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Basic Process Control Strategies

In a simple control system, a process variable (PV) is measured and compared with a setpoint value (SP). A manipulated variable (MV, or output) signal is generated by the controller and sent to a final control element, which then influences the process variable to achieve stable control. The algorithm by which the controller develops its output signal is typically PID (Proportional-Integral-Derivative), but other algorithms may be used as well:


This form of simple control may be improved upon and expanded for a greater range of process applications by interconnecting multiple controllers and/or redirecting measurement and control signals in more complex arrangements. An exploration of some of the more common control system configurations is the subject of this chapter.


Supervisory control

Cascade control

Ratio control

Relation control

Feedforward control

Feedforward with dynamic compensation

    1 Dead time compensation

    2 Lag time compensation

    3 Lead/Lag and dead time function blocks

Limit, Selector, and Override controls

    1 Limit controls

    2 Selector controls

    3 Override controls



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Lavigne, John R., An Introduction To Paper Industry Instrumentation, Miller Freeman Publications, Inc., San Francisco, CA, 1972.

Lavigne, John R., Instrumentation Applications for the Pulp and Paper Industry, The Foxboro Company, Foxboro, MA, 1979.

Lipt´ak, B´ela G., Instrument Engineers’ Handbook – Process Control Volume II, Third Edition, CRC Press, Boca Raton, FL, 1999.

Mollenkamp, Robert A., Introduction to Automatic Process Control, Instrument Society of America, Research Triangle Park, NC, 1984.

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Shinskey, Francis G., Energy Conservation through Control, Academic Press, New York, NY, 1978.

Shinskey, Francis G., Process-Control Systems – Application / Design / Adjustment, Second Edition,

McGraw-Hill Book Company, New York, NY, 1979.

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