Editing Proportional–integral–derivative controller (section)

===Cohen–Coon parameters===
This method was developed in 1953 and is based on a first-order + time delay model. Similar to the [[Ziegler–Nichols method]], a set of tuning parameters were developed to yield a closed-loop response with a decay ratio of <math>\tfrac{1}{4}</math>. Arguably the biggest problem with these parameters is that a small change in the process parameters could potentially cause a closed-loop system to become unstable.