A Hall Sensor-Based Three-Dimensional Displacement Measurement System for Miniature Magnetically Levitated Rotor

This paper presents a novel scheme for measuring the axial and radial displacements of a miniature magnetically levitated rotor based on linear Hall-effect sensors. The measurement system consists of six single-axis Hall-effect sensors attached to the stator with a ring shaped permanent magnet (PM) mounted on the rotor as the magnetic flux source. The system is configured such that the directions of the magnetic flux into the sensors for each axis are monitored. Consequently, the errors caused by uneven magnetization and the temperature dependence of the PM are minimized. The experimental results demonstrate measurement system satisfactory performance. Since only single-axis Hall sensors are used in the measurement system, this scheme provides a low-cost compact size solution for three-dimensional displacement measurement of miniature magnetically levitated rotors.