Incremental Nonlinear Dynamic Inversion-Based Trajectory Tracking Controller for an Agile Quadrotor

The interest in agile maneuvering unmanned aerial vehicles (UAVs) specifically the quadrotor has increased considerably. The control of UAVs at high speed becomes a challenging task due to unmodeled aerodynamic forces and moments. In this study, position and attitude tracking controllers are presented in a structured cascaded fashion using incremental nonlinear dynamic inversion (INDI). A new approach for yaw rotational dynamic INDI control law is introduced, which simplifies the nonlinear dynamic allocation equation and actuator state feedback calculation by eliminating rotor acceleration and motor time constant terms. The closed-loop stability of the rotational and translational INDI controller is analyzed in detail. The significant improvement over the legacy proportional-integral-derivative (PID) controller is shown in outdoor flight tests. Circle and lemniscate-shaped trajectories are tracked with a maximum speed of 15 m/s. The attitude hold and tracking performance are evaluated with a maximum speed of 30 m/s.