On the Effect of Contact Friction and Contact Compliance on the Grasp Performance of Underactuated Hands

摘要

Although adding compliant, frictional material on robotic fingers to improve the performance is generally accepted, at least for underactuated hands this effect is hardly quantified. In this study, the phalanges of an underactuated hand in an experimental setup were firstly covered with material of different friction coefficients but equal contact compliance, while the force to pull a grasped object completely out of the hand was measured. Then, the phalanges were covered with material of different compliance while the same measurements were done. In the latter experiment, the effect of contact friction was eliminated by using a specially designed testbed that emulates a frictionless object. The experiments showed an increase of the maximal pull force by 250% when the friction coefficient of the contact material increased from 0.25 to 1.51. The compliance of the contact material had a marginal effect on this maximum force. Finally, the pull force was calculated by a static grasp model, incorporating contact friction and linear contact compliance. Trends similar to the experiments were observed in these simulations.