Observer-based tracking control of superficial temperature

Heat treatments are recommended to decontaminate the surfaces of food. An ideal thermal treatment consists in carrying the superficial layer of food at a predetermined temperature according to a ramping period, an eventual plateau, and a decreasing period. An advanced process control solution is required to force the superficial temperature to perfectly respect the imposed profile. To predict this superficial temperature, we firstly develop an accurate simulator that takes into account heat and mass diffusion, evaporation or condensation and shrinkage. We secondly estimate, using a reverse technique, a crucial parameter of this process: the water activity. A control approach was designed to allow an efficient tracking control of a set point temperature. As this law requires the knowledge of internal temperatures, we develop an observer to avoid intrusive methods. The simulator has been validated online and technical modifications of the experimental bench are needed to implement the control law. (c) 2005 Elsevier Ltd. All rights reserved.