Matrix factorization method to stabilize multivariable control systems

A new method to study the stability of n-input-n-output linear time-invariant feedback systems is proposed. First, a new factorization of the transfer-functions matrix is developed which allows a direct analysis of the stability of a multivariable system. Then, some properties of this factorization are studied and finally, a design method is inferred from these properties. The method permits an easy design of stable controllers. It allows the influence of the off-diagonal elements of the controller on the stability of the closed loop system to be studied.