High-speed electrical connector assembly by structured compliance in a finray-effect gripper

TL;DR

This paper introduces a novel 3D-printed finray-effect gripper with structured compliance for high-speed electrical connector assembly, enabling precise, rapid, and adaptable insertion despite tight tolerances.

Contribution

It presents a new design of additively manufactured fingers with directionally-dependent stiffness, improving high-speed assembly accuracy and speed without sensors.

Findings

Achieved a 7.5 mm tolerance window in connector insertion

Supported approach speeds up to 1.3 m/s

Demonstrated effective directional compliance and force application

Abstract

Fine assembly tasks such as electrical connector insertion have tight tolerances and sensitive components, requiring compensation of alignment errors while applying sufficient force in the insertion direction, ideally at high speeds and while grasping a range of components. Vision, tactile, or force sensors can compensate alignment errors, but have limited bandwidth, limiting the safe assembly speed. Passive compliance such as silicone-based fingers can reduce collision forces and grasp a range of components, but often cannot provide the accuracy or assembly forces required. To support high-speed mechanical search and self-aligning insertion, this paper proposes monolithic additively manufactured fingers which realize a moderate, structured compliance directly proximal to the gripped object. The geometry of finray-effect fingers are adapted to add form-closure features and realize a directionally-dependent stiffness at the fingertip, with a high stiffness to apply insertion forces and lower transverse stiffness to support alignment. Design parameters and mechanical properties of the fingers are investigated with FEM and empirical studies, analyzing the stiffness, maximum load, and viscoelastic effects. The fingers realize a remote center of compliance, which is shown to depend on the rib angle, and a directional stiffness ratio of $14-36$. The fingers are applied to a plug insertion task, realizing a tolerance window of $7.5$ mm and approach speeds of $1.3$ m/s.