Trajectory Tracking for Agricultural Dynamic Multi Copter Aerial Robot

Abstract

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 cost effective 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 xii 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.