Error and Sensitivity Analyses in the Biomechanics of Human Multilink Models

Abstract

Error and sensitivity in the direct dynamic simulation of the motion of a human model were analyzed using an algorithm derived from the angular momentum method. The model consisted of rigid body segments interconnected by ideal pin joints, and simulated motions of the midstance phase of human walking were performed. Several methods of numerical integration were used to determine the appropriate method and conditions for individual problems. The sensitivity of the resulting motion to the joint torque input was investigated for several kinds of simulation modes. The results showed that the errors due to numerical integration can be reduced to an acceptable level by using appropriate methods and conditions depending on individual problems. The sensitivity to torque input was more serious in some types of problems where only small perturbations cause accumulated errors in a late period. These two sources of error should be distinguished clearly and tested for using particular simulation studies of human motion.