Study On The Taut-Slack Characteristics Of Tethered UAV System Tether Cable When Ship Motion Is Considered

Tethered unmanned aerial vehicle(UAV)has the advantages of simple structure,long endurance,and stable communication.It is widely used in emergency communication,high-camera live broadcast,environmental monitoring and other fields,and has achieved good economic benefits.When the shipborne tethered UAV system works,it will be affected not only by the external wind field,but also by the motion of the ship.The system composed of the tether line and UAV will have rich dynamic phenomena,such as the relaxation tension phenomenon of the tether line when the ship is moving.Therefore,it is significant to study the dynamics of the tethered UAV in the design and safe operation of UAV.In this paper,the mathematical model of the ship-borne moored UAV system is established by the concentrated mass method,and the movement characteristics of the system under the action of the periodic wind field and the discrete gust wind field and the change law of the internal tension of the tether cable are studied;The slack-tension phenomenon in the tether line is studied when the amplitude of ship motion is large;The actual flight experiment of the UAV under the excitation of the bottom end of the tether cable was carried out.The specific research content can be divided into the following parts:(1)The lumped mass method is used to discretize the tether line of the tethered UAV system,and the three-dimensional mathematical model of the tethered UAV system is established.Newton iteration method is used to solve the static configuration and tension of the tethered UAV system,which lays the foundation for the follow-up study on the dynamic characteristics of the system;(2)The howbolt difference scheme is used to solve the equations of motion iteratively.The initial condition of the system is the static configuration and tension of the tether line,the lower boundary is the ship,and the upper boundary is the UAV.The motion characteristics of UAV and tether line under periodic wind field and discrete gust wind field and the internal tension characteristics of tether line are studied,and the elongation curves of tether line under different working conditions are given.It is found that the larger the amplitude of wind field is,the larger the internal tension is,and the larger the range of motion is;The amplitude of tether line will be distributed in horizontal and vertical directions when wind field is in different periods.The range of UAV motion decreases with the increase of the period of periodic wind field;(3)The ship motion is simplified to sinusoidal motion,and the taut-slack phenomenon of tether cable is studied in the tether UAV system.The variation law of the number of taut-slack sections of the tether line under different excitation amplitude and frequency is given,and the amplification factor of tension snap at the bottom of the tether line is calculated when the slack tension phenomenon occurs.Finally,the parameter domain of the taut-slack phenomenon is summarized;(4)Based on the existing experimental model of the tethered UAV system,the tension of the upper and lower points of the tether bottom under different excitation amplitude and frequency in the wind field is studied.The results are as follows: When the lower end of the tether line has sinusoidal excitation,the tension at the upper and lower end also changes according to the sinusoidal law;The larger the excitation amplitude is,the larger the tension at the upper and lower ends of the tether line is;When the bottom end is excited,the tension at the upper and lower ends of the tether line will appear in the form of frequency doubling;The experimental results are compared with the theoretical calculation in Chapter 4 to qualitatively verify the correctness of the theoretical calculation.