ORBi Open Repository and Bibliography
(210,786 recursos)
In may 2007, the ULg's Administrative Board (joined in June 2007 by the FUSAGx) decided to create an institutional repository and defined a strong institutional self-archiving policy to increase the visibility, accessibility and impact of the University's publications (Board's decision).
This decision led to the official launch, in November 2008, of the ORBi platform including both the Academic Bibliography and the Institutional Repository of the Wallonia-Europe University Academy.

1.
Satellite Orbits in the Atmosphere: Uncertainty Quantification, Propagation and Optimal Control - Dell'Elce, Lamberto
From the massive international space station to nanosatellites, all space missions share a common principle: orbiting an object requires energy. The greater the satellite's mass, the higher the launch cost. In astrodynamics, this translates into the motto ``use whatever you can''. This concept encompasses a broad spectrum of missions, e.g., the Earth's oblateness is exploited for sun-synchronous orbits and the kinetic energy of a planet is used to accomplish fly-by maneuvers. Nowadays, the same paradigm is coming on stream in the context of distributed space systems, where complex missions are envisaged by splitting the workload of a single satellite into...

5.
Measuring nonlinear distortions: from test case to an F-16 fighter - Vaes, Mark; Schoukens, Johan; Rolain, Yves; Peeters, Bart; Debille, Jan; Dossogne, Tilàn; Noël, Jean-Philippe; Grappasonni, Chiara; Kerschen, Gaëtan
What are the similarities and differences between the behavior of a small vibrating test system and an F-16 fighter? To find it out, we compare measurements of the test system to measurements from the bolted connection of the wing and the missile of a F-16 Fighter Falcon from the Belgian air force. These measurements were done during a ground vibration test (GVT) campaign. Essentially, the behavior of these systems match, even though the test system is only the heart of a self-study kit for nonlinear system identification and the F-16 is a complex real life mechanical structure. This clearly shows...

6.
A comparison of grey-box and black-box approaches in nonlinear state-space modelling and identification - Noël, Jean-Philippe; Schoukens, Johan; Kerschen, Gaëtan
In the present contribution, it is shown that, in the case of mechanical systems where nonlinearities are physically localised, the general structure of black-box nonlinear state-space models can be drastically simplified. A more parsimonious, grey-box state-space representation is derived, which is found to be compatible with Newton's second law of dynamics. For demonstration purposes, black-box and grey-box state-space models of the Silverbox benchmark, i.e. an electrical mimicry of a single-degree-of-freedom mechanical system with cubic nonlinearity, are identified using a maximum likelihood estimator. It is found that the grey-box approach allows to reduce markedly modelling errors with respect to a black-box...

14.
State Space Analysis for The Relative Spacecraft Motion in Geopotential fields - Condurache, Daniel; Martinusi, Vladimir
The paper offers an approach to the relative orbital motion from a new point of view, which introduces a unified way to approach both the relative position and the relative velocity with the help of a single appropriately defined tensor operator. In the situation of an unperturbed gravitational field, this operator is written with respect to the eccentric anomaly associated to the deputy spacecraft inertial orbit. In the situation of the relative equatorial motion around an oblate planet, the operator may be written with the help of elliptic integrals. The six dimensional curve in the state space (position and velocity)...

15.
Exact solution to the relative orbital motion in a central force field - Condurache, D.; Martinusi, Vladimir
The paper presents the exact solution to the relative orbital motion that takes place in a central force field.This problem is a generalization of the problem of the Keplerian relative motion in a central force field. The solution is presented in a coordinate free vectorial form, offering closed form expressions for the law of motion and the velocity. The solution is offered to the non-linear model of the relative motion problem, and itgeneralizes the solutions found by Clohessy-Wiltshire, Lawden and Tschauner-Hempel for the case of the Keplerian relative motion. The applications of this problem are in satellite formation flying, satellite...

17.
Analytic solution to the relative orbital motion around an oblate planet - Condurache, D.; Martinusi, Vladimir
The paper offers a vectorial approach to the J2-perturbed relative orbital motion. The model uses mean orbital elements in order to derive closed form expressions for the relative position and relative velocity with respect to the LVLH frame attached on a main satellite. The advantage of the present approach is that only the motion of one satellite must be known, together with the initial conditions with respect to LVLH of the other satellites. As in the previous works of the authors, a tensorial instrument is used in order to transfer the motion from inertial to non-inertial reference frames and back....

18.
Hypercomplex eccentric anomaly in the unified solution to the relative orbital motion - Condurache, D.; Martinusi, Vladimir
The present work offers an approach to the relative orbital motion by using hypercomplex algebra. An extension to this notion is used for vectors, by introducing the hypercomplex vector in the same way as hypercomplex numbers are defined. The solution to the relative orbital motion is offered in all possible situations (it stands for any Keplerian reference or targeted trajectories). A unified view on the relative orbital motion is suggested, by generalizing the previous approaches. The solution is offered to the nonlinear model of the relative motion and it is expressed in a coordinate-free hypercomplex vectorial closed form. The key...

19.
Closed-form solutions for satellite relative motion in an axially-symmetric gravitational field - Martinusi, Vladimir; Gurfil, P.
A different approach is proposed for the study of satellite relative motion in an axially-symmetric gravitational field. Instead of using the Keplerian motion as the generating nominal orbit for the absolute motion, another "unperturbed" orbit is proposed instead: An equatorial orbit about an oblate planet. Based on the superintegrability of such motion, closed-form solutions for the equatorial relative motion are obtained. Analytic conditions for the periodicity of the relative motion in a generic central force field are presented, and utilized to design long-term bounded relative motion under high-order even zonal perturbations.

20.
A closed form solution of the two body problem in non-inertial reference frames - Condurache, Daniel; Martinusi, Vladimir
A comprehensive analysis, together with the derivation of a closed form solution to the two-body problem in arbitrary non-inertial reference frames are made within the present work. By using an efficient mathematical instrument, which is closely related to the attitude kinematics methods, the motion in the non-inertial reference frame is completely solved. The closed form solutions for the motion in the non-inertial frame, the motion of the mass center, and the relative motion are presented in the paper. Dynamical characteristics analogue to the linear momentum, angular momentum and total energy are introduced. In the general situation, these quantities may be...