Trajectory tracking and formation control of quadrotor UAVs based on modified super twisting sliding mode method.

Aiming at the problem that the trajectory tracking and formation flight of quadrotor unmanned aerial vehicles (UAVs) are vulnerable to complex and variable disturbances, this paper proposes a trajectory tracking controller is designed for both position and attitude subsystems of quadrotor UAV is designed in the formation, and a super twisting sliding mode (STSM) controller is designed for the formation control. First, by taking advantage of the finite-time convergence characteristic of the non-singular terminal sliding mode surface and the reducing chattering characteristic of the STSM, a non-singular terminal super twisting sliding mode (NSTSTSM) controller is designed for the position and attitude control of the leader and follower in the formation, and the controller can effectively reject the buffeting of the system and improve the response speed. Meanwhile, in order to enhance the disturbance rejection performance of the UAV, finite-time disturbance observers are separately designed for the position and attitude loops of the quadrotor UAV to compensate the controller, and it can further enhance the robustness of the system. Secondly, The UAV formation adopts the pilot-follower formation scheme, and the horizontal position relationship model between the leader and the follower is constructed. Then, the formation controller is designed based on modified STSM control method, and the stability and dynamic response speed of formation flight is improved. Meanwhile, the stability of the designed control scheme is proved by using Lyapunov and the finite-time Lemma. The simulation results show that the proposed trajectory tracking control scheme for the quadrotor UAV can achieve convergence within 1.2 s. Compared with the traditional terminal sliding mode, the convergence time is 20% faster, and the steady-state error is less than 0.0003 m, which is 50% smaller than that of the traditional terminal sliding mode. The proposed formation control scheme can achieve convergence within 5 s, with a steady-state error less than 0.01 m. It can quickly and accurately form the formation and track the predetermined trajectory.