The FRE Gripper with Planar Grasp Stability, using Spatial Form-Closure

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Abstract

Fin Ray Effect (FRE) grippers have proven versatile and effective in pick & place automation applications. However, spherical and lateral round objects are still a challenge for the state-of-the-art, as solutions are unstable when placing those objects off-centre from the longitudinal line. Resulting in large and heavy FRE gripper assemblies. The object often shoots out of the grip, since the gripper cannot counteract the lateral forces from the object with normal forces from the structure, but instead has to rely on friction forces. In this paper, a new spatially designed FRE based gripper is proposed that form-closes around the spherical object, providing a stable grip. The design variables, such as structural variations and different thicknesses of segments, are modelled using LiveLinks between SolidWorks, COMSOL and MATLAB, resulting in an optimal design. The optimal design is then compared to a basic FRE gripper design, using the model, and the stability of both is validated in the real world by an experiment. The new design shows improved performance compared to the Basic FRE grippers, and even shows centering capabilities for frictionless objects.