There has been considerable interest in fault detection and identification recently due to the increasing complexity of automation processes. A more suitable strategy of using knowledge-based techniques instead of traditional linearization techniques is used to produce a model of a non-linear system. A method to generate the training data is presented. A fuzzy relational sliding mode observer (FRSMO) and proportional integral observer (FRPIO) are proposed to estimate the magnitude of incipient faults in information-poor and non-linear systems. In the fuzzy PIO, fault size can be obtained from...