Control Barrier Functions in Multirotors: A Safety Filter for Obstacle Avoidance

Similar to the Control Lyapunov Functions (CLFs), whose objective is to achieve the stability of a system, Control Barrier Functions (CBFs) aim to achieve the safety of a system. They serve as a safety filter that guarantees that the system remains in a defined safety region. This article aims at presenting an introductory overview of the theoretical framework of CBFs and of their application. For doing this, we apply the CBFs framework as a safety filter for obstacle avoidance in the XY movement of a multirotor. The safety filter is designed using two different multirotor models, a single integrator model without considering the inertia of the system and a first-order model that captures the dynamics of a velocity control loop. The proposed safety framework is validated with simulations in Matlab and experiments with indoor flights. The results show the importance of correctly modeling the system.