Relay based PI-PD design for stable and unstable FOPDT processes

Abstract A simple identification method based on relay feedback test is proposed for stable and unstable first order plus time delay (FOPDT) processes. Initially, a relay in parallel with a proportional controller is applied to an inner feedback controller-stabilized process on the usual manner to induce limit cycle output. From the measurements made on the limit cycle output, two parameters of the FOPDT process model are estimated. The steady state gain of the FOPDT process is assumed to be known a priori. Then, these parameters are used to design a two degree of freedom proportional-integral–proportional-derivative (PI–PD) controller based on the loop phase margin and gain margin criteria. Simulation examples illustrate the effectiveness and the simplicity of the proposed identification and control method.

[1]  Nusret Tan,et al.  A simple procedure for improving performance of PID controllers , 2003, Proceedings of 2003 IEEE Conference on Control Applications, 2003. CCA 2003..

[2]  M. Chidambaram,et al.  Set Point Weighted Pid Controllers For Unstable Systems , 2005 .

[3]  M. Morari,et al.  Internal model control: PID controller design , 1986 .

[4]  Jin Hyun Park,et al.  An Enhanced PID Control Strategy for Unstable Processes , 1998, Autom..

[5]  G. Marchetti,et al.  Identification and control of open-loop unstable processes by relay methods , 2001, Autom..

[6]  M. Chidambaram.  SET POINT WEIGHTED PI/PID CONTROLLERS , 2000 .

[7]  D. Atherton,et al.  Online tuning of controllers for an unstable FOPDT process , 2000 .

[8]  Lothar Litz,et al.  Relay Based Closed-Loop Tuning of PID Controllers (Adaption der PID-Reglerparameter im geschlossenen Kreis durch Einkopplung eines Zweipunktreglers) , 2004 .

[9]  Alberto Leva,et al.  PID autotuning algorithm based on relay feedback , 1993 .

[10]  W. Ho,et al.  PID tuning for unstable processes based on gain and phase-margin specifications , 1998 .

[11]  M. Chidambaram,et al.  Closed-loop identification of transfer function model for unstable systems , 1999 .

[12]  Tore Hägglund,et al.  Automatic Tuning of Simple Regulators , 1984 .

[13]  Tore Hägglund,et al.  Automatic tuning of simple regulators with specifications on phase and amplitude margins , 1984, Autom..

[14]  J. G. Ziegler,et al.  Optimum Settings for Automatic Controllers , 1942, Journal of Fluids Engineering.

[15]  Cheng-Ching Yu,et al.  Use of saturation-relay feedback for autotune identification , 1996 .

[16]  I-Lung Chien,et al.  IMC-PID Controller Design - An Extension , 1988 .