VORAC: Vision-Guided Oblique Swivel Joint-Based Redundant Robotic Manipulator for Accessing Confined Spaces

Abstract

Accessing confined spaces such as storage tanks, process vessels and aircraft wings for performing inspection and maintenance tasks present significant safety risks and operational challenges for human workers. This paper introduces VORAC, a novel 7-DOF modular redundant robotic manipulator specifically designed for adapting limited entry and unstructured nature of these spaces. It features a unique kinematic configuration combining a prismatic joint, a twisting joint, and five oblique swivel (OS) joints. A key design feature is an internal tubular access path that enables the delivery of utilities from base to the end-effector (EE). The system is guided by an EE-mounted RGB-D camera for 3D environmental perception. The paper presents Particle Swarm Optimization (PSO) based path planning algorithm that enables collision-free passage for the manipulator through provided waypoints. Vision-based surface feature extraction algorithms were developed for waypoint identification, specifically by detecting circular openings and geometrically modeling pipe bends from point cloud data. The effectiveness of the integrated system is validated with a functional prototype, demonstrating successful semi-autonomous navigation in emulated confined space scenarios.