Research On The Classification Method Of Non-magnetic Metals Based On Electromagnetic Eddy Current Detection

The development of metal detection and classification methods and key industrial equipment in the recycling process of scrap metals is a hot research issue and an important challenge in metal recycling,especially for non-magnetic metals,there is a lack of a sound theoretical system and mature technical methods.This study adopts electromagnetic eddy current detection technology to study the classification method of non-magnetic metals,eliminates the influence of various factors in the classification process,proposes a nonmagnetic metal classification method for the case of changing lift-off height and inconsistent geometric characteristics of metal samples,and lays the method and technical foundation for realizing a real-time metal classification system.This thesis is a study of the non-magnetic metal classification method based on electromagnetic eddy current detection,and the main contents are as follows.For the influence of the change of lift-off height caused by mechanical vibration and other reasons on the electromagnetic detection results in the classification process,this study designs a triple-coil electromagnetic sensor,improves the range of the allowable lift-off height change,and makes a correction to the phase difference classification feature,so that the positive proportional relationship between the feature and the lift-off height in a certain range,eliminates the influence of the lift-off height change,and improves the classification accuracy.To address the problem of inconsistent geometry of the classified metal,this thesis introduces an analytical solution model for the impedance variation of a finite size metal plate and investigates the matching problem of the metal sample and the sensor coil size.The geometric size of the metal sample is decoupled from the time-frequency response of the sensor,thus eliminating the influence of the metal sample size on the measurement results.For the problem of different geometries of metal samples,the effect of metal geometry on measurement results is investigated in this study,and the classification method of nonmagnetic metals under different shapes is given considering the influence of the spatial position relationship between the metal sample and the sensor on the classification.The experimental results show that the proposed classification methods can all achieve more than 95% classification accuracy,which provides an effective method theory for building a real-time nonmagnetic metal classification system.