An electromagnetic tracking system using printed-circuit coils

Industry-standard six-degree-of-freedom electromagnetic tracking systems determine the position and orientation of one three-axis coil array with respect to a second three-axis coil array using the near-field properties of the coils. The coils are usually wirewound, and the mechanical variations from coil to coil necessitate the individual electromagnetic characterization of each three-axis coil assembly. The individual characterization can be eliminated by replacing each coil array with an accurately-built tetrahedron of four identical coils. Each coil is formed by tracks on a triangular printed-circuit board. Four such boards interlock to form one tetrahedron. The mutual inductance between two printed-circuit coils is modeled using a double integral which eliminates the dipole assumptions usually used in modeling electromagnetic tracking systems.