A comparison of workspace and force capabilities between classes of underactuated mechanisms

We propose a novel approach to study the ability of an underactuated mechanism, or a mechanism that has fewer actuators than degrees of freedom, to passively adapt to environmental constraints. While prior work in underactuated robotic hands has primarily focused on the mechanism´s ability to curl its distal degrees of freedom inward even after the proximal degrees of freedom are constrained by contact with the environment, this paper explores the mechanism´s adaptability in terms of both motion and force-application capabilities in the presence of external constraints. Specifically, using four different transmissions for a novel singly-actuated linear three degree-of-freedom mechanism, this paper analyzes how the system´s ability to reconfigure joints and apply new contact forces varies as a function of the transmission configuration and object geometry. We show that with more extensive re routing of a single actuator to multiple joints, the mechanism exhibits greater motion and force adaptability at the cost of decreased maximum joint travel and contact forces.