Symmetric Hall-Effect-Based Distance Sensor for Zero-Power Permanent-Electromagnetic Suspension (PEMS) System

The zero-power permanent-electromagnetic suspension (PEMS) system features the magnetic levitation system that consists of the electromagnet and the floating magnet. Since the payload gravity is balanced by the attractive magnetic force between the iron core and the magnet, the excitation current in the coil stabilizes the magnet and fluctuates about the zero value. However, the accurate distance measurement between the iron core and the magnet is still a technical challenge against the hardware cost and the external disturbance. This work proposes a symmetric Hall-effect-based distance sensor for the zero-power PEMS system. Under the small excitation current, the proposed sensor eliminates the magnetic field linearly excited by the current and outputs the magnetic field produced by the magnet to calibrate the floating distance. Additionally, the simulation results indicate its outstanding performance against the tilting angle and the lateral offset of the floating magnet. Nevertheless, the experimental demonstration shows the functionality of the proposed sensor.