and cooling unit
3/25/2010 Folie 19Jürgen Helmich, Adiro
Override control
Override control is used to take control of an output from one loop to allow a more important loop to manipulate the outputoutput.
The output from two or more controllers are combined in a high or low selector. The output from the selector is the highest or lowest individual controller output.
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Override control
Application Example
3/25/2010 Folie 21Jürgen Helmich, Adiro
Override control
PV1 CO1SP1
P
Application Compact Workstation
P
PV1 process value flow rate
SP1 setpoint flow rate
SP2
COCO1 controller output flow rate
PV2 process value pressure
SP2 i
CO2SP2PV2
SP2 setpoint pressure
CO2 controller output pressure
CO override controller output for pump
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CO override controller output for pump
Override control - HardwareMPS® PA Compact Workstation
3/25/2010 Folie 23Jürgen Helmich, Adiro
Selective control
Process variables to be controlled outnumber the final control elements. The control system must automatically decide how to share the final control elements decide how to share the final control elements.
A selective controls can be employed to switch easily and smoothly between the variables to be controlled.
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Selective control
Selective controls involve the use of signal selectors which choose either the lowest, median, or highest control signal from two or more signals. g
Selective controls are employed in five basic application areas:• Protection of equipmentProtection of equipment• Variable structuring• Auctioneering• Redundant instrumentation• Redundant instrumentation• Valve position control
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Selective control
Application Example
Low signal selector for protection of equipment
Pressure and flow rate should be kept below a certain limit.
3/25/2010 Folie 26Jürgen Helmich, Adiro
Selective control
PV1 process value temperature 1
Application Reactor Station
T
CO3PV3SP3
heat exchanger
SP1 setpoint temperature 1
CO1 controller output 1
PV2 process value temperature 2
TT
PV2 process value temperature 2
SP2 setpoint temperature 2
CO2 controller output 2PV1 CO1SP1
CO
PV2 process value temperature 2
SP2 setpoint temperature 2
CO2 controller output 2CO2
SP2PV2cooling unit
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CO selected controller output for heating
Selective control - HardwareMPS® PA Reactor Station with heat exchanger and cooling unit
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Further Information?
Please do not hesitate to contact us!Festo Didactic – Sales team Solution Center
Nicola BauerPhone: +49-711-3467-1413 E il ib@d f
Jan VeselyPhone: +49-711-3467-1448
il j @d f
Eckhard von TerziSales Manager Solutions
hEmail: [email protected] Email: [email protected]: ++49-711-3467-1346mobile: +49-1733089966email: [email protected]
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