CRAB
Development of a Tendon-Driven Robotic Device with Soft Flexible Wheels for Mobility on Biofouled Subsea Pipelines
R. Geerts (TU Delft - Mechanical Engineering)
J. Jovanova – Mentor (TU Delft - Mechanical Engineering)
M. Peirlinck – Graduation committee member (TU Delft - Mechanical Engineering)
Lotfollah Pahlavan – Graduation committee member (TU Delft - Mechanical Engineering)
Filippo Riccioli – Mentor
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Abstract
The autonomous inspection of subsea infrastructure is significantly hindered by marine biofouling, which frequently causes traditional rigid crawlers to stall or necessitates expensive, time-consuming surface cleaning. Furthermore, the subsea infrastructure itself introduces significant obstacles, as the path is frequently interrupted by geometrically complex architectures such as interconnected valve assemblies, flanges or varying pipeline diameters. To address these limitations, this research presents the design, computational modelling, and empirical validation of the Compliant Robotic Architecture for Biofouling (CRAB) prototype. The CRAB leverages inherent material compliance to overcome these obstacles on pipelines.
The architecture integrates three core subsystems: a tendon-driven, underactuated gripper for adaptive enclosure, a passive magnetic sliding track for variable circumference locking, and fluid-filled flexible wheels designed to deform over obstacles. Finite element analysis was
utilised to optimise the wheel morphology.
Empirical validation of the prototype confirmed the viability of the core design concept, with the CRAB successfully achieving a secure grasp and overcoming simulated radial biofouling up to 50 mm in radius. However, testing also exposed critical failures, specifically material ruptures at 60 mm obstacle and kinematic stalling within the variable locking mechanism.
Ultimately, this research validates the foundational methodology of using passive mechanical compliance for unstructured subsea mobility. While the core kinematics are proven effective, advancing the system toward autonomous field deployment requires the integration of anactive mobility actuation system, comprehensive dynamic stability analysis, structural refinements and material optimisation.