Linearization and decoupling controller for quadruple tank

Abstract

Quadruple Tank Process (QTP) is a nonlinear system that has four state variables in the form of a level of four tanks with two inputs of flow discharge. In addition to the non-linearity, each state on the QTP dynamics is coupled, and the level sensor is only installed on two tanks to be set, this adds to its complex QTP control issues. By performing the linearity using Nonlinear State Feedback Decoupling (NSFD) method, we can establish a closed loop system that is linear and meets specific response specifications in accordance with the desired design specifications. Since NSFD requires measurements of all states, it is necessary to add a Non-Linear State Observer (NLSO) so that the other two states can be observed from two measured states. By specifying time response design in the form of time constants T1 = 4 seconds, and T2 = 4 seconds for tank one and tank two respectively, and installing a 1st order low pass filter with time constants t = 0.2 second for Cross Coupled Error Feedback (CCEF) on NLSO, then we can obtain a simulation result that meets the specification of the desired transient response.