Dynamics and control of dual-quadrotors slung a slender beam with attitude-pendulum coupling effects

The dual-quadrotors slung system may be utilized in the handling service of heavy and bulky loads. However, the coupled oscillations between the quadrotor attitudes and suspended load exhibit complicated dynamic behaviors, which degrade the safety and efficiency of the transport system. Although many works have been focused on the multiple quadrotors suspending a load, those prior studies did not consider the coupling effects between the quadrotor attitudes and the cable pendulum. This paper established a nonlinear dynamic model of dual-quadrotors carrying a slender beam undergoing planar motions, which described the coupled attitude-pendulum oscillations. Then a frequency estimator was resulted from the system parameters for investigating the dynamics. In addition, a novel combined modified model-following control and discontinuous piecewise smoother was proposed to suppress oscillations. The technical results in the simulations not only describe the dynamic behavior of the analytical model but also validate the effectiveness of the control method.