Bio-inspired Cable-driven Knee Orthosis for Tibiofemoral Joint Load Distribution

Abstract

For a cable-driven knee joint soft wearable robot, the cable tension causes a compressive load on the tibiofemoral joint. Since it is a significant obstacle that aggravates arthritis and reduces the rehabilitation effectiveness, the load must be distributed through the rigid joint to protect the knee. However, conventional mechanical knee joints, which are widely used for knee orthoses, cannot be a right solution due to additional compressive load caused by kinematic and dynamic misalignment between the joint of human and the orthosis. This paper introduces a novel bio-inspired cable-driven knee orthosis (BiCKO). With the bio-inspired rigid joint structure, which is kinematically identical to the human knee joint shape on the medial and lateral sides, it is possible to prevent the occurrence of abnormal load due to the misalignment as well as reducing the load transmitted through the musculoskeletal system. The compression induced by cable assistance is analytically investigated, and the load on the tibiofemoral joint must be taken into account in the conventional cable-driven method. It is confirmed that the existence of rigid joint capable of distributing the load without generating unnecessary load is inevitable. In addition, experimental results of comparing the load reduction ratio are also presented to show the performance of BiCKO.