Task-Oriented Design Method for Monolithic Flexible Hands with Wire Drive Systems

This paper discusses a novel task-oriented design method for wire-driven flexible hands. For a monolithic hand fabricated using 3D printing, an analytical design method is proposed to enable it to perform the given tasks. First, the wiring-synergy equation, which relates the parameters of the hand mechanism, the wire tension, and the generated posture is derived based on an analytical model of a hand with wire drive systems. Next, the posture-synergy equation is derived, using principal component analysis for multiple desired postures given to perform a task. Based on the isomorphism of the mathematical structure in the two synergy equations, a method for designing a hand is developed. By quantitatively evaluating the posture reproducibility with respect to the number of wire drive systems, this method can analytically determine the mechanism parameters and wire tension for the desired postures. Subsequently, the proposed method is validated through case studies. Finally, a hand for an in-hand manipulation task is developed, and the feasibility of the proposed method is validated experimentally. The method potentially contributes to expediting the design procedure, increasing the accuracy of the posture reproduction, and reducing the number of actuators.