Reducing the Human-Exoskeleton Interaction Force Using Bionic Design of Joints

This paper presents a new method for design of lower body exoskeleton based on optimizing the human-exoskeleton physical interface to improve user comfort. The approach is based on mechanisms designed to follow the natural trajectories of the human hip and knee joints as flexion angles vary during motion. The motion of the hip joint center (HJC) with variation of flexion angle was experimentally measured and the resulting trajectory was modeled. Similarly, the knee joint rolling and sliding motion was calculated based on analytical knee joint model. An exoskeleton mechanism able to follow the hip and knee joints centers’ movements has been designed to cover the full flexion angle motion range and adopted in the lower body exoskeleton. The resulting design is shown to reduce human-exoskeleton interaction forces by 25.5 and 85.5 % during hip flexion and abduction, respectively with bionic hip joint and to reduce human-exoskeleton interaction forces by 75.4 % during knee flexion with bionic knee joint. The results of interaction forces led to a more ergonomic and comfortable way to wear exoskeleton system.