About revising the computational dynamic scheme of an unmanned aerial vehicle based on the results of ground-based modal test operations in the aeroelasticity problems

Abstract

The problem of revising the computational dynamic scheme of an unmanned aerial vehicle (UAV), based on the results of ground-based modal test operations, in order to study the UAV flutter and to assess the aeroelastic stability of an UAV with an automatic control system (ACS), is considered. It is noted that at the design stage, when there is no UAV prototype or its units yet, the determination of modal characteristics, specifically natural frequencies, modes and generalized masses, is carried out using the computational dynamic scheme developed according to the design documentation. However, the similar computations, performed even with the use of modern finite-element software systems, do not give sufficiently precise values of the parameters of the UAV design elastic-mass schematization. In this regard, it is relevant and important to specify the parameters of the design schematization in conformity with data of ground test operations for UAV prototypes. The provisions, allowing us to achieve satisfactory results when revising the UAV computational dynamic scheme, are made. The criteria of revising are considered. The features of revising the computational dynamic scheme, while studying the flutter and aeroelastic stability of the ACS-fitted UAV, are presented. It is noted that along with the provisions that are universal for dynamic aeroelasticity problems, specifically for flutter, and related to compensating of natural frequencies, modes and coefficients of structural damping for the UAV model according to the results of ground modal tests. In the problems of aeroelastic stability study of the UAV equipped with the ACS, it is also crucial to correct the UAV body transfer function from the section, corresponding to the axis of controls rotation, to the section where ACS sensors are installed. This is because the UAV hull is an integral part of the UAV stabilization loop and significantly affects its stability margin. The example of revising the computational dynamic scheme of a maneuverable cruciform UAV is given.