Design and Simulation of a Passive Wearable Robot for Knee Rehabilitation

The aim of this paper is to describe a novel passive robot for knee joint rehabilitation. The purpose of this wearable robot is to assist individuals with lower limb muscle weakness in walking, sit-to-stand and stand-to-sit tasks. Weight of the assistive robot is a significant characteristic of device. Thus, a novel lightweight robot has been designed to perform these tasks. This novel robot has three springs and one of these springs is only applied during standing and sitting; this spring saves energy during sitting and assists standing by providing the knee with the saved energy. Other two springs are for knee extension and flexion movements and the pressure on the small bag of water under the foot controls the movements of these springs by a cylinder-piston and locking mechanisms. User can take unlimited steps due to the innovative energy saving mechanism of this robot. Since wearable robot and exoskeleton must not impose any limitation on joints, instead of rigid parts, we use cable for connecting two major parts of the robot. The CAD design of this robot indicates its appropriate dimensions and a weight of approximately 800 grams which is suitable for an assistive robot. Simulation results of this robot on a CAD model of knee demonstrate its proper performance of the aimed tasks.