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Unmanned aerial vehicles (UAVs) have become a popular choice for spraying pesticide in
agricultural use due to their versatility and maneuverability. Quadcopters carrying
suspended water containers are widely used for firefighting services. The efficient
transportation of liquids by UAVs is of utmost importance in various autonomous
missions, including agriculture field spraying. A lot of research is being carried out on the
control of these UAVs subject to the constraints of unwanted forces created by the sloshing
liquid. However, the complex dynamics of this system can result in the degradation of
flight safety due to the linkage among the UAV maneuver, container swing, and liquid
sloshing.
Liquid sloshing in a container is a well-known and longstanding challenge within the field
of engineering. In this study, the word liquid sloshing refers to the variable wave surface
elevation of the fluid in a container. Nevertheless, liquid sloshing can lead to undesirable
effects such as instability, unwanted forces, position error, and increased control effort
resulting in inefficient power utilization and payload constraints.
To ensure the effective implementation of the control system for an agricultural spraying
drone, it is essential to estimate the pesticide slosh model. The objective of this study is to
ascertain sloshing parameters by employing an innovative technique that leverages a costeffective sensor. The proposed experimental setup employed during this investigation
comprises a rectangular beaker positioned on a conveyor belt. A Kalman estimator based
ultrasonic sensor, mounted atop the liquid-filled container whose slosh parameters
necessitate identification, is employed. System identification techniques were employed
to derive the system model. Comparative analysis involving calculation of the Root Mean
Square Error (RMSE) were conducted to evaluate accuracy and error. Following numerous
tests conducted at various slosh levels, the acquired data was subjected to analysis. The
results obtained substantiate the feasibility of our concept in measuring slosh under
dynamic conditions.
To mitigate the effects of liquid sloshing, an approach based on Lagrangian is utilized that
enables the development of dynamic model of UAV and resulting nonlinear coupled
dynamics of liquid carrying quadrotor. This developed hybrid model, incorporating both
slosh and drone dynamics, is thoroughly examined. It enables the application of different
control strategies to attain satisfactory performance and meet energy requirements based
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on actuator control efforts. The study delves into two specific control methods: Linear
Quadratic Regulator (LQR) and Proportional-Integral-Derivative (PID), extensively
presenting, investigating, validating, and comparing their effectiveness in achieving
stability and calculating energy demands for a hovering liquid-carrying quadcopter. The
utilization of LQR and PID controllers offers notable enhancements in the overall
quadcopter performance, accompanied by reduced operational expenses.
Simulations based on Coppelia V-rep are also presented to investigate the real-time
application of the suggested system. The results demonstrate a decrease in liquid slosh
amplitude and, consequently, a reduction in the control effort of the controller. These
findings have significant implications for improving the quality of quadcopter control in
various real-world applications.