Analysis of Stability and Error Criteria in Different Trajectory Conditions with PID Control in Agricultural Drones

In this study, a Proportional–Integral–Derivative (PID) controller was designed to address stability issues in agricultural unmanned aerial vehicles (UAVs) carrying liquid payloads. The primary goal was to mitigate the adverse effects of center-of-mass and inertia changes caused by liquid sloshing dynamics during flight. The inertia matrix was dynamically updated during flight to reflect center-of-gravity shifts and liquid sloshing effects. A MATLAB/Simulink model of a quadrotor UAV with three-axis (x, y, z) attitude control was developed. The same set of PID coefficients was applied to four distinct flight trajectories to assess performance. Evaluation was conducted using common error metrics, including the Integral of Time-weighted Absolute Error (ITAE), Integral of Absolute Error (IAE), Integral of Squared Error (ISE), and Integral of Time-weighted Squared Error (ITSE). The results demonstrated significant performance variations of the uniformly tuned PID controller across different trajectories, supported by quantitative performance metrics. These findings emphasize the importance of achieving a robust and trajectory-independent control structure for agricultural UAVs.