For safety-critical robotic systems, Control Barrier Functions (CBFs) provide a solid mathematical way to ensure that a system state always remains within a desired safe set. Usually, they are implemented as a secondary controller that alters the control input of the base controller when necessary.
In recent work we framed the CBF algorithm for robotics systems in a way to limit the total kinetic energy of the robot, which is instrumental for ensuring safety in collaborative scenarios [1]. In this work, we both analysed the effect of the CBF on the total energy of the system in a theoretical sense, and performed extensive experimental validation on a FRANKA EMIKA PANDA robot.
This project aims at extending the work in [1] in a crucial direction: in [1] we limited the total kinetic energy of the robot in the joint space, without considering any distinction between work space and null space, or specific directions in the work space. The latter specification is crucial in real collaborative scenarios, where limiting the kinetic energy in direction of a human operator becomes a crucial safety objective.
The theoretical framework that this project will build on was developed in the last year by F. Califano and W. Roozing and their previous supervised students. The theoretical extensions needed in this project are already worked out to a good degree. As such, even though a good theoretical understanding is required, the student will be able to focus on refinement and extensive experimental validation on the real robot.
[1] Califano, F., Logmans, D., & Roozing, W. (2024). Limiting Kinetic Energy through Control Barrier Functions: Analysis and Experimental Validation. arXiv preprint arXiv:2411.02186.
Some other references about CBFs:
[2] F. Ferraguti, C. T. Landi, A. Singletary, H.-C. Lin, A. Ames, C. Secchi, and M. Bonf`e, “Safety and Efficiency in Robotics: The Control Barrier Functions Approach,” pp. 15–30, 2015.
[3] A. Singletary, S. Kolathaya, and A. D. Ames, “Safety-Critical Kinematic Control of Robotic Systems,” Proceedings of the American Control Conference, vol. 2021-May, pp. 14–19, 2021.
[4] Ames, A. D., Coogan, S., Egerstedt, M., Notomista, G., Sreenath, K., & Tabuada, P. (2019, June). Control barrier functions: Theory and applications. In 2019 18th European control conference (ECC) (pp. 3420-3431). IEEE.