Grasp Stability and Design Analysis of a Flexure-Jointed Gripper Mechanism via Efficient Energy-Based Modeling

For flexure-based gripper mechanisms, the arrangement and design of joint elements may be chosen to allow enclosure of objects in grasping. This must provide stable containment under load, without causing excessive stress within the joint materials. This paper describes an energy-based model formulation for a cable-driven flexure-jointed gripper mechanism that can accurately describe the nonlinear load-deflection behavior for a grasped object. The approach is used to investigate the limits of grasp performance for a gripper with two single-joint fingers through simulation studies, including the accurate prediction of stability limits due to joint buckling. Hardware experiments are set up and conducted to validate the theoretical model over a range of loading conditions that exceed limits for stable grasping. Parametric design studies are also presented to show the influence of joint geometry on both grasp stability and flexure peak stress. Considering the intersection of feasible design sets, generated from simulation data over a range of possible object geometries, is shown to be an effective approach for selecting gripper design parameters.