SLITHER

This project aims to develop a novel type of robots with a hyper-redundant, multi-segment, snake-like architecture, specifically designed to navigate inside confined spaces that are today inaccessible to conventional rigid-link robots. This robot will deploy tools or sensors in such challenging environments. Each segment will incorporate an innovative 3D helical tensegrity structure, featuring independent actuation through intrinsic or extrinsic methods. The use of tensegrity structures is driven by 3 key advantages: (1) the capacity to support significant payloads while remaining lightweight and compliant, (2) the ability for large reconfiguration within a compact design, and (3) the potential to adjust stiffness by modulating the system's prestress. Besides, the helical design will be considered to improve torsional stiffness, a common issue in small-scale snake-like robots. While design methods exist for large-scale robots to obtain high torsional stiffness, scaling down can lead to a significant reduction in torsional stiffness. Therefore, our approach involves proposing a scale-invariant design method to optimize performance, particularly regarding torsional stiffness, ensuring effectiveness even at smaller scales. The development of this robot presents 3 key challenges: (1) designing a one-segment 3D helical tensegrity structure with specified bending, longitudinal and torsional stiffness to support a predetermined payload under gravitational forces, which requires establishing adequate models and synthesis approaches; (2) designing a multi-segment, discrete snake-like robot by cascading segments, developing a synthesis method to determine the minimum number of required cables, planning their routing, and selecting appropriate materials; and (3) developing a pose and stiffness controller to manage the configuration as well the stiffness variation of the mechanism.