pybullet-helpers

Some utility functions for PyBullet. Copied and modified from predicators, which in turn was heavily based on the pybullet-planning repository by Caelan Garrett (https://github.com/caelan/pybullet-planning/). In addition, the structure is loosely based off the pb_robot repository by Rachel Holladay (https://github.com/rachelholladay/pb_robot). Will Shen made huge contributions.

Requirements

• Python 3.10+
• Tested on MacOS Catalina

Installation

1. Recommended: create and source a virtualenv.
2. pip install -e ".[develop]"

Check Installation

Run ./run_ci_checks.sh. It should complete with all green successes in 5-10 seconds.

Adding New Robots

To add a new robot, build off an existing example. For inverse kinematics, PyBullet's IK solver will be used by default. It is not very good. IKFast is much better, but then you need to compile robot-specific IK models. This process needs to be automated further, but here is some guidance:

1. Install Docker on an Ubuntu machine. (You will only need Ubuntu to compile once; IKFast should work cross-platform.)
2. Follow the instructions on pyikfast.
3. Save the cpp file that is generated. You won't need the other files.
4. Make a new directory in this repository inside third_party/ikfast. Copy in the cpp file and rename it to match the existing examples (e.g., ikfast_panda_arm.cpp.)
5. Modify the cpp file in two ways: (1) Add #include "Python.h" at the top; (2) add python bindings at the bottom (copy and change the robot name from an existing example like ikfast_panda_arm.cpp).
6. Copy in the other files from an example directory like third_party/ikfast/panda_arm. Modify robot_name in setup.py.
7. Add IKInfo inside your new robot class in robots/.

Contributions are welcome to improve this process, especially steps 3 onward.

*Note for Robot URDFs: For consistency with Bullet IK, ensure that the inertial frame of the robot URDF's base link is not offset from the its link frame. If that's necessary, a possible workaround is to add a dummy base link to the URDF and connecting this to the real base link via a fixed joint.

<link name="dummy_base" />

<joint name="dummy_joint" type="fixed">
    <parent link="dummy_base"/>
    <child link="panda_link0"/>
    <origin xyz="0 0 0" rpy="0 0 0"/>
</joint>