Teaching multivariable control using the quadruple-tank process

A multivariable laboratory process is presented together with its use in a graduate control course. The process is called the quadruple-tank process and demonstrates a multivariable level control problem. The multivariable zero dynamics of the system can be made both minimum phase and nonminimum phase by simply changing a valve. This makes the quadruple-tank process suitable for illustrating many concepts in linear and nonlinear multivariable control. In the paper some of these are described together with the basic setup of the process. Two computer exercises and one laboratory exercise have been developed as part of a course in multivariable and nonlinear control. These are detailed and some experience from the course is presented.