A Time-Grating Displacement Sensor with Spherical Array Structure Based on a Radial Magnetic Field

Abstract To address the challenge of simultaneously achieving a large measurement range and high precision in traditional displacement sensors, a displacement sensing method based on a spherical array mechanical structure and time-grating technology using a radial magnetic field was proposed. Spatially orthogonally arranged excitation windings were employed to generate an alternating magnetic field by applying temporally orthogonal excitation currents. The magnetic field was distributed along the radial direction of the ball array, while a periodic permeable steel ball array was utilized to spatially modulate the radial magnetic field. The modulated signals were acquired using induction windings to establish the mapping correlation between the periodic variation in magnetic reluctance and the measured spatial displacement, thereby enabling displacement measurement. Electromagnetic simulations were conducted to verify and optimize the sensing model. A sensor prototype was fabricated, and an experimental platform was constructed to investigate the measurement accuracy of the prototype. Experimental results demonstrated that the sensor prototype achieved a measurement error of ± 8.58 μm within a measurement range of 512 mm. Compared with traditional displacement sensors that rely on ultraprecision micro–nanofabrication and traditional electronic interpolation technology, this method utilizes millimeter-scale sensing units to achieve micrometer-level measurement accuracy, significantly reducing manufacturing complexity while offering the flexible scalability of the measurement range. In particular, its fully enclosed structure effectively mitigates the negative impacts of harsh industrial environments, such as heavy oil contamination, on displacement measurement accuracy, demonstrating significant academic value and promising engineering application prospects.