Search for: All records

Abstract This paper presents a new two-step design procedure and preliminary kinematic evaluation of a novel, passive, six-bar knee-ankle-foot orthosis (KAFO). The kinematic design and preliminary kinematic gait analysis of the KAFO are based on motion capture data from a single healthy male subject. Preliminary kinematic evaluation shows that the designed passive KAFO is capable of supporting flexion and extension of the knee joint during stance and swing phases of walking. The two-step design procedure for the KAFO consists of (1) computational synthesis based on user's motion data and (2) performance optimization. In the computational synthesis step, first the lower leg (knee-ankle-foot) of the subject is approximated as a 2R kinematic chain and its target trajectories are specified from motion capture data. Six-bar linkages are synthesized to coordinate the angular movements of knee and ankle joints of the 2R chain at 11 accuracy points. The first step of the design procedure yields 332 six-bar KAFO design candidates. This is followed by a performance optimization step in which the KAFO design candidates are optimally modified to satisfy specified constraints on end-effector trajectory and shape. This two-step process yields an optimally designed passive six-bar KAFO that shows promising kinematic results at the knee joint of the user during walking. The preliminary prototype manufactured is cost effective, easy to operate, and suitably demonstrates the feasibility of the proposed concept. 

The paper presents the design of a lower leg orthotic device based on dimensional synthesis of multi-loop six-bar linkages. The wearable device is comprised of a 2R serial chain, termed the backbone, sized according to the wearer’s limb anthropometric dimensions. The paper is a result of our current efforts in proposing a systematic process for the development of 3D printed customized assistive devices for patients with reduced limb mobility, based on anthropometric data and physiological task. To design the wearable device, the physiological task of the limb is obtained using an optical motion capture system and its dimensions are set such that it matched the lower leg kinematics as closely as possible. As a next step a six-bar linkage is synthesized and ensured that its motion is as close as possible to the physiological task. Next, the 2R backbone is replaced by the wearer’s limb to provide the skeletal structure for the multiloop wearable device. During the final stage of the process the 2R backbone is relocated to parallel the human’s limb on one side, providing support and stability. The designed device can be secured to the thigh of the user to guide the lower leg without causing any discomfort and to ensure a natural physiological gait trajectory. This results in orthotic device for assisting people with lower leg injuries with compact size and better wearability.