Alternative motion control frameworks

[stephane-caron]

If any of the features and non-features in Upkie's spine-agent design is a no-go to you, you can check out these existing alternatives:

• kodlab_mjbots_sdk - C++-only framework integrated with LCM for logging and remote I/O. Still a work in progress, only supports torque commands as of writing this note.
• mc_rtc - C++ real-time control framework from which we inherited several components, for instance dictionaries and logging. The choice of a weakly-typed dictionary-based IPC was also inspired by mc_rtc's data store. C++ controllers are bigger cathedrals to build but they can run at higher frequencies.
• robot_interfaces - Similar IPC between non-realtime Python and real-time C++ processes. The main difference lies in the use of Python bindings and action/observation types (more overhead, more safeguards) where on Upkies IPC is structureless (faster changes, faster blunders). Also, robot_interfaces enforces process synchronization with a time-series API while on Upkies this is up to the agent (most agents act greedily on the latest observation).
• ros2_control - A C++ framework for real-time control using ROS2 (still a work in progress). Its barrier of entry is steeper than the other alternatives, making it a fit for production rather than prototyping, as it aims for compatibility with other ROS frameworks like MoveIt. An Upkie C++ spine is equivalent to a ROS ControllerInterface implementing the dictionary-based IPC protocol.

If your robot is built with some of the following open hardware components, you can also use their corresponding Python bindings directly:

• moteus - bindings for moteus brushless controllers also run well up to 200 Hz.
• odri_control_interface - interface to control robots built with the ODRI Master Board.

Using control bindings directly is a simpler alternative if you don't need the action-observation loop and simulation/real-robot switch.