Comparing the Performance of a Cable-Driven Active Leg Exoskeleton (C-ALEX) Over-Ground and on a Treadmill

Robotic rehabilitation devices have gained significant popularity in the past decade. Over-ground leg exoskeletons commonly use traditional rigid link architectures or support the weight of a user by strapping the user in a harness. This results in bulky and large architectures which are cumbersome and restrictive. C- ALEX is a leg exoskeleton without a rigid link structure which has been used in gait training on a treadmill. In this paper, we explore the feasibility of using the C-ALEX exoskeleton over-ground. We converted C-ALEX into a carted system for over-ground use. We tested the architecture on eight healthy subjects to compare the controller's RMS joint torque errors, the effects on step height, joint angles and the deviation of ankle trajectories from target trajectories. The results show that C-ALEX's controller and tension planner have comparable RMS torque errors with no significant difference between the two use cases. C-ALEX is able to increase the step height, affect knee flexion in both walking conditions with no significant difference. There is significant difference between C-ALEX's ability to control hip flexion angles and deviation area over-ground and on a treadmill.