Tuning smith predictors using simple formulas derived from optimal responses

Good control of processes with long dead time is often achieved using a Smi th predictor configuration. However, not much work has been carried out on obtaining simple tuning rules for a Smith predictor scheme. This paper deve lops optimal analytical tuning formulas for proportional-integral-derivativ e (PID) controllers in a Smith predictor configuration assuming perfect mat ching. Exact limit cycle analysis has been used to estimate the unknown par ameters of a first-order plus dead time (FOPDT) or second-order plus dead t ime (SOPDT) plant transfer function. Simple analytical tuning rules based o n these FOPDT and SOPDT are then derived which can be used to tune a PID co ntroller in a Smith predictor scheme. Some examples are given to show the v alue of the approach presented.