IMC-PID Controller Design - An Extension

Abstract

PID controller design based on Internal Model Control (IMC) design procedure by Rivera and co-workers has been extended to cover a wider range of process models. PID tuning parameters for processes up to second-order with first-order numerator dynamics and dead time will be given with only one tuning parameter (closed-loop time constant). In order to obtain the PID formulation, dead time is approximated by either a first-order Padé or a first-order Taylor series expansion depending on whether a PI or PID controller is desired. Various industrial PID implementations which require different PID settings will also be examined in this paper.Several examples including a first-order plus dead time, second-order plus dead time and inverse response, an industrial level control problem, and a nonlinear distillation column model will be used to compare the performance of IMC-PID controller design with more traditional tuning rules, eg, Ziegler-Nichols, Cohen-Coon, and frequency response maximum peak criterion. Model mismatches in process gain, dead time, and time constant will also be introduced to compare the robustness of various controller design methods.