Case study: Level and temperature multivariable control and design via arduino through control loop decoupling

In recent years, the use of automatic control has grown exponentially in the world industry, together with the complexity of its plants, which can be explained by the increase in the number of control loops in the same plants. The focus of this work is based on the study and development of temperature and level multivariable control system composed of three tanks, one for mixing and the other two for cold and hot water supply. It is a MIMO (Multiple-Input and Multiple-Output) system with two inputs (hot and cold water) and two outputs (level and temperature process variable), where the system actuators are 12V pumps to control the two input levels. In the second tank, the temperature is controlled independently by a heating resistor. The control actions on the level and temperature variables can be supervised and have their SetPoints changed via a graphical interface. To simplify the controllers tuning, the control loop decoupling technique was used, seeking to decrease the interaction between them. Simulations and tests were performed to choose the best controller configuration, which in turn was embedded in an Arduino MEGA2560 board. The tests carried out showed that the significant interaction between control loops interfere in an incisive way in the controller's performance for large temperature SetPoints. Within a specific range of operation used in this work, the system has proved to be functional.