A Human-Prosthesis Coupled Musculoskeletal Model for Transtibial Amputees

In this paper, we present a human-prosthesis coupled full-body musculoskeletal model that integrates the dynamics of the muscle-driven human body and a motor-driven robotic prosthesis. This model can be used to perform the inverse kinematics and dynamics calculation based on measurements for amputees wearing a force-controlled or position-controlled prosthesis. As a result, we can analyze the impacts of prostheses on amputee kinetic states, such as joint torques and muscle forces. To verify the proposed model, we conducted experiments involving four transtibial amputees wearing passive prostheses and our self-developed robotic prostheses. We estimated the joint angles, joint torques, and muscle forces on the intact side and on the residual side of the subjects. The indexes reflecting the symmetry and magnitude of muscle forces were introduced to evaluate the effects of different prostheses on transtibial amputees. The indexes of muscle force magnitude indicate that the posterior thigh muscles of the residual limb exhibit significant compensation during walking. And the indexes of muscle force symmetry indicate that active prostheses with higher damping rates work better for fast walking speeds, while those with lower damping rates are more suitable for slow walking speeds. The proposed approach may offer a novel method for evaluating prostheses that considers muscle-level kinetics, thus enhancing understanding of the impact of different prostheses on the movements of amputees.