Modeling and Control of an Industrial Continuous Furnace

This paper describes a furnace model in state space formulation for a continuous heat treating process specifically suitable for controller design. The model comprises the heat transfer in the conveyed steel strip, the heat transmission from the heating or cooling elements to the steel strip, the inner dynamics of the heating elements and the related furnace portion, heat losses to the ambience, and time-varying parameters of both the strip material and the process (strip velocity, set temperature profile). Model inputs are the heating powers of the individual heaters, and the outputs are either strip or furnace temperatures at specific furnace positions. The model is also suitable for on-line simulation, and due to the flexible and versatile structure of the heater model a wide range of furnace types can be covered with high accuracy. Simulation results for classical PID zone temperature control and a proposed feed forward extension demonstrate the efficiency of the furnace model.