Design, modelling and control of hyper-redundant robots in constrained environments: A review

Hyper-redundant robots (HRs), with their slender, flexible, and highly redundant structures, are uniquely suited for operation in hazardous, harsh, and confined environments where traditional rigid robots face limitations. This review systematically examines developments in the design, modeling, and control of HRs over the past two decades (2005∼2025), based on comprehensive literature retrieval from Web of Science and Scopus. We categorize key advances in actuation technologies-including electric motors, cable, pneumatic, and bionic muscle actuators-and structural innovations enabling compliance and dexterity in constrained spaces. The review contrasts traditional geometric modeling approaches, such as piecewise constant curvature and Cosserat rod theories, with modern data-driven and hybrid learning-based control methods. Applications span diverse domains, including nuclear facilities, aerospace engine inspection, pipeline and underwater maintenance, aerial robotics, and minimally invasive surgery. We further identify major research challenges, such as stiffness regulation, real-time dynamic modeling, integration of smart materials, miniaturization, proprioceptive sensing, and safe human-robot collaboration. By synthesizing design principles, modeling frameworks, and control methods, this review not only evaluates the current maturity of HR research but also identifies potential opportunities for future advancement. The purpose of this review is to provide a reference point for researchers interested in the design, modeling, and control of HRs operating in constrained environments.