Passive control of HALE aircraft wings with tuned mass dampers / Controle passive de asas de aeronaves HALE com tuned mass dampers

In this paper we study the control of vibrations of a HALE aircraft wing using TMD devices. The structure was modeled using a commercial structural analysis software. The wing profile and material characteristics used were provided in available literature. Aerodynamic loads of random nature are simulated. When the first natural frequencies of the structure are close to the aerodynamic loads frequencies it can lead to unsafe flying conditions due to resonance. In addition, it can shorten the frame life due to material fatigue and further maintenance may be required. Processing suggests the presence of accelerations above the desired or anticipated by several international standards on the subject. To mitigate them, passive vibration absorber (TMD's, Tuned Mass Dampers) control is proposed for vertical and lateral vibrations.  

Impact of falling cables on bulkhead beams / Impacto da queda de cabos nas vigas das anteparas

In this work, 585.95 meters long falling cable will be considered to compute its impact on a steel beam. The beam is lifted by two cranes and used as a shield to protect structures under the cables, during its installation. Using energy conservation concepts, it is possible to find the impact force on the beam, and, with that, to design the ideal steel cross section to support such impact. A model was also developed using the STRAP software, via Finite Element Method, to perform a more refined analysis and check the design of the metal beam

Anuário científico da Escola Superior de Tecnologia da Saúde de Lisboa - 2016

A publicação do Anuário Científico da Escola Superior de Tecnologia da Saúde de Lisboa é uma constante desde o ano de 2011. Neste documento, onde foi coligida a produção científica dos docentes, não docentes e estudantes da ESTeSL, referente ao ano 2016, podem-se encontrar, não só, as publicações em livros ou revistas da especialidade, mas também os resumos das comunicações orais e dos pósteres apresentados em congressos e os trabalhos finais de mestrado e de licenciatura defendidos pelos estudantes da ESTeSL em 2016. Apesar dos constrangimentos financeiros, que continuaram, em 2016, a dificultar a dedicação dos docentes, não docentes e estudantes a atividades de investigação, a ESTeSL manteve um favorável desempenho científico. Este desempenho foi conseguido com a contribuição dos Departamentos da ESTeSL e/ou dos grupos de investigação que integram o Centro de Investigação em Saúde e Tecnologia da ESTeSL (CIST ESTeSL) e, simultaneamente, com uma significativa participação dos docentes e não docentes, da ESTeSL, que integram centros externos acreditados pela FCT. O Anuário Científico da ESTeSL começa a apresentar-se, cada vez mais, como a referência oficial da atividade científica da instituição, aumentando o número de dados submetidos e compilados neste documento.info:eu-repo/semantics/publishedVersio

SDRE APPLIED TO POSITION AND VIBRATION CONTROL OF A ROBOT MANIPULATOR WITH A FLEXIBLE LINK

This paper presents position and vibration control of a flexible robot composed of two rigid and one flexible links. Position is controlled by the current applied to the DC motor armature. To control vibrations of the flexible structure, Shape Memory Alloys (SMA) are used. Due to phase transformations, the SMA can change its stiffness through temperature variation, considering and taking advantage of this characteristic the vibration control is done. Control is achieved via the State Dependent Ricatti Equations (SDRE) technique, which uses suboptimal control and system local stability search. The simulation results show the feasibility of the proposed control for the considered system

Exact Solution of the Elastica with Transverse Shear Effects

A new derivation of Euler's Elastica with transverse shear effects included is presented. The elastic potential energy of bending and transverse shear is set up. The work of the axial compression force is determined. The equation of equilibrium is derived using the variation of the total potential. Using substitution of variables an exact solution is derived. The equation is transcendental and does not have a closed form solution. It is evaluated in a dimensionless form by using a numerical procedure. Finally, numerical examples of laminates made of composite material (fiber reinforced) and sandwich panels are provided

A Short Note on Transverse Vibrations of a Shaft Carrying Two (or One) Disk Excited by a Nonideal Motor

The paper presents a number of numerical simulations of the transverse vibrations of two (or one) imbalanced rotors forced by an electric motor with limited power supply, during the passage through of the two resonance zones (increasing and decreasing input voltages). The predominant presence of the Sommerfeld effect. when the rotational velocity of the motor is captured, in the second resonance frequency is demonstrated. We have shown that the hysteretic jump phenomenon exists in a rotor system with two (or one) disks, and with this, we have shown that a torque is influenced by the dynamical behavior of die rotor [DOI: 10.1115/1.3007979]CNPqCNPq Conselho Nacional de Desenvolvimento Cientifico e TecnologicoFAPESP[06/59742-2]FAPESP Fundacao de Amparo a Pesquisa do Estado de Sao Paul

Vibração de barras em pequena amplitude com efeito geométrico

In engineering a large number of structures may be modeled as cantilevers. Due to their intrinsic characteristics some of these structures are sensitive to actions of a dynamic nature. Gusts of wind are excitations of a dynamic nature upon which the fundamental frequency of vibration is an important factor for the calculation of the structural response. Taking into account the effect of the axial force upon the natural frequencies of a structure usually leads towards systems of differential equations of unviable solution from the engineer’s practical point of view. This article develops a simple mathematical expression for the calculation of the fundamental frequency of balanced structures in small ranges and takes into account the presence of the axial demand. This expression has been validated by dynamic laboratory testing.Na engenharia, um grande número de estruturas podem ser modeladas como barras em balanço. Algumas dessas estruturas, por características que lhe são intrínsecas, são sensíveis a ações de natureza dinâmica. A frequência fundamental de vibração é fator preponderante para o cálculo das forças devidas ao vento. Normalmente, a consideração do efeito da força axial sobre as frequências naturais de uma estrutura remete a sistemas de equações diferenciais com solução inviável do ponto de vista da vida prática do engenheiro. Este artigo desenvolve uma expressão matemática simples para o cálculo, em pequenas amplitudes, da frequência fundamental para barras em balanço, que leva em conta a presença da solicitação axial. Essa expressão foi validada por ensaios dinâmicos em laboratório.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

On suppression of chaotic motions of a portal frame structure under non-ideal loading using a magneto-rheological damper

We consider chaotic motions of a portal frame structure under non-ideal loading. To suppress this chaotic behavior, a controlling scheme is implemented. The control strategy involves application of two control signals and nonlinear feedforward control to maintain a desired periodic orbit, and state feedback control to bring the system trajectory into the desired periodic orbit. Additionally, the control strategy includes an active magneto-rheological damper to actuate the system. The control force of the damper is a function of the voltage applied in the coil of the damper that is based on the force given by the controller.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP