Electromagnetic Position Measurement System Immune to Ferromagnetic Disturbances

Heng Wang, Ryan Madson, Rajesh Rajamani

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


This paper develops an electromagnet-based position measurement system for industrial actuators which offers significant advantages compared with traditional position measurement systems. These advantages include low cost, non-contacting operation, easy installation, and robustness to magnetic disturbances. In the first embodiment of the sensor, the electromagnet is located on the stationary actuator housing while the sensor is mounted on the actuator's moving piston rod. This requires power to be supplied to the electronics on a moving object, and therefore a second embodiment that eliminates this disadvantage is developed. The second embodiment locates both the electromagnet and the powered sensor on the stationary housing. A mu-metal film of high magnetic permeability is located on the moving piston. Due to its high magnetic permeability, a significant fraction of the magnetic field measured by the sensor is coupled through the piston of the actuator. Hence, as the piston position changes, the magnetic field measured by the sensor changes. This leads to an excellent position measurement system with high sensitivity. The experimental results show that the second position sensor embodiment can provide 1% accuracy in position measurement, can reject the influence of disturbances from magnetic objects and can measure positions for stroke lengths up to 20 cm. Longer stroke lengths can be handled using additional daisy-chained sensors.

Original languageEnglish (US)
Article number8770234
Pages (from-to)9662-9671
Number of pages10
JournalIEEE Sensors Journal
Issue number21
StatePublished - Nov 1 2019

Bibliographical note

Funding Information:
Manuscript received June 12, 2019; accepted June 30, 2019. Date of publication July 23, 2019; date of current version October 4, 2019. This work was supported in part by a Research Grant from the National Science Foundation (NSF) under Grant CMMI 1562006. The associate editor coordinating the review of this paper and approving it for publication was Dr. Sanket Goel. (Corresponding author: Rajesh Rajamani.) The authors are with the Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455 USA (e-mail: rajamani@umn.edu). Digital Object Identifier 10.1109/JSEN.2019.2929229

Publisher Copyright:
© 2019 IEEE.


  • Industrial actuators
  • electromagnetic position sensing
  • magnetic sensing
  • position estimation
  • position sensors


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