The KUKA youBot of the University of Twente has not been operational in years. With renewed interest in the robot from a theatre perspective, the goal of this project is to revive the youBot and enable it for the development of expressive, safe and robust puppeteering. The onboard computer, battery pack, and emergency button are replaced, but all other hardware is kept and taken into account in the design of the new software stack.
This new software stack for the youBot is written for ROS2. The architecture consists of 3 main layers: the input adapter, controllers, and EtherCAT adapter. The input adapter is for interaction with the youBot on the input side, enabling the configuration of different input devices and input-to-output mappings. The controller layer converts high-level commands to individual wheel and joint commands. The EtherCAT adapter sits as far downstream in the ROS2 domain as possible, bridging the ROS2 domain and EtherCAT domain, and ensuring all commands pass through the safety layer before reaching the wheels and joints. The safety features implemented are software- and hardware emergency buttons, monitoring of the system's operational status and endstop protection for all the joints of the manipulator. For safety regarding operation around humans, the software- and hardware emergency buttons put the youBot to a halt with no noticeable latency. The same holds true when any of the subsystems crash or stop responding. The youBot is partly prevented from damaging itself via endstop protection in the form of the implementation of virtual endstops. Before reaching these endstops, the joint velocity is clamped based on its current velocity, ensuring a timely slowdown.
Extensive documentation on the software stack is written to provide easy onboarding of future developers and aid understandability and extendability of the youBot’s capabilities. This documentation is validated by a third-party non directly involved in development.
With the youBot being up and running again, the goal of revival can be concluded to have been reached. The system architecture allows for future extension of youBot’s capabilities and theatre-tailored features, aided by extensive documentation.