Abstract Incipient faults almost occur gradually at a low rate in systems and usually are unnoticeable during their early stages. If diagnostic tools or proper monitoring systems ignore them, they could not be detectable until their effects become severe and cause catastrophic damages to systems. This paper presents a survey on model-based (incipient) fault diagnosis approaches to show the significance of the incipient faults diagnosis in nonlinear closed-loop systems and, by taking a glance through data-based incipient fault diagnosis advancements, a picture of their present state of the art is also briefly discussed for completeness. Moreover, a classification of the most used state estimation filters is also provided. Consequently, recent works on incipient fault diagnosis approaches are reviewed, and an incipient fault diagnosis case study is investigated for a discrete-time nonlinear open-loop system affected by stochastic noise and disturbances. Specifically, a numerical example of a closed-loop three-tank system is considered, and simulations are accomplished, to demonstrate the inability of open-loop incipient fault diagnosis approaches in detecting incipient faults in the proposed closed-loop system.

中文翻译：

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早期故障诊断方法综述与分类

摘要 系统中的早期故障几乎以低速率逐渐发生，并且在早期阶段通常不易察觉。如果诊断工具或适当的监控系统忽略它们，直到它们的影响变得严重并对系统造成灾难性破坏时，它们才能被检测到。本文对基于模型的（初期）故障诊断方法进行了调查，以展示非线性闭环系统中初期故障诊断的重要性，并通过浏览基于数据的初期故障诊断进展，了解它们目前​​的情况。为了完整性，还简要讨论了现有技术。此外，还提供了最常用的状态估计滤波器的分类。因此，回顾了关于早期故障诊断方法的最新工作，并对受随机噪声和扰动影响的离散时间非线性开环系统进行了初期故障诊断案例研究。具体而言，考虑了闭环三罐系统的数值示例，并完成了仿真，以证明开环早期故障诊断方法无法检测所提出的闭环系统中的早期故障。