1. DeltaV Tune for Fieldbus PID
Support in DeltaV v7.2 and v7.3

2. Implementation Options with Fieldbus
Where will PID be Assigned??
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.

3. Control Performance Achieve Using Fieldbus
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.

4. Scheduled Control Execution With Fieldbus
250 ms AI
PID AO CD
DATA
Macro Cycle
2.3 ms
5.4 ms
Bus Traffic

5. Minimum Execution Time With Only One(1) Control Loop on an H1 SegmentAI
PID
XFR AO
20ms ms ms ms ms
Macrocycle = 165 ms
Assumptions: 3rd Generation Transmitter, AI&PID executed in Transmitter, Second generation Valve executes AO

6. Executing PID in the Valve Reduces the Number of Communications But Increases Loop Execution TimeAI
XFR
PID AO
20ms ms ms ms
Macrocycle = 230 ms
Assumptions: 3rd Generation Transmitter, AI executed in Transmitter, Second generation Valve executes AO&PID

7. Minimum Execution Time With Only Two(2) Control Loop on an H1 SegmentAI
PID
XFR AO AI
PID
XFR AO
XFR
ACYCLIC
20ms ms ms ms ms ms ms
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)

8. Impact of Splitting Control Between Fieldbus 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.

9. PID executed in the Control System
250
PID
PID
250
Minimum Delay
Max Delay
250
250
PID
PID
250 AI AO CD
DATA
250 AI AO CD
DATA
Macrocycle
Macrocycle

10. Recommendation on Splitting Control Between 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.

11. Original 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.

12. DeltaV v7.2 Tuning Support for all Manufacturer’s FF Devices
Shadow PID with Autotune Modifier
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.

13. Launching DeltaV Tune
The DeltaV Tune application may be launched in context by right clicking on the module or fieldbus block

14. Testing the Process
When “test” is selected, the PID Autotune modifier changes the PID output by the amount specified and captures the process response.

15. Select Tuning Rule
The default ( “normal” user ) tuning rules be used with fieldbus PID.
The “normal” rules apply to all process dynamics

16. DeltaV v7.3 Tuning Support for 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

17. Conclusion
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.