Measurement method for screw conveyors based on electrostatic primary and secondary frequency signals

Screw conveyors are widely used in industries such as construction, grain processing, and mining due to their low cost, ease of operation, and simple structure. Real-time measurement of the operational status of screw conveyors is crucial for enhancing conveyor efficiency, reducing energy consumption, and ensuring the safety of the production process. However, effective real-time measurement methods are currently lacking. This paper designs an electrostatic sensor that synchronously accounts for the influence of screw blades and finds that the detected electrostatic signals contain distinct primary and secondary frequency information. The signals are extracted using Harmonic Wavelet Transform (HWT), and the coal powder particle signals and screw blade signals are distinguished based on the presence of time delays in the decomposed signals. The results indicate that the primary frequency primarily reflects the motion of the screw blades, while the secondary frequency mainly corresponds to the motion of the coal dust particles. Using the proposed velocity measurement method, the absolute value of the relative error for the measured screw rotation speed was less than 1 %, and the absolute value of the relative error for the coal dust particle lifting speed was less than 2 %.