# New On-Line MFL Testing Method and Apparatus for Winding Mine Hoist Wire Rope
## 1 Introduction  
Mine hoisting (WMH) wire rope is an essential component for connecting the hoisting conveyance and hoister, as well as a significant tool in the transmission of power. It has been widely used in various industrial fields, including cranes, elevators and metallurgy [1, 2, 3]. However, wire rope defects may occur as a result of wear, corrosion, fatigue, broken wire, and other damage, resulting in a decrease in strength or, at times, safety issues and even fatalities [4, 5, 6]. The traditional wire rope safety strategy relies mostly on experience and the routine replacement of wire ropes, resulting in greater economic costs and the risk of unexpected abnormal damage during reinstallation, leading to more sudden and serious accidents.  
The NDT methods for wire rope include magnetic flux leakage (MFL) testing methods [7, 8], ultrasonic testing (UT) methods [9], X-ray inspection [10], acoustic emission (AE) inspection methods [11, 12], and eddy current testing (ECT) methods [13]. Among them, the MFL testing method is considered to be the most effective method for detecting wire rope defects [14, 15]. For the purpose of enhancing the sensitivity and effectiveness of signal acquisition of leakage magnetic fields at defects, it is necessary for the structural design of the MFL detection device and the magnetic sensitivity sensor to be optimized in order to increase the ability of the MFL device to stimulate leakage magnetic fields at defects and also to increase the ability of the magnetic sensitivity sensor to acquire signals. For example, [PERSON] [16] used an orthogonal test method (OTM) to optimize the design of an MFL sensor consisting of Helmholtz-like excitation coils, a magnetic shield and a TMR device. [PERSON] [17] used an improved small-habitat adaptive genetic algorithm to reduce the weight of the detector and improve the robot's carrying capacity. [PERSON] [18] proposed an iron core as a coil winding skeleton for the nondestructive testing of wire ropes, which altered the MFL path of defects and improved the signal-to-noise ratio of the coil's output. [PERSON] [19] developed a wire rope wire breakage detection sensor based on the magnetic concentration principle and optimized the structural parameters of a toroidal multi-loop permanent magnet exciter (CMPME) to identify external wire breaks in 24 mm diameter wire ropes. [PERSON] [20; 21] designed a simple and portable magnetic detection device based on a magnetic probe structure to qualitatively and positionally detect wire rope defect. [PERSON] [22] proposed a novel magnetic aggregation bridge detection method using magneto resistive (MR) sensor arrays that can detect multiple types of wire ropes damage with a maximum signal-to-noise ratio of 60 dB. [PERSON] [23] developed a flexible GMR array sensor for detecting defects of LF and LMA types on 64 mm diameter wire ropes. The transducer consisting of a fluxgate sensor proposed in [24] demonstrated the feasibility of detecting low frequency and LMA defects in weak magnetic fields with greater sensitivity and better signal-to-noise ratio, compared to Hall elements or induction coils. The fast speed of the wire ropes in operation on the site causes jitter and swings that can cause wear between the wire rope detection sensor and the wire rope; therefore, it was necessary to design a detection sensor with simple structure that is able to adapt to the actual operating conditions of the wire rope.  
In order to accommodate jitter and random oscillations among ropes running at high speed, an open-loop permanent magnetization method [25] was used in this study to design an on-line floating tracking testing device incorporating a rocker arm coordinated with an open-close probe. The effect of the magnetizer size and MFL signals of defects was also studied in depth, and the applicability and effectiveness of this online testing device were confirmed through experimental and field testing.