Three term controller selection, tuning, and interaction factors

’ Controller interaction factor. K ~ [ Effective proportional gain of controller r’ Effective controller time constant ratio T~IT;. rlax Maximum possible value of r’. T Basic process time constant. ~’’~, ?&dquo;~ Controller numerator time constants. T D Effective derivative time constant. T; Effective integral time constant. tu The ultimate period of sustained oscillation. Z,Z¡,Z2 Controller zeros. t The relative damping associated with the dominant underdamped denominator factor of a process transfer function. ~ r The required value of relative damping associated with the response of the tuned system. tz The relative damping associated with the controller numerator.