March 2007

In this issue

	Conference and article
	Classes
	Book
	Top Control, Texas
	Trick of the month: Do I need advanced control?
	To contact us

Conference And Article

ExperTune User Group

• "Cascade control", by Michel Ruel, Top Control Inc.
• "Lime Kiln Control", by Martin Emond, Top Control Inc.
• Also: round table, discussions, and various activities

To learn more...

Article
Advantage of Monitoring The Performance Of Industrial Process
Claude Gosselin, Compagnie Minière Québec Cartier, Port-Cartier, Québec, Canada
Michel Ruel, Top Control, Québec, Canada and Hartland WI, USA
in ISA Management Division NewsLetter. If you are a member, see the article.

Upcoming Classes And Seminars

Analytical Methods For Troubleshooting And Control Loop Tuning
March 20-22, Calgary, AB and
May 8-10, Sault Ste-Marie, ON

Control Valve Selection
March 27-29, Ottawa, ON

Seminar on Advanced Tools in Process Control
April 24-26, Houston, TX

PlantTriage - Performance Supervision And Process Control Optimization
May 1-3, Hartland, WI and
September 18-20, Hartland, WI

Detailed Loop Analysis With ExperTune
May 14-16, Houston, TX

ExperTune Advanced Tools
May 16-18, Houston, TX

PID Loop Tuning
June 5, Portland, ME

Introduction to Instrumentation and Process Control, Process Control Basics for Non-Specialists
June 6-7, Portland, ME

See our 2007 courses calendar

Book

Many chapters are written by Michel Ruel in "Process Control, Vol. 2", edited by Bela Liptak.
To learn more...

Top Control in Texas

Starting in Spring 2007, Top Control will have a staff member based in Houston, TX; Martin will be covering the Gulf states.

This Month's Tip : Do I need advanced control?

When evaluating advanced control systems, you must consider:

• the process;
• the control objectives;
• the operation;
• the control systems.

Process

All basic instrumentation (valves, transmitters) has to be in good shape. Do loops interact? If not, basic PID control is probably sufficient. If yes, an advanced control system implemented using standard functions from your DCS could be developed. Alternatively, separate advanced control systems can be used to deploy complex control strategies.

Can the process reach expected control performance following efficient optimization? If not, first consider advanced regulatory control strategies such as characterizer, cascade, feedforward, ratio, override, split-range, coarse and fine, and variable structure. These strategies can be developed in your control system. If this is not enough, you will need to select a modeled based or rule based system (see below).

Is dead time excessive? If yes, first consider dead time compensation on the integral action (for its better robustness), then consider model predictive control (e.g., Smith predictor, internal model control). However, keep in mind that this latter is not robust if the dead time varies. Feedforward should always be evaluated first.

Model based or rule based system?

If the model varies, consider to add fuzzy logic to your system. This is a major change in the approach: doing so, control strategies are no longer based on models but rather on a set of rules. A fuzzy logic system behaves as an excellent operator, manipulating variables according to rules as an operator would do. (We can drive cars in many different areas without knowing all the details of their "models"; indeed, intuitively our drive is based on rules.)

Is the process comprised of many cross-interactions with multiple variables? If yes, and if the process model is pretty much constant, then an advanced multi-variable approach might be good to decouple variables from interaction. If there are a few interactions, feedforward paths will do the work.

Control objectives

Constraints are better handled by advanced control systems since the ability of PID schemes is relatively poor - unless astute programming is done. Advanced control systems and model predictive control predict future; hence take into account constraints when manipulating variables.

Operation procedures

Grade changes, abnormal conditions, and start-ups are good candidates for advanced control schemes. We can even develop control strategies to find the soft spot to operate at your process based on economical or other conditions. Again, these strategies can be implemented in your DCS or in a separate system.

Control systems

Advanced control systems implementation:

• Using basic PID functions and adding feedforward, cascade, override or other special functions;
• Using standard functions in your DCS or PLC, also named "advanced regulatory control";
• Advanced control package offered by many vendors, running on a different system that exchanges data with the DCS or PLC.

At Top Control, we are specialized in process optimization, so we can:

• Help you select the best approach for your plant;
• Optimize your regulatory control before implementing an advanced control system;
• Develop these advanced control strategies in your system or implement special advanced control packages;
• Train your personal (design, maintenance, operation);
• Support your team to help you make the right decision.

To Contact Us

	Lévis' office	+1 (418)834-4321
	Pointe-Claire's office	+1 (514)695-3492
	Hartland's office	(877)867-6473
	Toll free	(877)867-6473
	Email	info@topcontrol.com