It is quite a difficult problem of fault detection in nonlinear system.In this paper

a new method based on LLE is proposed to solve the problem.Firstly

tangent space distance is introduced to LLE(Locally Linear Embedding) algorithm

which can satisfy the hypothesis of locally linear patch of LLE

and so it can preserve the local manifold features of the original data better.And then

fault state is combined with special distribution to complete the fault detection.Out of sample extension is also considered

and combined with fault detection algorithm

which can reduce computation obviously and improves real time capability of the Thereby algorithm.provides a new effective method for the fault diagnosis of complicated nonlinear system.