  Safe control for inherently unstable systems such as quadrotors is crucial.
Imposing multiple dynamic constraints simultaneously on the states for safety
regulation can be a challenging problem. In this paper, we propose a quadratic
programming (QP) based approach on a cascaded control architecture for
quadrotors to enforce safety. Safety regions are constructed using control
barrier functions (CBF) while explicitly considering the nonlinear
underactuated dynamics of the quadrotor. The safety regions constructed using
CBFs establish a non-conservative forward invariant safe region for quadrotor
navigation. Barriers imposed across the cascaded architecture allows
independent safety regulation in quadrotor's altitude and lateral domains.
Despite barriers appearing in a cascaded fashion, we show preservation of
safety for quadrotor motion in SE(3). We demonstrate the feasibility of our
method on a quadrotor in simulation with static and dynamic constraints
enforced on position and velocity spaces simultaneously.
