As a supervised machine learning algorithm, conditional
random
fields are mainly used for fault classification, which cannot detect
new unknown faults. In addition, faulty variable location based on
them has not been studied. In this paper, conditional random fields
with a linear chain structure are utilized for modeling multimode
processes with transitions. A linear chain conditional random field
model is trained by normal data with mode label. This model is able
to distinguish transitions from stable modes well. After mode identification,
the expectation of state feature function is developed for fault detection
and faulty variable location. Case studies on the Tennessee Eastman
process and continuous stirred tank reactor (CSTR) testify the effectiveness
of the proposed approach.