Implementation and experimental results of a quaternion-based Kalman filter for human body motion tracking

Abstract—Real-time tracking of human body motion is an im-portant technology in synthetic environments, robotics, and other human–computer interaction applications. This paper presents an extended Kalman filter designed for real-time estimation of the orientation of human limb segments. The filter processes data from small inertial/magnetic sensor modules containing triaxial angular rate sensors, accelerometers, and magnetometers. The filter represents rotation using quaternions rather than Euler angles or axis/angle pairs. Preprocessing of the acceleration and magnetometer measurements using the Quest algorithm produces a computed quaternion input for the filter. This preprocessing reduces the dimension of the state vector and makes the mea-surement equations linear. Real-time implementation and testing results of the quaternion-based Kalman filter are presented. Experimental results validate the filter design, and show the feasibility of using inertial/magnetic sensor modules for real-time human body motion tracking. Index Terms—Inertial sensors, Kalman filtering, magnetic sen-sors, motion measurement, orientation tracking, pose estimation, quaternions, virtual reality. I