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

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. © 2018, Springer Nature Singapore Pte Ltd.