deltav tune for fieldbus pid
DESCRIPTION
DeltaV Tune for Fieldbus PID. Support in DeltaV v7.2 and v7.3. Where will PID be Assigned??. Implementation Options with Fieldbus. DeltaV allows all elements of the control loop to be assigned to fieldbus The loop PID may be assigned to the transmitter or the valve. - PowerPoint PPT PresentationTRANSCRIPT
DeltaV Tune for DeltaV Tune for Fieldbus PIDFieldbus PIDSupport in DeltaV v7.2 and v7.3
Implementation Options with FieldbusImplementation Options with Fieldbus
DeltaV allows all elements of the control loop to be assigned to fieldbus
The loop PID may be assigned to the transmitter or the valve.
Portions of the control loop, such as the PID, may be assigned to the DeltaV controller and the remaining functions such as AI and AO done in fieldbus devices.
Where will PID be Assigned??
Control Performance Achieve Using Control Performance Achieve Using FieldbusFieldbus
Function block execution, maximum response time for compel data and slot time ( dependent of the device technology/design – specific to manufacturer) - see ISA2002 Fieldbus Tutorial
Whether control is done in the field or in the control system (customer decision)
Scheduling of block execution and communications on the FF segment.
Scheduled Control Execution With FieldbusScheduled Control Execution With Fieldbus
0 250
ms
AI PID AO
CD CDDATA
DATA
Macro Cycle
Macro Cycle Macro CycleMacro CycleMacro Cycle
2.3 ms 5.4 ms
Bus Traffic
Minimum Execution Time With Only Minimum Execution Time With Only One(1) Control Loop on an H1 SegmentOne(1) Control Loop on an H1 Segment
AI PID XFR XFRAO
20ms 25ms 30ms 60ms 30ms
Macrocycle = 165 ms
Assumptions: 3rd Generation Transmitter, AI&PID executed in Transmitter, Second generation Valve executes AO
Executing PID in the Valve Reduces the Number of Executing PID in the Valve Reduces the Number of Communications But Increases Loop Execution TimeCommunications But Increases Loop Execution Time
AI XFR PID
20ms 30ms 120ms 60ms
Macrocycle = 230 ms
Assumptions: 3rd Generation Transmitter, AI executed in Transmitter, Second generation Valve executes AO&PID
AO
Minimum Execution Time With Only Minimum Execution Time With Only Two(2) Control Loop on an H1 SegmentTwo(2) Control Loop on an H1 Segment
AI PID XFR XFRAO20ms 25ms 30ms 30ms 60ms 30ms 55ms
Macrocycle = 250 ms
Assumptions: 3rd Generation Transmitter, AI&PID executed in Transmitter, Second generation Valve executes AO, 50ms for every 125ms of the execution schedule (for display update)
AI PID XFR XFRAO
ACYCLIC
Impact of Splitting Control Between Impact of Splitting Control Between Fieldbus and Control SystemFieldbus and Control System DeltaV module execution is not synchronized with
function block execution on fieldbus segments.
Lack of synchronization introduces a variable delay into the control loop as great as the segment macrocycle e.g. 1/2 sec loop may have up to 1/2 sec of added variable delay when control is split between fieldbus device and the DeltaV controller.
Added delay will impact control loop tuning and result in increase variability in fast control loop.
PID executed in the Control System PID executed in the Control System
0 250
AI AO
CD CDDATA
DATA0 250
PID
Minimum Delay
Max Delay
Macrocycle
0 250
PID
0 250
AI AO
CD CDDATA
DATA
Macrocycle
0 250
PID
0 250
PID
Recommendation on Splitting Control Recommendation on Splitting Control Between Fieldbus and Control SystemBetween Fieldbus and Control System
Execute control loops in Fieldbus for better performance when the process dynamics are fast e.g. liquid pressure or flow.
If target loop execution is ½ sec or faster, then implement the control in fieldbus and limit the number of control loops to no more than two(2) per segment.
Original DeltaV Tune CapabilityOriginal DeltaV Tune Capability Only supported PID/ Fuzzy Blocks
in DeltaV Controller
Dynamics are captured by a (hidden) Autotuner Modifier so no error is introduced by communications delay/jitter.
DeltaV v7.2 Tuning Support for DeltaV v7.2 Tuning Support for all Manufacturer’s FF Devicesall Manufacturer’s FF Devices
DeltaV Tune appears and operates the same.
The PID mode changing to Man (rather than LO) during the Test phase
Tuning of fast loops may be conservative because of deadtime introduced by fieldbus communications.
Patent pending.
Shadow PID with Autotune Modifier
Launching DeltaV TuneLaunching DeltaV Tune
The DeltaV Tune application may be launched in context by right clicking on the module or fieldbus block
Testing the ProcessTesting the Process
When “test” is selected, the PID Autotune modifier changes the PID output by the amount specified and captures the process response.
Select Tuning RuleSelect Tuning Rule The default
( “normal” user ) tuning rules be used with fieldbus PID.
The “normal” rules apply to all process dynamics
DeltaV v7.3 Tuning Support DeltaV v7.3 Tuning Support for Emerson Fieldbus Devicesfor Emerson Fieldbus Devices
All new Emerson fieldbus devices will include the Autotune modifier as part of the PID. Initially available on 3244, 3051, 3144
DeltaV Tune looks and operates the same.
No communications delay or jitter in identifed dynamics.
Patent pending
In Emerson fieldbus devices
ConclusionConclusion Tuning of PID in any fieldbus devices is supported in v7.2.
Conservative tuning will be obtained for fast loops.
An improved tuning capabilty is provided in v7.3 for Emerson fieldbus devices. Even the fastest loop may be accurately tuned.
DeltaV Tune support of fieldbus devices enables utilizing control in the field. This can lead to reduced control variability for fast process dynamics.