Robust Control Study for Tethered Payload Transportation Using Multiple Quadrotors
Longhao Qian, Hugh H. T. Liu
Abstract
A novel robust path-following flight controller for multiple quadrotors carrying a slung payload is proposed. The payload is manipulated by a group of quadrotors with cables so that every agent shares the payload weight. The system is decomposed into the payload subsystem and the quadrotor attitude subsystems. The controller is hierarchical. The outer loop is a robust path-following controller that stabilizes the payload subsystem. An uncertainty and disturbance estimator is designed to estimate and eliminate the disturbances. The inner loop is an attitude tracker implemented on each quadrotor that follows the target attitude generated by the outer-loop controller. The overall stability of the complete system is shown using the Lyapunov method. Simulations and flight demonstrations show that the controller can stabilize the slung load according to the given path command under exogenous disturbances.