Nonlinear Flight Control Strategy for an Underactuated Quadrotor Aerial Robot

This paper presents development of nonlinear model and nonlinear control strategy for a 6-DOF quadrotor aerial robot. The nonlinear model of quadrotor aerial robot is based on Newton-Euler formalism. Model derivation comprises determining equations of motion of the quadrotor in three dimensions and seeking to approximate actuation forces through modeling of the aerodynamic coefficients and electric motor dynamics. The derived model is dynamically unstable. Thus a nonlinear control strategy is implemented for the quadrotor. The control strategy includes feedback linearization for translational subsystem and backstepping based nonlinear controller for the rotational subsystem of quadrotor aerial robot. Nonlinear Backstepping control design is based on constructing Lyapunov function for closed loop system and guarantees stability and tracking performance through Lyapunov energy dissipation. Effectiveness of the control design scheme is shown through nonlinear simulations.