2018 : Stability Criterion of Modified Inverse Nyquist Array on a Simple Non-square MIMO Process

Prof.Ir. Renanto M.Sc Ph.D


The idea of applying Inverse Nyquist Array (INA) to analyse characteristic of a non-square MIMO (Multi-input, Multi-output) system is first put forward. Inverse Nyquist Array is a method which was proposed by Rosenbrock in 1969 to indicate the degree of interaction among loops and to evaluate the stability of square MIMO system by utilizing Nyquist plot. However, this method has not been applied to evaluate the stability of non-square MIMO system due to limitations of the inverse. Non-square matrix is a complex matrix which cannot be inverted directly. Therefore, in this work pseudo-inverse has been applied to the non-square matrix to get its inverse. Subsequently, the result of INA evaluation was compared with the dynamic response given by SIMULINK to find out the accuracy of the INA method. The result of this comparison shows that the stability of the simple non-square MIMO system can be evaluated by INA theory if the system is diagonally dominant.