Design and Application of Rough Controller in Three-Tank System

Rough set theory is an important soft computing method. Some useful knowledge can be extracted from original data with it. In this paper, a design method for rough controller is proposed based on rough set theory, and it be used to control the water-levels of a three-tank system. The key element to design rough controller is how to extract rule sets from human control behavior data according to rough set theory algorithm. The three-tank system consists of two variable frequency controllers, two ac-motors, two pumps and three tanks. The rough controller design steps include sampling control behavior data from a human operator for controlling the levels of the tanks, constructing the primal decision information tables using these data, extracting the control rules from these tables, completizating the rule sets, designing the controller and checking rules. Finally, the rough controllers are used to control the actual system. The experimental results indicate that design method of the rough controller is feasible and control effect is satisfying.

I. Introduction

Human operators are able to control some complex objects controlled, while they do not need to know their quantitative models. One of the intelligent control methods is how let machine to imitate the control-behavior of the human beings. The aim is that the control actions of the human are used to synthesize an automatic control system. This paradigm is called learning from examples [1]. The RST is a very useful soft computing technique to achieve this idea.