The harmonic oscillatory tests for a fighter aircraft configuration using the Dynamic Plunge-Pitch-Roll (DyPPiR) model mount at Virginia Tech Stability Wind Tunnel are described and analyzed. The corresponding data reduction methods are developed on the basis of multirate digital signal processing techniques. Since the model is sting-mounted to the support system of DyPPiR, the Discrete Fourier Transform (DFT) is first used to identify the frequencies of the elastic modes of sting. Then the sampling rate conversion systems are built up in digital domain to resample the data at a lower rate without introducing distortions to the signals of interest. Finally linear-phase Finite Impulse Response (FIR) filters are designed by Remez exchange algorithm to extract the aerodynamic characteristics responses to the programmed motions from the resampled measurements. These data reduction procedures are also illustrated through examples. The results obtained from the harmonic oscillatory tests are then illustrated and the associated flow mechanisms are discussed. Since no significant hysteresis loops are observed for the lift and the drag coefficients for the current angle of attack range and the tested reduced frequencies, the dynamic lags of separated and vortex flow effects are small in the current oscillatory tests. However, large hysteresis loops are observed for pitch moment coefficient in the current tests. This observation suggests that at current flow conditions, pitch moment has large pitch rate and alpha-dot dependencies. Then the nondimensional maximum pitch rate q__max is introduced to characterize these harmonic oscillatory motions. It is found that at current flow conditions, all the hysteresis loops of pitch moment coefficient with same nondimensional maximum pitch rate are tangential to one another at both top and bottom of the loops, implying approximately same maximum offset of these loops from static values. Several cases are also illustrated. Based on the results obtained and those from references, a state-space model is developed to describe the unsteady aerodynamic characteristics up to the high angle of attack regime. A nondimensional coordinate is introduced as the state variable describing the flow separation or vortex burst. First-order differential equation is used to govern the dynamics of flow separation or vortex bursting through this state variable. To be valid for general configurations, Taylor series expansions in terms of the input variables are used in the determination of aerodynamic characteristics, resembling the current approach of the stability derivatives. However, these derivatives are longer constant. They are dependent on the state variable of flow separation or vortex burst. In this way, the changes in stability derivatives with the angle of attack are included dynamically. The performance of the model is then validated by the wind-tunnel measurements of an NACA 0015 airfoil, a 70 degree delta wing and, finally two F-18 aircraft configurations. The results obtained show that within the framework of the proposed model, it is possible to obtain good agreement with different unsteady wind tunnel data in high angle-of-attack regime. / Ph. D.

Simulation of a dynamic system is known to be sensitive to various factors and one of them could be the precision of model parameters. While the sensitivity of flight dynamic simulation to small changes in aerodynamic coefficients is typically not studied, the simulation of aircraft required to operate in nonlinear flight regimes usually at high angles of attack can be very sensitive to such small differences. Determining the significance and impact of the differences in aerodynamic characteristics is critical for understanding the flight dynamics and designing suitable flight control laws. This thesis uses this concept to study the effect of the differences in aerodynamic data for different aerodynamic models provided for a same aircraft which is F-18 HARV combat aircraft. The aircraft was used as a prototype for the high angles of attack technology program. However modeling an aircraft at high angles of attack requires an extensive aerodynamic data which are usually di cult to access. All aerodynamic models were collected from open literature and implemented within a nonlinear six degree of freedom aircraft model. Inspection of aerodynamic data set for these models has shown mismatches for certain aerodynamic derivatives, especially at higher angles of attack where nonlinear dynamics are known to exist. Nonlinear simulations are used to analyse three different types of flight dynamic models that use look-up-tables, arc-tangent formulation and polynomial functions to represent aerodynamic data that are suitable for high angles of attack application. To achieve this, a nonlinear six degree of freedom Simulink model was developed to accommodate these aerodynamic models separately. The trim conditions were obtained for different combinations of angles of attack and airspeed and the models were linearized in each case. Properties of the resulting state matrices such as eigenvalues and eigenvectors were studied to determine the dynamic behaviour of the aircraft at various flight conditions.

Resumo: O projeto de aeronaves convencionais, em geral, apresentam uma série de dificuldades de se realizar de maneira eficiente um amplo número de missões, uma vez que para atender esses requisitos estas aeronaves deveriam ser capazes de realizar grandes alterações em sua geometria. Surge então um novo conceito de projeto de aeronaves, as chamadas aeronaves adaptativas, as quais são capazes de alterar sua geometria, de modo a adaptar a aeronave a um dado tipo de missão. Este novo conceito se tornou ainda mais atrativo com os avanços tecnológicos promovidos pelo estudo de novos materiais, os chamados materiais inteligentes, que apresentam alta densidade de energia, vantagem que leva a uma redução de peso nos mecanismos atuados desta maneira. Este trabalho apresenta um novo modelo adaptativa, utilizando fios atuadores de ligas de memória de forma para realizar uma rotação relativa entre duas seções de um aerofólio, este mecanismo possibilitaria a variação da linha de arqueamento de uma seção aeronáutica. Neste trabalho uma modelagem matemática para se descrever o comportamento deste sistema é apresentada, bem como um modelo aerodinâmico para se verificar o comportamento do sistema em funcionamento. Um controlador do tipo nebuloso é ainda projetado para se controlar a forma do perfil, e ensaios experimentais são conduzidos para se verificar a modelagem termo-mecânica apresentada. / Abstract: Conventional airplane design, in general, has a large difficulty to attend in an efficient way several mission requirements, once that to attend these requirements the airplane has to perform great shape changes in its structure. Motivated by this problem a new concept in airplane design arise, one called morphing airplanes, which are air vehicles capable of changing its shape to adapt it self to a defined mission. This new concept became even more attractive with the development of active smart material, which can be a high power density actuator, reducing the weight of such morphing mechanism. This work proposes a novel model for morphing wings, using a pair of shape memory alloy wires to create a rotation between two wing sections, this mechanism allows the airfoil to change its camber line. A mathematical model is derived to describe the thermo-mechanical structure behavior, and also an aerodynamic model is investigated. A fuzzy controller is designed to control the system shape, and some experimental tests are used to verify the thermo-mechanical modeling proposed. / Orientador: Vicente Lopes Junior / Coorientador: Carlos de Marqui Junior / Banca: Gustavo Luiz Chagas Manhães de Abreu / Banca: Álvaro Martins Abdalla / Mestre

Made available in DSpace on 2014-06-11T19:27:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-07-27Bitstream added on 2014-06-13T19:55:32Z : No. of bitstreams: 1 faria_ct_me_ilha.pdf: 2001879 bytes, checksum: 8c06397bc7d8057b53383eaa08ea1d01 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O projeto de aeronaves convencionais, em geral, apresentam uma série de dificuldades de se realizar de maneira eficiente um amplo número de missões, uma vez que para atender esses requisitos estas aeronaves deveriam ser capazes de realizar grandes alterações em sua geometria. Surge então um novo conceito de projeto de aeronaves, as chamadas aeronaves adaptativas, as quais são capazes de alterar sua geometria, de modo a adaptar a aeronave a um dado tipo de missão. Este novo conceito se tornou ainda mais atrativo com os avanços tecnológicos promovidos pelo estudo de novos materiais, os chamados materiais inteligentes, que apresentam alta densidade de energia, vantagem que leva a uma redução de peso nos mecanismos atuados desta maneira. Este trabalho apresenta um novo modelo adaptativa, utilizando fios atuadores de ligas de memória de forma para realizar uma rotação relativa entre duas seções de um aerofólio, este mecanismo possibilitaria a variação da linha de arqueamento de uma seção aeronáutica. Neste trabalho uma modelagem matemática para se descrever o comportamento deste sistema é apresentada, bem como um modelo aerodinâmico para se verificar o comportamento do sistema em funcionamento. Um controlador do tipo nebuloso é ainda projetado para se controlar a forma do perfil, e ensaios experimentais são conduzidos para se verificar a modelagem termo-mecânica apresentada. / Conventional airplane design, in general, has a large difficulty to attend in an efficient way several mission requirements, once that to attend these requirements the airplane has to perform great shape changes in its structure. Motivated by this problem a new concept in airplane design arise, one called morphing airplanes, which are air vehicles capable of changing its shape to adapt it self to a defined mission. This new concept became even more attractive with the development of active smart material, which can be a high power density actuator, reducing the weight of such morphing mechanism. This work proposes a novel model for morphing wings, using a pair of shape memory alloy wires to create a rotation between two wing sections, this mechanism allows the airfoil to change its camber line. A mathematical model is derived to describe the thermo-mechanical structure behavior, and also an aerodynamic model is investigated. A fuzzy controller is designed to control the system shape, and some experimental tests are used to verify the thermo-mechanical modeling proposed.

This doctoral study aims to develop a methodology for use in determining aerodynamic models and parameters from actual flight test data for different types of autonomous flight vehicles. The stepwise regression method and equation error method are utilized for the aerodynamic model identification and parameter estimation. A closed loop aerodynamic parameter estimation approach is also applied in this study which can be used to fine tune the model parameters. Genetic algorithm is used as the optimization kernel for this purpose. In the optimization scheme, an input error cost function is used together with a final position penalty as opposed to widely utilized output error cost function. Available methods in the literature are developed for and mostly applied to the aerodynamic system identification problem of piloted aircraft / a very limited number of studies on autonomous vehicles are available in the open literature. This doctoral study shows the applicability of the existing methods to aerodynamic model identification and parameter estimation problem of autonomous vehicles. Also practical considerations for the application of model structure determination methods to autonomous vehicles are not well defined in the literature and this study serves as a guide to these considerations.