Human gait modeling: dealing with holonomic constraints

Dynamical models are fundamental for the study of human gait. This work presents a complete and systematic approach to deriving control system models for both the single support phase and the double support phase of a gait cycle. We consider a nine segment model in the sagittal plane. Emphasis is placed on two important aspects of the modeling process: dealing with the holonomic constraints and dealing with the ground reaction forces. We start with a raw model which is a direct result of Newton's law and which is subject to holonomic constraints. By characterizing the ground reaction forces, these constraints are eliminated to generate standard control system models for every possible situation in a gait cycle. These models are verified via both inverse dynamics and forward simulations on experimental data.