Set point weighted modified Smith predictor with PID filter controllers for non-minimum-phase (NMP) integrating processes

A simple modified Smith predictor design for the control of non-minimum-phase integrating processes with/without a zero is proposed. The method consists of two controllers, one for set point tracking and the other for disturbance rejection. The controllers are designed based on direct synthesis approach. The set point tracking controller is designed as a proportional-integral-derivative (PID) with lag filter and the disturbance rejection controller is designed as a proportional-derivative (PD) with lead lag structure. Typical types of integrating processes with/without zero are considered and the controllers are designed in a unified approach for all the types of integrating processes. Extensive simulation studies have been carried out on various integrating processes with/without zero. The present method gives good disturbance rejection response and significant improvement when compared to the recently reported methods in the literature.