Gait2D documentation

Contents:

Introduction

gait2d is a dynamics model that contains the essential elements for simulating human gait in the sagittal plane. The model has been used in earlier forms by Gerritsen et al. (1998) [Gerritsen1998] and Ackermann and van den Bogert (2010) [Ackermann2010]. The main features of the model are:

  • Seven body segments

  • Hunt-Crossley style foot contact model

  • Sixteen musculotendon actuators

  • Differentiable dynamics

  • Fast execution

Model dynamics and outputs are twice differentiable with respect to all inputs and the numerical model is designed to execute at high computational efficiency, both of which are important for certain numerical methods for simulation and optimal control. The model is intended for education and research. The model can be used for studies such as Ackermann and van den Bogert (2010) [Ackermann2010] and Geyer and Herr (2010) [Geyer2010].

The included Autolev dynamics model was originally written by Ton van den Bogert and adapted by Jason K. Moore. The SymPy Mechanics model was created by Jason to match the Autolev model results and then futher extended for use with PyDy and opty. These two models are provided in two packages in this distribution: algait2de and pygait2d.

License

All files in this repository are licensed under the Apache 2.0 open source license.

Dependencies

Run time dependencies:

  • matplotlib

  • numpy

  • pydy

  • python

  • pyyaml

  • symmeplot

  • sympy

Build dependencies:

  • cython [with a C compiler]

  • numpy

  • python

  • setuptools

Development dependencies:

  • pytest

  • sphinx

  • sphinx_gallery

Dependencies used in the examples:

  • cython [with a C compiler]

  • opty

  • scipy

Install

This package has not yet been released to PyPi, so install from the development source:

git clone https://github.com/csu-hmc/gait2d
cd gait2d
conda env create -f gait2d-dev.yml
conda activate gait2d-dev
python -m pip install --no-deps --no-build-isolation --editable .

Usage

pygait2d

See examples/plot_forward_sim.py for a basic use example.

algait2de

To manually rebuild the Autolev model and make use of it in Python:

$ cd algait2d
$ al gait2de.al
$ python autolevclean.py
$ cd ..
$ python -m pip install --no-deps --no-build-isolation --editable .

The above will install algait2de and then it is importable and used with:

$ python
>>> from algait2de import gait2de
>>> gait2de.evaluate_autolev_rhs(...)

References

[Gerritsen1998]

Gerritsen, K. G. M., Bogert, A. J. van den, Hulliger, M., & Zernicke, R. F. (1998). Intrinsic Muscle Properties Facilitate Locomotor Control—A Computer Simulation Study. Motor Control, 2(3), 206–220. https://doi.org/10.1123/mcj.2.3.206

[Ackermann2010] (1,2)

Ackermann, M., & van den Bogert, A. J. (2010). Optimality principles for model-based prediction of human gait. Journal of Biomechanics, 43(6), 1055–1060. https://doi.org/10.1016/j.jbiomech.2009.12.012

[Geyer2010]

Geyer, H., & Herr, H. (2010). A Muscle-Reflex Model that Encodes Principles of Legged Mechanics Produces Human Walking Dynamics and Muscle Activities. Neural Systems and Rehabilitation Engineering, IEEE Transactions On, 18(3). https://doi.org/10.1109/TNSRE.2010.2047592