Hybrid adaptive sliding mode control for quadcopter unmanned aerial vehicle

Abstract

Quadcopter unmanned aerial vehicle (UAV) systems are receiving remarkable attention from researchers due to their numerous applications, particularly at the current time in which the quadcopter unmanned aerial vehicles are playing a significant role in combating the COVID-19 pandemic. The quadcopter is a nonlinear and underactuated system, and such properties require an advanced control technique design to enable the quadcopter to achieve the assigned tasks precisely and successfully. The sliding mode control is among the best robust nonlinear control technique that can be implemented in the quadcopter to perform robust trajectory tracking. However, the drawback of the sliding mode control is the chattering phenomenon. Thus, this research aims to benefit the sliding mode control robust trajectory tracking meanwhile attenuating the unwanted chattering that creates critical problems such as the vibration in the quadcopter UAV mechanical parts and generating heat in the onboard electronic kits. The main objective of this work is to design a hybrid adaptive sliding mode control scheme for quadcopter systems considering the unwanted chattering attenuation induced by unbound parameter uncertainties and unknown disturbances meanwhile provide robust tracking. To implement the proposed control scheme, the dynamic equations of the quadcopter have been formulated and presented into two subsystems, the attitude, and the position dynamics subsystems. The hybrid proposed control scheme is composed of two controllers, an inner control loop and outer control loop. Firstly, the sliding mode controller has been proposed and assigned to act as an inner loop controller, where the improvement covered, the equivalent control, and the switching control terms in the sliding mode control law. The equivalent control term has been estimated and developed based on the Lyapunov approach. Essentially, the switching control term is a multiplication of a switching function and the switching gain. The switching function is approximated by an error function, while the switching gain is calculated based on an improved adaptive formula. Secondly, an interval type-2 fuzzy proportional integral derivative controller has been proposed and assigned to act as an outer loop controller to control the quadcopter position. The performance of the proposed hybrid adaptive sliding mode control scheme has been evaluated and investigated by Matlab/Simulink platform. The simulation results have been obtained in two different scenarios: Firstly, the performance of the proposed hybrid adaptive sliding mode control scheme has been evaluated considering only an ideal case where the parameter uncertainty and external disturbance are ignored. Secondly, the performance of the proposed hybrid adaptive sliding mode control scheme has been investigated in the presence of parameter uncertainty and external disturbance that influence the quadcopter operation. The simulation results have been performed for the quadcopter trajectory tracking in 6-DOFs. The obtained results prove that the proposed hybrid adaptive sliding mode control scheme provided a robust trajectory tracking with integral square error in the attitude and position have been improved by 37%, and 26% respectively, compared to the benchmark adaptive sliding mode control, and significantly attenuating the chattering impact.