Autotuning of Centralized PID Controllers for a Non-square Unstable MIMO System

The settings of the centralized PID controller are acquired with the simultaneous relay autotuning method for a non-square unstable Multi Input and Multi Output (MIMO) system. By investigating the continuous oscillation in the relay outputs the higher order harmonics are analyzed for the proposed method. The improved ultimate gain value is obtained by the accurate selection of higher order harmonics term. The performance of the centralized PID controller is investigated on 3 inputs and 2 output systems using simulation. The significance of higher order harmonics is discussed. The centralized PID controller designed using the conventional method of investigating the relay tests do not stabilize the process.