Robotic inspection and maintenance are gaining importance due to the number of different scenarios in which robots can operate. The use of robotic systems to accomplish such tasks has deep implications in terms of safety for human workers and can significantly extend the life of infrastructures and industrial facilities. In this context, long-reach cable-driven hyper-redundant robots can be employed to inspect areas that are difficult to reach and hazardous environments such as tanks and vessels. This paper presents a novel long-reach cable-driven hyper-redundant robot called SLIM (Snake-Like manipulator for Inspection and Maintenance). SLIM consists of a robotic arm, a pan and tilt mechanism as end-effector, and an actuation box that can rotate and around which the arm can wrap. The robot has a total of 15 degrees of freedom and, therefore, for the task of positioning the tool centre point in a bi-dimensional Cartesian space with a specific attitude, it has 10 degrees of redundancy. The robot is designed to operate in harsh environments and high temperatures and can deploy itself up to about 4.8 m. This paper presents the requirements that drove the design of the robot, the main aspects of the mechanical and electronic systems, the control strategy, and the results of preliminary experimental tests performed with a physical prototype to evaluate the robot performances.

Due to their uniqueness, hyper-redundant manipulators are becoming increasingly relevant in robotics research. The abundance of degrees of freedom makes them adaptable to a variety of applications across various fields, including inspection, medical procedures, and space exploration. These manipulators are particularly effective where high maneuverability is needed, particularly in constrained environments, thanks to their surplus of degrees of freedom. While this hyper-redundancy offers significant benefits, it also introduces complexities in developing effective actuation strategies and innovative design solutions. This work is the first of two parts of a survey conducted on hyper-redundant manipulators, their design, and actuation strategies. This first part of the review provides an examination of the current state of tendon-driven hyper-redundant manipulator design and actuation, analyzing both continuum and rigid-link manipulators. The article synthesizes recent advancements, explores various designs, and identifies key challenges.

Due to their distinctiveness and potential uses, hyper-redundant manipulators are becoming increasingly relevant in robotics research. The high number of degrees of freedom makes them suitable for various applications across various fields, including inspection, minimally invasive surgery, and space applications. These manipulators are especially useful where high manoeuvrability is needed, particularly in constrained environments, thanks to their abundance of degrees of freedom. While having significant benefits, this redundancy introduces complexities in developing robust actuation and innovative designs. This work is the second of two parts of a survey conducted on hyper-redundant manipulators, analyzing continuum, and rigid-link manipulators. The aim of this survey is to provide a comprehensive analysis of non-tendon-driven hyper-redundant manipulators, examining their unique design and actuation strategies and identifying their potential advantages and challenges compared to tendon-driven counterparts. By focusing on these alternatives, this survey seeks to expand the understanding of hyper-redundant manipulator technology and highlight innovative approaches in this evolving field. The article synthesizes recent advancements, explores various designs, and identifies critical challenges.

This work describes the advancement in developing a cable-driven gear transmission joint designed as a basic element for a long-reach hyper-redundant robot. Hyper-redundancy allows the robot to perform auxiliary tasks such as obstacle avoidance and joint limits satisfaction. This feature makes hyper-redundant robots particularly useful for performing tasks in confined and hazardous environments and areas that are not reachable by a human operator. The long-reach feature of the robot requires a detailed study of the overall structure and its components. The joint must be capable of transmitting forces and movements over a long distance without losing the precision and accuracy of the end-effector, so it is designed to optimise the robot’s performance in terms of stiffness, structural resistance, and functional characteristics. In light of the above considerations, the main focus of this work is to improve the structural performance of the entire robotic system. Consequently, since the most critical component of the robot in terms of torsional deformation is the gear transmission joint, this paper aims to design a torsional stiffener element to reduce its deformation and, thus, an increase of torsional stiffness of the overall robotic system. Tube-shaped and rectangular-shaped stiffener elements, which can fit the joint design satisfying its geometrical constraints, are proposed. A computer-aided engineering approach is implemented to improve the precision of positioning of the end-effector by adding stiffener elements in the joint. Two sensitivity analyses, varying the geometry of the proposed stiffener elements, are performed to evaluate their performance in terms of added mass and displacement reduction.

In recent years, significant advancements have been made in robotics, especially with the introduction of continuum and hyper-redundant robots. These robots can be highly flexible and manoeuvrable, which makes them suitable for intricate underwater maintenance, exploration, and inspection tasks. Inspired by the motions of aquatic life, underwater snake-like robots offer a good way to accomplish subsea maintenance, exploration, and inspection activities. While many studies have been conducted on hyper-redundant, snake-like robotic arms for maintenance and inspection in land-based applications, not as much about robotics intended for marine or underwater applications has been studied. This review critically examines recent advancements in the design, actuation, and modelling of these robotic systems, categorising them into two primary families: untethered mobile robots and tethered robotic manipulators. Key insights include the identification of strengths and limitations associated with various designs and actuation strategies, such as the high manoeuvrability but limited speed of bioinspired swimming robots compared to thruster-driven designs, and the complexity versus precision trade-offs inherent in tendon-driven manipulator arms. Furthermore, the modelling techniques employed across categories are systematically analysed, as well as challenges such as the modelling of fluid–structure interactions and the need for improved real-time models for compliant and soft robots.