Simple and Optimal PI/PID Tuning Formulae for Unstable Time Delay Processes

Many PI and/or PID design methods can be found in the literature for controlling open loop stable processes. However, less PID design methods for controlling unstable processes are considered. Hence, this paper introduces simple and optimal tuning rules for controlling unstable time delay systems. Design method requires a model of the actual process. Here, an unstable first order plus dead time (UFOPDT) model has been used. Based on the UFOPDT model, optimal analytical expressions have been obtained using the ISTE and (ISTE)-E-2 criteria, well-known integral performance indexes. Simulation examples are provided to show the use of the obtained tuning rules.