Control Barrier Functions and Input-to-State Safety With Application to Automated Vehicles

• Published in: IEEE transactions on control systems technology Vol. 31; no. 6; pp. 1 - 16
• Main Authors: Alan, Anil, Taylor, Andrew J., He, Chaozhe R., Ames, Aaron D., Orosz, Gabor
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.11.2023; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Actuation; Automation; Automobiles; Automotive engineering; Connected automated vehicles (CAVs); control barrier functions (CBFs); Control systems; Control systems design; Controllers; Disturbances; input-to-state safety (ISSf); Performance degradation; Performance evaluation; Robot sensing systems; Robust control; robust safety-critical control; Robustness; Safety; Safety critical; Simulation; Tutorials
• ISSN: 1063-6536; 1558-0865
• DOI: 10.1109/TCST.2023.3286090

Balancing safety and performance is one of the predominant challenges in modern control system design. Moreover, it is crucial to robustly ensure safety without inducing unnecessary conservativeness that degrades performance. In this work, we present a constructive approach for safety-critical control synthesis via control barrier functions (CBFs). By filtering a hand-designed controller via a CBF, we are able to attain performant behavior while providing rigorous guarantees of safety. In the face of disturbances, robust safety and performance are simultaneously achieved through the notion of input-to-state safety (ISSf). We take a tutorial approach by developing the CBF-design methodology in parallel with an inverted pendulum example, making the challenges and sensitivities in the design process concrete. To establish the capability of the proposed approach, we consider the practical setting of safety-critical design via CBFs for a connected automated vehicle (CAV) in the form of a class-8 truck without a trailer. Through experimentation, we see the impact of unmodeled disturbances in the truck's actuation system on the safety guarantees provided by CBFs. We characterize these disturbances and using ISSf, produce a robust controller that achieves safety without conceding performance. We evaluate our design both in simulation, and for the first time on an automotive system, experimentally.