Robot Assisted Gait Training With Active Leg Exoskeleton (ALEX)

Abstract

Gait training of stroke survivors is crucial to facilitate neuromuscular plasticity needed for improvements in functional walking ability. Robot assisted gait training (RAGT) was developed for stroke survivors using active leg exoskeleton (ALEX) and a force-field controller, which uses assist-as-needed paradigm for rehabilitation. In this paradigm undesirable gait motion is resisted and assistance is provided towards desired motion. The force-field controller achieves this paradigm by effectively applying forces at the ankle of the subject through actuators on the hip and knee joints. Two stroke survivors participated in a 15-session gait training study each with ALEX. The results show that by the end of the training the gait pattern of the patients improved and became closer to a healthy subject's gait pattern. Improvement is seen as an increase in the size of the patients' gait pattern, increased knee and ankle joint excursions and increase in their walking speeds on the treadmill.

An admittance shaping controller for exoskeleton assistance of the lower extremities

“…The prevalent view is that control of the walking task must be shared by the user and the exoskeleton, with the device allowing for the user's intention and voluntary efforts Vallery et al 2009b;Bernhardt et al 2005). Strategies for shared control include timing the exoskeleton's response to the phases of the gait cycle (Blaya and Herr 2004;Kawamoto and Sankai 2005;Malcolm et al 2013), leading the patient towards a clinically correct trajectory via soft constraints (Banala et al 2009) and modifying the dynamic response of the lower limbs by means of active admittance (AguirreOllinger et al 2011) or generalized elasticities (Vallery et al 2009a). Also, the view of human gait as a stable limit cycle has led to the emergence of oscillator-based exoskeleton control.…”

“…(b) Propulsion of the unconstrained leg, for example during the swing phase of walking (Veneman et al 2005;Banala et al 2009). (c) Gravitational support of the extremities (Banala et al 2006).…”

“…(d) Correcting anomalies of the gait trajectory (Banala et al 2009;Van Asseldonk et al 2007). (e) Balance recovery and dynamic stability during walking (European Commission (CORDIS) 2013).…”

Assist-as-Needed Control of a Robotic Orthosis Actuated by Pneumatic Artificial Muscle for Gait Rehabilitation

“…Most of the commercial rehabilitation systems are driven by electric motors [1][2][3][4][5][6][7][8] due to the fact that advanced control techniques can easily be applied to achieve the best performance. One typical example is the LOKOMAT system from Hocoma AG, Volketswill, Switzerland [1].…”

“…The hip and knee joints are actuated by a direct current (DC) motor with helical gears. Similar systems such as ReoAmbulator (Motorika Ltd., Mount Larel, NJ, USA) [5], lower extremity powered exoskeleton (LOPES) [6,7], or active leg exoskeleton (ALEX) [8][9][10] with linear actuator are also available with AAN rehabilitation strategy. However, these motorized systems are fairly expensive due to the high cost of the servo system including the driver, motor, sensors and gear.…”