Safety Barrier Certificates for Path Integral Control: Safety-Critical Control of Quadrotors

The safety issue arises as one of the most important requirements for autonomous quadrotor flight. Recently, control barrier function (CBF) technique has been developed to provide necessary and sufficient conditions on safety for robot systems. Previous works unified CBF with control techniques in an optimization fashion. However, these methods could not provide consistent performance, especially in clutter environments. In this letter, we present a novel predictive control algorithm that combines CBF and path integral control to develop a safety-critical controller for quadrotors. An efficient sequential projection algorithm is adopted to steer unsafe sampled inputs to a feasible region limited by safety barrier certificates. Comparing to existing methods, one distinguishing feature of our proposed method is that we provide collective thrusts and body rates (CTBR) control policies. Simulations and experiments demonstrate that our controller can deliver more robust maneuvers in the course of obstacle avoidance than state-of-the-art safe controllers.