Motion Analysis of Upper Limb and Hand in a Haptic Rotation Task

TL;DR

The results showed that the wrist joint, the sideways finger movement in the proximal joints, and the distal finger joints contributed significantly to overshooting, which suggests that two phenomena are behind the overshooting.

Abstract

Humans seem to have a bias to overshoot when rotating a rotary knob blindfolded around a specified target angle (i.e. during haptic rotation). Whereas some influence factors that strengthen or weaken such an effect are already known, the underlying reasons for the overshoot are still unknown. This work approaches the topic of haptic rotations by analyzing a detailed recording of the movement. We propose an experimental framework and an approach to investigate which upper limb and hand joint movements contribute significantly to a haptic rotation task and to the angle overshoot based on the acquired data. With stepwise regression with backward elimination, we analyze a rotation around 90 degrees counterclockwise with two fingers under different grasping orientations. Our results showed that the wrist joint, the sideways finger movement in the proximal joints, and the distal finger joints contributed significantly to overshooting. This suggests that two phenomena are behind the overshooting: 1) The significant contribution of the wrist joint indicates a bias of a hand-centered egocentric reference frame. 2) Significant contribution of the finger joints indicates a rolling of the fingertips over the rotary knob surface and, thus, a change of contact point for which probably the human does not compensate.

Figures (8)

• Figure 1: Grasping orientations from the top view. T denotes the thumb's position and IF the index finger's position on the rotary knob. Participants were standing, in relation to the figure's displayed top view, below the figure.
• Figure 2: Schematic representation of the upper limb and hand model used in this work to estimate joint angles based on motion data. The upper limb model was created based on the example in Yahya2019MCS. The hand model is part of the automatic motion tracking software Maycock2015FAO and was created by Schroder2014RTH.
• Figure 3: Standardized body posture from the side and top view.
• Figure 4: Schematic representation of finger joint movements. Top: Movements of the thumb. Bottom: Movements of the index finger.
• Figure 5: Illustration of the rolling mechanism. T denotes the thumb and IF the index finger. The column top view, row start position shows with the blue and red dot the initial contact point between the fingers and the rotary knob. The row end position shows the fingers after the 90 rotation, while the initial contact points are still marked. It is visible, that since the fingers have rolled over the rotary knobs surface, the new contact points are different. It also becomes apparent that in case the fingers perform a 90 rotation, the rotary knob rotated slightly more. The side view columns are just for reference to show how the index finger's DIP is flexed, the MCP is abducted and the thumb's IP and TMC are flexed.