Robust Nonlinear Backstepping SMC for QUAV Subjected to External Disturbances

In this chapter, the problem of controlling the orientation and position of the quadrotor is considered in the presence of parametric uncertainties and external disturbances. Previous works usually assume that the parameters of the flight controllers are constants. In reality, these parameters depend on the desired trajectory. Two approaches to control the quadrotor have been proposed. The control techniques are designed on the basis of on-line estimators of the dynamic parameters. These adaptation methods allow to improve the control performance of this system, and to compensate the parametric errors due to the coupling of the position with the orientation of the UAV. The first control is based on the robust nonlinear fast control, structured for the tracking of the position and attitude trajectory of the quadrotor. Two control loops have been designed, an outer loop (position loop) uses a new version of the adaptive backstepping (AB) based control while the inner loop (attitude loop) uses a new controller based on a combination of the backstepping technique and the fast terminal sliding mode control (AB-FTSMC) to control the yaw motion and the tilt angles. In order to estimate the proposed parameters of the position controller and the upper bounds of uncertainties and attitude perturbations, adaptive online rules are proposed.