Achieving Target Control Performance Using Fieldbus Devices

• • • Terry Blevins Marcos Peluso Dan Christensen [File Name or Event] Emerson Confidential 27-Jun-01, Slide 2

Presenters

Introduction

• • • • • • Overview – FF Block Applications that May be Addressed – Single loop feedback control – – Feedforward control Cascade control – Interlock, Input selection, Flow integration, Calculations and characterization Control Performance – Variation if Block Execution Time – – Impact of Device Response Time and Slot Time What determine Macrocycle – Example – Single Loop Splitting Control Between Fieldbus and the Control System – Impact on delay on loop response, guidelines – – Future – Assigning blocks to execute in DeltaV H1 card Future – Viewing Execution Schedule Summary References [File Name or Event] Emerson Confidential 27-Jun-01, Slide 3

FF Function Blocks Function Blocks Addressed by FF Interoperability Testing, v4.5

• • • • • • • AI – Analog Input AO – Analog Output PID – PID Control DI – Discrete Input DO – Discrete Output ISEL – Input Selector ARITH – Arithmetic • • • • • • SC – Signal Characterizer INT – Integrator MAI – Multiple Analog Input MAO – Multiple Analog Output MDI – Multiple Discrete Input MDO – Multiple Discrete Output [File Name or Event] Emerson Confidential 27-Jun-01, Slide 4

Applications that may be addressed using FF function block capability

• • • • • • • Single loop feedback control Feedforward control Cascade control Interlock based on a discrete input Input selection when redundant measurements are available Flow integration Calculations and signal characterization [File Name or Event] Emerson Confidential 27-Jun-01, Slide 5

Example: Single Loop

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Feed Tank FC 101 FT 101

Feed

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Single Loop - Fieldbus

Example: Interlock Based on Status of Blocking Valve

FC 151 FT 151

Reactor 1 Feed

ZT 150

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Interlock Example: Use of Discrete Input From Upstream On-Off Valve

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Example: Selection of Redundant Measurement

Feed A

Static Mixer AC 302 AY 302 AT 301 AT 302 Reactor 1

Feed B

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Automatic Input Selection for Redundant Measurements

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Example: Cascade Control

TC 201 TT 202 TC 202

RSP

TT 201

Coolant

Reactor 1

Discharge

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Cascades Loop - Fieldbus

Arithmetic Block May be used to address a Variety of Calculations

• • • • • • • • • Flow Compensation – Linear Flow Compensation – Square root Flow Compensation – Approximate BTU Flow Multiply and Divide Average of inputs Sum of inputs Fourth order polynomial Simple HTG compensate level [File Name or Event] Emerson Confidential 27-Jun-01, Slide 14

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Example: Calculation and Integration of Mass Flow

Pressure & Temperature Compensation

FY 3-4 FY 3-4

Totalized Mass Flow

TT 3-4 PT 3-4 FT 3-4

Process Steam

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Example: Arithmetic and Integrator Function Blocks

Fieldbus enables Multi-sensor Applications

Steam [File Name or Event] Emerson Confidential 27-Jun-01, Slide 17 Feed

Distillate Receiver

Distillate

Column TE 801A TE 801B TE 801C TE 801D TE 801E TT 801 Distillation

Bottoms

Multi-sensor Applications (Cont)

• Chemical Reactors Process In

TT 901 TE 901 A-H

Cooling Fluid In Cooling Fluid Out Process Out [File Name or Event] Emerson Confidential 27-Jun-01, Slide 18

Example: Multiple Analog Input Block Supports a Maximum of 8 Inputs From a Fieldbus Device

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Other Function Blocks Are Defined by FF and Supported by Some Devices

• • • • • • • • • Blocks not included in device testing/registration ITK v4.5 , v5.0

DC – Device Control (motor control) OS – Output Splitter (split range control) LL – Lead Lag (dynamic compensation of feedforward) DT – Deadtime (dynamic compensation of feedforward) SPG – Setpoint Ramp Generator (Program setpoint change) AAL – Analog Alarm (alarming based on calculated value) CS – Control Selector (override control for constraint handling) B/G – Bias Gain (coordination of multiple loops) RA – Ratio (blending to specified feed ratio) [File Name or Event] Emerson Confidential 27-Jun-01, Slide 20

Control Performance Using Fieldbus

• • • The control performance that may be achieved is dependent on many factors: Function block execution, maximum response time for compel data and slot time ( dependent of the device technology/design – specific to manufacturer) Whether control is done in the field or in the control system (customer decision) Scheduling of block execution and communications on the FF segment (dependent of control system design) [File Name or Event] Emerson Confidential 27-Jun-01, Slide 21

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AI Function Block Execution Time

AI Function Block Execution Time (Based on 22 manufacturers)

0-50msec 51-100msec 101-150msec 151-200msec

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AO Function Block Execution Time

AO Function Block Execution Time (Based on 13 manufacturers)

0-50msec 51-100msec 101-150msec 151-200msec

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PID Function Block Execution Time

PID Function Block Execution Time (Based on 16 manufacturers)

0-50msec 51-100msec 101-150msec 151-200msec

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DI Function Block Execution Time

DI Function Block Execution Time (Based on 9 Manufacturers)

0-25msec 26-50msec 51-75msec 76-100msec 101-125msec

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DO Function Block Execution Time

DO Function Block Execution Time (Based on 10 Manufacturers)

0-25msec 26-50msec 51-75msec 76-100msec 101-125msec

Calculation Block Execution Times

Execution Time of Blocks Used in Calculations

101-125msec 51-75msec 0-25msec 0 0.5

1 1.5

2

Number of Manufacturers

2.5

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Third Generation Devices Offer Significant Improvement if Block Execution Time

Example*:

Second Generation AI = 30ms PID = 45ms Third Generation AI = 20ms PID = 25ms Improvement 33% 44%

* Execution times based on Rosemount 3051

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Variation in Device Response Time of Different Fieldbus Devices

Maximum Response Delay Time (Based on 29 Manufacturers)

0-5msec 6-10msec 11-15msec 16-20msec [File Name or Event] Emerson Confidential 27-Jun-01, Slide 29

Typical Slot Time for Different Devices

Slot Time (Based on 29 Manufacturers)

<1.1msec

1.1-1.5msec

1.6-2.1msec

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Control Execution is Scheduled Based on the Segment Macrocycle

A Macrocycle is determined by: Function Block Execution times.

- Transmission time of the cyclic messages.

-Gaps between messages determined by the Network parameters.

-Time reserved for acyclic messages

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Macrocycle

• • Function Block execution time depends on the type of block and on the hardware and software design.

In the time calculation, only blocks that must be executed consecutively are considered.

TT FT FCV AI=30 AI=30 PID=45 PID=45 Cascade Control Example AO=80

• • Block Execution Time = 30+45+45+80 = 200 ms *Note that the AI in the flow device is executed in parallel.

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Scheduled Control Execution

0 AI PID CD DAT A AO CD DATA 2.3 ms Macro Cycle Bus Traffic 5.4 ms Macro Cycle Macro Cycle Macro Cycle 250 ms Macro Cycle

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Macrocycle

MID MID FB CD DATA DATA DATA FB (MRD+ 2xSLT) SLT - Slot time MRD - Maximum Response Delay MID - Minimum Inter PDU Delay Some manufactures may by default assume conservative constant values for MRD and SLT. The user may change these values.

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Network Parameters

• • Network Parameters establish how the network operates.

The LAS must be set with the larger parameter values of the devices participating in the Network.

LAS MRD= 4 4 Backup LAS SLT = 10 MRD= 3 MID = 12 Link Settings SLT = 8 MRD= 3 MID = 10 SLT = 4 MRD= 4 MID = 8

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Impact of Network Parameters on Maximum Number of Communications/Second

SLT= 16 MRD=10 MID= 12 CD 2.3

41 49.50ms

SLT= 8 MRD=3 MID=12 CD DATA 2.3

6.14

17 ms 5.4

SLT= 1 MRD=1 MID= 1 CD DATA CD 2.3

8 ms 5.4

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3.1

CD DATA 5.4

3.1

CD

Ideal Max.

20 / s

Ideal Max.

58 / s

Ideal Max.

125 / s

Minimum Execution Time With Only One(1) Control Loop on an H1 Segment

AI PID XFR AO XFR 20ms 25ms 30ms 60ms 30ms Macrocycle = 165 ms

Assumptions: 3 rd Generation Transmitter, AI&PID executed in Transmitter, Second generation Valve executes AO

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Executing PID in the Valve Reduces the Number of Communications But Increases Loop Execution Time

AI XFR PID AO 20ms 30ms 120ms 60ms Macrocycle = 230 ms

Assumptions: 3 rd Generation Transmitter, AI executed in Transmitter, Second generation Valve executes AO&PID

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Minimum Execution Time With Only Two(2) Control Loop on an H1 Segment

AI PID XFR AO XFR AI PID XFR AO XFR ACYCLIC 20ms 25ms 30ms 30ms 60ms 30ms 55ms Macrocycle = 250 ms

Assumptions: 3 rd Generation Transmitter, AI&PID executed in Transmitter, Second generation Valve executes AO, 50ms for every 125ms of the execution schedule (for display update)

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Impact of Splitting Control Between Fieldbus and Control System

• • • Execution in the control system is typically 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 variable delay.

Added delay will increase variability in the control loop.

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PID executed in the Control System

PID PID 0

Minimum Delay

PID 0 CD DAT A AI 0 AO

Max Delay

CD DATA

Macrocycle

PID CD DAT A AI CD DATA AO

Macrocycle

250 250 250

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Recommendation on Splitting Control Between Fieldbus and Control System

• • • Oversampling of the fieldbus measurement to compensate for lack of synchronization i.e. setting macrocycle faster than control execution is often not practical if the loop execution is fast Conclusion: Execute control loops in Fieldbus for better performance.

If target execution is ½ sec or faster, then limit the number of control loops to no more than two(2) per segment. [File Name or Event] Emerson Confidential 27-Jun-01, Slide 43

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Execution of Function Block in H1 Card

• • • Capability is targeted of v9.x release of DeltaV Will allow synchronization of block execution on the H1 card with those on the segment i.e. the H1 card acts as a FF device with function blocks.

Block execution time on H1 cards is significantly less and will allow a shorter macrocycle or more to be done within a given macrocycle.

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Auto-Assigned Execution to H1 – Module Property

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PID Execution in The Controller

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PID Assigned to Execute in H1 Card

PID Assigned to Execute in the Device

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Viewing Execution Schedule

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Schedule – PID in Controller

Schedule – PID in H1 Card

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Schedule – PID in FF Transmitter

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Schedule – Showing Execution Divided Between Controller, H1 and FF Device

Summary

• • • • • A variety of control applications may be implemented using the function block capability of FF devices.

The performance of fast process control loops may be influenced by block execution times and number of loops implemented on a segment.

Control may be split between the DeltaV Control and FF devices for slower processes.

Future DeltaV releases are targeted to support assignment of function blocks to execute in the H1 card. This new capability will allow a variety of applications to be addressed with no impact on control performance. Please direct questions or comments on this presentation to Terry Blevins ( [email protected]

) or Marcos Peluso ( [email protected]

). [File Name or Event] Emerson Confidential 27-Jun-01, Slide 55

• • • • • • • •

Where To Get More Information

“Reliability and Performance of Fieldbus installations (Tutorial)”, Marcos Peluso, Terry Blevins, ISA2002.

“Application of High Speed Ethernet With Fieldbus Foundation Devices (Tutorial)”, Marcos Peluso, Terry Blevins, ISA2001 “Advanced Functionality and Diagnostics of Fieldbus Devices (Tutorial)”, Marcos Peluso, Terry Blevins, ISA2000 “Rules of thumb for applying Fieldbus (Tutorial)”, Marcos Peluso, Terry Blevins, ISA1999.

“Installation and Checkout of Foundation Fieldbus Installations (Tutorial)”, Marcos Peluso, Terry Blevins, Jim Cameron, Duane Toavs, ISA1998.

“Planning and Engineering Design for Foundation Fieldbus Installations (Tutorial)”, Marcos Peluso, Terry Blevins, ISA1997 “Application Solutions Using Fieldbus Devices (Tutorial)”’ Marcos Peluso, Terry Blevins, ISA1996.

“How Fieldbus May Influence Your Next Project (Tutorial)”, Marcos Peluso, Terry Blevins, Tom Kinney, ISA1995.

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