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Mejore la seguridad y el rendimiento de su planta gracias a la gestión de alarmas, la supervisión de rendimiento y de activos, la visualización web de datos, la optimización, el control avanzado y la sintonía con la nueva herramienta TaiJi.

Repiensen sus métodos de trabajo y obtengan resultados inmediatos gracias a nuestros servicios, nuestra capacitación y nuestra pericia en asesoría. Manejen el cambio inteligentemente con nuestras soluciones probadas.

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June 2006

In this issue

puce Classes
puce Free Seminars
puce Trick of the month: Should I invest in advanced control?
puce To contact us



Coming classes and seminars

Detailed Loop Analysis with ExperTune
June 12-14, Milwaukee, WI

ExperTune Advanced Tools
June 14-16, Milwaukee, WI

PlantTriage - Performance supervision and Process Control Optimization
September 12-14, Houston, TX

PlantTriage, What's new in V6?
September 15, Houston, TX

See our calendar for 2006

Free Seminars

We offer free seminars:
  • Join us for a series of FREE 20-minute sessions in Phoenix, AZ, June 14 2006
    Process Control Data Mining,
    Quickly Tune Control Loops at Start-up,
    Benchmarking Process Performance.

    Click here to learn more.

  • One day in Orange Tx, June 22 2006
    Plant Performance Seminar - "Golden Triangle", TX :
    Squeeze more from your assets by combining alarm management and loop performance.

    Click here to learn more.

This month's tip : Should I invest in advanced control?

  • Where should I start?
  • How to choose?
  • Multi variable, Fuzzy Logic, MPC, DMC, Expert System, which one?
First, what is advanced control? Unfortunately, the definition varies…

Simple loop

A simple loop consist of :
  • Process,
  • Transmitter,
  • Controller, usually PID (Proportional, Integral, Derivative)
  • Valve or Variable Speed Drive (or other device)
The controller could be more than a PID controller:
  • PID plus special functions
    • Variable gain, for example based on controller output
    • Characterizer on controller output or on inputs
    • Gap on error where tuning parameters are different
    • Tuning parameters modified by a condition
    • Different structure for SP changes
    • P2ID
    • Filter on SP
    • Smith Predictor
    • Sloah filter (to reduce waves impact on level controller)
    • Etc.
  • Other controllers types
    • Internal model controller
    • Dahlin
    • Special algorithms

Control strategies

  • Cascade
  • Feedforward
  • Ratio
  • Split range
  • Mid Range or Coarse/Fine
  • Constraint or Override
  • Variable Structure

Multi variable

  • Model based
    • MPC ("Model Predictive Control")
    • DMC ("Dynamic Model Control")
  • Rule based
    • Expert systems (large number of rules to take in account most possible cases)
    • Fuzzy Logic (few simple rules to mimic an operator)
  • Learning based
    • Neural network
  • R.T.O., Real Time Optimization

Loop or strategy or advanced control?

To summarize, often everything different from a simple loop could be qualified of « advanced control ».
Frequently, many strategies and special algorithms are combined together and it is not easy to name it. For example the level loop for boiler drum level is usually a cascade scheme plus feedforward.
Sometimes, we use rules to determine constraints or we use a neural network as a soft sensor.

Control pyramid:

This pyramid illustrate the hierarchy. To move form one level to a superior one, the lower level has to be in perfect order. For example a pump with a too low capacity will not pump more with advanced control!

Conclusions

How many advanced control projects failed? How many systems were turned off after less than a year? How many projects were justified?

Where should we start?

Simple solutions are always preferred. Complexity will be increased if performances (production, quality, etc.) are not sufficient. Profitability analysis should be done to validate project viability. Top Control offer this service; this analysis can be done in days, even in hours.

How to choose?

Choices should be led by needs, not trends of the moment!
For example, if traditional methods failed and a good operator succeeds, maybe constraint control or fuzzy logic could be used. At the opposite, if models are available, multi variable could be an option. Top Control specialist can guide your choices.

Special Algorithms, Complex Strategies, Multi variable, Fuzzy Logic, MPC, DMC, Expert System, which one?

Before increasing complexity, one must defines the needs, the goals, the technical support, the budget, etc. All these approaches have strengths and weaknesses. It is hazardous to build a project on a technology rather than on needs. Top Control has the right expertise to help you decide how you should proceed. Top Control does not rely on a specific product and is independent. Our specialists can also train your personnel to ensure that you stay independent from manufacturers.

To contact us

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