Exoskeletons can track the wearer’s movements in real time, thereby enhancing physical performance or restoring mobility for individuals with gait impairments. These wearable assistive devices have demonstrated significant potential in both rehabilitation and industrial applications. This review focuses on the major advancements in exoskeleton technology published since 2020, with particular emphasis on the development of structural designs for lower-limb exoskeletons employed in locomotion assistance. We employed a systematic literature review methodology, categorizing the included studies into three main types: rigid exoskeleton, soft exoskeleton, and tethered platform. The current development status of robotic exoskeletons is analyzed based on publication year, system weight, target assistive joints, and main effects. Furthermore, we examine the factors driving these advancements and their implications for the field. The key challenges and opportunities that may influence the future development of exoskeleton technologies are also highlighted in this review.

Cable-driven exosuits have the advantages of being lightweight, compact, and well-adapted due to avoiding extensive usage of rigid structures to transmit power. However, applying too many flexible materials into the system will cause some problems such as insufficient stiffness, easy deformation, and non-negligible friction, thus increasing the difficulty of synergistic control between the human and cable-driven exosuit. In this letter, we attempt to control the exosuit effectively and reliably to provide assistance for the elbow, by analyzing the force and position relationship of connecting parts between the power source and the joint. The fundamental laws of Tendon-Sheath Mechanism (TSM) are deeply analyzed, which has obtained the corresponding mathematical description of force transmission and cable elongation. A spring-damping model is introduced between the tendon end and forearm to describe the character of textile-based interface, whose parameters could be identified by the least square method with the forgetting factor. Then, these theoretical analyses are incorporated into the human-in-the-loop modeling that can achieve appropriate motion generation from the desired joint torque to the actuator output. In the experiments, we have evaluated the output performance of the fabricated prototype and its efficacy on muscle activity based on the identification of spring coefficient and damping coefficient. The results demonstrate that the exosuit is able to respond appropriately to the changes of elbow position while realizing accurate tracking of the torque profile (the RMSE is 0.092 ± 0.011 Nm). In addition, it can effectively reduce the magnitude of muscle activation (29.52% reduction in biceps activation), thereby alleviating physical fatigue.