Second order sliding mode attitude tracking and robust control of flying-wing UAV

We propose a second order sliding mode attitude tracking and robust control strategy for the flying-wing unmanned aerial vehicle (UAV) with unknown external interferences. We take into account its timescale separation property and design its attitude control system into outer loop and inner loop. The outer loop uses the adaptive second order sliding mode controller and the adaptive algorithm to adjust the switch gains and suppress the influence of compound interference on the performance of the flying-wing UAV. The second order sliding mode controller adds the discontinuous sign function to the derivative of the control volume and obtains through integration the continuous sliding mode law, thus effectively eliminating the chattering of the conventional sliding mode controller. The inner loop uses the integral sliding mode controller based on the adaptive super twisting sliding mode observer. The adaptive super twisting sliding mode observer is for estimating and compensating for the compound interference of the inner loop. Finally, we use control allocation to allocate control moment to the rudder surface of the control system. The simulation results show preliminarily that our strategy is effective.