2-DoF ankle-foot system: Implementation of balance for lower extremity exoskeletons

Exoskeletons are increasingly being used for assistance or augmentation of gait for individuals with ambulation disabilities. The current state of lower extremity exoskeletons focuses on the motion at the hips and knees while having limited range of motion or passive joints for the ankles. Kinematic analyses of human gait and quiet standing have shown how the ankles play a vital role in balance in the anteroposterior and the mediolateral directions. This article puts forth a design for a powered ankle-foot system that would give the user access to their full anatomical range of motion driven by two custom linear actuators located along the posterior of the shank. The design also accounts for the user's safety in both the hardware and software portions of the design, allowing for redundancy. The design will be incorporated into a lower extremity exoskeleton that our lab has been developing and will provide the first strategy when balancing.