Measurement of Three-Dimensional Information by Single Eddy Current Displacement Sensor

The eddy-current displacement sensor (ECDS), due to features of small size and high-measurement accuracy, has great potential for high-precision measurement in a compact space. However, most applications of ECUS are one-dimensional (ID) or two-dimensional displacement measurements. In this paper, a measurement method of three-dimensional (3D) coordinates only by virtue of single ECDS is proposed. In order to realize the 3D coordinates measurement by ECDS, the virtual displacement measurement starting point (VDMSP) and the displacement vector of ECDS are used as the prior information of ECDS to obtain the 3D absolute measuring point coordinate of a spatial target by ECDS from the 1D displacement relative quantity of ECUS. Besides, a 3D measurement method by ECDS based on the spatial vector and optimization has been proposed to obtain the 3D absolute coordinates of the VDMSP and the spatial displacement vector (the prior information). Then, the measurement of 3D absolute coordinates of the measuring point on the target by single ECDS can he realized due to the prior information. Moreover, the plane datum transformation method is analyzed to reduce the impact of data drift on the measurement method. Finally, the experiments of six ECDSs are conducted. The results indicate that the proposed measurement method is universally applicable to different ECDSs. The average measurement accuracy is 0.0212 mm and the mean square error is 0.0127 mm, which can meet the measurement requirement of 3D detection in a compact space.