"In this book, the methods of identifying such models are given for linear multivariable systems both by open-loop as well as closed-loop methods. The closed-loop reaction curve method and optimization method fall under closed-loop identification methods. In open-loop identification methods, methods of identifying transfer function model for stable First Order Plus Time Delay model and critically under-damped second-order system are presented. An extension of the method for identifying the transfer function matrix for an unstable system is also discussed in this book. The main contribution is in the selection of the initial guess values for the model parameters for the optimization method. The design of multivariable PI controllers based on the Steady-State Gain Matrix is described for stable and unstable systems. The method of identifying SSGM for multivariable is given for stable and unstable systems. The method is also extended for stable and unstable non-square systems. The genetic algorithm's method of designing multivariable PI controllers for non-square systems is also explained"--