2014 Summer Project Week:Open source electromagnetic trackers usingOpenIGTLink

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  Projects List

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  Stylized image of three orthogonal coils used in 6-DOF electromagnetic tracker sensor

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  Handmade assembly of three commercial solenoidal coils; each solenoid is 11 millimeters long

Key Investigators

• Retired: Peter Traneus Anderson
• BWH: Tina Kapur, Sonia Pujol

Objectives

• This open-source electromagnetic tracker project aims to teach and develop open-source electromagnetic trackers, to enable extending performance in directions that existing proprietary trackers do not address.
• This project aims, in part, to develop methods of accurately characterizing transmitter and receiver coils without the use of costly precision robots.

Approach, Plan

• Over the past year, Peter has developed and tested a simple and fast buffer design between the steady-streaming ADC data and the bursty USB interface. This fast interface replaces two-years-ago's very-slow USB interface in Pete's prototype three-transmitter-coil three-receiver-coil 6DOF (six degrees of freedom) hardware. Pete still needs to update his web page with details of the changes for the new interface.
• With the electronics now understood, Peter's attention is returning to the problem of accurately characterizing coils. Understanding of how the electromagnetics behaves, permits design of simpler and better characterization protocols than naive protocols that just try to optimize position and orientation accuracy.
• The 6DOF position-and-orientation tracking problem naturally divides into one distance and five angles, as shown by Raab, Blood, Steiner, Jones.
• Peter intends to explore characterization data collection at constant distance between transmitter and receiver, rotating both transmitter and receiver so that, over the data set, all six transmitter coil ends are pointed at all six receiver coil ends, with each of these 36 combinations including all four 90-degree rotations of the receiver about the axis pointed at the transmitter.

Progress

• Jean-Christophe set up github repository for this project. See https://github.com/traneus/emtrackers
• Peter started development of coil-characterization process.
• Peter raised the issue of which open hardware licenses are appropriate. An answer is not needed for at least a year.

References

• Pete's published work to date is on Open Source Electromagnetic Trackers and on [http://home.comcast.net/~traneus/dry_emtrackertricoil.htm].

• Frederick H. Raab, Ernest B. Blood, Terry O. Steiner, Herbert R. Jones, "Magnetic Position and Orientation Tracking System", IEEE Transactions on Aerospace and Electronic Systems, Vol. AES-15, No. 5, September 1979, pages 709 to 718.