Dynamic inversion of quadrotor with zero-dynamics stabilization

For a typical quadrotor model, one can identify the two well known inherent rotorcraft characteristics; under-actuation and strong coupling in pitch-yaw-roll. To confront these problems and design a station-keeping tracking controller, dynamic inversion is used here. Typical applications of dynamic inversion require the selection of the output control variables to render the internal dynamics stable. This means that in many cases tracking can not be guaranteed for the actual desired outputs. Instead, here, the internal dynamics of the feedback linearized system is stabilized with a robust control term. Stability and tracking performance are guaranteed using a Lyapunov-type proof. The approach could be called ldquoforward steppingrdquo in contrast with the well known backstepping design. Simulation with a typical nonlinear quadrotor dynamic model is performed to show the effectiveness of the designed control law in the presence of noise and disturbances.