Systematic Review on Wearable Lower-Limb Exoskeletons for Gait Training in Neuromuscular Impairments

Abstract

Gait disorders can reduce the quality of life for people with neuromuscular impairments. Therefore, walking recovery is one of the main priorities for counteracting sedentary lifestyle, reducing secondary health conditions and restoring legged mobility. At present, wearable powered lower-limb exoskeletons are emerging as a revolutionary technology for robotic gait rehabilitation. This systematic review provides a comprehensive overview on wearable lower-limb exoskeletons for people with neuromuscular impairments, addressing the following three questions: (1) what is the current technological status of wearable lower-limb exoskeletons for gait rehabilitation?, (2) what is the methodology used in the clinical validations of wearable lower-limb exoskeletons?, and (3) what are the benefits and current evidence on clinical efficacy of wearable lower-limb exoskeletons? We analyzed 87 clinical studies focusing on both device technology (e.g., actuators, sensors, structure) and clinical aspects (e.g., training protocol, outcome measures, patient impairments), and make available the database with all the compiled information. The results of the literature survey reveal that wearable exoskeletons have potential for a number of applications including early rehabilitation, promoting physical exercise, and carrying out daily living activities both at home and the community. Likewise, wearable exoskeletons may improve mobility and independence in non-ambulatory people, and may reduce secondary health conditions related to sedentariness, with all the advantages that this entails. However, the use of this technology is still limited by heavy and bulky devices, which require supervision and the use of walking aids. In addition, evidence supporting their benefits is still limited to short-intervention trials with few participants and diversity among their clinical protocols. Wearable lower-limb exoskeletons for gait rehabilitation are still in their early stages of development and randomized control trials are needed to demonstrate their clinical efficacy.

Closed-loop Control Design and Motor Allocation for a Lower-limb Cable-driven Exoskeleton: A Switched Systems Approach

“…A motorized exoskeleton with a user can be modeled as a four-link bipedal walking system in the sagittal plane as follows M (q)q + C(q, q) q + G(q) + P (q, q) + d(t) = τ e (q, q, t), (1) where q : R ≥t0 → R 4 denotes the measurable hip and knee joint angles on both sides, q, q : R ≥t0 → R 4 denote the measurable joint angular velocities and unmeasurable joint angular accelerations, respectively, where t 0 ∈ R >0 is denoted as initial time; M : R 4 → R 4×4 >0 denotes the combined human-exoskeleton inertia; C : R 4 × R 4 → R 4×4 and G : R 4 → R 4 denote centripetal-Coriolis and gravitational effects, respectively; P : R 4 ×R 4 → R 4 denotes the damping and viscoelastic effects; and d : R ≥t0 → R 4 denotes unmodeled terms and disturbances. The torque produced by the electrical motors are expressed as τ e : R 4 ×R 4 ×R ≥t0 → R 4 .…”

“…Powered exoskeletons vary in their design, wearability, sensing, and actuation. Existing powered exoskeletons use electrical motors [1], hydraulic [2] and pneumatic actuators [3], [4]. The actuators used to outfit the exoskeleton influence the magnitude and response of the inputs applied to the body and thus the human-robot interaction.…”

“…Cable-driven transmission mechanisms offload actuators away from the human to reduce the weight imposed on the body and thus reduces the burden on the user-side. 1 Department of Mechanical and Aerospace Engineering, Syracuse University, Syracuse NY 13244, USA. Email: {cchang21, jacasasb, vhduenas}@syr.edu Such mechanisms have been widely applied for orthotic devices (e.g., lower-limb [7], [8], upper-limb [9], [10], hand orthoses [11]) to provide torques about the joints to assist or augment human function.…”

“…Since cables cannot transmit compression forces, at least l + 1 cables are required to control l DOFs to provide an agonist-antagonist movement [12]. Despite the benefits of cable-driven mechanisms, two critical issues arise: (1) cables experience a slack behavior if the tension is not accurately controlled, thus affecting the response time; (2) undesired agonist-antagonist coordination may produce counteracting torques about a joint. Hence, it is essential to develop effective control strategies to ensure coordinated or synchronized motion in a multi-joint system.…”

Control strategies used in lower limb exoskeletons for gait rehabilitation after brain injury: a systematic review and analysis of clinical effectiveness

“…High variability was found in the number of partici-702 pants (14.87 ± 13.53), number of sessions (11.77 ± 12.20),703 session frequency (times per week; 3.09 ± 1.68), and 704 session duration (50.57 ± 34.06 min) (see Figure 5.C). 705 Previous reviews that analyzed the protocol of robotic 706 treatment reported similar high variability [40,46]. 707 Some studies did not provide complete information 708 about the experimental protocol, e.g., they did not mention the number (15.09 %), duration (33.33 %), or frequency (31.44 %) of the training sessions.…”