TOUCH PROCESSING MODEL IN HUMAN GRASPING BASED ON THE STICK RATIO WITHIN A FINGERTIP

本研究以日常生活中产生触觉的典型基本动作--握力运动为研究对象，对完成握力动作所需的基本触觉信息进行了建模。具体地说，讨论了基于弹性理论的指尖接触模型，并利用原始的触觉测量装置进行了心理物理实验。在切向夹持弹性球体的接触界面上，部分滑移(初滑)发生在外围，这被认为与握力控制有明显的关系。在本研究中，引入了粘结率，即粘结区与接触区的比率。这是一个标量参数，表示弹性球体的广义接触状态。在此基础上，提出了基于杆比的抓持力控制假设。据报道，无论被抓取的物体如何，握力都具有类似的安全裕度。因此，杆比被认为是抓握过程中主要的触觉输入。由于粘着比是广义滑移裕度，适当的握力只需收敛于粘着比的近似值即可实现。通过对抓持过程中粘着比的测量，验证了该假设的正确性。在实验中，受试者被要求在重量和虚构随机改变的情况下反复举起设备。因此，可以观察到杆比和握力/负载力从没有经验的情况到有经验的情况的转变。结果表明，在不同条件下，多次实验后，粘附率都收敛到相似的值，这些结果表明，皮肤内的受体可以检测到粘附率，并且在人类抓取时，它收敛到相似的值。也就是说，这些结果有力地支持了所提出的假设

In this research, grasping movement, typical and fundamental action entailing the touch sensation in a daily life, is investigated, and essential touch information necessary to accomplish the "grasping" is modeled. Concretely, a fingertip contact model derived from the theory of elasticity is discussed, and psychophysical experiments are carried out with an original touch measurement device.First, a fingertip contact is modeled using the theory of an elastic contact. In a contact interface of a tangentially baded elastic sphere, partial slip (incipient slip), suggested to have explicit relations with the grip force control, occurs from the peripheral. In this research, the stick ratio, defined as the ratio of the stick region to the contact region, is introduced. This is a scalar parameter indicating the generalized contact state of an elastic sphere. Then, the grip force control hypothesis based on the stick ratio is proposed. The grip force is reported to have similar safety margin regardless of the grasped object. SO, the stick ratio is *umed as a major tactile input in grasping. Since the stick ratio is a generalized slip margin, proper grip force can he realized just converges the stick ratio in a similar value.Measurement of the stick ratio during grasping are carried out to show the validness of the hypothesis. In the experiments, subjects are asked to lift up the device with its weight and fiction randomly changed, repeatedly. So, the transition of the stick ratio and the grip/load force from inexperienced to well experienced situations can be observed. The results demonstrate that the stick ratio converges to a similar value after several trials regardless of the condition.These results suggest that the stick ratio can be detected by receptors within a skin, and it converges to a similar value in human grasping. That is, these results strongly support the proposed hypothesis