Hybrid FES–robotic gait rehabilitation technologies: a review on mechanical design, actuation, and control strategies

Abstract

Gait disorders in neurologically disabled people can be treated by various techniques available today which include passive orthoses, functional electrical stimulation (FES) and robot assisted gait training devices (RAGT). However, each system has its own drawback. For example, gait rehabilitation with orthosis is physically taxing for the patient with no significant functional improvement. FES uses muscle powers as physiological actuators to promote balance and improve gait but leads to fatigue, along with poor control of joint trajectories. RAGT devices including powered exoskeletons, gait rehabilitation systems employing programmable footplates and mobile training platforms, have shown significant advantages but the devices are not yet mature due to numerous drawbacks associated with physical and cognitive interaction, energy-management and portability issues. The combination of FES technology and RAGT devices, often named hybrid FES-robot technologies, has arisen as a promising approach to aid in gait restoration. This work reports a comprehensive review on the hybrid FES-robot technologies over the last decades, focusing on different mechanical structures, actuator designs, sensing technologies, and control approaches. The hybrid robotic structures are classified into two categories: (i) orthotic-based hybrid systems, where (a) FES is used to stimulate the muscles and produce joint torque while the robotic system acts as energy dissipating device, and (b) FES and robotic systems are both torque-generating devices; and (ii) non-orthotic based hybrid systems. The review compiles a variety of sources and illustrates the technology's most important challenges in the fields of hybrid rehabilitation robotics which may contribute towards further development of hybrid robot systems.

System Transparency in Shared Autonomy: A Mini Review

“…Wearable robots like exoskeletons are coupled to the user, and the robot moves with the wearer cooperatively (Awad et al, 2017 ; Anaya et al, 2018 ; Bai et al, 2018 ; Fani et al, 2018 ). In this case, the design should be able to follow the human movements minimizing resistive forces felt by the human, i.e., the design should be mechanically transparent.…”

Supplemental Stimulation Improves Swing Phase Kinematics During Exoskeleton Assisted Gait of SCI Subjects With Severe Muscle Spasticity

“…Depending primarily on FES alone for gait can be metabolically taxing, is prone to rapid fatigue, and may lack limb control and stability. For these reasons effort has gone into combining FES with orthotic devices, generally called hybrid FES systems, which can provide several advantages relative to using FES alone (Andrews et al, 1988 ; Isakov et al, 1992 ; Goldfarb et al, 2003 ; Bulea et al, 2013 ; del-Ama et al, 2014 ; Chang et al, 2017 ; Anaya et al, 2018 ), and one prior study investigated a hybrid FES system that couples FES with a robotic exoskeleton (Ha et al, 2016 ). That study specifically coupled a lower limb exoskeleton with FES of the quadriceps and hamstrings muscle groups of each leg, and demonstrated reduced exoskeleton motor torque and power when used in a hybrid FES manner.…”

Design of the Cooperative Actuation in Hybrid Orthoses: A Theoretical Approach Based on Muscle Models

“…In this first approach, we take the weighting factors to be the same for both actuators (δ = 0.5). The weighting factors can be associated with the level of assistance in a hybrid orthosis (Anaya et al, 2018). The parameter δ basically represents some priority given to the use of either the FES actuation or the motor actuators.…”

“…Using hybrid orthosis to stimulate the lower extremity muscles has proven to evoke muscle hypertrophy, increase strength, improve cardiopulmonary fitness, and reduce fatigue during gait, even in subjects with severe spasticity (Nightingale et al, 2007; Qiu and Taylor, 2016; Deley et al, 2017; Ekelem and Goldfarb, 2018; Lambach et al, 2018). Complete recent reviews of hybrid exoskeletons can be found in Stewart et al (2017) for the upper limbs, and Anaya et al (2018) for the lower limbs.…”