Dynamic Modeling And Preliminary Simulation Of Hovering State Ducted Fan UAV

In recent years,with the more and more extensive application of unmanned equipment in the military field,how to carry out collaborative operation between unmanned ships,unmanned aerial vehicles and other unmanned equipment has become a hot topic in current research.The autonomous take-off and landing technology of UAV in unmanned boat is one of the key steps,which requires the UAV to be well controlled in the vertical take-off and landing of unmanned boat.Because of its convenient vertical takeoff and landing and hover features,ducted-fans UAVs are gradually coming into people’s field of vision.At present,the research on the ducted-fans UAV is still in the initial stage in China,and there are many difficulties to be overcome in both aerodynamic performance prediction and flight control design.In this paper,a new carrier-borne ducted fan UAV is taken as the research object,and the aerodynamic performance of UAV is studied based on CFD numerical simulation method.Then,according to the calculated aerodynamic coefficients,the dynamics model of the UAV hovering in the passageway was constructed.Finally,a PID controller with three channels is designed to control the attitude of UAV.The specific research contents are as follows:Firstly,the development history,aerodynamic performance and flight control research methods of the ducted-fans UAV are investigated.According to V-bat UAV,a new type of ductedfans VTOL UAV is constructed,and it is divided into three parts: fuselage,ducted-fans and control rudder.The sliding grid is used to calculate the aerodynamic performance of the rotating part of the UAV.The ducted fan part of UAV is studied in detail.1.Compared with isolated propellers,the study found that the presence of ducted fans increased the lift of the system by 56%.2.The lift force variation of the hovering fans in the three ducted fans at different speeds is obtained.3.The influence of ground effect on the aerodynamic characteristics of the ducted fan is studied.It is found that when the height from the ground is reduced to twice the diameter of the ducted fan,the aerodynamic performance of the ducted fan begins to change dramatically.With the decrease of the elevation from the ground,the lift force of the propeller in the ducted fan increases,the lift force generated by the ducted fan itself decreases,and the power coefficient of the ducted fan system increases.It is found that the influence of ground effect on lift coefficient and quality factor of culvert is related to the number of propeller blades.After that,the distribution and stress of the UAV control rudder plate were analyzed.Combined with the aerodynamic performance calculated by CFD method,the overall stress situation of the UAV was finally obtained,and based on this,the dynamics model of the UAV under the hovering state of the culvert was constructed.After the model is simplified,PID controller is designed for the attitude dynamics part of the UAV.The cascade PID control method is used to design the internal and external loop controllers of the UAV yaw,pitch and roll respectively.The controller design results show that the ideal closed-loop model of the three channels of UAV has good time-domain and frequency-domain characteristics,which preliminarily validates the rationality of the ducted-fans UAV model constructed in this paper.