Design, fabrication and interfacing of a cascaded three-tank system with micro-controller board for research and education in process control

Abstract

A laboratory course and a well-furnished laboratory are essential components of process control education as they provide an avenue for students to apply the principles learned in class to real-life processes. However, there is a dearth of these basic facilities in higher institutions. This, therefore, creates a big gap between theory and practice and makes the understanding of control concepts seem abstract and uninteresting to students. This paper presents the efforts of our research group in bridging this gap. Also, it primarily focuses on the design, fabrication, and interfacing with an Arm-cortex M3 processor board of a cascaded three-tank system for direct digital control. The satisfactory experimental results obtained revealed the success of the interfacing. Multivariable control system design for the cascaded three-tank system is also addressed to further corroborate the effectiveness of design. Three state-of-the-art multivariable controllers are designed for comparative purposes, viz, centralized controller by simplified decoupling, linear model predictive controller, and non-linear model predictive controller. Also, 1-1/2-2/3-3 decentralized proportional plus integral plus derivative (PID) controllers are designed for the cascaded tanks. The results of the validation experiments conducted shows the derived non-linear model and the linearized model matched well, the experimental tank system, with the non-linear model showing the best fit. The closed-loop simulation and experimental results matched very closely, with the centralized controllers (by simplified decoupling) and predictive controllers having better performance than the decentralized PID controller. In all, the non-linear model predictive controller displays an overall superior performance.