Design of hybrid control system for path tracking of a quadrotor subject to uncertain disturbances

In this research, a novel nonlinear control strategy along with its simulation for a quadrotor helicopter is proposed. In the present work, a six-DOF dynamic equations of the quadrotor system subjected to unknown external disturbances based on the Newton-Euler equations is developed completely and without any simplification. Considering the under-actuated and strongly coupled characteristics of quadrotor helicopter, a nonlinear control method is designed using integral backstepping combined with the sliding mode control (integral BS-SMC) to stabilize the qudrotor attitude and to tracking the desired trajectory. The designed controllers based on the hierarchical control scheme can be used to control the rotational and translational movements and their stability are validated by the Lyapunov stability theorem. Using the proposed controller, the chattering phenomenon and discontinuousness of the control inputs faced by traditional sliding mode control (SMC) can be avoided. The feasibility and performance of the presented control approach is verified by the simulations under different scenarios. The results show that the proposed nonlinear control method not only has a better tracking performance than PID controller, but also has a higher robustness when unknown disturbances occur.