# Cable-Driven Exoskeleton for Ankle Rehabilitation in Children with Cerebral Palsy
## 1 Introduction
These systems typically involve minimal attachment to the user, where the assisted joints are treated as an end effector [23], enhancing comfort and preserving a greater degree of natural interaction [24]. Recent studies confirm that CDPR-based exoskeletons can provide task-specific, controlled assistance that supports neuroplasticity and motor recovery, especially in populations with motor impairments such as stroke or cerebral palsy [25]. Moreover, end-effector-based lower-limb rehabilitation platforms have demonstrated outcomes that match or surpass those of traditional rigid exoskeletons in terms of safety, usability, and clinical efficacy [26; 27]. These findings underscore the potential of cable-driven systems as a robust and user-friendly alternative for robotic gait rehabilitation. The disruptive and innovative nature of CDPR-based exoskeletons has led to the emergence of several models in recent years [23]. One of the most documented and popular models is the CAREX-7 exoskeleton. This 7-degrees-of-freedom (DOF) cable-driven arm exoskeleton is designed to provide both translational and rotational assistance for upper-limb rehabilitation. Unlike traditional rigid exoskeletons, CAREX-7 employs lightweight cables to transmit forces, reducing inertia and allowing for a more natural interaction with the human arm [28]. The system consists of multiple cuffs attached to the shoulder, upper arm, forearm, and hand, enabling precise assistance and dexterous motion training while minimizing joint misalignment [26]. With its innovative wrench-field control strategy, CAREX-7 can dynamically adjust assistance levels based on the user's needs, promoting functional motor recovery and rehabilitation [28]. Other examples of cable-actuated exoskeletons are CAFE, a 3-degrees-of-freedom robotic exoskeleton designed for hand rehabilitation following stroke [29]; exoskeleton for human rehabilitation by [PERSON] et al., which is a fully actuated parallel cable-driven exoskeleton designed for shoulder rehabilitation, utilizing antagonistic cable pairs to enhance stability and motion control [24]; and Diego exoskeleton (Tyromotion, Austria), an electromechanical device designed for upper-limb rehabilitation, providing arm gravity compensation to assist patients in unilateral or bilateral arm movements, enabling three-dimensional movements of the shoulder joint, and integrating virtual reality training to enhance patient engagement during therapy [25; 30; 31]. Although cable-actuated exoskeletons have had great development during the last decade in upper-limb rehabilitation, development for lower-limb and gait rehabilitation is much less documented and widespread. A remarkable work is the one developed by [PERSON] et al., an exoskeleton designed for populations with gait impairments such as CP or stroke. This robot is composed of a frame with a variable number of cables (from one to six) and controls movement over the hip, knee, and ankle [32]. Of note also is the one developed by [PERSON] et al., a cable-driven parallel motion platform designed to help patients with waist injuries perform rehabilitation exercises. The system provides flexion/extension, adduction/abduction, and internal/external rotation of the waist by controlling cable tension [33]. Another relevant example is the ankle rehabilitation robot by [PERSON] et al. [34], which uses a CDPR mechanism to guide a mobile platform for ankle mobilization. However, this system is intended for isolated joint training in static conditions, and not for use during gait. Among the most promising recent developments is the cable-driven Lower limb Rehabilitation Exoskeleton (C-LREX) [35; 36], a conceptual robotic platform that uses four cables to control the leg in 3 degrees of freedom. It enables hip abduction/adduction and flexion/extension of the hip and knee, allowing the execution of full-leg rehabilitation trajectories toward healthy gait patterns.