The Influence and Compensation Method of Eccentricity for Cylindrical Specimens in Eddy Current Displacement Measurement

Abstract

The eddy current displacement sensor (ECDS) is used to realize the precise detection of the rotor radial position in the magnetic suspension motor. The eccentricity between the probe axis and the measured surface normal reduces the measurement accuracy. An ECDS mathematical model is established to analyze the influence of the measured surface curvature and eccentricity on detection results. The eddy current density distribution law of the measured surface is obtained by using the finite element method (FEM). The experimental platform is set up based on the practical engineering structure, which contains two kinds structures of the single probe and the differential. The compensation method is introduced to reduce the error caused by the eccentricity. The displacement measurement error with and without compensation are tested separately. The results show that the largest full-scale error is less than 0.8% after compensation in the single probe structure, and 0.6% in the differential structure. For the engineering application, the orthogonal direction measured value is used as the eccentricity, and the compensation order of big then small is proposed. It is thus proved that the compensation method provides a guarantee for accurate feedback and control of the rotor radial position in the magnetic suspension motor system.

Recycling of Electrical Cables—Current Challenges and Future Prospects

“…The separation of plastics from metals in cables is most commonly achieved using a device such as an ECS (eddy current separator) [80][81][82][83][84]. An ECS consists of a conveyor belt system and a magnetic drum, as shown in Figure 10.…”

Coupling Interference between Eddy Current Sensors for the Radial Displacement Measurement of a Cylindrical Target

“…As the locations of the ECSs for the radial displacement measurement of a cylindrical target change the axial symmetry, 2D models are no longer applicable. Therefore, three-dimensional (3D) simulation models were established in ANSYS Maxwell, which is a commonly used software [21,27,28], as shown in Figure 3a. To cover most ECSs in use, the excitation frequencies of the coils were set to 1, 10, 100, and 1,000 kHz.…”

“…To eliminate the influence of the curvature on crack detection, Zhang et al studied the lift-off noise of probe coils on curved specimens with small radii of curvature and presented a phase rotation and signal enhancement technique to eliminate the noise [ 26 ]. Zhan et al studied the influence of eccentricity on cylindrical specimens and introduced a compensation method to reduce the error [ 27 ]. Sheng et al studied the interference between arrayed ECSs [ 28 ]; however, the interference between sensors for radial displacement measurement has not been studied sufficiently.…”

A decoupling calculation method of separating temperature component from the nano-scale metal film thickness measurement output by the eddy current sensor

“…sensors have been widely used in micro-nano measurement fields, such as metal film thickness [2,3], lubricant oil film thickness [4,5], vibration monitoring [6], and micro displacement [7], due to the advantages of non-contact measurement, non-destructive testing [8,9], high resolution and strong environmental adaptability. For example, in the copper (Cu) chemical mechanical planarization (CMP) process [10], the eddy current sensor can be used to measure the Cu film thickness variation in-situ for achieving a flat wafer surface with a high quality.…”