I. Introduction
With the development of science and technology, mechanical equipment is becoming more and more integrated, and traditional repair and maintenance strategies can no longer meet the demand for efficient and accurate maintenance. Machinery and equipment operating under relatively harsh working conditions also leads to a certain degree of wear and degradation of its internal parts. For some important machinery and equipment such as aircraft engines, rolling bearings, etc., failure may cause serious economic losses or even casualties. Remaining useful life (RUL) prediction as an important part of prognostics and health management (PHM) technology has received much attention from experts and scholars in recent years, among which, aero-engine is one of the key objects of concern in daily aviation maintenance operations. Achieving accurate RUL prediction for aero engines is of great importance for companies to make reasonable maintenance plans and reduce maintenance costs. At present, there are two main types of methods to predict the RUL of aero engines: physical model-based prediction methods and data-driven prediction methods [1].