Effect of object and human-factor characteristics on the preference of thumb-index finger grasp type

Abstract

This work is to investigate the factors affecting the preference of human thumb-index finger grasping type. A multinomial logistic regression analysis shown that the object characteristics (equivalent diameter and shape) and human-factor characteristics (hand-used, finger-length sum and finger-length ratio) had significant contributions on the preference of thumb-index finger grasp type (p < 0.05) but the gender had not (p > 0.05). Subsequently, two mathematical equations were proposed for predicting the probability at which the precision-pinch and power-grasp were chosen for grasping an object. The probability at which the precision-pinch was chosen gradually decreased with the increase in the equivalent diameter of objects, but it is opposite for the power-grasp case. The shorter the finger-length sum, the more likely the participant was to select the power-grasp for grasping an object compared to the precision-pinch. The power-grasp was the most frequently chosen for the finger-length ratios of 1.0–1.25 and 1.75–2.0.

Practitioner summary: This fruitful study gave explanation of the relationship between the object and human-factor characteristics and the preference of human thumb-index finger grasp type, which would be helpful to make intelligent grasping planning strategies for two-finger bionic mechanical hands.

Keywords:

• Thumb-index finger
• object characteristics
• human-factor characteristics
• grasping type
• robotic hand

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by a European Marie Curie International Incoming Fellowship [326847 and 912847], a Special Foundation for Talents of Northwest A&F University [Z111021801], a Shaanxi Project of Science and Technology Activities for Returning from Overseas [2018030] and a Key Research and Development Plan of Shaanxi Province [2019NY-172].