Poin to Point Control of a Liquid Carrying Quadrotor

Liquid transport by UAVs is a necessary task in autonomous firefighting and field spraying missions. On the other hand, transient and residual sloshing of the liquid during and after the movement can cause instability, increase position error and control effort and create danger or damage if the liquid is flammable. Therefore, in this study, control of a liquid carrier quadrotor has been studied and a controller has been presented that, unlike previous studies, can provide stability in point-to-point transmission 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 system and assuming the liquid is rigid via pole placement. On the other hand, in order for the behavior of the system to be similar to the behavior of the design model and to maintain the stability of the system, the liquid sloshing must be reduced as much as possible. Therefore, a command smoother based on the natural frequencies of the liquid sloshing modes is used. The ability of the proposed control system has been investigated, validated and compared with a similar study by simulation. Also, the simulation results show that implementation of the designed command smoother can significantly reduce the amplitude of liquid sloshing, the deviation of the system states from the equilibrium state and the control effort.