Design and Gait Control of an Active Lower Limb Exoskeleton for Walking Assistance

In the development of assistive lower-limb exoskeletons, both exoskeleton design, and gait control are critical for their successful applications. This paper introduces an assistive lower-limb exoskeleton (ALEXO) for active walking assistance. The development of the ALEXO including mechanical design, sensors and gait control is described. The exoskeleton adopts a hierarchical control. A 2-link model is built for dynamic analysis and lower-level control purposes. A trajectory tracking control method based on the computed torque control is proposed, in which physical interaction between the exoskeleton and the user is included. Simulations were conducted for different levels of interaction forces to verify the feasibility of the gait control. Moreover, walking trials of a healthy subject were performed, with muscle activities measured through EMG systems. Both simulation and system test results demonstrated the effectiveness of the developed exoskeleton with the proposed control method for walking assistance.