Three potential problems exist in multifingered hands. The impact forces that result during each instant of grasping a rigid object can affect the functioning of the finger tip sensor. A hand with hard fingers cannot securely grasp objects that have uneven surfaces due to the poor conformability of the fingers. Repetitive strains are induced into the fingers throughout manipulation task. Carefully chosen materials-plastic, rubber sponge, a fine powder, a paste, and a gel-were experimentally compared for their ability to overcome these three problems. Results showed that sponge is the most suitable and plastic is the least suitable for the application. For practical reasons, however, the gel was a good compromise over the sponge. It is recommended that future robotic hands constitute a soft finger or at least fingers with soft tips, constructed out of carefully chosen materials.>

Extending the grasp compliance center concept to grasps in dynamic situations, previous work formulated a concept termed the grasp admittance center and showed that a grasp with an admittance center will have four distinct advantages: stability, decoupled force/motion relation, decoupled time response, and the ease of assigning the grasp dynamic behavior. The authors obtain the analytical conditions that must be satisfied for an admittance center to be achievable. They develop a procedure for computing the necessary fingertip impedances to achieve a desired admittance center. The results of experiments showing the regulation of the apparent impedances of a typical finger are presented.>

A grasp with an admittance center will have the following three consequential advantages: (1) the disturbing forces and motions experienced by the grasped object result in motions and forces on the respective degrees of freedom only; (2) the task of specifying the behavior of the object then reduces to that of specifying the behaviors of a finite number of linear second-order systems; and (3) each degree of freedom of the grasp will then be a linear second-order system and will always be stable. Since all such degrees of freedom are dynamically decoupled, the grasp as a whole will be stable. Contributing to achieve such a behavior in articulated multifingered grasps is the prime objective of the work.>