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Currently, the electromagnetic detection methods for mining steel wire ropes have limitations: the main flux detection method has low accuracy in detecting local damage, while magnetic leakage-based detection methods have limited quantitative accuracy in local damage assessment. A dual-source magnetic detection method was proposed to simultaneously detect both the main flux and magnetic leakage in mining steel wire ropes, leveraging the complementary strengths of these two methods in local damage detection. Two excitation loop designs were proposed: a double-source ring-shaped tubular excitation loop and an independent separation excitation loop. Finite element simulation was used to verify the feasibility of the two schemes, and the independent separation loop was chosen as the basic structure of the magnetic circuit. The effects of various armature parameters, such as size and magnet properties, on the magnetization performance were studied, as well as the influence of the magnetic bridge structure parameters on the magnetic field distribution. The results indicated that:① The magnetization amplitude was positively correlated with the number of loops and negatively correlated with the armature length, while the height had almost no effect on the magnetization performance; ② The magnetization amplitude was positively correlated with the material grade, length, and thickness, and negatively correlated with the lift-off distance; ③ The magnetization amplitude was positively correlated with thickness, negatively correlated with air gap size, while lift-off distance had little effect on the magnetization performance; ④ The air gap of the magnetic bridge significantly influenced the magnetic flux density distribution within the bridge circuit.

The belt conveyor self-checking roller installs wireless sensor nodes inside the roller to collect and wirelessly transmit temperature and vibration signals, which provides a new idea for the health checking of coal mine belt conveyor rollers. In order to solve the energy supply problem of the wireless sensor nodes in the closed roller, an energy harvester based on the Halbach permanent magnet array is designed. This paper introduces the structural design of the energy harvester, and analyzes the energy supply requirements based on the actual energy consumption of the wireless sensor nodes and the efficiency of the energy management circuit. COMSOL Multiphysics 5.5 is used for finite element analysis of the energy harvester to verify that Halbach permanent magnet array has obvious advantages over conventional permanent magnet array when used in small rotating body energy harvesters. The effect of air gap thickness, permanent magnet thickness and rotor speed on the power generation performance of the energy harvester is analyzed. And it is concluded that the induced voltage of the energy harvester can be increased effectively by reducing the air gap thickness, increasing the permanent magnet thickness and increasing the rotor speed. Based on the analysis of energy supply demand, installation space requirement and finite element analysis, the parameters of the energy harvester are optimized, and a prototype is built for testing. The results show that at 5 r/s rotor speed, the effective value of the induced voltage of the energy harvester is 4.77 V, the maximum power is 171.33 mW, and the power density is 6.78 mW/cm3, which meets the energy consumption requirements (165.722 mW) of wireless sensor nodes.

Piezoelectric energy harvesting technology is a promising strategy for powering wireless sensor networks. However, piezoelectric energy harvesters (PEHs), especially linear PEHs, usually have narrow operating frequency bandwidth. In this study, in order to broaden frequency bandwidth, a nonlinear multi-stable magnetically induced PEH array (MPEHA) with asymmetric potential wells is proposed. Specifically, the proposed MPEHA is consisted of piezoelectric energy harvesting technique, multi-resonance array technique and magnetic force based nonlinear technique. Both theoretical and experimental studies are conducted to investigate the energy performance and to analyze the dynamic characteristics of MPEHA with snap-through motions among the multiple stable positions. As for theoretical study, a mathematic model of the potential function of the proposed harvester is established and the influence of magnetic force on the potential well configuration is quantitively investigated. As for experimental study, experiments including open-circuit voltage experiment and capacitance charging experiment are conducted using MPEHA with three-beam arrays. Our experimental study demonstrates that MPEHA has better performance than the traditional PEHA due to the magnetic coupling effect. Under excitation acceleration of 3 m s−2, the performance of bi-stable MPEHA is improved by 80.2%, compared with PEHA. [ABSTRACT FROM AUTHOR]