RS3™ to DeltaV™ Tuning - Instrumentation and...

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Slide 1 RS3™ to DeltaV™ Tuning Conversion by James F. Beall Emerson Process Management February 26, 2013 [email protected]

Transcript of RS3™ to DeltaV™ Tuning - Instrumentation and...

Page 1: RS3™ to DeltaV™ Tuning - Instrumentation and Controlinstrumentationandcontrol.net/.../2017/...DeltaV-Tuning-Conversion.pdfSlide 3 RS3 and DeltaV Tuning Constant Units RS3 DeltaV

Slide 1

RS3™ to DeltaV™ Tuning

Conversion

by

James F. Beall

Emerson Process Management

February 26, 2013

[email protected]

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Slide 2

“ All PIDs are not Created Equal”

• Units of RS3 and DeltaV Tuning Constants,

including PV filter

• PID Form

• RS3 – Standard

• DeltaV – Standard (default) or Series

• ARW settings

• PID “Structure” Options

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Slide 3

RS3 and DeltaV Tuning Constant Units

RS3 DeltaV

• Gain %PB1 or Gain1,2 Gain2

• Reset Second, minute or hour3 Second

• Rate Second, minute or hour3 Second

• PV_Filter Note 4 Second

• Notes

1. Selected on a system wide basis

2. Gain has units of %OUT/%PV

3. Selected on a loop by loop basis, Rate and Reset units can be

different

4. See next slide

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Slide 4

RS3 PV Filtering

• PV filtering is provided on the Analog-In block. It is a first

order filter, enter the time constant in seconds

• Additional filtering is provided in the PID block if

Derivative is activated (PID, PD or ID), even if Rate = 0.

• The PID filter is non adjustable and its first order time

constant is the greater of (2*Sample time) or (Rate/8).

Note “sample time” is the greater of the ControlBlock

sample time, if configured, or the Controller Processor

card scan time. Units are selectable as seconds, minutes

or hours.

• Note the PID filter applies to the value being acted upon

by the Proportional, Integral and Derivative terms. This is

different than DeltaV where this filter (α*Rate) is applied

only to the value going to the Derivative function.

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Slide 5

PID Form – Parallel, Standard, or Classical

• Three Common PID Forms

– Parallel Form

– Standard (aka ISA) Form,

– Series (aka Classical) Form.

• The same tuning constants may produce

different response in each PID Form

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Slide 6

PID “Form” Selection

• RS3 has a “Standard” form

• DeltaV is selectable – “Series” or “Standard”

– “Standard” is the DeltaV default selection

• If the Derivative is not used (Rate = 0 min),

then “Series” and “Standard” are the same

• Use the “Standard” Form in DeltaV!

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Slide 7

Series and Standard Forms

• Series

• Standard

PROCESS

PV +

- SP

Output

+

Error

+

+

P

I

D SD

T

sR

T1

CK

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Slide 8

RS3 Tuning Conversion

• Choose DeltaV Form = Standard (default) for

ease of conversion

• So, DeltaV Tuning will be simply a conversion of

units:

Parameter RS3 DeltaV (Standard Form)

Gain %PB Gain = 100/%PB

Gain Gain = Gain

Reset Ti - seconds Reset = Ti

Ti - minutes Reset = 60*Ti

Ti - hours Reset = 3600*Ti

Rate Td - seconds Rate = Td

Td - minutes Rate = 60*Td

Td - hours Rate = 3600*Td

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Slide 9

RS3 PV Filtering

• The default α in DeltaV for filtering ONLY the

signal to the derivative function only is 0.125

(1/8). This is the close to the equivalent of PV

filtering in RS3 when Derivative is active (PID,

PD or ID even if Rate = 0) and you are using a

typical Derivative setting.

• Consider the filter setting in the RS3 Analog-In

block also.

• The DeltaV PID block has a first order PV_Filter,

set in seconds, in addition to the Derivative

filtering above.

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Slide 10

Anti-Reset Windup (ARW) Settings

• IMPORTANT!!!!!!!!

• RS3 performs ARW limits based on the 0-100%

out limits. There are not separate ARW limits.

• DeltaV ARW settings are “OUT EU’s”. Set ARW

limits to OUT LIMITS in DeltaV (range is -10 to

110% of OUT_SCALE, in EU’s)

– If OUT_SCALE = 0-15,000 lb/hr, example ARW

settings would be ARW_LO_LIM= 0 (lb/hr) and

ARW_HI_LIM= 15000 (lb/hr)

• Incorrect DeltaV ARW Limits will cause poor

control action!!

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Slide 11

Anti-Reset Windup (ARW) Settings

ARW Limits use

OUT_SCALE EU’s

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Slide 12

PID “Structure”

• The PID “Structure” has to do with whether the

Gain and Derivative act on the Error (SP-PV) or

on the PV. (Integral (I) action is always on

Error.)

• The RS3 allows you to choose whether the

Proportional (P) acts Error, PV or SP

• The RS3 allows you to choose whether the

Derivative (D) acts Error, PV or SP.

• There are several DeltaV PID Structure options

though it does not allow P and D on SP. The

most common is PI on error, D on PV

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Slide 13

DeltaV PID Structure Options

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Slide 14

Other RS3 PID Considerations

• The RS3 PID has a both the “positional” (default)

and a “velocity” PID implementation. DeltaV has

only the “positional” PID implementation. The

two implementations may act differently when the

output comes out of a limit.

• Check the feed forward scaling systems. Both

RS3 and DeltaV use a “Feed forward Gain” but

the DeltaV PID block has a “feed forward scale”.

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Slide 15

Other RS3 PID Considerations

• RS3 has several more options like error squared,

gap, etc. that can be implemented in DeltaV.

• Gain and Ratio functions in the RS3 Control

Block are implemented in separate blocks in

DeltaV