Flow Field Analysis Of Four Rotor Unmanned Aerial Vehicle In Flight

After entering the new century,the four rotor unmanned aerial vehicle(UAV)started a new stage of development: miniaturization.Due to the unique flight mode different from the traditional helicopter,following the advent of Parrot AR.Drone in 2010,the four rotor UAV quickly enter the public view.Low cost,high maneuverability make the four rotor drone popular,and gradually applied to military,agriculture,forestry,social activities and other fields.But,the relatively small model structure and complex low-altitude aerodynamic environment make the actual flight of UAVs subject to a large degree of restrictions.At present,the small UAV can only flight in the air stable external environment or indoor.While the study on air disturbance in the process of four rotor UAV flight have rarely been published,So the response research of the four rotor UAV under flow disturbance is necessary.The wind influence function polynomial of the small unmanned helicopter reduced to the third order is simpler than the sixth order polynomial,and the results of parameter identification and experimental verification all show the validity and accuracy of the third order polynomial.The proposed wind influence function is a new direction for the study of wind-induced jamming of four rotor UAVs.The simulation results of different wind speed and wind direction of single rotor compared with the theoretical results show the validity and reliability of the simulation experiment.The analysis of the rotor lift,torque and flow fields for different cross-wind configurations of a simple cross structure proves that when there is an incoming disturbance the position of each rotor in the fuselage structure has a large effect on rotor’s lift and torque.Especially in horizontal winds,The significant difference in the lift of the nose and tail rotor requires a high degree of attention in the control design.The comparison of the simulation results between the simplified Phantom 3 model and the cross structure shows that the main factors influencing the stability of the UAVs are the mutual interference among rotors.Parameter identification results and it’s verification of Wind impact function of four rotor UAV under different flight state prove that the wind influence function is effective when wind speed is variable under horizontal wind.