An Improved Design of Integral Sliding Mode Controller for Chattering Attenuation and Trajectory Tracking of the Quadrotor UAV

The quadrotor unmanned aerial vehicles (UAV) are rich system with attractive and challenging properties such as nonlinearities and underactuated dynamics, which motivates researchers to design advanced and robust control algorithms. In this paper, we contribute to a further improved design of quadrotor UAV. The quadrotor dynamics and kinematics equations are briefly presented. Then, an improved integral sliding mode controller (ISMC) has been proposed and applied within an inner loop to stabilize and track the quadrotor attitude at the desired values. The aim is to enhance the performance of the ISMC controller by eliminating the chattering problem, meanwhile maintaining the trajectory tracking in a robust fashion. In our design, the switching function (sign(s)), causing the chattering, is replaced by the approximated functions (tan h, error, saturation, quasi-sliding mode method) in the ISMC control law. PD controller is applied as an outer loop controller to enable the quadrotor to track the desired position. The performance of the proposed ISMC controller is studied with regard to the chattering attenuation and trajectory tracking robustness and tested by simulation MATLAB/SIMULINK. Finally, a comparison with the switching function (sign(s)) is performed to alleviate the superior performance of the proposed design.