PID Control Of Sampled Measurements - Greg McMillan Deminar Series

Interactive Opportunity Assessment Demo and Seminar (Deminar) Series for Web Labs – PID Enhancement for Sampled Measurements April 7, 2010 Sponsored by Emerson, Experitec, and Mynah Created by Greg McMillan and Jack Ahlers

Welcome
Gregory K. McMillan
Greg is a retired Senior Fellow from Solutia/Monsanto and an ISA Fellow. Presently, Greg contracts as a consultant in DeltaV R&D via CDI Process & Industrial. Greg received the ISA “Kermit Fischer Environmental” Award for pH control in 1991, the Control Magazine “Engineer of the Year” Award for the Process Industry in 1994, was inducted into the Control “Process Automation Hall of Fame” in 2001, and was honored by InTech Magazine in 2003 as one of the most influential innovators in automation. Greg is the author of numerous books on process control, his most recent being Essentials of Modern Measurements and Final Elements for the Process Industry. Greg has been the monthly “Control Talk” columnist for Control magazine since 2002. Greg’s expertise is available on the web site: http://www.modelingandcontrol.com/

The Latest on Smart and Wireless Instrumentation Royalties are donated to the University of Texas Research Campus for Energy and Environmental Resources for Development of Wireless Instrumentation and Control

Top Ten Ways to Make Process Control Enticing
(10) Travel programs focusing on the process control systems of cruise ships
(9) Sci-fi flicks devoted to the process control systems in star ships
(8) Reality shows where teams compete to improve process control performance
(7) Entourage shows where groupies use process control to keep their star from self-destruction
(6) Sport analysis programs where commentators and listeners talk about the dynamics and feedforward control opportunities in football
(5) Robot movies where advanced parallel processing robots optimize plants
(4) Detective shows where a special investigator with cute compulsive obsessive habits and an incredibly keen mind for details solves mysterious process control problems
(3) “Who done it” novels where the culprit is a bad acting control valve
(2) Web video with cute animal antics in the foreground and engineers talking about process control opportunities in the background
(1) “Cash for clunkers” programs to replace inefficient old distributed control systems, transmitters, and valves

Self-Learning Web Lab (Web Access Starts May, 2010)

Loop Lab01 Demo of Base Case
Show access to “Operate Run” user interface
Show access to PID faceplate and detail
Show access to “Process History View” trend chart
Make setpoint changes to show existing response
Show access to valve, process, and measurement parameters for sensitivity, noise, and dynamics

Question
What will dramatically improve the performance of loops using at-line analyzers making tuning easier and virtually eliminating oscillations?
What can increase control valve packing life by factor of 10?
What can make battery life of wireless measurements a non issue?
What will eliminate the limit cycle from measurement sensitivity limits?
What will smoothly handle a loss in I/O communication?
Answer : An Enhanced PID

Loop Lab01 Demo of Sample Time Effect
Look at response of traditional PID for base case
Increase measurement sample time to 20 sec and set sensitivity out of range (e.g. 100%)
Make setpoint changes to show traditional PID response to large sample time (e.g. twice process time constant) for self-regulating process

PID integral mode is restructured to provide integral action to match the process response in the elapsed time (reset time set equal to process time constant)
PID derivative mode is modified to compute a rate of change over the elapsed time from the last new measurement value
PID reset and rate action are only computed when there is a new value
If transmitter damping is set to make noise amplitude less than sensitivity limit, valve packing and battery life is dramatically improved
Enhancement compensates for measurement sample time suppressing oscillations and enabling a smooth recovery from a loss in communications further extending packing -battery life
http://www.modelingandcontrol.com/repository/WirelessPrimeTime.pdf Traditional and Enhanced PID (PIDPLUS)

Look at response of traditional PID for large sample time
Cut reset time in half (double reset action)
Make setpoint changes to show traditional PID response to large sample time (e.g. twice process time constant) for self-regulating process with halved reset time

Self-Learning Web Lab (Web Access Starts May, 2010) Checkout on March 10 – April 2 Entries on Integrated and Peak Errors on the website http://www.modelingandcontrol.com/

Peak and Integrated Error Check List

Look at response of traditional PID for halved reset time for large sample time
Change to enhanced PID (PIDPLUS)

Control Studies of Reset Factor & Wireless PID for Real Time Integrating Process (20 sec analyzer sample time) Improvement in stability is significant for any integrating process with analyzer delay Reset Factor = 0.5 Standard PID Standard PID Standard PID Reset Factor = 1.0 Reset Factor = 2.0 Enhanced PID Enhanced PID Enhanced PID Reset Factor = 0.5 Reset Factor = 1.0 Reset Factor = 2.0

Control Studies of Lambda Factor & Wireless PID for Real Time Integrating Process (20 sec analyzer sample time) Improvement in stability is significant for any integrating process with analyzer delay Gain Factor = 1/1.5 Standard PID Standard PID Standard PID Gain Factor = 1/2.0 Gain Factor = 1/2.5 Enhanced PID Enhanced PID Enhanced PID Gain Factor = 1/1.5 Gain Factor = 1/2.0 Gain Factor = 1/2.5

Look at response of enhanced PID to see if it decayed the oscillations started by traditional PID
Make setpoint changes to show enhanced PID response to large sample time (e.g. twice process time constant) for self-regulating process with halved reset time

Control Studies of Reset Factor & Wireless PID for Real Time Self-Regulating Process (40 sec analyzer sample time) Improvement in stability and control is dramatic for any self-regulating process with analyzer delay Standard PID Standard PID Standard PID Reset Factor = 0.5 Reset Factor = 1.0 Reset Factor = 2.0 Enhanced PID Enhanced PID Enhanced PID Reset Factor = 0.5 Reset Factor = 1.0 Reset Factor = 2.0

Control Studies of Lambda Factor & Wireless PID for Real Time Self-Regulating Process (40 sec analyzer sample time) Improvement in stability and control is dramatic for any self-regulating process with analyzer delay Standard PID Standard PID Standard PID Gain Factor = 1/1.5 Gain Factor = 1/2.0 Gain Factor = 1/2.5 Enhanced PID Enhanced PID Enhanced PID Gain Factor = 1/1.5 Gain Factor = 1/2.0 Gain Factor = 1/2.5

Loop Lab01 Demo of Sensitivity Effect
Look at setpoint response of enhanced PID with halved reset time for large sample time
Set measurement sample time to out of range (e.g.1000 sec) and set sensitivity to large value (e.g. 2%)
Change to traditional PID and make setpoint change to show traditional PID response to poor sensitivity

Top Ten Reasons I Use a Virtual Plant
(10) You can’t freeze, restore, and replay an actual plant batch
(9) No separate programs to learn, install, interface, and support
(8) No waiting on lab analysis
(7) No raw materials
(6) No environmental waste
(5) Virtual instead of actual problems
(4) Batches are done in 14 minutes instead of 14 days
(3) Plant can be operated on a tropical beach
(2) Last time I checked our wallet I didn’t have $100,000K
(1) Actual plant doesn’t fit in my suitcase

Virtual Plant Synergy Dynamic Process Model Online Data Analytics Model Predictive Control Loop Monitoring And Tuning DCS batch and loop configuration, displays, and historian Virtual Plant Laptop or Desktop Personal Computer Or DCS Application Station or Controller Embedded Advanced Control Tools Embedded PAT Tools Process Knowledge

Virtual Plant Continuity Explore Discover Prototype Deploy The consistent platform offered by the virtual plant can insure maximum flow of knowledge gained at each step in the commercialization process from bench top to pilot plant to industrial plant operation Train

Look at response of traditional PID with halved reset time for poor measurement sensitivity
Change to enhanced PID (PIDPLUS) and make setpoint change to show enhanced PID response for poor sensitivity

Demographic Time Bomb
Average age of process industry worker is over 50
Half of the current work force will retire (more than 500,000 workers) in 5 to 10 years
Irreplaceable knowledge loss
Newer generation of workers with less mechanical inclination and exposure
Scenario for control engineers and technicians may be even more severe due to suspension in hiring in 1980s
Process plants in danger of closing due to lack of qualified personnel
Delayed retirement plans will be accelerated as equity markets recover

Virtual Plant Essentials DeltaV Simulate Product Family MiMiC Simulation Software

Dynamic, Accurate Simulations “High Fidelity”
Advanced IEC Objects and Functions with Streams
Thermo / Flash / Stream Property Functions
Advanced Modeling Core Objects
Vessel, Valve, Pump, PRV, HX, DHX, Stream T
PF Solver
Energy Management Objects
Boiler with Furnace, Steam Header, Desuperheater, Fuel, Turbine
Distillation Objects
Column, Reboiler, Stripper
Separator Objects
2-phase, 3-phase Separator, Physical Absorber
Process Model Development

Graphics and Simulation Control

Look at response of enhanced PID with halved reset time for poor measurement sensitivity to see if it stopped the limit cycle from the traditional PID

Help Us Improve These Deminars! WouldYouRecommend.Us/105679s21/

Join Us April 21, Wed 1:00 CDT
PID Control of Valve Sticktion and Backlash
Look for a recording of Today’s Deminar later this week at:
www.ModelingAndControl.com
www.EmersonProcessXperts.com

QUESTIONS?

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PID Control Of Sampled Measurements - Greg McMillan Deminar Series

by Jim Cahill on Apr 07, 2010

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PID Control Of Sampled Measurements - Greg McMillan Deminar Series Presentation Transcript