control using two manipulated parameters terry blevins (principal technologist) and greg mcmillan...
TRANSCRIPT
Control Using Two Manipulated Control Using Two Manipulated Parameters Parameters
Terry Blevins (Principal Technologist) andGreg McMillan (Principal Consultant)
[File Name or Event]Emerson Confidential27-Jun-01, Slide 2
PresentersPresenters
• Terry Blevins
• Greg McMillan
[File Name or Event]Emerson Confidential27-Jun-01, Slide 3
IntroductionIntroduction• Overview – Typical Examples• Split-Range Control
– Concept, variations in implementation– Setup in field vs. Splitter Block and IO for each valve. – Using Splitter Block, Example.
• Valve Position Control– Concept and typical implementation– Setup of I-only control in implementation – Impact of mode/status, Example.
• Combining Split Range and Valve Position Control– How to implement in DeltaV– Example
• Utilizing Predict/PredictPro for Control Using Two Manipulated Parameters– Advantage if process has large deadtime, difference in dynamics– Setup of MPC and MPC-Pro Blocks– Example Applications
• Summary• References
[File Name or Event]Emerson Confidential27-Jun-01, Slide 4
Control Using Two Manipulated ParametersControl Using Two Manipulated ParametersControl Using Two Manipulated ParametersControl Using Two Manipulated Parameters
• Under specified problem that has multiple solutions for unlimited operation.
• Extra degree of freedom is used to achieve unique solution that satisfied specific control objective.
• Most common techniques are: split range, valve position control.
• Combination of these technique and MPC offer new capability to address this class of problems
Controller Process
SP
Unmeasured Disturbance
One(1) Controlled Parameter
Two(2) Manipulated Parameters
[File Name or Event]Emerson Confidential27-Jun-01, Slide 5
Split Range – Traditional Implementation Split Range – Traditional Implementation Split Range – Traditional Implementation Split Range – Traditional Implementation
IP101
TT101
TIC101
Process
• Sequencing of valve accomplished through calibration of positioner, selection of actuator (A/O or A/C)
• Pro – Less expensive installation (1 pair of wires to field and 1 I/P)
• Con – You are not using the best technology for valve performance (e.g. digital positioners).
• Con -Difficult to initially calibrate and continuously improve to get best gap and most constant gain.
• Con -Individual valves not accessible for trouble shooting loop and actuator/valve problem.
• Con – The actuator, pneumatic positioner, and I/P performance shift with time and field conditions
• Con – I/P failure disables 2 valves• Con - Replacements in the night
may not have the special settings
Temperature Example
4-20ma
Heating
Cooling
3-15PSI
ValvePosition(% of Span)
IP Output ( PSI )153
0
100
Cooling
Heating
A/C
A/O
[File Name or Event]Emerson Confidential27-Jun-01, Slide 6
Split Range – Traditional ImplementationSplit Range – Traditional ImplementationSplit Range – Traditional ImplementationSplit Range – Traditional Implementation
• Sequencing of fine and coarse valve requires pressure switch, two solenoid valves and associated wiring and tubing
• Con – Complex installation • Con – You are not using the best
technology for valve performance (e.g. digital positioners).
• Con -Difficult to initially calibrate and continuously improve to get best gap and most constant gain.
• Con -Individual valves not accessible for trouble shooting loop and actuator/valve problem.
• Con – The switch, actuator, pneumatic positioner, and I/P performance shift with time and field conditions
• Con – I/P failure disables 2 valves• Con - Replacements in the night
may not have the special settings
IP102
AT102
AIC102
Process
pH Example
4-20ma
Coarse Valve
Fine Valve
3-15PSI
A/O
pH
ValvePosition(% of Span)
I/P Output ( PSI ) 1530
100
Fine ValveCoarse Valve
A/O
PS102
[File Name or Event]Emerson Confidential27-Jun-01, Slide 7
Split Range – DeltaV Implementation Split Range – DeltaV Implementation Split Range – DeltaV Implementation Split Range – DeltaV Implementation • Splitter bock is used
to implement split range control.
• When using traditional valves, split range control may implemented in DeltaV Controller using two(2) current outputs
• Split range control may be partially or fully assigned to fieldbus devices.
AI PID SPLT
AO
AO
AI PID SPLT
AO
AO
[File Name or Event]Emerson Confidential27-Jun-01, Slide 8
Split Range Control in DeltaVSplit Range Control in DeltaVSplit Range Control in DeltaVSplit Range Control in DeltaV
[File Name or Event]Emerson Confidential27-Jun-01, Slide 9
Splitter Block CalculationSplitter Block CalculationSplitter Block CalculationSplitter Block Calculation
[File Name or Event]Emerson Confidential27-Jun-01, Slide 10
IN_ARRAY ParameterIN_ARRAY ParameterIN_ARRAY ParameterIN_ARRAY Parameter
• The SP range associated with each output is defined by IN_ARRAY.
• SP range of outputs may be defined to overlap
• The SP upper end of range must be greater that lower end of range for each output
SP range associated with OUT1
SP range associated with OUT2
[File Name or Event]Emerson Confidential27-Jun-01, Slide 11
OUT_ARRAY ParameterOUT_ARRAY ParameterOUT_ARRAY ParameterOUT_ARRAY Parameter
• When SP is outside defined range, then the value at the end of range is used to determine the output.
• LOCKVAL determines if OUT1 value is held if SP is greater that the upper end of range defined for OUT1.
• No restrictions are placed on the output range.
OUT1 Range for associated SP range
[File Name or Event]Emerson Confidential27-Jun-01, Slide 12
Splitter BlockSplitter BlockSplitter BlockSplitter Block
SP
0 1000
100
0
100
0
100
100
100
0
0
OUT_1
OUT_2
LOCK_VAL “holds”
LOCK_VAL “is zero”
OUT_ARRAY 0 100 0 100
IN_ARRAY 0 100 0 100
OUT_ARRAY 100 0 0 100
IN_ARRAY 0 40 35 100
OUT_ARRAY 0 100 0 100
IN_ARRAY 0 40 35 100HYSTVAL
[File Name or Event]Emerson Confidential27-Jun-01, Slide 13
AI PID SPLT
AO
AO
IP103A IP
103B TT103
FY103
TIC103
COOLERHEATER
TT103 TIC103 FY103 IP103A
IP103B
Heating-Cooing ExampleHeating-Cooing ExampleHeating-Cooing ExampleHeating-Cooing Example
[File Name or Event]Emerson Confidential27-Jun-01, Slide 14
ValvePosition(% of Span)
TIC103 Output (% of Span)1000
0
100
Cooling (IP103B)
Heating (IP103A)
Split Range Output (FY103)Split Range Output (FY103)Split Range Output (FY103)Split Range Output (FY103)
[File Name or Event]Emerson Confidential27-Jun-01, Slide 15
AI PID SPLT
AO
AO
IP104A
IP104B
PT104
FY104
PIC104
PT104 PIC104 FY104 IP104A
IP104B
Steam Header ExampleSteam Header ExampleSteam Header ExampleSteam Header Example
400# Header
1475# HeaderBoiler
Turbo Generator
[File Name or Event]Emerson Confidential27-Jun-01, Slide 16
ValvePosition(% of Span)
PIC104 Output (% of Span)1000
0
100
Valve 104A
Valve 104B
Split Range Output (FY104) - CapacitySplit Range Output (FY104) - CapacitySplit Range Output (FY104) - CapacitySplit Range Output (FY104) - Capacity
[File Name or Event]Emerson Confidential27-Jun-01, Slide 17
Basic Neutralizer ExampleBasic Neutralizer ExampleBasic Neutralizer ExampleBasic Neutralizer Example
Neutralizer
Discharge
Reagent
AI PID SPLT
AO
AOAT105 AIC105 FY105 IP105A
IP105B
AIC105
AT105
IP105B
FY105
IP105A
Coarse Valve
Fine Valve
[File Name or Event]Emerson Confidential27-Jun-01, Slide 18
pH Nonlinearity and SensitivitypH Nonlinearity and SensitivitypH Nonlinearity and SensitivitypH Nonlinearity and Sensitivity
pH
Reagent FlowInfluent Flow
6
8
[File Name or Event]Emerson Confidential27-Jun-01, Slide 19
Split Range Output – Valve SequencingSplit Range Output – Valve SequencingSplit Range Output – Valve SequencingSplit Range Output – Valve Sequencing
ValvePosition(% of Span)
AIC105 Output (% of Span)1000
0
100
Fine Valve (IP105B)
Coarse Valve (IP105A)
HYSTVAL
[File Name or Event]Emerson Confidential27-Jun-01, Slide 20
Calculating Splitter SP RangesCalculating Splitter SP RangesCalculating Splitter SP RangesCalculating Splitter SP Ranges• A 1% change in controller
output to the splitter should have the same impact on control parameter when operating with either valve.
• When manipulating the same or similar material e.g. steam flow to header, then the range may be calculated based on valve rating.
• Tests may be performed to determine impact of each valve on the controlled parameter.
Example: Steam flow to Header, splitter interfacing directly to PRV’s, no overlap
Valve 1 rating = 50kph
Valve2 rating = 150kph
Desired Splitter Span valve 1 = 100*(50/(150+50)) = 25%
SP range for valve 1 = 0-25%
SP range for valve 2 = 25-100%
[File Name or Event]Emerson Confidential27-Jun-01, Slide 21
Testing Process to Determine Testing Process to Determine Splitter SP RangesSplitter SP Ranges
Testing Process to Determine Testing Process to Determine Splitter SP RangesSplitter SP Ranges
• With the process at steady state and AO’s in Auto mode, determine the magnitude of change in the controlled parameter for a 1 percent change in each valve.
• Calculate the splitter SP span and range for each output based on the observed response
Time
Cooling
Heating 1%
1%
1.1degF 2.2degF
Desired Splitter Span cooling valve = 100*(1.1/(1.1+2.2)) = 33%
SP range for cooling valve = 0-33%SP range for heating valve = 33-100%
Controlled Temperature
Example: Slaker feed temperature controlled using heating and cooling valves
[File Name or Event]Emerson Confidential27-Jun-01, Slide 22
Example – Split RangeExample – Split RangeExample – Split RangeExample – Split Range
[File Name or Event]Emerson Confidential27-Jun-01, Slide 23
Response to SP Change – Split Range Response to SP Change – Split Range Output To Large Valve/Small ValveOutput To Large Valve/Small Valve
Response to SP Change – Split Range Response to SP Change – Split Range Output To Large Valve/Small ValveOutput To Large Valve/Small Valve
Small Valve
Large Valve
PID OUT
SP
PV
[File Name or Event]Emerson Confidential27-Jun-01, Slide 24
Split Range – Strengths and WeaknessesSplit Range – Strengths and WeaknessesSplit Range – Strengths and WeaknessesSplit Range – Strengths and Weaknesses
• Pro - Process operation in simplified since two actuators are treated as one control manipulated parameter.
• Pro – immediate change in target actuator position can be achieved over the entire operating range independent of the size of change in the splitter SP
• Con – To achieve stable control over the entire operating range, Controller tuning must be established based on the slower responding manipulated parameter.
• Con- Does not take advantage of difference in resolution of actuator e.g. fine vs. coarse valve.
• Valve position control may be used in place of split range control when there are differences in dynamic response or resolution in actuators.
[File Name or Event]Emerson Confidential27-Jun-01, Slide 25
Valve Position Control – Traditional Valve Position Control – Traditional Implementation Implementation
Valve Position Control – Traditional Valve Position Control – Traditional Implementation Implementation
IP106A
AT106
AIC106
Process
• PID control is implemented using the actuator with finer resolution or fastest impact on controlled parameter
• The actuator with coarse resolution or slower impact on the controlled parameter is adjusted by an I-only controller to maintain the long term output of the PID controller at a given target
• I-Only controller must be disabled when the PID controller is not in an Automatic mode.
pH Example
Fine Valve
A/O
ZC106
IP106B
Coarse Valve
I-Only Controller
Mode
Target Valve Position
Time
pH
Fine Valve
Coarse ValveTarget Valve Position
[File Name or Event]Emerson Confidential27-Jun-01, Slide 26
Valve Position Control – DeltaV Valve Position Control – DeltaV Implementation Implementation
Valve Position Control – DeltaV Valve Position Control – DeltaV Implementation Implementation
• I-Only control is achieved by configuration of the PID Block STRUCTURE, GAIN and RESET parameters.
• It is possible to implement valve position control in the DeltaV controller or for this function to be distributed to fieldbus devices.
AI PID AO
AI PID
AO
AO
I-Only AO
I-Only
Traditional field devices
Fieldbus devices
[File Name or Event]Emerson Confidential27-Jun-01, Slide 27
Valve Position Control in DeltaV Valve Position Control in DeltaV Valve Position Control in DeltaV Valve Position Control in DeltaV
• Actuator with fastest impact or highest resolution is used to maintain the controlled parameter at setpoint.
• The OUT of the PID used for control is wired to IN on the PID block used for I-Only regulation of slower responding or coarse resolution.
PID configured for I-Only control
[File Name or Event]Emerson Confidential27-Jun-01, Slide 28
Configuring PID for I-Only ControlConfiguring PID for I-Only ControlConfiguring PID for I-Only ControlConfiguring PID for I-Only Control
• The STRUCTURE parameter should be configured for “I action on Error, D action on PV”
• The GAIN should be set to 1 to allow normal tuning of RESET (even though proportional action is not implemented.
• RESET should be set significantly slower than that the product of the PID gain and reset time used for control e.g. 5X slower
[File Name or Event]Emerson Confidential27-Jun-01, Slide 29
AI PID AO
IP107A
IP107B
FT107
FIC107
FT107 FIC107IP107A
Precise Flow Using Big/Small ValvePrecise Flow Using Big/Small ValvePrecise Flow Using Big/Small ValvePrecise Flow Using Big/Small Valve
ZC107
I-Only AOIP107B
ZC107
[File Name or Event]Emerson Confidential27-Jun-01, Slide 30
Neutralizer Using Valve Position ControlNeutralizer Using Valve Position ControlNeutralizer Using Valve Position ControlNeutralizer Using Valve Position Control
Neutralizer
Discharge
Reagent
AIC108
AT108
IP108A
IP108B
Coarse Valve
Fine Valve
AI PID AOAT108 AIC108
IP108A
ZC108
I-Only AOIP108B
ZC108
[File Name or Event]Emerson Confidential27-Jun-01, Slide 31
Example -Boiler BTU DemandExample -Boiler BTU Demand Example -Boiler BTU DemandExample -Boiler BTU Demand
ZC109
FT109A
IP109B
AI PID AOFT109B FIC109
IP109A
ZC109
I-Only AOIP109B
FIC109
FT109B
IP109A
FY109
Low BTU – Waste Fuel
HI BTU Fuel Boiler
BTU Demand
AIFT109A
SUM
FY109
[File Name or Event]Emerson Confidential27-Jun-01, Slide 32
Example –Reformer Air DemandExample –Reformer Air Demand Example –Reformer Air DemandExample –Reformer Air Demand
ZC110
AI PID AOFT110 FIC110
IP110
ZC110
I-Only AOSC110
FIC110
FT110
SC110
Air Machine
Secondary Reformer
Total Air Demand
IP110
[File Name or Event]Emerson Confidential27-Jun-01, Slide 33
Example – Valve Position ControlExample – Valve Position ControlExample – Valve Position ControlExample – Valve Position Control
[File Name or Event]Emerson Confidential27-Jun-01, Slide 34
Response to SP Change - Valve Position Response to SP Change - Valve Position Control with Large Valve/Small Valve Control with Large Valve/Small Valve
Response to SP Change - Valve Position Response to SP Change - Valve Position Control with Large Valve/Small Valve Control with Large Valve/Small Valve
Fine Valve
Coarse Valve
SP
PV
• Target position for fine valve is 30%.
• When the fine valve saturates, then response is limited to be reset of the I-Only control
Limited
[File Name or Event]Emerson Confidential27-Jun-01, Slide 35
Valve Position Control – Strengths and Valve Position Control – Strengths and WeaknessesWeaknesses
Valve Position Control – Strengths and Valve Position Control – Strengths and WeaknessesWeaknesses
• Pro – Immediate control response is based on actuator with finest resolution and/or faster impact on controlled parameter.
• Pro – Actuator with coarse resolution or slower impact on controlled parameter is automatically adjusted to maintain the output of the controller output long term at a specified operating point.
• Con – The controller output may become limited in response to a large disturbance or setpoint change. For this case, the dynamic response becomes limited by the slower tuning of the I-only controller.
• Con – Since stick-slip or resolution limits are a % of stroke, the big valve will go into a slow limit cycle
• The features of split range control and valve position control may be combined to provide immediate response to large changes in demand while retaining the features of valve position control for normal changes.
[File Name or Event]Emerson Confidential27-Jun-01, Slide 36
Combining the Best Features of Combining the Best Features of Split Range and Valve Position ControlSplit Range and Valve Position Control
Combining the Best Features of Combining the Best Features of Split Range and Valve Position ControlSplit Range and Valve Position Control
• A composite Block can be created that combines the features of split range and valve position control
• Support for BKCAL_IN and BKCAL_OUT can be implemented to provide bumpless transfer
[File Name or Event]Emerson Confidential27-Jun-01, Slide 37
Composite AlgorithmComposite AlgorithmComposite AlgorithmComposite Algorithm
Filter
CAS_IN
MODE
SPx +
x
x
T
ScalingRANGE SPAN
NORMAL
OUT_1
OUT_2
BKCAL_OUTBKCAL_IN1
BKCAL_IN2
Balance Calculation
-
-FILTER_TC
[File Name or Event]Emerson Confidential27-Jun-01, Slide 38
Composite ImplementationComposite ImplementationComposite ImplementationComposite Implementation• Parameters that
must be configure are: FILTER_TC, SPAN (of SP), RANGE (of OUT1), and NORMAL (desired position of
• The FILTER_TC should be configured similar to the reset time of the I-Only Controller that would be used for valve position control.
[File Name or Event]Emerson Confidential27-Jun-01, Slide 39
Demo – Composite Combining Valve Demo – Composite Combining Valve Position and Split Range ControlPosition and Split Range Control
Demo – Composite Combining Valve Demo – Composite Combining Valve Position and Split Range ControlPosition and Split Range Control
[File Name or Event]Emerson Confidential27-Jun-01, Slide 40
Example: Response to SP Change Example: Response to SP Change Example: Response to SP Change Example: Response to SP Change
SP, PV
OUT of PID
Fine Valve
Coarse Valve
• For small changes in SP or load disturbance, the response is similar to that provided by valve position control
• For large changes in SP or load disturbance, the immediate response is similar to split range control
Small change Large change
[File Name or Event]Emerson Confidential27-Jun-01, Slide 41
Composite for Valve Position/Split Range Composite for Valve Position/Split Range Control – Strengths and WeaknessesControl – Strengths and Weaknesses
Composite for Valve Position/Split Range Composite for Valve Position/Split Range Control – Strengths and WeaknessesControl – Strengths and Weaknesses
• Pro – All the advantage of valve position control without the dynamic limitations on large setpoint change or load disturbance.
• Con – If there is a significant delay in the control parameter response to changes in the two valves, then this limits the response that can be achieved using PID for the control .
• Model Predictive control automatically compensates for process dynamic and may be configured to provide the best features of valve position and split range control and can also address operating constraints.
[File Name or Event]Emerson Confidential27-Jun-01, Slide 42
Example of Different Dynamic Response – Example of Different Dynamic Response – Waste Fuel Boiler ControlWaste Fuel Boiler Control
Example of Different Dynamic Response – Example of Different Dynamic Response – Waste Fuel Boiler ControlWaste Fuel Boiler Control
• Objective: Maximize use of bark, only use gas when required to maintain Steam SP.
• Steam response to change in bark is much slower than for a change in gas.
• Bark alone may not be sufficient to address a sudden increase in steam demand.
o o o
MPC
Steam Flow Constraints
Bark Gas
Hi Cost FastFuel Gas
Lo Cost Slow Waste Bark
Steam Flow
Steam SP
20 Desired Response to unmeasured disturbance
[File Name or Event]Emerson Confidential27-Jun-01, Slide 43
Example of Different Dynamic Response – Example of Different Dynamic Response – Bleach Plant ControlBleach Plant Control
Example of Different Dynamic Response – Example of Different Dynamic Response – Bleach Plant ControlBleach Plant Control
• Objective: Maintain KAPPA target though the addition of Chemical 1 and Chemical 2. Minimize the use of Chemical 2.
• Desired operation is for Chemical 2 to be used for short term correction in KAPPA to replace Chemical 2 with Chemical 1 in the longer term.
AT
MPC
20 minutes
60 minutes
Lo Cost SlowChemical 1
Hi Cost Fast Chemical 2
Hi Cost Fast Chemical 2
Lo Cost SlowChemical 1
KAPPA
KAPPA SP
Desired response to unmeasured disturbance
[File Name or Event]Emerson Confidential27-Jun-01, Slide 44
Utilizing MPC for ControlUtilizing MPC for ControlUtilizing MPC for ControlUtilizing MPC for Control
• Both Predict and PredictPro can be configured and tuned for maintaining the critical controlled variable (CV), such as steam or composition, at its target and maximizing the low cost slow MV set point as an optimization variable.
manipulated variables
High Cost FastFeed SP
Critical PV(normal PE)
Low Cost SlowFeed SP
(lowered PE)
contr
olled
vari
able
Maximize
MPC Low Cost SlowFeed SP
null
opti
miz
ati
on
vari
able
[File Name or Event]Emerson Confidential27-Jun-01, Slide 45
MPC Guidelines for This ApplicationMPC Guidelines for This ApplicationMPC Guidelines for This ApplicationMPC Guidelines for This Application
• The best load and set point response for the critical CV is obtained with a short term tradeoff in efficiency by reducing the penalty on error (PE) for the optimization variable.
• When riding the low cost MV maximum set point, this PE lets both the slow and fast MV to move to improve the load and set point response of the critical CV.
• When riding the high cost MV low set point limit, it does not slow down the response of the other MV to upsets and set point changes to the critical CV. Only the response of the optimization variable is slowed down. This is consistent with the general theme that disturbance rejection must be fast while optimization can be slow.
• For coarse and fine valve control, the small valve is a low cost (low stick-slip) fast MV and the big valve is a high cost (high stick-slip) slow MV. The optimization variable is fine valve set point with a strategy of keeping it within limits (mid range throttle position). The PE for the optimization variable is reduced rather then the PM increased for the coarse valve so that both are available for load disturbance rejection.
• For the following examples, the slow MV has a lower cost, so its optimization strategy is maximization.
[File Name or Event]Emerson Confidential27-Jun-01, Slide 46
DeltaV Predict ConfigurationDeltaV Predict ConfigurationDeltaV Predict ConfigurationDeltaV Predict Configuration• MPC block
should be configured for two control and two manipulate parameters.
• The controlled measurement is wired to CNTRL1
[File Name or Event]Emerson Confidential27-Jun-01, Slide 47
DeltaV Predict Configuration (Cont)DeltaV Predict Configuration (Cont)DeltaV Predict Configuration (Cont)DeltaV Predict Configuration (Cont)
• CNTRL2 is configured as an optimized parameter - Maximize (not wired)
[File Name or Event]Emerson Confidential27-Jun-01, Slide 48
Control Generation - DeltaV Predict Control Generation - DeltaV Predict Control Generation - DeltaV Predict Control Generation - DeltaV Predict
• In Predict, the Penalty on Error (PE) is significantly decreased on the “Controller Generation” screen as shown in this example.
• The PE was lowered form 1.0 to 0.1 to make the optimization of the slow MV much less important than the control of the critical PV at its target
[File Name or Event]Emerson Confidential27-Jun-01, Slide 49
MPC Response to Disturbance and Set MPC Response to Disturbance and Set Point Changes Point Changes
MPC Response to Disturbance and Set MPC Response to Disturbance and Set Point Changes Point Changes
• In this example, low cost MV initially is riding its maximum set point, which leaves the fast cost MV free to respond
• Later, the maximum for the low cost MV has been increased to the point where it is no longer achievable, which drives the high cost MV to its low set point limit.
Riding Max SPon Lo Cost MV
Riding Min SPon Hi Cost MV
Critical CV
Lo Cost Slow MV
Hi Cost Fast MV
LoadUpsets
Set PointChanges
LoadUpsets
Set PointChanges
Low Cost MV Maximum SP Increased
Low Cost MV Maximum SP Decreased
Critical CV
[File Name or Event]Emerson Confidential27-Jun-01, Slide 50
• When configuring the MPC-Pro block, selects “Target” in the optimize column for the critical PV, and “Maximize” for the low cost MV.
• Browse to specify the RCAS_IN of the low cost slow MV (FC1-2) to specify the measurement associated with the low cost slow MV..
DeltaV PredictPro ConfigurationDeltaV PredictPro ConfigurationDeltaV PredictPro ConfigurationDeltaV PredictPro Configuration
[File Name or Event]Emerson Confidential27-Jun-01, Slide 51
Control Parameter - MPC-Pro BlockControl Parameter - MPC-Pro BlockControl Parameter - MPC-Pro BlockControl Parameter - MPC-Pro Block
[File Name or Event]Emerson Confidential27-Jun-01, Slide 52
Control Generation - DeltaV PredictProControl Generation - DeltaV PredictProControl Generation - DeltaV PredictProControl Generation - DeltaV PredictPro
• The Penalty on Error (PE) is significantly decreased on the “Controller Generation” screen
• In this example, the PE was lowered form 1.0 to 0.1 to make the optimization of the slow MV much less important than the control of the critical PV at its target.
[File Name or Event]Emerson Confidential27-Jun-01, Slide 53
MPC-Pro Response to Disturbance and Set MPC-Pro Response to Disturbance and Set Point ChangesPoint Changes
MPC-Pro Response to Disturbance and Set MPC-Pro Response to Disturbance and Set Point ChangesPoint Changes
• In this example, the low cost MV initially is riding its maximum set point, which leaves the fast cost MV free to respond
• Later, the maximum for the low cost MV has been increased so it is no longer achievable, which drives the high cost MV to its low set point limit.
Riding Max SPon Lo Cost MV
Riding Min SPon Hi Cost MV
Critical CV
Lo Cost Slow MV
Hi Cost Fast MV
LoadUpsets
Set PointChanges
LoadUpsets
Set PointChanges
Low Cost MV Maximum SP Increased
Low Cost MV Maximum SP Decreased
Critical CV
[File Name or Event]Emerson Confidential27-Jun-01, Slide 54
SummarySummarySummarySummary
• Split range control allows fully dynamic response to major setpoint of load disturbance changes. Valve position control may be used to takes advantage of any difference in control response or resolution in the manipulated parameters. A composite block has been demonstrated that combines the best features of split range and valve position control.
• DeltaV Predict and PredictPro and the associated MPC and MPC-Pro blocks may be effective used to address control using two manipulated parameters. Improved performance over PID is expected if the process has significant dead time or the manipulated variables have significantly different dynamics. Also, using this approach allow operating constraints and feedforward to be easily incorporated into the control strategy.
• Please direct questions or comments on this presentation to Terry Blevins ([email protected]) or Greg McMillan ([email protected] ).
[File Name or Event]Emerson Confidential27-Jun-01, Slide 55
Where To Get More InformationWhere To Get More InformationWhere To Get More InformationWhere To Get More Information
• “Effectively Addressing Control Applications”, Terry Blevins, Emerson Exchange, 2004.
• “Addressing Multi-variable Process Control Applications”, Dirk Thiele, Willy Wojsznis, Pete Sharpe, Emerson Exchange, 2004
• “Advanced Control Unleashed, Plant Performance Management for Optimum Benefit”. Terry Blevins, Gregory McMillan, Willy Wojsznis, Mike Brown, ISA Publication, ISBN 1-55617-815-8, 2003.