Safety Barrier Certificates for Collisions-Free Multirobot Systems

• Published in: IEEE transactions on robotics Vol. 33; no. 3; pp. 661 - 674
• Main Authors: Wang, Li, Ames, Aaron D., Egerstedt, Magnus
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.06.2017; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Aerospace electronics; Barrier certificates; Braking; Certificates; Collision avoidance; control barrier function; Controllers; Mobile robots; Multi-robot systems; Multiple robots; multirobot systems; Programmable logic devices; Quadratic programming; Real time; Robot kinematics; Robots; Safety; Safety barriers
• ISSN: 1552-3098; 1941-0468
• DOI: 10.1109/TRO.2017.2659727

This paper presents safety barrier certificates that ensure scalable and provably collision-free behaviors in multirobot systems by modifying the nominal controllers to formally satisfy safety constraints. This is achieved by minimizing the difference between the actual and the nominal controllers subject to safety constraints. The resulting computation of the safety controllers is done through a quadratic programming problem that can be solved in real-time and in this paper, we describe a series of problems of increasing complexity. Starting with a centralized formulation, where the safety controller is computed across all agents simultaneously, we show how one can achieve a natural decentralization whereby individual robots only have to remain safe relative to nearby robots. Conservativeness and existence of solutions as well as deadlock-avoidance are then addressed using a mixture of relaxed control barrier functions, hybrid braking controllers, and consistent perturbations. The resulting control strategy is verified experimentally on a collection of wheeled mobile robots whose nominal controllers are explicitly designed to make the robots collide.