This is a basic example for a package that can be submitted to the robots of the Real Robot Challenge 2021.

It is a normal ROS2 Python package that can be build with colcon. However, there are a few special files in the root directory that are needed for running/evaluating your submissions. See the sections on the different challenge phases below for more on this.

This example uses purely Python, however, any package type that can be built by colcon is okay. So you can, for example, turn it into a CMake package if you want to build C++ code. For more information on this, see the ROS2 documentation.

There are two example scripts using the simulation:

• sim_move_up_and_down: Directly uses the TriFingerPlatform class to simply move the robot between two fixed positions. This is implemented in rrc_example_package/scripts/sim_move_up_and_down.py.

• sim_trajectory_example_with_gym: Wraps the robot class in a Gym environment and uses that to run a dummy policy which simply points with one finger on the goal positions of the trajectory. This is implemented in rrc_example_package/scripts/sim_trajectory_example_with_gym.py.

To execute the examples, build the package and execute

ros2 run rrc_example_package <example_name>

For evaluation of the pre-stage of the challenge, the critical file is the evaluate_policy.py at the root directory of the package. This is what is going to be executed by rrc_evaluate_prestage.py (found in scripts/).

For more information, see the challenge documentation

evaluate_policy.py is only used for the simulation phase and not relevant anymore for the later phases that use the real robot.

For the challenge phases on the real robots, you need to provide the following files at the root directory of the package such that your jobs can executed on the robots:

• run: Script that is executed when submitting the package to the robot. This can, for example, be a Python script or a symlink to a script somewhere else inside the repository. In the given example, it is a shell script running a Python script via ros2 run. This approach would also work for C++ executables. When executed, a JSON string encoding the goal is passed as argument (the exact structure of the goal depends on the current task).
• goal.json: Optional. May contain a fixed goal (might be useful for testing/training). See the documentation of the challenge tasks for more details.

It is important that the run script is executable. For this, you need to do two things:

1. Add a shebang line at the top of the file (e.g. #!/usr/bin/python3 when using Python or #!/bin/bash when using bash).
2. Mark the file as executable (e.g. with chmod a+x run).

When inside of run you want to call another script using ros2 run (as it is done in this example), this other script needs to fulfil the same requirements.