The Experts below are selected from a list of 270 Experts worldwide ranked by ideXlab platform
Pavel Trivailo - One of the best experts on this subject based on the ideXlab platform.
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Spin Axis stabilisation of underactuated rigid spacecraft under sinusoidal disturbance
International Journal of Control, 2008Co-Authors: H H Zhang, F Wang, Pavel TrivailoAbstract:Spin-Axis stabilisation of spacecraft is a problem of partial stabilisation for non-linear dynamical systems. In this article the analysis of Spin-Axis stabilisation of underactuated rigid spacecraft in the presence of sinusoidal disturbances is presented. By using the Euler-Poisson form to describe the equations of motion and assuming the disturbances in three axes are decoupled with known frequencies, the paper first studies the problem of the underactuated rigid Axisymmetric spacecraft by applying the internal modal principle to eliminate the sinusoidal disturbance. Then the paper turns to the more complicated asymmetric spacecraft, where the boundedness of the angular velocity for the underactuated Axis is analysed in detail. The paper also proves the global asymptotic stability of the closed-loop systems for both Axisymmetric spacecraft and asymmetric spacecraft by combining the Lyapunov direct method with the LaSalle's theorem. The simulation results show that the proposed control law is effective in the presence of sinusoidal disturbance.
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Spin Axis stabilisation of underactuated rigid spacecraft under sinusoidal disturbance
International Journal of Control, 2008Co-Authors: H H Zhang, F Wang, Pavel TrivailoAbstract:Spin-Axis stabilisation of spacecraft is a problem of partial stabilisation for non-linear dynamical systems. In this article the analysis of Spin-Axis stabilisation of underactuated rigid spacecraft in the presence of sinusoidal disturbances is presented. By using the Euler-Poisson form to describe the equations of motion and assuming the disturbances in three axes are decoupled with known frequencies, the paper first studies the problem of the underactuated rigid Axisymmetric spacecraft by applying the internal modal principle to eliminate the sinusoidal disturbance. Then the paper turns to the more complicated asymmetric spacecraft, where the boundedness of the angular velocity for the underactuated Axis is analysed in detail. The paper also proves the global asymptotic stability of the closed-loop systems for both Axisymmetric spacecraft and asymmetric spacecraft by combining the Lyapunov direct method with the LaSalle's theorem. The simulation results show that the proposed control law is effective in the presence of sinusoidal disturbance.
H H Zhang - One of the best experts on this subject based on the ideXlab platform.
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Spin Axis stabilisation of underactuated rigid spacecraft under sinusoidal disturbance
International Journal of Control, 2008Co-Authors: H H Zhang, F Wang, Pavel TrivailoAbstract:Spin-Axis stabilisation of spacecraft is a problem of partial stabilisation for non-linear dynamical systems. In this article the analysis of Spin-Axis stabilisation of underactuated rigid spacecraft in the presence of sinusoidal disturbances is presented. By using the Euler-Poisson form to describe the equations of motion and assuming the disturbances in three axes are decoupled with known frequencies, the paper first studies the problem of the underactuated rigid Axisymmetric spacecraft by applying the internal modal principle to eliminate the sinusoidal disturbance. Then the paper turns to the more complicated asymmetric spacecraft, where the boundedness of the angular velocity for the underactuated Axis is analysed in detail. The paper also proves the global asymptotic stability of the closed-loop systems for both Axisymmetric spacecraft and asymmetric spacecraft by combining the Lyapunov direct method with the LaSalle's theorem. The simulation results show that the proposed control law is effective in the presence of sinusoidal disturbance.
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Spin Axis stabilisation of underactuated rigid spacecraft under sinusoidal disturbance
International Journal of Control, 2008Co-Authors: H H Zhang, F Wang, Pavel TrivailoAbstract:Spin-Axis stabilisation of spacecraft is a problem of partial stabilisation for non-linear dynamical systems. In this article the analysis of Spin-Axis stabilisation of underactuated rigid spacecraft in the presence of sinusoidal disturbances is presented. By using the Euler-Poisson form to describe the equations of motion and assuming the disturbances in three axes are decoupled with known frequencies, the paper first studies the problem of the underactuated rigid Axisymmetric spacecraft by applying the internal modal principle to eliminate the sinusoidal disturbance. Then the paper turns to the more complicated asymmetric spacecraft, where the boundedness of the angular velocity for the underactuated Axis is analysed in detail. The paper also proves the global asymptotic stability of the closed-loop systems for both Axisymmetric spacecraft and asymmetric spacecraft by combining the Lyapunov direct method with the LaSalle's theorem. The simulation results show that the proposed control law is effective in the presence of sinusoidal disturbance.
Gwenael Boue - One of the best experts on this subject based on the ideXlab platform.
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Secular Spin-Axis dynamics of exoplanets
Astronomy and Astrophysics, 2019Co-Authors: M Saillenfest, Jacques Laskar, Gwenael BoueAbstract:Context. Seasonal variations and climate stability of a planet are very sensitive to the planet obliquity and its evolution. This is of particular interest for the emergence and sustainability of land-based life, but orbital and rotational parameters of exoplanets are still poorly constrained. Numerical explorations usually realised in this situation are therefore in heavy contrast with the uncertain nature of the available data.Aims. We aim to provide an analytical formulation of the long-term Spin-Axis dynamics of exoplanets, linking it directly to physical and dynamical parameters, but still giving precise quantitative results if the parameters are well known. Together with bounds for the poorly constrained parameters of exoplanets, this analysis is designed to enable a quick and straightforward exploration of the Spin-Axis dynamics.Methods. The long-term orbital solution is decomposed into quasi-periodic series and the Spin-Axis Hamiltonian is expanded in powers of eccentricity and inclination. Chaotic zones are measured by the resonance overlap criterion. Bounds for the poorly known parameters of exoplanets are obtained from physical grounds (rotational breakup) and dynamical considerations (equipartition of the angular momentum deficit).Results. This method gives accurate results when the orbital evolution is well known. The detailed structure of the chaotic zones for the solar system planets can be retrieved from simple analytical formulas. For less-constrained planetary systems, the maximal extent of the chaotic regions can be computed, requiring only the mass, the semi-major Axis, and the eccentricity of the planets present in the system. Additionally, some estimated bounds of the precession constant allow to classify which observed exoplanets are necessarily out of major Spin-orbit secular resonances (unless the precession rate is affected by the presence of massive satellites).
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secular Spin Axis dynamics of exoplanets
Astronomy and Astrophysics, 2019Co-Authors: M Saillenfest, Jacques Laskar, Gwenael BoueAbstract:Context: Seasonal variations and climate stability of a planet are very sensitive to the planet obliquity and its evolution. This is of particular interest for the emergence and sustainability of land-based life, but orbital and rotational parameters of exoplanets are still poorly constrained. Numerical explorations usually realised in this situation are thus in heavy contrast with the uncertain nature of the available data. Aims: We aim to provide an analytical formulation of the long-term Spin-Axis dynamics of exoplanets, linking it directly to physical and dynamical parameters, but still giving precise quantitative results if the parameters are well known. Together with bounds for the poorly constrained parameters of exoplanets, this analysis is designed to allow a quick and straightforward exploration of the Spin-Axis dynamics. Methods: The long-term orbital solution is decomposed in quasi-periodic series and the Spin-Axis Hamiltonian is expanded in powers of eccentricity and inclination. Chaotic zones are measured by the resonance overlap criterion. Bounds for the poorly known parameters of exoplanets are obtained from physical grounds (rotational breakup) and dynamical considerations (equipartition of AMD). Results: This method gives accurate results when the orbital evolution is well known. The chaotic zones for planets of the Solar System can be retrieved in details from simple analytical formulas. For less constrained planetary systems, the maximal extent of the chaotic regions can be computed, requiring only the mass, the semi-major Axis and the eccentricity of the planets present in the system. Additionally, some estimated bounds of the precession constant allow to classify which observed exoplanets are necessarily out of major Spin-orbit secular resonances (unless the precession rate is affected by the presence of massive satellites).
Y.d. Song - One of the best experts on this subject based on the ideXlab platform.
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Spacecraft Spin Axis attitude determination via genetic algorithm
Proceedings of 1994 American Control Conference - ACC '94, 1994Co-Authors: D.k. Bowe, Abdollah Homaifar, Y.d. SongAbstract:This paper investigates the problem of spacecraft Spin Axis attitude determination from a set of noisy measurements. A genetic algorithm (GA) approach is used in this work. The motivation behind employing the GA stems from the fact that under measurement noise, many of the existing methods may not be applicable. It is shown that the GA is effective for this type of nonlinear constrained optimization problem because of its generality and robust nature. A simulation example is presented to verify the effectiveness of this method.
Sean C Solomon - One of the best experts on this subject based on the ideXlab platform.
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Effect of core–mantle and tidal torques on Mercury’s Spin Axis orientation
Icarus, 2014Co-Authors: Stanton J. Peale, Jean-luc Margot, Steven A. Hauck, Sean C SolomonAbstract:Abstract The rotational evolution of Mercury’s mantle plus crust and its core under conservative and dissipative torques is important for understanding the planet’s Spin state. Dissipation results from tidal torques and viscous, magnetic, and topographic torques contributed by interactions between the liquid core and solid mantle. For a spherically symmetric core–mantle boundary (CMB), the system goes to an equilibrium state wherein the Spin axes of the mantle and core are fixed in the frame precessing with the orbit, and in which the mantle and core are differentially rotating. This equilibrium exhibits a mantle Spin Axis that is offset from the Cassini state by larger amounts for weaker core–mantle coupling for all three dissipative core–mantle coupling mechanisms, and the Spin Axis of the core is separated farther from that of the mantle, leading to larger differential rotation. Relatively strong core–mantle coupling is necessary to bring the mantle Spin Axis to a position within the uncertainty in its observed position, which is close to the Cassini state defined for a completely solid Mercury. Strong core–mantle coupling means that Mercury’s response is closer to that of a solid planet. Measured or inferred values of parameters in all three core–mantle coupling mechanisms for a spherically symmetric CMB appear not to accomplish this requirement. For a hydrostatic ellipsoidal CMB, pressure coupling dominates the dissipative effects on the mantle and core positions, and dissipation with pressure coupling brings the mantle Spin solidly to the Cassini state. The core Spin goes to a position displaced from that of the mantle by about 3.55 arcmin nearly in the plane containing the Cassini state. The core Spin lags the precessing plane containing the Cassini state by an increasing angle as the core viscosity is increased. With the maximum viscosity considered of ν ∼ 15.0 cm 2 / s if the coupling is by the circulation through an Ekman boundary layer or ν ∼ 8.75 × 10 5 cm 2 / s for purely viscous coupling, the core Spin lags the precessing Cassini plane by 23 arcsec, whereas the mantle Spin lags by only 0.055 arcsec. Larger, non-hydrostatic values of the CMB ellipticity also result in the mantle Spin at the Cassini state, but the core Spin is moved closer to the mantle Spin. Current measurement uncertainties preclude using the mantle offset to constrain the internal core viscosity.
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effect of core mantle and tidal torques on mercury s Spin Axis orientation
Icarus, 2014Co-Authors: Stanton J. Peale, Jean-luc Margot, Steven A. Hauck, Sean C SolomonAbstract:Abstract The rotational evolution of Mercury’s mantle plus crust and its core under conservative and dissipative torques is important for understanding the planet’s Spin state. Dissipation results from tidal torques and viscous, magnetic, and topographic torques contributed by interactions between the liquid core and solid mantle. For a spherically symmetric core–mantle boundary (CMB), the system goes to an equilibrium state wherein the Spin axes of the mantle and core are fixed in the frame precessing with the orbit, and in which the mantle and core are differentially rotating. This equilibrium exhibits a mantle Spin Axis that is offset from the Cassini state by larger amounts for weaker core–mantle coupling for all three dissipative core–mantle coupling mechanisms, and the Spin Axis of the core is separated farther from that of the mantle, leading to larger differential rotation. Relatively strong core–mantle coupling is necessary to bring the mantle Spin Axis to a position within the uncertainty in its observed position, which is close to the Cassini state defined for a completely solid Mercury. Strong core–mantle coupling means that Mercury’s response is closer to that of a solid planet. Measured or inferred values of parameters in all three core–mantle coupling mechanisms for a spherically symmetric CMB appear not to accomplish this requirement. For a hydrostatic ellipsoidal CMB, pressure coupling dominates the dissipative effects on the mantle and core positions, and dissipation with pressure coupling brings the mantle Spin solidly to the Cassini state. The core Spin goes to a position displaced from that of the mantle by about 3.55 arcmin nearly in the plane containing the Cassini state. The core Spin lags the precessing plane containing the Cassini state by an increasing angle as the core viscosity is increased. With the maximum viscosity considered of ν ∼ 15.0 cm 2 / s if the coupling is by the circulation through an Ekman boundary layer or ν ∼ 8.75 × 10 5 cm 2 / s for purely viscous coupling, the core Spin lags the precessing Cassini plane by 23 arcsec, whereas the mantle Spin lags by only 0.055 arcsec. Larger, non-hydrostatic values of the CMB ellipticity also result in the mantle Spin at the Cassini state, but the core Spin is moved closer to the mantle Spin. Current measurement uncertainties preclude using the mantle offset to constrain the internal core viscosity.
