The EXACT Pattern Recognition Adaptive Controller, a User-Oriented Commercial Success

  • E. H. Bristol


A pattern recognition-based adaptive control concept (termed EXACT 1) has been commercialized successfully as a universal successor to The Foxboro Company’s current electronic controllers. The delay in market entry was a consequence of a design, incredible (for different reasons) to both academic and practitioner. Yet it evolved not as a regression from the now standard, theory motivated, model-based designs, but as an artificial intelligence related advance over them, suggested by studies on the effects of mismodeling. In this regard, it offers superior adaptation through direct performance feedback. In the absence of a general adaptation theory, an essential element contributing to the development of the EXACT concept was an experimental analysis technique which permitted rigorous demonstration of the general applicability of the method.

Its current success is also derived from a clear understanding of the fundamental role of the PID controller in process control, a role that has allowed the PID controller to prevail and outperform practically its many proposed competitors, each of which, by itself, exhibits apparently superior theoretical performance. The distinctive character makes the design an interesting case study subject of the interplay between market, technology, and innovation. The EXACT Controller has been recognized by three commercial awards.


Adaptive Design Nonminimum Phase Adaptive Loop Adaptive Process Control Exact Controller 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. [1]
    T.W. Kraus and T.J. Myron, “Self-Tuning PID Controller Uses Pattern Recognition Approach,” Control Engineering, vol. 31, No. 6, pp. 106–111, June 1984.Google Scholar
  2. [2]
    E.H. Bristol and T.W. Kraus, “Life with Pattern Recognition,” 1984 ACC, San Diego, Ca., June 6–8, Session TP3, pp. 888–892.Google Scholar
  3. [3]
    E.H. Bristol, “Adaptive Control Odyssey,” ISA Conference, Philadelphia, October 1970, Paper 561–70.Google Scholar
  4. [4]
    E.H. Bristol, “Pattern Recognition: An Alternative to Parameter Identification in Adaptive Control,” Automatica, vol. 13, pp. 197–202, March 1977.zbMATHCrossRefGoogle Scholar
  5. [5]
    E.H. Bristol, “Experimental Analysis of Adaptive Controllers,” Third Yale Workshop on Applications of Adaptive Systems Theory, Center for Systems Science, Yale University, New Haven, Ct., June 15–17, 1983, pp. 249–253.Google Scholar
  6. [6]
    C.E. Rohrs, G. Stein and K. Aström, “Uncertainty in Sampled Systems,” 1985 ACC, Boston, Ma., June 19–21, 1985, pp. 95–97.Google Scholar
  7. [7]
    H.J. Chizeck, G.I. Voss and P.G. Katona, “A Self Tuning Controller for Nonminimum Phase Plants,” Internal Memo, Case Western Reserve University, Cleveland, Oh. 44106, November 1984.Google Scholar

Copyright information

© Springer Science+Business Media New York 1986

Authors and Affiliations

  • E. H. Bristol
    • 1
  1. 1.The Foxboro CompanyFoxboroUSA

Personalised recommendations