A simple test to assess the static and dynamic accuracy of an inertial sensors system for human movement analysis.

In the present study we introduced a simple test to assess the orientation error of an inertial sensors system for human movement analysis, both in static and dynamic conditions. In particular, the test was intended to quantify the sensitivity of the orientation error to direction and velocity of rotation. The test procedure was performed on a 5 MT9B sensors Xsens acquisition system, and revealed that the system orientation error, expressed by Euler angles decomposition, was sensitive both to direction and to velocity, being higher for fast movements: for mean rotation velocities of 180 degrees/s and 360 degrees/s, the worst case orientation error was 5.4 degrees and 11.6 degrees, respectively. The test can be suggested therefore as a useful tool to verify the user specific system accuracy without requiring any special equipment. In addition, the test provides further error information concerning direction and velocity of the movement which are not supplied by the producer, since they depend on the specific field of application.