Cohen-Coon tuning
An open-loop reaction-curve tuning method from the same era as Ziegler-Nichols, fitted for setpoint response rather than load.
What it means
Cohen-Coon is a reaction-curve method of the same generation as Ziegler-Nichols, built on the same three FOPDT numbers. Where the Ziegler-Nichols open-loop rules target a quarter-amplitude response, the Cohen-Coon formulas were fitted to give a fast, well-damped response to setpoint changes.
The controller's three terms are computed from the ratio of dead time to time constant, and the formulas are explicit enough to apply by hand. That ease is why the method still appears in textbooks long after the experiments it was fitted to.
The premise is the weakness. Tuning fitted to a particular disturbance shape is aggressive when the loop's real disturbances come from elsewhere, and on an operating plant load regulation — not setpoint — is usually the job. Cohen-Coon makes a defensible starting point and a poor gospel.
Related
Where this comes up
Last reviewed 2026-09-18.