A sensor model for defect detection in mine hoisting wire ropes based on magnetic focusing

摘要

In view of the limitations in the currently applied defect detection techniques for the large-diameter hoisting wire ropes used in coal mines, this study proposes a new method for detecting magnetic excitation in wire ropes by combining the structural models for dynamic magnetic field balancing and magnetic focusing. The paper first describes a structural model that applies the principle of magnetic field balancing to integrate sensors for defect detection in wire ropes. Next, it presents the design of a structural model for magnetic focusing, which is applicable to large-diameter wire ropes and can achieve all-round detection without exception. A detection method that uses a Hall-element array in combination with the magnetic focusing technique, which can reduce the interference produced by the interactions between the environmental magnetic fields and the wire rope strand, is also proposed. Finally, the proposed detection sensor is tested through simulations and experiments. As the proposed sensor is equipped with a permanent magnet made of N35-type material, which has a smaller remanence and is 20 mm less wide and 20 mm less thick than conventional magnetic flux leakage defect detection sensors, the volume, weight and cost of the sensor is lower. Moreover, in comparison, the proposed sensor detected six defects accurately in the experiment, while the conventional sensor missed one. The signal-to-noise ratio of the proposed sensor is 6.5 dB higher than that of the conventional one, which reveals that it provides better detection capabilities.