Design of a Compliant Mechanical Device for Upper Leg Rehabilitation

Abstract

In this letter, a fully passive mechanism is introduced that is capable of generating a potential energy field, and therefore restoring forces, around a cyclic trajectory closely matching the normal human gait. The mechanism uses two sets of cable and pulley transmissions complemented by coupling gears to relate the elongation of two compliant cables to the angular positions of a user's hip and knee articulations. The design introduced does not require any sensor, actuator, or control scheme to help restoring a normal gait motion. Designing such a lightweight and inexpensive wearable gait training device for rehabilitation purposes, while minimizing interaction forces between the mechanism and the user if a prescribed trajectory is followed (i.e., maximizing transparency), is expected to decrease the dependence of patients on external care and therefore, increase their autonomy.