摘要 :
This paper describes a sliding mode control (SMC)-based disturbance observer-based controller (DOBC) to improve coaxial helicopter UAVs' robust attitude control performance. A coaxial rotor aerodynamics test environment is establi...
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This paper describes a sliding mode control (SMC)-based disturbance observer-based controller (DOBC) to improve coaxial helicopter UAVs' robust attitude control performance. A coaxial rotor aerodynamics test environment is established to select motors and propellers suitable for the propulsion system of a coaxial helicopter UAV. The motor rotation speed required for the operation of the UAV is identified, and the rotor diameter and motor are selected. Then, the aerodynamic data of the rotor are analyzed to calculate the aerodynamic coefficient. In this paper, a coaxial helicopter UAV is developed based on the rotor experiment. The developed UAV has a seesaw, feathering, and napping hinge mounted on the blade hub like a typical helicopter. The numerical dynamics modeling consisted of the forces and moments of the propulsion and the body of the UAV using the aerodynamic coefficients for the rotor from aerodynamic experiments. The aerodynamic interference of the upper and lower rotors of the coaxial rotor acts as a disturbance to the UAV. In addition, this disturbance increases the model uncertainty and degrades the attitude-tracking performance of the controller. For robust attitude control against disturbance, in this paper, SMC-based DOBCs are designed and implemented. SMC is designed with angle, angular velocity, and altitude controllers in a cascade structure. DOBC is connected to the angular velocity loop to eliminate disturbances that are difficult to model and cannot be estimated by SMC. In the numerical simulation, disturbances are applied to the roll, pitch, and yaw axes, and model uncertainty is considered. The attitude-tracking performance of SMC-based DOBC is superior to that of SMC, and disturbance estimation and compensation effects are improved. The controller is implemented in the flight control computer (FCC) to check the controller's performance. A tether test environment and a hovering and attitude command tracking test of a coaxial helicopter UAV is conducted.
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