Inertial Measurements for Tongue Motion Tracking Based on Magnetic Localization With Orientation Compensation

• Published in: IEEE sensors journal 2021-03, Vol.21 (6), p.7964-7971
• Main Authors: Sebkhi, Nordine, Bhavsar, Arpan, Anderson, David V., Wang, Jun, Inan, Omer T.
• Format: Article
• Language: English
• Subjects: Accelerometers; Algorithms; Inertial measurement unit; Inertial platforms; Localization; magnet; Magnetic fields; magnetic localization; Magnetic measurement; Magnetic resonance imaging; Magnetic sensors; Magnetism; Magnetometers; motion tracking; neural network; Orientation; orientation estimation; permanent magnet localization; Permanent magnets; Pitch (inclination); Rolling motion; Sensors; Strip; Strips; Tongue; tongue tracking; Tracking
• ISSN: 1530-437X; 1558-1748
• DOI: 10.1109/JSEN.2020.3046469

Permanent magnet localization (PML) is designed for applications requiring non-line-of-sight motion tracking with millimetric accuracy. Current PML-based tongue tracking is not only impractical for daily use due to many sensors being placed around the mouth, but also requires a large training set of tracer motion. Our method was designed to overcome these shortcomings by generating a local magnetic field and removing the need for the localization to be trained with tracer rotations. An inertial measurement unit (IMU) is used as a tracer that moves in a local magnetic field generated by a magnet strip. The magnetic strength can be optimized to enable the strip to be placed further away from the tracer, thus hidden from view. The tracer is small ( 6\times 6\times 0.8 mm 3 ) to reduce hindrance to natural tongue movements, and the strip is designed to be worn as a neckband. The IMU's magnetometer measures the local magnetic field which is compensated for the tracer's orientation by using the IMU's accelerometer and gyroscope. The orientation-compensated magnetic measurements are then fed into a localization algorithm that estimates the tracer's 3D position. The objective of this study is to evaluate the tracking accuracy of our method. In a 8\times 8\times 5 cm 3 volume, positional errors of 1.6 mm (median) and 2.4 mm (third quartile, Q3) were achieved on a tracer being rotated ±50° along both pitch and roll. These results indicate this technology is promising for tongue tracking applications.