An Integrated Differentiation-Projection Approach for the Kinematic Data Consistency of Biomechanical Systems

Abstract

Several sources of error corrupt the results obtained in the kinematic and dynamic analysis of biomechanical systems and reduce its usefulness. The main source of error is the inaccuracy of velocities and accelerations derived from experimentally measured displacements of markers placed on the skin of joints. This error is mainly due to the amplification of high-frequency low-amplitude noise introduced by the motion capture system when the raw displacement signals are differentiated. Another source of error is the skin motion artifact, that produces violations of the kinematic constraint equations of the multibody system. An integrated differentiation-projection approach to ensure the kinematic data consistency in the context of the analysis of biomechanical systems is presented. The raw data differentiation problem is solved by applying a smoothing-differentiation technique based on the Newmark integration scheme. Several benchmark kinematic signals that include computer generated data of a four-bar mechanism were processed using the differentiation-projection method to study its performance.