A fault detection method in an uncertain aluminium plate thermal process control system with input constraints is presented. The method is based on a robust right coprime factorization approach. The detailed explanation is as follows. Based on right coprime factorization dynamics, a model of the thermal process is developed. Using the concept of robust right coprime factorization of non-linear operators, a robust tracking operator system for the process is designed. For checking the tracking operator system, a fault detection design scheme is proposed. Further, simulation and experimental results are also presented to support the theoretical results.