43 research outputs found
Dynamic Response and Pitch Damper Design for a Moderately Flexible, High-Aspect Ratio Aircraft
No full textTCC (graduação) - Universidade Federal de Santa Catarina. Campus Joinville. Engenharia Aeroespacial.This work presents the dynamic response of a slightly flexible hight-aspect-ratio aircraft in time domain and the design of a pitch damper controller to augment pitch moments. The methodology adopted in this work extends the rigid body equations of motion and consider the effects of structural flexibility on the aircraft flight dynamics. The aircraft equations of motion are linearized and a flight control system to augment the pitch rate is designed. Firstly, the methodology to model a slightly flexible hight-aspect-ratio aircraft in time domain is revised. The mean axes reference frame is presented to situate the aircraft in time and space. Next, in order to consider the flexibility effects in the flight dynamics, the linearized structural dynamics in modal coordinates as well as the traditional modal superposition technique are briefly explained. The aerodynamic theory adopted in the methodology is also revised, where the incremental aerodynamic theory with the unsteady strip theory formulation in the time domain based on the Wagner function is described. The equations of motion are written by adding the flexible with rigid body terms. The methodology has been implemented at TU Berlin resulting in the software FlexSim, which was used in this work. Moreover, the linearized equations of motion in state space formulation and the decoupling to model the longitudinal aircraft dynamics are given to design the pitch damper. The controller gains are calculated following the frequency and damping values presented in the flying qualities for piloted aircrafts given by the American Military Specifications MIL-F-8785C. Two aircraft are investigated in this work. The first one is the motor glider Stemme S15, which is referred in this work as the reference aircraft. Since the Stemme S15 has its wing structural properties redesigned without changes in geometry. The Stemme S15 had its name changed to Ecarys ES15. Due this fact, the flight dynamic model is updated, comprehending the second aircraft model. The utility aircraft Ecarys ES15 is investigated using two configurations: with and without attached pods at wing. The structural properties of the aircraft are obtained by means of a linear interpolation of ground vibrations test data (GVT). The results compare the flight dynamic responses of aircraft’s rigid body model and the flexible model. The comparison gives the flight dynamic angle rates in pitch, roll and yaw after an input step in aircraft’s elevator and rudder controls. Furthermore, the modal amplitudes are also presented and the effects of longitudinal and lateral controls on the excitation of the vibrational modes is shown. The pitch damper is implemented and the variation of system roots is depicted. Besides that, the controller gains for the two aircraft models. The results compare the responses of the rigid aircraft model and the flexible aircraft models to step inputs in elevator and rudder.O presente trabalho tem como objetivo investigar a resposta dinâmica de uma aeronave moderadamente flexível com alta razão de aspecto no domínio do tempo e projetar um controlador de resposta de arfagem. Primeiramente, a metodologia aplicada nesse trabalho para modelar os efeitos elásticos da aeronave é revisada. O sistema de coordenadas dos eixos médios é apresentado para situar a aeronave no tempo e espaço. Em seguida, as equações de dinâmica estrutural em coordenadas modais bem como a técnica de superposição modal são brevemente revisadas. Na sequência a teoria aerodinâmica incremental com formulação não estacionária baseada na teoria das faixas é apresentada no domínio do tempo com a função de Wagner. O equacionamento apresentado na revisão da metodologia foi implementado pela TU Berlim no software FlexSim, o qual é utilizado no presente trabalho com o intuito de automatizar a análise aeroelástica. Ademais, com a linearização das equações do movimento o sistema de equações é reescrito na forma de espaço de estados e o sistema de controle é apresentado. As equações linearizadas de primeira ordem são então desacopladas e reescritas para o movimento longitudinal. A aproximação com dois graus de liberdade para o período curto é dada e um sistema de controle em malha fechada é definido. A frequência e o amortecimento das qualidades de voo requeridas para projetar o controlador são definidas com base na especificação militar americana MIL-F-8785C. Duas aeronaves são investigadas no trabalho. A primeira aeronave é o motoplanador Stemme S15, que é considerado como aeronave de referência, devido ao mesmo ser investigado na literatura para validação da metodologia utilizada no presente trabalho. A segunda aeronave é a Ecarys ES15, fruto de modificações nas propriedades estruturais da longarina e da superfície da asa da aeronave Stemme S15. Duas configurações da aeronave Ecarys ES15 são investigadas: com e sem pods fixados na parte inferior da asa. As propriedades estruturais da Ecarys ES15 são obtidas com ensaios de vibração em solo. Os resultados do ensaio são interpolados linearmente sobre toda a geometria da aeronave para consideração dos efeitos elásticos. Os resultados apresentados comparam as respostas dinâmicas das duas aeronaves com modelos de corpo rígido e flexível da estrutura. As variações das velocidades de rolamento, arfagem e guinada são plotadas com comandos no profundor e leme para representar a resposta dinâmica . Além disso, as amplitudes modais são representadas e a relação entre as superfícies de comando e a excitação de modos de vibração simétricos e não simétricos é comentada. Finalmente, o controlador de resposta de arfagem é implementado e os ganhos são calculados. A influência dos efeitos de flexibilidade nas raízes do sistema de equações, bem como na resposta dinâmica são apresentados e a relevância da consideração dos efeitos elásticos da estrutura é justificada
Search for exclusive photoproduction of Z(3900) at COMPASS
No full textA search for the exclusive production of the hadron by virtual photons has been performed in the channel . The data cover the range from 7~GeV to 19~GeV in the centre-of-mass energy of the photon-nucleon system. The full set of the COMPASS data set collected with a muon beam between 2002 and 2011 has been used. An upper limit for the ratio of has been established at the confidence level of 90%.A search for the exclusive production of the Zc±(3900) hadron by virtual photons has been performed in the channel Zc±(3900)→J/ψπ± . The data cover the range from 7 GeV to 19 GeV in the centre-of-mass energy of the photon–nucleon system. The full set of the COMPASS data set collected with a muon beam between 2002 and 2011 has been used. An upper limit for the ratio BR(Zc±(3900)→J/ψπ±)×σγN→Zc±(3900)N/σγN→J/ψN of 3.7×10−3 has been established at the confidence level of 90%.A search for the exclusive production of the hadron by virtual photons has been performed in the channel . The data cover the range from 7 GeV to 19 GeV in the centre-of-mass energy of the photon-nucleon system. The full set of the COMPASS data set collected with a muon beam between 2002 and 2011 has been used. An upper limit for the ratio of has been established at the confidence level of 90%
Design & modelling of a composite rudderless aeroelastic fin structure
No full textThis thesis presents the study of a gapless and rudderless aeroelastic fin (GRAF) to
enhance the directional stability and controllability of an aircraft. The GRAF concept
was proposed and developed in the wake of previous research, targeted to improve
flight performance and manoeuvrability, and to reduce fuel consumption and
airframe weight. The study involved the subjects of aerodynamics, structural design
and analysis, and flight mechanics.
The work includes conceptual design, structural modelling, aeroelastic analysis and
flight performance evaluation of a GRAF variant designed for a small subsonic
Unmanned Aerial Vehicle (UAV). The Eclipse UAV, a platform designed by part
time students at the Department of Aerospace Engineering of Cranfield University,
was chosen as a case study.
A new approach to design a more effective fin with an unconventional structural
layout and novel techniques which have not been investigated in previous research is
proposed. Despite the GRAF planform being similar to classical fin-hinged rudder
configurations, it is provided with a flexible gapless control surface, kept as one
continuous piece and integrated with the fin primary structure. With its fixed root
and rudderless feature, the GRAF adopts an original method of operation. Its way of
working relies upon an unconventional technique of combining morphing technology
and aeroelastic effect. The morphable configuration is twisted to gain an
aeroelastically beneficial effect to enhance the efficiency and manoeuvrability of the
aircraft. This warping capability of the fin is the key role player enabling the GRAF
surface to seamlessly generate the required aerodynamic forces.
Unlike the conventional structures designed to be as rigid as possible to withstand the
external loads, the GRAF will exploit its structure‟s flexibility to use the
aeroelastically induced twist deformations for a self-adaptive warping behaviour and
improve flight dynamic response and performance.
In order to ensure the above features are achievable in practice, further study on the
structural configuration was conducted. To achieve performance improvement,
together with the original structural layout and aeroelastic effect exploitation, another
three novel key components are investigated, proposed and introduced in the GRAF
model. A structurally integrated actuation system, termed L-shape stringers device
(LSS), is designed to transform actuator axial forces in spanwise distributed bending
moments, to create seamless deformations of the trailing edge (TE) section. An
innovative trailing edge joint, namely the swivel edge closure, is specifically
designed to enhance the mobility and degrees of freedom of the trailing edge box. It
is a revolutionary concept which, by virtually interrupting the structural integrity of
the closed TE section, allows relative translation and rotation of the TE panels.
Finally, it is the novel concept of the slot-connection that, whilst appearing to clamp
the GRAF structure inside the slot, actually enables the design to increase the twist
angle at the tip of the fin without overstressing the materials.
In order to enhance the GRAF efficiency, a tailored design of the fin structure was
conducted. A novel internal structure configuration integrated with the key
components has been designed to be connected to a flexible cladding skin, rotating
ribs and a load-carrying tubular beam all of which constitute the primary parts of the
GRAF model. With the ultimate goal of a lighter tail version, the entire design has
been made by using composite, light frames, in an engineering trade-off of stiffness,
elasticity, weight and cost of both glass and carbon fibre laminates.
The analysis via 2-D aerodynamic codes and FEA was conducted to assess and
validate the GRAF model and the obtained performance. Static linear elastic analysis
has been carried out to verify the structural layout of the novel design subject to
strength and stiffness criteria in addition to the fin warping and cambering
capabilities. Also an investigation of aeroelastic stability related to steady and
unsteady aerodynamic conditions has been carried out during the model analysis
phase. The study has shown that although the GRAF divergence and flutter margins
are slightly smaller than those of the conventional fin, the design and performance
requirements are satisfied within the very challenging objective of a lighter vertical
tail structure.The dynamic analysis study has also demonstrated the beneficial effect
obtained by damping yawing oscillations when such a self-adaptive structure,
compared to a rigid one, can be operated under cross wind circumstances. The
manufacturing feasibility and assembly of the GRAF structure has been explored
with the construction of a 1:1 scale model of the fin prototype. The model has been
used as concept demonstrator to assess the functionality of the introduced technical
novelties, the ease of manufacturing and the structural weight of the final assembly
Resonance production and pi pi S-wave in pi(-) + p -> pi(-) pi(-) pi(+) + p(recoil) at 190 GeV/c
No full textThe COMPASS collaboration has collected the currently largest data set on diffractively produced pi(-) pi(-) pi(+) final states using a negative pion beam of 190 GeV/c momentum impinging on a stationary proton target. This data set allows for a systematic partial-wave analysis in 100 bins of three-pion mass, 0.5 < m(3 pi) < 2.5 GeV/c(2), and in 11 bins of the reduced four-momentum transfer squared, 0.1 < t' < 1.0 (GeV/c)(2). This two-dimensional analysis offers sensitivity to genuine one-step resonance production, i.e. the production of a state followed by its decay, as well as to more complex dynamical effects in nonresonant 3 pi production. In this paper, we present detailed studies on selected 3p partial waves with J(PC) = 0(-+) ,1(++) ,2(-+) ,2(++) ,and 4(++). In these waves, we observe the well-known groundstate mesons as well as a new narrow axial-vector meson a(1)(1420) decaying into f(0) (980)pi. In addition, we present the results of a novel method to extract the amplitude of the pi(-)pi(+) subsystem with I(G)J(PC) = 0(+)0(++) in various partial waves from the pi(-)pi(-)pi(+) data. Evidence is found for correlation of the f (0)(980) and f(0)(1500) appearing as intermediate pi(-)pi(+) isobars in the decay of the known pi(1800) and pi(2)(1880)
Observation of a new narrow axial-vector meson
No full textThe COMPASS collaboration at CERN has measured diffractive dissociation of 190 GeV pions into the final state using a stationary hydrogen target. A partial-wave analysis (PWA) was performed in bins of mass and four-momentum transfer using the isobar model and the so far largest PWA model consisting of 88~waves. A narrow signal is observed in the channel. We present a resonance-model study of a subset of the spin-density matrix selecting states with and decaying into and with decaying into . We identify a new meson with mass MeV and width MeV. Within the final states investigated in our analysis, we observe the new decaying only into , suggesting its exotic nature. To our knowledge, such a state has never been predicted.The COMPASS Collaboration at CERN has measured diffractive dissociation of 190 GeV/c pions into the π-π-π+ final state using a stationary hydrogen target. A partial-wave analysis (PWA) was performed in bins of 3π mass and four-momentum transfer using the isobar model and the so far largest PWA model consisting of 88 waves. A narrow peak is observed in the f0(980)π channel with spin, parity and C-parity quantum numbers JPC=1++. We present a resonance-model study of a subset of the spin-density matrix selecting 3π states with JPC=2++ and 4++ decaying into ρ(770)π and with JPC=1++ decaying into f0(980)π. We identify a new a1 meson with mass (1414-13+15) MeV/c2 and width (153-23+8) MeV/c2. Within the final states investigated in our analysis, we observe the new a1(1420) decaying only into f0(980)π, suggesting its exotic nature.The COMPASS collaboration at CERN has measured diffractive dissociation of 190 GeV/ pions into the final state using a stationary hydrogen target. A partial-wave analysis (PWA) was performed in bins of mass and four-momentum transfer using the isobar model and the so far largest PWA model consisting of 88 waves. A narrow signal is observed in the channel. We present a resonance-model study of a subset of the spin-density matrix selecting states with and decaying into and with decaying into . We identify a new meson with mass MeV/ and width MeV/. Within the final states investigated in our analysis, we observe the new decaying only into , suggesting its exotic nature
Experimental study of the pd(d p) → 3 He ππ reactions close to threshold
No full textNew experimental data on the pd → 3
He π+π− reaction obtained with the COSY-MOMO detector below
the three-pion threshold are presented. The reaction was also studied in inverse kinematics with a deuteron beam
and the higher counting rates achieved were especially important at low excess energies. The comparison of
these data with inclusive pd → 3
He X0 rates allowed estimates also to be made of π0π0 production. The results
confirm our earlier findings that, close to threshold, there is no enhancement at low excitation energies in the
π+π− system, where the data seem largely suppressed compared with phase space. Possible explanations for
this behavior, such as strong p waves in the π+π− system or the influence of two-step processes, are explored
