Comparison of Direct and Indirect Continuous-Time System Identification Methods on a Pasteurisation Process

System identification of continuous-time systems can be realized using either direct or indirect methods. Both methods are considered in this paper to identify linear models for a direct steam injection pasteurization process of an industrial evaporator in the dairy industry. The results of the system identification indicate that the plant can be reliably modeled by two first-order lag plus delay models-one representing the process, the other the disturbance. A statistical analysis of the results reveals that the direct-continuous time method estimates models whose coefficients have less variance than the models estimated by the indirect method