Decentralized PID Controllers by Synthesis method for Multivariable Unstable Systems

The simple method of designing decentralised PID controllers for stable systems by the synthesis method is extended to unstable systems. The effectiveness of the proposed method is compared with that of the available decentralised controllers. The robustness of these controllers is evaluated by the inverse maximum singular value versus frequency plot for both the input multiplicative uncertainty and the output multiplicative uncertainty. Simulation results for two input - two output (TITO) systems demonstrate that the proposed method guarantees robust stability and it provides better servo and regulatory responses.