Case Studies of Improved Relay Auto-tuning of PID Controllers for TITO Systems

The present work proposes an improved analysis of a simultaneous relay auto-tuning method to calculate the maximum controller gains for two-input two-output (TITO) systems by considering the higher order harmonics. Improved results are obtained from the controller ultimate values under the decentralised PID control systems. The method is applied to three different TITO transfer function matrices with different levels of interactions. The proposed method gives closed loop performances with reduced interactions and improved responses when compared to that of the conventional method of analysing the relay auto-tuning.