A Robust Observer-Based Nonlinear Trajectory Tracking Control Strategy for a Quadrotor with a Suspended Payload

A observer-based robust nonlinear load trajectory tracking method is proposed for hoisting systems that encounter unmodeled dynamics and external disturbances. According to the uncertainty of each control loop, three nonlinear disturbance observers are designed respectively. Based on this, an observer-based robust nonlinear control approach is suggested for the quadrotor system. The solution of the closed-loop system is then demonstrated to be uniformly ultimately bounded by Lyapunov analysis based on fully nonlinear dynamics. The robustness of the method is shown through a series of comparative experiments using a load geometry controller and the proposed controller.