A simple method for tuning controllers on-line for unstable processes
is proposed. The step response data of the closed loop system with a p
roportional controller gain is used to identify model parameters of an
unstable first order plus time delay transfer function. Reported tuni
ng formulae for PI controllers for unstable systems are applied to obt
ain the controller parameters. The response of the closed loop system
with the controller settings of the identified model is compared with
that of the actual system's controller parameters.