Online Safety under Multiple Constraints and Input Bounds using gatekeeper: Theory and Applications

NCREASING use of robotic systems in real-world applications necessitates advanced controllers that ensure safety, robustness, and effectiveness in human-machine teaming [1]. This letter formalizes and builds upon our recent work on online safety verification and control [2], which introduces gatekeeper as a novel algorithmic component between the planner and the controller of the autonomous system. To briefly illustrate the principle behind gatekeeper, consider a Unmanned Aerial V ehicle (UA V) navigating an unknown environment. The UA V follows a nominal trajectory, generated by its planner and tracked by its controller. At each iteration, gatekeeper performs two key steps: (i) it evaluates the currently known safe set (derived from onboard sensing), and a backup set, which represents a region the UA V can retreat to if the nominal trajectory is predicted to exit the safe set in the future; (ii) it constructs a candidate trajectory by stitching together the nominal trajectory (up to a future time horizon) and a backup trajectory that leads safely into the backup set. The authors would like to acknowledge the support of the National Science Foundation (NSF) under grant no.