I. Introduction
Abnormal wear is one of the leading causes of mechanical equipment failure [1], [2]. Wear particles can directly reflect the wear conditions of tribo-pairs, which is beneficial to equipment’s early failure detection and fault diagnosis [3], [4]. Therefore, the monitoring technology of lube oil wear particles is of great significance to the intelligent maintenance of mechanical equipment [5], [6]. Nowadays, on-line wear particle sensors are mainly divided into optical sensors [7], ultrasonic sensors [8], capacitive sensors [9], resistive sensors [10], metamaterial sensor [11], and inductive sensor [12]. Among them, the inductive sensor is favored by more and more researchers because of its good stability, high precision, and strong adaptability [5].