Energy coupling-based double-pendulum variable rope length underactuated control for quadrotor UAV with slung load

The quadrotor UAV with slung load exhibits strong underactuation. In the actual transportation process, traditional control methods face challenges in solving problems such as double pendulum. Accordingly, an underactuated control approach based on energy coupling is introduced for the quadrotor UAV with slung load, specifically considering the double-pendulum and variable rope length. A smooth expected trajectory is used to ensure the steady operation of the UAV. According to the energy coupling relationship between the UAV and hook with load, the anti-swing controller is constructed. The system’s steady-state performance is assessed using Lyapunov and Barbalat’s lemma. Through comparative experiments and results analysis, it is shown that the proposed control method effectively minimizes residual swing angles and enables precise UAV positioning. Meanwhile, the proposed controller demonstrates robustness against unknown resistance parameters and external disturbances.