A Novel Walking Parallel Robot for On-Structure Three-Axis Machining of Large Structures

Abstract

AbstractThis paper presents a novel walking hybrid-kinematics robot having three degrees-of-freedom for on-structure machining of large structures. A symmetric 3PRRR parallel mechanism having maximally regular properties is used to provide three-dimensional translational manipulation. Three attachment pads are connected to the base of the parallel mechanism through passive spherical joints, whereas multiple attachment pads are connected to the moving platform of the parallel mechanism. A machining task is performed by using a retractable tool holder attached to the parallel mechanism's moving platform. Two walking patterns, namely rotational and translational walking patterns, are defined for the robot. The kinematics of the manipulation and walking motions was derived and simulated. Several schemes to perform multi-step walking motions were also discussed. Subsequently, using an energy-based approach with the Stribeck friction model, the robot's dynamics was modeled and experimentally verified. Finally, an implementation of the robot to perform an on-structure machining task is discussed.