# Application of Dynamic Time Warping (DTW) in Comparing MRT Signals of Steel Ropes
## 2 Materials and Methods
### Subject of Research  
The verification of the possibility of using the DTW algorithm in the extended MRT data analysis was performed as follows:  
* During an active experiment in the AGH UST laboratory carried out on a looped (endless) single-layer six-strand Seale 6x19+NF steel rope with a Drumet natural Figure 12a. At the stage of production and braiding, artificial defects in the structure of various types were modeled into the lines and introduced at different depths of the rope cross-section [68]. The rope was located in a dry room and was not exposed to corrosion and fatigue. It was subject to demagnetization during classes with students mastering the technology of MRT testing and verification of new measurement paths and algorithms for steel rope diagnostics. The analyzed measurement data came from a recording in which the rope was not loaded with longitudinal force and was set in translational motion at a set stabilized forward speed through a wheel driven by an electric motor controlled from an inverter. The laboratory stand ensured long-term reproducibility of the diagnostic symptoms of rope damage.
* During passive experiments based on archival results from periodic tests of the technical condition of steel ropes using the MRT method in the Polish hard coal and copper mining industry, including the following:
* Two-layer round-strand steel rope 22.0 17x7+Ao Z/s-n-I-N-g-1570-WT-75/TT-2 containing 119 wires in 11 external strands and 6 internal strands on a natural fiber core (Figure 12b), used since 6.12.2004 in the \"Guido\" shaft of the Coal Mining Museum in Zabrze as a carrying rope for a cage hoist. Rope diameter 22 mm, rope coil stroke 180 mm, total rope length 190 m, safety factor when applied 9.84, min. safety factor 7.5. There is one stable wire break in the rope, which has so far been used for the initial synchronization of time series by the visual method. The symptom of wire breakage was used in the DTW algorithm to optimize the width of the rope fragment analysis window. Characteristics of the mining shaft hoist are as follows: hoisting machine B 1200/AC; hoisting class II; type, telling machine; driving speed 2 m/s; environmental conditions in exhaust shaft, wet; pulling depth, 170 m; number of pulls, approx. 5/week. Corrosion processes dominate in the lines. 1. Single-layer wire rope NRHD24 by Arcelor Mittal containing 360 wires in 12 outer strands and 12 Warrington type core strands (Figure 12c). Rope used in a copper mine as an equalization rope is exposed to material fatigue and corrosion of external and core wires in places where the zinc-based protective layer is worn. 2. Double-layer steel line impregnated with STRATOPLAST MF 40.0 8x26 WS+EPIWRC 1960 B/N(Zn/Al) z/Z (s/S) by CASAR containing wires in 8 outer strands, 6 inner strands, and 3 core strands. The strands are separated from each other by a polymer layer (Figure 12d). A rope mined in a hard coal mine in an exhaust shaft with aggressive shaft waters. Hoisting machine with KOEPA wheel; traveling speed 16 m/s; pulling number, more than 400/day. The line mainly involves fatigue processes in the presence of developing pitting corrosion of the outer wires in places where the protective layer of Bekaert BEZINAL(r) 3000 has been wiped off. The risk of corrosion of wires of the internal and core strands is very low until the polymer layer is damaged.