Design of sliding mode and backstepping controllers for a quadcopter

The quadcopter is a great platform for control systems research as it is highly nonlinear and under-actuated system. The nonlinear dynamic model of the quadcopter is formulated using the Newton-Euler method. The motion of the quadcopter can be divided into two subsystems; a rotational subsystem (attitude and heading) and a translational subsystem (altitude, x and y motion). In this paper two Non-linear Control strategies, sliding mode control (SMC) and Backstepping control (BSC) have been proposed. A SMC is a type of Variable Structure Control. It uses a high speed switching control law to force the state trajectories to follow a specified user defined surface in the states space and to maintain the state trajectories on this surface. BSC is a recursive control algorithm that works by designing intermediate control laws for some of the state variables. These state variables are called "virtual controls" for the system. These Controllers have been implemented on the Quadcopter through simulations using MATLAB/Simulink. The results have been compared with traditional PID controller.