GTDynamics

This library is still under very active development, hence bleeding edge, and not "supported" in the way GTSAM is. In particular, we are still actively re-factoring the way we deal with time and time intervals.

Full kinodynamics constraints for arbitrary robot configurations with factor graphs.

GTDynamics is a library that allows the user to express the full kinodynamics constraints of an arbitrary robot configuration on a factor graph. These constraints can be used to solve the forward and inverse dynamics problems.

Dependencies

• GTSAM4
• gtwrap
• sdformat12

Installing SDFormat

GTDynamics uses the SDFormat parser to parse SDF/URDF files containing robot descriptions.

Homebrew

Using Homebrew is the easiest way to get SDFormat installed and it also makes switching versions straightforward.

$ # Install homebrew.
$ /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"
$ # Set up the tap ind install sdformat12
$ brew tap osrf/simulation
$ brew install sdformat12

Source

Alternatively, you can install from source if you are on Linux or want more fine-tuned control.

We provide an Ubuntu-based process below. Please reference this tutorial for complete details on installing from source.

# Install basic dependencies
sudo apt-get install -y ruby-dev build-essential libboost-all-dev cmake pkg-config wget lsb-release

# Setup the repo
sh -c 'echo "deb http://packages.osrfoundation.org/gazebo/ubuntu-stable `lsb_release -cs` main" > /etc/apt/sources.list.d/gazebo-stable.list'
wget http://packages.osrfoundation.org/gazebo.key -O - | sudo apt-key add -
sudo apt-get update

# Install SDFormat dependencies
sudo apt-get install -y libtinyxml2-dev liburdfdom-dev libignition-cmake2-dev libignition-tools-dev libignition-math6-dev

# Set the version to install
export GTD_SDFormat_VERSION="10.5.0"

# Download specific version of SDFormat
wget http://osrf-distributions.s3.amazonaws.com/sdformat/releases/sdformat-${GTD_SDFormat_VERSION}.tar.bz2

tar -xvjf sdformat-${GTD_SDFormat_VERSION}.tar.bz2

cd sdformat-${GTD_SDFormat_VERSION}
mkdir build && cd build

cmake -DCMAKE_INSTALL_PREFIX=../install ..
make -j4
sudo make install

Installing GTDynamics

$ git clone https://github.com/borglab/GTDynamics.git
$ cd GTDynamics
$ mkdir build; cd build
# We can specify the install path with -DCMAKE_INSTALL_PREFIX
$ cmake -DCMAKE_INSTALL_PREFIX=../install ..
$ make
$ sudo make install

Running Tests

$ make check

Running Examples

The /examples directory contains example projects that demonstrate how to include GTDynamics in your application. To run an example, ensure that the CMAKE_PREFIX_PATH is set to the GTDynamics install directory.

1. Navigate to the example's subdirectory and create a build directory. e.g.

cd GTDynamics/examples/example_forward_dynamics
mkdir build; cd build

2. Make the example.

If GTDynamics was installed to ~/JohnDoe/gtdynamics_install, then run the cmake command with:

cmake -DCMAKE_PREFIX_PATH=~/JohnDoe/gtdynamics_install ..
make

3. Run the example!

./exec

Python Wrapper (Recommended use case)

GTDynamics now supports a Pybind11-based Python API.

GTWrap comes bundled with GTSAM, which generates a corresponding GTSAM Python API. The same GTWrap package can be used to generate python bindings for GTDynamics (i.e. it is not necessary to manually install a separate GTWrap).

Note: when using CMake, it is ideal for GTSAM and GTDynamics to have the same, non /usr/local prefix for installing packages. To update the CMake prefix from a system directory, use the flag CMAKE_INSTALL_PREFIX=/path/to/install/dir when running cmake.

To compile and install the GTDynamics python library:

1. Ensure that GTSAM is built with generated python bindings. If not, go to the build directory and run cmake with the flag GTSAM_BUILD_PYTHON=ON. It is highly advised to specify a non user/local CMake prefix for installing packages. Afterwards, install the GTSAM python package.

   cmake -DGTSAM_BUILD_PYTHON=ON -DCMAKE_INSTALL_PREFIX=/path/to/install/dir ..
   make && make install && make python-install

2. In the GTDynamics build directory, run cmake with the flag GTDYNAMICS_BUILD_PYTHON=ON. It is highly advised for the GTDynamics CMake prefix to match the CMake prefix used for GTSAM. Again, use the CMAKE_INSTALL_PREFIX=/path/to/install/dir flag to specify the updated prefix.

   cmake -DGTDYNAMICS_BUILD_PYTHON=ON -DCMAKE_INSTALL_PREFIX=/path/to/install/dir ..

3. Build as normal and install the python package.

   make && make python-install

4. To run the Python tests, you can simply run:

   make python-test

   You can also run individual test suites, e.g. with:

   make python-test.base
   make python-test.cablerobot

(Alternative) Python Wrapper installation

If preferred, GTWrap can be downloaded and installed separately. Afterwards, follow the instructions above from step 2 for building and installing the GTDynamics python bindings.

Citing This Work

Please cite the following paper if you use this code as part of any published research:

@misc{2011.06194,
    Author = {Mandy Xie, Alejandro Escontrela, and Frank Dellaert},
    Title = {A Factor-Graph Approach for Optimization Problems with Dynamics Constraints},
    Year = {2020},
    Eprint = {arXiv:2011.06194},
}