Modeling and control of quadrotor UAV subject to variations in center of gravity and mass

Variations of a center of gravity (COG) and mass make difficulties for control of quadrotors. For example, there are situations such as flight with swing load or with sloshing fuel. These problems leave room for uncertainties in the attitude and position control systems. To mitigate the above-mentioned effects, effective control algorithm must be developed based on modified dynamics of the quadrotors with considering mass and COG variations. The complete mathematical formulations of translation and rotational dynamics of the quadrotor are derived with considering the effect of swing load motion. Hence, the formulations are quite different with the one used in the existing quadrotor dynamics. The proposed model consists of 6-DOF quadrotor dynamics model, and 3-DOF of swing load model. A cascade PD control algorithm is considered for the attitude and position control for such quadrotor. Simulation results indicate that the control algorithm works well in the quadrotor flight with the COG and mass variations.