Experimental study on human upper link point-to-point movements which require positioning accuracy

Abstract

In this paper, characteristics of point-to-point movements of a human upper link are investigated. First, we examine movement without constraint on the target point. The results show that both the hand trajectory and the velocity pattern are consistent with the minimum jerk theory. Second, we examine movement which requires accuracy of positioning at the target point. It is found that the hand trajectory is straight as the minimum jerk theory. However, the velocity pattern differs from bell shaped velocity pattern explained by the minimum jerk theory, and has its peak in the first half of duration. When high accuracy of positioning is required, velocity peak position moves from the beginning of the duration toward the center of the duration with the number of trials and the duration decreases with the number of trials. Third, to examine movement which requires constraint on the arm posture at the target point, we conduct experiments that a human tries to grasp a glass. A roundabout trajectory around the target is observed. In addition, the similar velocity pattern as the above experiment is obtained. The duration becomes larger due to the roundabout trajectory.