Posture from motion

This paper presents an estimator to obtain the posture of a moving skeleton, i.e. all relative orientations of the skeleton´s bodies that are connected via a common joint. The estimator uses inertial sensor data only, the relative orientation around all axes is obtained without magnetometers. Instead, the accelerations of the skeleton´s motion provide information about the otherwise missing degree of freedom. The method also yields the orientation of the skeleton as a whole except for the heading. In addition, a technique to decouple the estimation rate from the sensor sampling rate is introduced. The estimator both with and without rate decoupling is evaluated against ground truth data and yields relative orientations about 5 degrees off ground truth while the skeleton moves.