Research and application of nonlinear control techniques for quad rotor UAV

Quad rotor UAV is a classical multi-input and multi-output system, which is nonlinear, complicated and dynamically unstable. In this paper, quad rotor dynamics is considered to consist of translation and rotation subsystem. Nonlinear control strategy that includes Backstepping method and Slide mode technique for both translational and rotational dynamics are implemented for the quad rotor. The stability of the control design is ensured by Lyapunov global stability theorem. Additionally, in order to improve the dynamic response and avoid the violation of the control input constraints, the piecewise differentiable input is applied instead of the step input for the control of rotational subsystem. The performance of the nonlinear control algorithm is evaluated by simulation. Results from simulation validate effectiveness of the designed control strategy for quad rotor near quasi stationary (hover or near hover) flight. Finally, comparison between Backstepping and Slide mode is carried out briefly to highlight respective characteristics. In addition to that, conclusion is derived for this study and future work is proposed.