798 research outputs found
Dynamics of a Gyrostat Satellite with the Vector of Gyrostatic Moment along the Principal Plane of Inertia
Artificial satellites are one of the most crucial components of modern life. The study of attitude control and stabilization of satellite is necessary to ensure a successful operation. There are two types of stabilization schemes: the passive methods and active methods.
In this dissertation is investigated the dynamics of a gyrostat satellite, subjected to a semi-passive method of stabilization, namely the gravitational torque and the gyroscopic proprieties of rotating rotors, along a circular orbit.
In a particular case, when the gyrostatic moment vector is along one of satellite’s principal central planes of inertia. To solve the problem is proposed a mathematical analytical-numerical method for determining all equilibrium positions of the gyrostat satellite in the orbital coordinate system in function of dimensionless gyrostatic moment vector components (???? ??=1,2,3) and the dimensionless inertial parameter ??. The conditions of existence of the equilibrium solutions are obtained. Sufficient conditions of stability for each group of equilibrium solutions are derived from the analysis of the generalized integral energy used as a Lyapunov’s function.
The study of the evolution of equilibria bifurcation of the gyrostat is carried out in function of parameter ?? in detail. Also, the evolution of equilibrium solutions in function of spacecraft angles is analyzed and it is verified the existence of small regions of 12 and 16 equilibrium positions referred in [14] and [20].
This work shows that the number of equilibria of a gyrostat satellite, in this particular case, does not exceeds 24 and does not go below 8. The study of the equilibria bifurcation shows that there are small regions of 12 equilibrium positions that approach each other for infinite ??3 and never vanish, these regions seems to have a relation with the regions referred by Santos in [14] and Santos et. al. [20].
The study of the evolution of stability for every equilibrium solution in function ?? and ??3, shows that the number of stable equilibria varies between 2 and 6.Satélites artificias são uns dos componentes cruciais da vida moderna. O estudo do controlo da atitude e estabilização de um satélite é necessário para assegurar uma missão bem-sucedida. Existem dois tipos de métodos de estabilização: os métodos passivos e os métodos ativos.
Nesta dissertação é investigado a dinâmica de um satélite tipo giróstato, sujeito a um método semi-passivo de estabilização, nomeadamente o momento gravítico e as propriedades giroscópicas de rotores, ao longo de uma órbita circular.
No caso particular, quando o vetor de momento girostático está ao longo de um dos principais planos de inércia do satélite. Para resolver este problema é proposto um modelo matemático numérico-analítico para determinar todos as posições de equilíbrio de um satélite giróstato, em um sistema coordenado orbital em função das componentes adimensionais do vetor de momento girostático (???? ??=1,2,3) e do parâmetro inercial adimensional ??. As condições de existência das soluções de equilíbrio são obtidas. As condições suficientes de estabilidade para cada grupo de soluções de equilíbrio são derivadas, a partir da análise do integral de energia generalizado como uma função de Lyapunov.
O estudo da evolução da bifurcação do equilíbrio foi realizado em detalhe em função do parâmetro ??. Também, a evolução das soluções de equilíbrio em função dos ângulos do satélite é analisada e é verificado a existência de pequenas regiões de 12 e 16 posições de equilíbrio referidas em [14] e [20].
Este trabalho mostra que o número de posições de equilíbrio de um satélite tipo giróstato, neste caso particular, não ultrapassa 24 e não é inferior a 8. O estudo da bifurcação do equilíbrio revela a existência de regiões de 12 posições de equilíbrio que se aproximam, para valores infinitos de ??3 e que nunca desaparecem, estas regiões sugerem ter uma relação com as regiões referidas por Santos [14] e Santos et al.[20].
O estudo da evolução da estabilidade para cada solução de equilíbrio em função de ?? e ??3 revela que o número de posições de equilíbrio estáveis varia entre 2 e 6
Dynamics of a gyrostat satellite with the vector of gyrostatic moment tangent to the orbital plane
In this paper, a gyrostat satellite in a circular orbit with its gyrostatic moment tangent to the orbital plane and collinear with the orbital speed is studied regarding its equilibria, bifurcation of equilibria, and asymptotic stability conditions. In the general case, where any gyrostat angular momentum is aligned with any of the orbital coordinate frames, interesting results arose regarding its equilibria bifurcation regarding conditions near to the ones presented in this paper, namely equilibria regions outside their main regions near to the orbital plane tangent. For equilibria and bifurcation of equilibria, a symbolic-numerical method is used to obtain the polynomial equations in function of non-dimensional parameters whose roots are equivalent to the number of equilibria positions. For the asymptotic stability, the results are tested using the Lyapunov stability theory scheme
The dynamics of a flexible Motorised Momentum Exchange Tether (MMET)
This research presents a more complete flexible model for the Motorised Momentum Exchange Tether (MMET) concept. In order to analyse the vibration aspect of the problem the tether is modelled as a string governed by partial differential equations of motion, with specific static and dynamic boundary conditions and the tether sub-span is flexible and elastic, thereby allowing three dimensional displacements of the motorised tether. The boundary conditions lead to a specific frequency equation and the Eigenvalues from this provide the natural frequencies of the orbiting flexible motorised tether when static, accelerating in spin, and at terminal angular velocity. The rotation matrix is utilized to get the position vectors of the system’s components in an inertial frame. The spatio-temporal coordinates u(x,t), v(x,t) and w(x,t) are transformed to modal coordinates before applying Lagrange’s equations and the pre-selected linear modes are included in generating the equations of motion. The equations of motion contain inertial nonlinearities of cubic order, and these show the potential for intricate intermodal coupling effects.
The study of planar and non-planar motions has been carried out and the differences in the modal responses in both motions between the rigid body and flexible model are highlighted and discussed. The dynamics and stability of the flexible MMET is investigated using the dynamical analysis tools for representing the behaviour of the tether system. The study is also includes the engineering side of the MMET by investigating the power requirements of an electric motor located in the central facility of the Motorised Momentum Exchange Tether (MMET). A simulation was run using a specially written computer program to obtain the required minimum power for a typical duty cycle, and also to study the responses for three different operating conditions; before payload release, torque-off and reverse torques conditions for both the propulsion and outrigger system on both circular and elliptical orbits. The differences in the responses when using rigid body and flexible models of MMET are highlighted and discussed in order to look at the sensitivity of the model to the power budget calculations. The study then continues with a comparative study between the MMET and conventional propulsion systems in terms of the energy used specifically for an Earth-Moon return mission for circular and elliptical orbits
Proceedings of the NASA Conference on Space Telerobotics, volume 5
Papers presented at the NASA Conference on Space Telerobotics are compiled. The theme of the conference was man-machine collaboration in space. The conference provided a forum for researchers and engineers to exchange ideas on the research and development required for the application of telerobotics technology to the space systems planned for the 1990's and beyond. Volume 5 contains papers related to the following subject areas: robot arm modeling and control, special topics in telerobotics, telerobotic space operations, manipulator control, flight experiment concepts, manipulator coordination, issues in artificial intelligence systems, and research activities at the Johnson Space Center
NASA Tech Briefs, March 1988
Topics include: New Product Ideas; NASA TU Services; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences; and Life Sciences
Proceedings of the NASA Conference on Space Telerobotics, volume 3
The theme of the Conference was man-machine collaboration in space. The Conference provided a forum for researchers and engineers to exchange ideas on the research and development required for application of telerobotics technology to the space systems planned for the 1990s and beyond. The Conference: (1) provided a view of current NASA telerobotic research and development; (2) stimulated technical exchange on man-machine systems, manipulator control, machine sensing, machine intelligence, concurrent computation, and system architectures; and (3) identified important unsolved problems of current interest which can be dealt with by future research
Pjezorobotų trajektorijų valdymas nanopalydovų stabilizavimui
Rapid industrial advancement requires novel ideas, new scientific approaches and effective technologies that would ensure quality and precision. Application of piezoelectric actuators in robotics opens many possibilities to create systems with extreme precision and control. A very important step in the development of autonomous robots is the formation of motion trajectories. Classical interpolation methods used for formation of the trajectories are suitable only when robots have wheels, legs or other parts for motion transmission. Piezorobots that are analyzed in this dissertation have no additional components that create motion, only contact points with the static plane. Therefore, traditional motion formation methods are not suitable and a problem arises how to define motion trajectory of such device.
The aim of this work is to create a trajectory control algorithm of multi-degrees-of-freedom piezorobot used for nanosatellite stabilization.
In order to achieve the objective, the following tasks had to be solved: to analyze constructions of precise piezorobots, their operating principles and motion formation methods; to analyze stabilization problems of satellites and application of multi-degrees-of-freedom piezorobots for nanosatellite stabilization; to create piezorobots’ motion formation algorithms according to electrode excitation schemes, to perform an experimental research; to determine quantitative characteristics of the constructed piezorobots and their motion trajectories.
The introduction describes the importance and novelty of this thesis, goals of this work, its practical value and defended statements. The first chapter analyses the principals of ultrasonic devices, gives a thorough review of constructions of ultrasonic devices with multi-degrees-of-freedom. The second chapter provides a review of satellite stabilization principles and how multi-degrees-of-freedom piezorobots can be applied for nanosatellite stabilization. Motion formation methods for ultrasonic devices with multi-degrees-of-freedom are presented. The third chapter presents the detailed analysis of different piezorobots. In the fourth chapter experimental results are provided. Trajectory planning of piezorobot is shown, results are compared to numerical calculations performed in the third chapter. The conclusions about applicability of piezorobots’ motion formation algorithms according to electrode excitation schemes are given. Seven articles focusing on the subject of the dissertation have been published, two presentations on the subject have been presented in conferences at international level.
The research for the dissertation has been funded by the Lithuanian State Science and Studies Foundation: European Regional Development Fund, Project No. DOTSUT-234 and Research Council of Lithuania, Project No. MIP-084/2015.Dissertatio
14th Conference on Dynamical Systems Theory and Applications DSTA 2017 ABSTRACTS
From Preface:
This is the fourteen time when the conference “Dynamical Systems – Theory and
Applications” gathers a numerous group of outstanding scientists and engineers, who deal with
widely understood problems of theoretical and applied dynamics.
Organization of the conference would not have been possible without a great effort of the
staff of the Department of Automation, Biomechanics and Mechatronics. The patronage over
the conference has been taken by the Committee of Mechanics of the Polish Academy of
Sciences and the Ministry of Science and Higher Education.
It is a great pleasure that our invitation has been accepted by so many people, including good
colleagues and friends as well as a large group of researchers and scientists, who decided to
participate in the conference for the first time. With proud and satisfaction we welcome nearly
250 persons from 38 countries all over the world. They decided to share the results of their
research and many years experiences in the discipline of dynamical systems by submitting many
very interesting papers.
This booklet contains a collection of 375 abstracts, which have gained the acceptance of
referees and have been qualified for publication in the conference proceedings [...]
Advanced Computational Fluid Dynamics for Emerging Engineering Processes
As researchers deal with processes and phenomena that are geometrically complex and phenomenologically coupled the demand for high-performance computational fluid dynamics (CFD) increases continuously. The intrinsic nature of coupled irreversibility requires computational tools that can provide physically meaningful results within a reasonable time. This book collects the state-of-the-art CFD research activities and future R&D directions of advanced fluid dynamics. Topics covered include in-depth fundamentals of the Navier-Stokes equation, advanced multi-phase fluid flow, and coupling algorithms of computational fluid and particle dynamics. In the near future, true multi-physics and multi-scale simulation tools must be developed by combining micro-hydrodynamics, fluid dynamics, and chemical reactions within an umbrella of irreversible statistical physics
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