Modelagem numérica de um cabo adaptada à simulação de um par de aviões conectados

Abstract

The dynamic modeling of a pair of aircraft connected by a cable allows the aircraft's behavior to be studied in different flight conditions, enabling the assessment of safe operating conditions for cases such as aerial refueling or glider towing. In addition, this model could also be used to design flight control laws for both aircraft involved, in order to enhance the operation's safety. In light of that, this work proposes the study and development of a dynamic numerical model involving the two aircraft connected by cable. Hence, we started from a literature review on a series of instabilities that could occur in the cable, so as to attempt to verify them in the simulation and avoid dangerous flight envelopes. Then, the research, implementation, and adaptation of structural-dynamics numerical models, which could be used for modeling a pair of tethered airplanes, were performed. Three of them have been studied and implemented. The first is based on the Lumped Parameter Method, the second is based on the Finite Element Method using a member element and the last is a Finite Element Method using a non-linear beam element. The simulations have shown that the first method was not suitable for the proposed problem, whereas the latter two were easily implemented and tested. In addition, a comparison was made between the last two to determine which one was the most suitable for different contexts. The results have shown that the behavior of the Finite Element Method using bar elements was statically identical to that using beam elements. However, dynamically, the methods have presented considerable differences, in which the beam element has been deemed to be more physically consistent. Finally, using both types of element, we sought to verify the stability criterion found, according to which a disturbance would be amplified if it traveled downwind. It was concluded that, for both cases, the stability criterion was verified, but with different behaviors between the element types.