On the Effect of Slung Load on Quadrotor Performance

Quadrotors are one of the Unmanned Aerial Vehicles (UAV) which have drawn great attention in recent years because of their movement capability. Researchers from academia and industry concentrate mostly on the control, design and communication of the quadrotors. Many forms of quadrotors are employed for many tasks; including search and rescue, defense industry, gaming & sports and delivery purposes. The dynamics of a quadrotor is already nonlinear, with that when there is payload/cargo which is not solid (i.e. a bottle containing fluid), the stability of the system becomes difficult to achieve. In this paper, an LQR controller is designed to maintain the stability of the quadrotor under the influences of a non-solid payload which is treated as a suspended load. First, nonlinear dynamics of the quadrotor is derived and it is extended by introducing the suspended load dynamics. A control-oriented linear model is obtained to evaluate the control gains. Finally, the controller is applied to the extended nonlinear model to quantify the controller. Results revealed that the controller considering the influence of the suspended load decreased the magnitude of oscillation on the altitude of the quadrotor and the swing angle of the pendulum up to 13.02% and 51.23%, respectively.