Standalone ALIP 1-Step Controller

This is a standalone repository containing the Angular Momentum Linear Inverted Pendulum (ALIP) 1-step controller and corresponding Python bindings for the Digit humanoid robot. This is based on an old version of Grant Gibson's Digit C++ Controller.

Setup for quick working example

This has been tested on Ubuntu 20 and Ubuntu 22.

conda env create -f alip-env.yml
mkdir build
mkdir extern
git submodule add -f https://github.com/pybind/pybind11.git extern/pybind11
make all

Makefile

To build the dependencies for the controller:

make init

To build the controller (assuming you have the object files from init).

make controller

To build the Python bindings:

make pybind

To do all of these:

make all

Example usage

We have an example running the controller within MuJoCo. From the root directory of this repository, after having built the Python bindings (there should be a .so file in your example/ directory):

$ cd example
$ python mujoco_test.py

If you run into an error you may need to rename the .so file to digit_controller_pybind.so.

Information on Python bindings

src/pybind/digit_controller_pybind.cpp contains the currently existing bindings. Currently, you can initialize the controller as follows:

import digit_controller_pybind as dc  # assuming .so bindings file is in same directory

gc = dc.Digit_Controller()
gc.Initialize_(init_ctrl_mode, flag_torque_only)
gc.Set_Initial_Standing_Gains_()
gc.Set_Initial_Walking_Gains_()

and then run the controller via:

gc.Update_(command, observation, limits)

Adding new bindings

If you would like to add new bindings to other variables or functions within the controller code, please consult the pybind11 documentation. You may wish to do this, for example, if you would like access to the variables in include/controller/Digit_Controller.hpp via the DigitController object.

References

Grant Gibson's Digit C++ controller
Angular Momentum about the Contact Point for Control of Bipedal Locomotion: Validation in a LIP-based Controller