Model Experimental Study On The Dynamics Of Shipborne Tethered Unmanned Aerial Vehicles Without Wind Load

Tethered UAV(Unmanned Aerial Vehicle)have the characteristics of long working hours,controllable lift,and convenient equipment.They are widely used in different tasks,such as emergency communications,environmental monitoring,search and rescue tasks.In the shipborne tethered UAV system,the geometric nonlinearity and material nonlinearity of the tethered cable,the coupling of the tethered cable and the UAV,and other factors make the tethered UAV system have complex nonlinear vibration characteristics and sometimes cause the structure larger vibration,even the crash.Therefore,it is of great significance to conduct experimental research on the dynamics of shipborne tethered UAVs.In this paper,experimental methods are used to study the modalities of the tethered UAV,the dynamic response of the shipborne tethered UAV and the impact response of the tethered UAV.The specific work and results are as follows:(1)This article summarizes the research status of tethered UAVs;according to the experimental objects,the experimental similarity relationship and simulation devices are determined,such as the selection of excitation mechanism,the design of the tension measuring device of the end force of the tethered cable and the intermediate measuring point,displacement and acceleration measuring devices,etc.(2)Study the modalities of the tethered UAV with wind load and without wind load through the modal experiment analysis method,use camera shooting to realize non-contact measurement,and use image reconstruction technology to analyze the displacement response of the tethered cable.Domain decomposition and parameter extraction analyze the mode shape,frequency and damping ratio of the tethered cable.It is found that the existence of the UAV mass under wind load reduces the first-order natural frequency of the tethered cable,increases the second-order natural frequency,and the damping ratio,both have increased.The moving boundary of the UAV reduces the natural frequency of the tethered cable,but the damping ratio increases.The same method is used to obtain the inherent characteristics of the tethered UAV without wind load.(3)Analyze the dynamic response of the shipborne tethered UAV through model experiments,and analyze the influence of different factors on the response.The results show that as the horizontal excitation frequency and amplitude,and the vertical excitation frequency and amplitude increase,the system maximum tension of the cable end and the middle measuring point has increased,and the dynamic tension amplitude of the tethered cable end and the middle measuring point has also increased.The vertical excitation of the lower end of the tethered cable has a greater influence on the maximum tension of the upper end of the tethered cable.By manipulating the actual tethered UAV,the results of the system under the excitation of the lower endpoint were tested,and the reliability of the model experiment was verified.(4)The impact of tethered UAVs is studied,and the impact of tethered cable length and UAV speed on the impact response is analyzed through simplified models.The results show that as UAV impact speed increases,the two ends of the tethered cable,the tension increases,and the maximum tension at the fixed end of the tethered cable is greater than the maximum tension at the moving end of the tethered cable.The impact is transmitted from the moving end of the tethered cable to the fixed end of the tethered cable.The impact experiment of the actual flying tethered UAV verifies the rationality of the simplified model analysis.