Modelling of Interactive Multivariable Systems for Control

Higher order transfer function models are approximated by a three parameters models such as critical damped SOPTD and FOPTD models. A design method for centralized PID controllers using Tanttu and Lieslekto method for the identified critical damped Second order plus time delay (SOPTD) is proposed. Centralized PI controllers are designed by the Tanttu and Lieslekto method from the identified First order plus time delay (FOPTD) model. The Centralized SOPTD-PID control system gives enhanced main responses and lesser interactions. This improvement is shown for TITO systems having high interactions (λ₁₁ > 1). The robustness study for the controllers is carried out by using the Inverse Maximum Singular Value versus Frequency plot for the input and output multiplicative uncertainties. Simulation results are given for one TITO system having λ₁₁ > 1. The centralized SOPTD-PID controllers give improved results in comparison with the centralized FOPTD-PID/PI controllers.