Effects of Movement Speed and Magnetic Disturbance on the Accuracy of Inertial Measurement Units.

This study evaluated the effects of motion speed and magnetic disturbance on the spatial orientation accuracy of an inertial measurement unit (IMU) on the hand. Thirteen participants performed six trials of a repetitive material transfer task. Movement speed (15, 30, 45 transfers/minute) and magnetic disturbance (absent, present) were the independent variables. Optical motion capture was the reference. Root-mean-square differences (RMSD) exceeded 20° when inclination measurements (pitch and roll) were calculated using the IMU accelerometer. A linear Kalman filter and a proprietary, embedded Kalman filter reduced inclination RMSD to <3° across all movement speeds. The RMSD in the heading direction (i.e., about gravity) increased (from <5° to 17°) under magnetic disturbance. The linear Kalman filter and the embedded Kalman filter reduced heading RMSD to <12° and <7°, respectively. Use of IMUs and Kalman filters can improve inclinometer measurement accuracy. However, magnetic disturbances continue to limit the accuracy of three-dimensional IMU motion capture.