DeltaV Tune for
Fieldbus PID
Support in DeltaV v7.2 and v7.3
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.
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.
Scheduled Control Execution With Fieldbus
CD
AI
PID
DAT
A
CD
DATA
AO
0
250
Macro Cycle
ms
Bus Traffic
2.3 ms
Macro Cycle
5.4 ms
Macro Cycle
Macro Cycle
Macro Cycle
Minimum Execution Time With Only
One(1) Control Loop on an H1 Segment
AI
20ms
PID
25ms
XFR
30ms
AO
XFR
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
Communications But Increases Loop Execution Time
AI
XFR
PID
20ms
30ms
120ms
AO
60ms
Macrocycle = 230 ms
Assumptions: 3rd Generation Transmitter, AI executed in
Transmitter, Second generation Valve executes AO&PID
Minimum Execution Time With Only
Two(2) Control Loop on an H1 Segment
AI
PID
AI
PID
20ms
25ms
XFR
AO
XFR
30ms
30ms
XFR
AO
60ms
XFR
ACYCLIC
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)
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.
PID executed in the Control System
PID
PID
0
250
0
250
Max Delay
Minimum
Delay
PID
0
CD
AI
PID
DAT
A
CD
DATA
250
0
AO
0
CD
AI
DAT
A
CD
DATA
AO
250
0
Macrocycle
250
250
Macrocycle
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.
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.
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.
Launching DeltaV Tune

The DeltaV Tune
application may be
launched in context
by right clicking on
the module or
fieldbus block
Testing 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 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
for Emerson Fieldbus Devices
In 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
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.