Robust trajectory tracking control for a quadrotor using recursive sliding mode control and nonlinear extended state observer

The trajectory tracking performance of a quadrotor is affected by the load variations, wind gusts, inaccurate model parameters, etc. This study proposes a novel robust trajectory tracking controller for a quadrotor via a nonlinear extended state observer and recursive sliding mode control (NESO-RSMC). First, a novel NESO is applied to observe the lumped disturbance in quadrotor dynamics, and the parameter design of the NESO does not rely on the information of the unknown lumped disturbance. Subsequently, based on NESO, the RSMC scheme is constructed in detail, which reduces chattering and ensures a fast response. In addition, the finite-time convergence of tracking errors based on the NESO-RSMC scheme was rigorously proved. The numerical simulation results verify the robustness of the proposed NESO-RSMC scheme in the case of external disturbances and model parameter uncertainties. Ultimately, the NESO-RSMC scheme was implemented on a real quadrotor, and its effectiveness was further proven by outdoor flight experiments.