Just-in-Time Emergency Trajectories: A Formulation Towards Safety in Autonomous Navigation

Abstract

Emergency trajectories enable one to move faster through an environment while still moving safely. Having an emergency trajectory within an observed vacant space makes it possible to safely navigate through unknown territory or through a door without slowing down. Emergency trajectories allow for safe navigation of a vehicle into a safe system state, e.g. a stop, in the event of recognition of an obstacle. This work formally proves the benefit of using emergency trajectories to generate safe and faster motion controls as compared to vehicle operation without such trajectories. Furthermore, this work also presents a working integration of this formalism into a vehicle's low level control system in a Moving Horizon Trajectory Planner (MHTP) with an update rate of 10Hz. Using an MHTP along with a dynamic model of the environment and the proposed constraints, the system is able to derive emergency trajectory candidates which fulfill our safety requirements. This distinguishes the approach from that of others, which replans discrete paths that are then followed by the vehicle's local control system. This approach was implemented on a differential-drive mobile agent and tested using non-static environment assumptions. Simulated and real-robot experimental results illustrate the quality of our approach.