Point to point control of a liquid carrying quadrotor

Carrying liquids by drones is essential in the automated performance of missions such as firefighting and field spraying. On the other hand, transient and residual turbulence of the liquid during and after transportation can cause instability, increase position error, increase control effort, and cause danger and damage in the event of liquid flammability. Therefore, in this study, the control of a liquid-carrying quadrotor has been studied and a controller has been presented that, unlike previous studies, can provide quadrotor stability in point-to-point transportation without the need to measure or estimate liquid states. For this purpose, a controller is first designed by linearizing the equations of motion of the liquid-carrying quadrotor and assuming that the liquid is rigid through appropriate placement of poles. On the other hand, in order for the system behavior to be similar to the behavior of the design model and to maintain system stability, the liquid turbulence must be reduced as much as possible. For this purpose, a steering smoother designed based on the natural frequencies of fluid turbulence modes has been used. The capability of the proposed control system has been verified by simulation and compared with a similar reference. Also, the simulation results show that the use of the designed steering smoother can significantly reduce the fluid turbulence amplitude, the deviation of the system states from the equilibrium state, and the control effort.