A novel absolute displacement detecting magnetic sensor

HaoShuangHui, LiuYong, SONG Bao-yu, HaoMingHui

School of Mechatronic Engineering,Harbin Institute of Technology,Harbin 150001,China



Abstract:

A novel magnetic grating based on calibration was proposed.Two tracks,look-up track and index track,were used to realize absolute output.Magnets of look-up track were magnetized according to N-S-N-S,and magnetic field was sensed by 6 linear Hall sensors.Three signals whose phase shift is 120° were obtained through difference,and the offset of magnetic head in a signal period could be obtained by look-up table;Magnets of index track were magnetized according to pseudorandom binary sequence.Hall sensors were used to get the absolute offset of the signal period to which the magnetic head is belonged.The magnetic grating was calibrated using a higher resolution optical grating:output of optical grating and signals from magnetic grating were sampled at the same time and transmitted to computer,the relation between them could be got and stored in MCU for looking-up.The displacement was got according to Hall signals while in working state.A magnetic grating prototype was made,and it could realize absolute detecting in 2048 mm and the resolution could achieve to 0.001 mm.Its structure is simple,cost is very low and it is suitable for mass production.

Key words:  displacement detecting  absolute output  pseudorandom binary sequence

DOI：10.11916/j.issn.1005-9113.2011.02.017

Clc Number:TP212.13

Fund: