Design of a six DOF reconfigurable gripper for flexible fixtureless assembly

In this paper, the design and development of a six degrees-of-freedom (DOF) reconfigurable gripper for implementation of robot based flexible fixtureless assembly (FFA) is described. FFA is a novel technique in which traditional fixtures used, for example, in automotive body assembly industries, are eliminated by the use of several robots, with multifinger grippers that are used to grasp and assemble parts. The objective of this work is to design, build, and test a reconfigurable gripper for the purpose of FFA. The gripper developed in this work is capable of precisely grasping parts of different geometries, rigidly holding the parts in space, and choosing different grasping points while allowing sufficient clearance for welding gun access. The overall design procedure, which is subdivided into the conceptual, configuration and parametric design, includes wrench system determination, kinematic and mechanism design. A novel three-finger gripper is developed. Each finger has two movable joints and two point-contacts with which to grasp the part. Finite element analysis is used to simulate deflections of the gripper components under load to determine critical design parameters. Finally, the workspace and the kinematic model of the reconfigurable gripper have been developed. The gripper was fabricated and tested in grasping experiments using several automotive body panels. The reconfigurable gripper is shown to achieve the objectives set out in this work.