Research on the Contact Force of Fingers as Grasping Bottles

Abstract

In order to study the rule of finger contact force and the cooperative control mechanism as grasping objects by hand, this paper studies the finger contact force of the user as grasping the bottle and drinking water. In this study, the contact force data of the thumb, index finger, middle finger and ring finger are collected. Experiment subjects were 10 young people and 10 aged. The contact force collecting equipment is RFP-CJ8 pressure instrument. Four bottles with different materials surface and weighing 500 g are used in the experiment. The paper find the following rules based on collected data. (1) When bottle is touched until it is lifted vertically, the contact force of fingers gradually increases and reaches the peak value and then keep stable. When the bottle is inclined to the horizontal position, the contact force of the thumb slowly increases, and the contact force of the other four fingers slowly decreases and stays the same value. Gripping control is constantly seeking the optimal solution process. (2) Each finger of young people exerts relatively stable force. There is a significant difference in the force exerted by each finger. The contact force of thumb is 6–15 N. The contact force of middle finger is 4–8 N. The index finger and ring finger are between 2–4 N. (3) The contact force of thumbs of the aged was less than 10 N. The force of the other three fingers had no significant difference, and are 2–5 N. The synergistic control ability of fingers of young people is better than that of the aged. (4) As grasping different bottle with different materials surface, contact force of the young people’s finger has less difference, contact force of the aged finger changes significantly. So, contact force of the aged is more sensitive to the material than young people’s. This study is a certain value to bionic hand development and the aged rehabilitation research.