Adaptive nonsingular fast terminal sliding mode control based finite-time disturbance observer for a quadrotor system

The present paper introduces an adaptive non-singular fast terminal sliding mode control (ANFTSMC) combined with a finite-time disturbance observer (FTDO), designed to address the trajectory tracking problem of a quadrotor system under the influence of external perturbations, model uncertainties, and mass variations. First, the nonlinear simplified dynamic model of the quadrotor is derived using the Newton-Euler approach. Then, an ANFTSMC method is employed to formulate control strategies for both the inner and outer loops of the quadrotor system. Backpropagation laws are used to tune the gains of the discontinuous reaching law. In addition, the paper integrates a finite-time disturbance observer with the proposed approach to estimate and counteract external disturbances. The closed-loop control stability is verified using Lyapunov theory. To assess the effectiveness of the suggested method, multiple flight tests are proposed using numerical simulations carried out in MATLAB/SIMULINK software. Simulation results are compared with an adaptive nonsingular fast terminal sliding mode controller (ANFTSMC). Numerical simulations demonstrate the superior performance of the suggested approach in terms of convergence time, tracking precision, and ability to reject external disturbances and uncertainties.