Two-Degree-of-Freedom PID Controllers — Their Functions and Optimal Tuning

Abstract "Two-degree-of-freedom (2DOF) PID controller" is a 2DOF controller whose serial compensator is a PID element and whose feedforward compensator is a PD element. In this article, the previous researches on its equivalent transformations and interpretations of its advantages are surveyed first. Then, formulae for optimal tuning is reported.