Enabling Safety for Aerial Robots: Planning and Control Architectures

To do this, it uses the concept of a perceived safe set B k, and of a backup safe set C k. The perceived safe set B k is constructed using the sensory information available up to time t k, and is possibly time-varying. Similarly, the backup safe set C k (also potentially time-varying) represents the set where the robot should terminate its trajectory in case a violation of safety is predicted. More specifically, at each iteration k, gatekeeper constructs a candidate trajectory (defined later) using newly available information, checks whether the candidate trajectory is valid, and if so, replaces the old committed trajectory with the new candidate trajectory. The candidate trajectory is constructed as a concatenation "stitching" of the nominal mission-optimized trajectory and of the backup trajectory, which by construction terminates at the backup set, which is a robustly controlled-invariant set. The candidate trajectory is considered valid if it lies strictly within the perceived safe set. Thus, if a candidate trajectory is valid, it can be safely tracked for all t t k, otherwise the committed trajectory from the prior iteration is used and tracked by the controller. Since the committed trajectory is updated with a candidate trajectory only if the latter is valid, it follows that the committed trajectory can always be safely tracked. B. Energy-Aware Planning: Introducing eware and meSch The Energy-A ware Filter ( eware) introduced in [2] is an application of gatekeeper .