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Control of a Sprayer Hexacopter with Continuous Varying Mass in the Presence of Fluid Sloshing Disturbance

Borhani, Mohammad | 2025

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 58450 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Alasty, Aria; Vosughi, Gholamreza
  7. Abstract:
  8. Unmanned aerial vehicles (UAVs), particularly hexacopters, are increasingly used in agricultural spraying due to their high payload capacity and stable flight performance. However, changes in liquid mass during spraying alter flight dynamics, and fluid sloshing within the tank introduces internal disturbances that may affect stability. This study presents an Active Disturbance Rejection Control (ADRC) for velocity control of spraying hexacopters to maintain performance under varying mass and internal/external disturbances. A real tank was used to analyze variations in the fluid’s center of mass under different conditions, revealing a nearly spherical distribution. Based on this, a two-degree-of-freedom (2-DoF) pendulum model was developed to represent both sloshing and mass variation. Model parameters were identified using the ordinary least squares (OLS) method. The dynamic equations of the hexacopter with the attached pendulum, including time-varying parameters, were derived using the Lagrangian method. Analysis indicated that the most significant disturbances occurred at fluid masses of 4 kg and 14 kg. The proposed ADRC, employing six virtual control inputs, was implemented in simulation. Results showed that the offset between the center of mass and the geometric center of the hexacopter significantly affects rotor angular velocities, while the modeled fluid sloshing has a negligible effect. The controller demonstrated robust performance under continuous mass variation, external disturbances, and measurement noise
  9. Keywords:
  10. Active Disturbance Rejection Control (ADRC) ; Unmanned Aerial Vehicles (UAV) ; Fluid Sloshing Control ; Ordinary Least Squares (OLS)Regression ; Extended State Observer ; Agricultural Drone ; Least Squares Method ; Payload Variation ; Lagrangian Dynamics

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