3D bipedal model for biomechanical sit-to-stand movement with coupled torque optimization and experimental analysis

Abstract

Sit-to-stand (STS) movement is a common human task which involves combination of a musculoskeletal structure integrated with neural control. We present a conceptual 3D bipedal nonlinear model for STS task with optimal controller design for exoskeleton torques. This model has 7 sagittal plane angles, 3 frontal plane angles, and 3 foot translational variables with 3 position based holonomic constraints. We regulate the model with optimal controller design by coupled torque optimization due to muscular interaction between ankle, knee and hip joints. Our simulation results show the improvement in the results from previous controller design schemes. We further obtain experimental data for STS task on a force plate to compare the ground reaction forces of experimental data with our mathematical framework. This proves the validity of the model to extend this mathematical framework for further analysis of healthy and neuro-deficient subjects and accordingly designs of ergonomics and rehabilitation robotics.