Design and Simulation of a Patient-Specific Ankle Orthosis for Drop-Foot Assistance

Abstract

rop foot is a gait disorder that weakens the ankle dorsiflexor muscles, causing the foot to drag along the ground during the swing phase of gait, as well as foot slap at the onset of gait. Robotic devices have been developed to assist drop-foot patients in achieving a more natural gait pattern. However, personalized devices are still required for individual patients that bear compactness and enhance the leg's movement. This paper proposes an ankle-foot orthosis that adjusts stiffness for each patient. It uses a cam-based variable stiffness actuator to offer a customized range of stiffness for each patient based on their individually designed cam. The stiffness is passively altered to different phases of gait. The ankle's range of motion is corrected through an offset inverted slider-crank mechanism that provides the required joint deflection. The design and simulation of the orthosis is achieved using MATLAB and the Computer-aided design is achieved on Solidworks. The simulations demonstrated the feasibility of the design in providing the full range of motion, emulating the torque profile required, and emulating the gait trajectory all within the general normal walking speed.

Keywords: Drop-foot, Ankle-foot orthosis (AFO), Variable stiffness actuator, Cam-based mechanism, Personalized rehabilitation device