Identification of 3-by-3 MIMO system using relay feedback

Relay feedback tests are carried out on 3- by- 3 multi input multi output (MIMO) system. The system considered here consists of component transfer functions of first order plus dead time (FOPDT) type with variable time delays. Analytical expressions for relay responses in time domain for the interactive transfer functions of the systems are derived. All parameters of the system are estimated with the help of relay responses. The proposed approach is illustrated using Ogunnaike Ray (OR) distillation column model. The model parameters thus obtained can be used to develop model based control schemes.