
In most of the process industries, the processes are highly non-linear and dynamic. Design of Multivariable control system is of great demand in the process industries. Systems with more than one actuating control input and more than one sensor output are considered as multivariable systems or Multi-Input-Multi-Output (MIMO) systems. These systems are one in which interactions are not negligible. This paper describes a multivariable process with the mathematical modeling of a laboratory process, the quadruple conical tank system using which the nonlinearities and uncertainties in industrial process can be analyzed. Here the mathematical modeling is done using the First principle. Here steady state analysis and linearization of the quadruple tank system in both minimum and non minimum phase is obtained (Process Control Modeling, Design, and Simulation by B.Wayne Bequette, Chapter 14; Modern Control Engineering, Fourth Edition by Katsuhiko Ogata; Anna Joseph and Samson Isaac 2013).