Design of a modified terminal sliding mode controller with time varying delayed output observer for a quad-rotor system

The paper presents a robust control technique based on a modified terminal - sliding mode controller (MT-SMC) with time varying delayed output observer in order to stabilize the rotational quad-rotor subsystem in finite time. The outer loop is stabilized using a modified super twisting - sliding mode controller (MST-SMC). The quad-rotor dynamical system is developed at first using Newton-Euler formalism, then the controller structure is formulated based on the new proposed structure which guarantees fast convergence rate, robustness against external and internal uncertainties, and finite time convergence. The controller also mitigates chattering phenomenon, which help reducing control effort on actuators. Stability analysis of the proposed structure is evaluated by Lyapunov theory for each subsystem. In order to demonstrate the effectiveness of the proposed control scheme, a comparison with MST-SMC (designed for inner and outer loops) is established using Matlab/Simulink environment.