Identification model and PI and PID controller design for a novel electric air heater

Abstract

In this article, the software and hardware control architecture for a novel high-temperature three-phase electric air heating furnace is presented. It consists of a multiple-input singleoutput (MISO) nonlinear plant designed to heat air at flow rates in a range between 10 and 60 Nm3/h, from ambient temperature up to 1000 °C. A divide-and-conquer (D&C) approach is applied. It consists in discretizing the air flow rates and working temperatures in intervals where the system behaviour is considered as single-input single-output (SISO) linear plant. Process identification techniques have been used to obtain empiric models for different operation ranges of the electric furnace. The controller parameters have been calculated using the Ziegler–Nichols tuning method. The resulting output air temperature control is composed of a set of 12 PI and PID controllers. The switch among controllers as a function of air flow rates and temperatures is carried out using programming logic and gain scheduling technique, respectively. The resulting multiple controller has been tested under real conditions and the results are presented and discussed.