The Experts below are selected from a list of 237 Experts worldwide ranked by ideXlab platform

Dennis S. Bernstein - One of the best experts on this subject based on the ideXlab platform.

  • Spacecraft Tracking using sampled-data Kalman filters
    IEEE Control Systems, 2008
    Co-Authors: Bruno O. S. Teixeira, Mario Santillo, Richard Scott Erwin, Dennis S. Bernstein
    Abstract:

    The goal of this article is to illustrate and compare two algorithms for nonlinear sampled-data state estimation. Under idealized assumptions on the astrodynamics of bodies orbiting the Earth, we apply SDEKF and SDUKF for range-only as well as range and angle observations provided by a constellation of six LEO satellites in circular, equatorial orbits. We study the ability of the filters to acquire and track a target satellite in geosynchronous orbit as a function of the sample interval, initial uncertainty, and type of available measurements. For target acquisition, SDUKF yields more accurate position and velocity estimates than SDEKF. Moreover, the convergence of SDEKF is sensitive to the initialization of the error covariance; in fact, a nondiagonal initial covariance is found to be more effective than a diagonal initial covariance. Like SDUKF, by properly setting a nondiagonal initial error covariance, SDEKF also exhibits global convergence, that is, convergence is attained for all initial true-anomaly errors.

  • Globally convergent adaptive control of Spacecraft angular velocity without inertia modeling
    Proceedings of the 1999 American Control Conference (Cat. No. 99CH36251), 1999
    Co-Authors: Jasim Ahmed, Dennis S. Bernstein
    Abstract:

    The problem of a Spacecraft Tracking a desired angular velocity trajectory is addressed using adaptive feedback control. The control law, which has the form of a sixth-order dynamic compensator, does not require knowledge of the inertia or center of mass of the Spacecraft. A Lyapunov argument is used to show that Tracking is achieved globally. A constant spin about a body fixed axis is commanded to illustrate the control algorithm. Finally, periodic commands are used to identify the inertia matrix of the Spacecraft.

  • asymptotic Tracking of Spacecraft attitude motion with inertia matrix identification
    Conference on Decision and Control, 1997
    Co-Authors: Jasim Ahmed, Vincent T Coppola, Dennis S. Bernstein
    Abstract:

    The problem of a Spacecraft Tracking a desired trajectory is defined and addressed using adaptive feedback control. The control law, which has the form of a sixth-order dynamic compensator, does not require knowledge of the inertia of the Spacecraft. A Lyapunov argument is used to show that Tracking is achieved globally. A simple spin about the intermediate principal axis and a coning motion are commanded to illustrate the control algorithm. Finally, periodic commands are used to identify the inertia matrix of the Spacecraft.

H. Schuh - One of the best experts on this subject based on the ideXlab platform.

  • Probing the solar corona with very long baseline interferometry
    Nature Communications, 2014
    Co-Authors: B. Soja, R. Heinkelmann, H. Schuh
    Abstract:

    Understanding and monitoring the solar corona and solar wind is important for many applications like telecommunications or geomagnetic studies. Coronal electron density models have been derived by various techniques over the last 45 years, principally by analysing the effect of the corona on Spacecraft Tracking. Here we show that recent observational data from very long baseline interferometry (VLBI), a radio technique crucial for astrophysics and geodesy, could be used to develop electron density models of the Sun’s corona. The VLBI results agree well with previous models from Spacecraft measurements. They also show that the simple spherical electron density model is violated by regional density variations and that on average the electron density in active regions is about three times that of low-density regions. Unlike Spacecraft Tracking, a VLBI campaign would be possible on a regular basis and would provide highly resolved spatial–temporal samplings over a complete solar cycle. Very long baseline interferometry is an astronomical technique that uses radio telescopes on Earth to observe extragalactic radio sources. Here, the authors show that it can be used to measure the electron density of the Sun’s corona and compare their findings to models from Spacecraft Tracking data.

  • Probing the solar corona with very long baseline interferometry.
    Nature communications, 2014
    Co-Authors: B. Soja, R. Heinkelmann, H. Schuh
    Abstract:

    Very long baseline interferometry is an astronomical technique that uses radio telescopes on Earth to observe extragalactic radio sources. Here, the authors show that it can be used to measure the electron density of the Sun’s corona and compare their findings to models from Spacecraft Tracking data.

B. Soja - One of the best experts on this subject based on the ideXlab platform.

  • Probing the solar corona with very long baseline interferometry
    Nature Communications, 2014
    Co-Authors: B. Soja, R. Heinkelmann, H. Schuh
    Abstract:

    Understanding and monitoring the solar corona and solar wind is important for many applications like telecommunications or geomagnetic studies. Coronal electron density models have been derived by various techniques over the last 45 years, principally by analysing the effect of the corona on Spacecraft Tracking. Here we show that recent observational data from very long baseline interferometry (VLBI), a radio technique crucial for astrophysics and geodesy, could be used to develop electron density models of the Sun’s corona. The VLBI results agree well with previous models from Spacecraft measurements. They also show that the simple spherical electron density model is violated by regional density variations and that on average the electron density in active regions is about three times that of low-density regions. Unlike Spacecraft Tracking, a VLBI campaign would be possible on a regular basis and would provide highly resolved spatial–temporal samplings over a complete solar cycle. Very long baseline interferometry is an astronomical technique that uses radio telescopes on Earth to observe extragalactic radio sources. Here, the authors show that it can be used to measure the electron density of the Sun’s corona and compare their findings to models from Spacecraft Tracking data.

  • Probing the solar corona with very long baseline interferometry.
    Nature communications, 2014
    Co-Authors: B. Soja, R. Heinkelmann, H. Schuh
    Abstract:

    Very long baseline interferometry is an astronomical technique that uses radio telescopes on Earth to observe extragalactic radio sources. Here, the authors show that it can be used to measure the electron density of the Sun’s corona and compare their findings to models from Spacecraft Tracking data.

Guo Xin - One of the best experts on this subject based on the ideXlab platform.

  • Effect of drive control on dynamic characteristics of Spacecraft Tracking-drive flexible systems
    Mechanical Systems and Signal Processing, 2021
    Co-Authors: Zhu Shi-yao, Li Dong-xu, Lei Yong-jun, Guo Xin
    Abstract:

    Abstract An equivalent modal analysis method that considers the influence of the drive control is presented for operational Spacecraft Tracking-drive flexible systems (STFS). The proposed method is verified by simulations and laboratory experiments using a Spacecraft model with fixed connections. The effects of the parameters of the drive control, such as the drive speed and control gains of the current loop, on the system’s dynamic characteristics are determined. The results indicate that the drive mechanism with the influence of drive control can be regarded as a torsional spring-dashpot boundary. The drive control causes a decrease in the equivalent stiffness of the drive mechanism but does not affect the equivalent damping. In general, the decrease in the equivalent stiffness is positively correlated with the drive speed and negatively correlated with the control gains. The drive control of the STFS has relatively low influence at low drive speeds but has a significant influence on the system’s dynamic characteristics at high drive speeds. The torsion-mode natural frequencies of the STFS are directly proportional to the control gains and inversely proportional to the drive speed. The relationships between the parameters of the drive control and the torsion-mode modal damping ratios, however, do not conform to a uniform pattern and require further study.

R. Heinkelmann - One of the best experts on this subject based on the ideXlab platform.

  • Probing the solar corona with very long baseline interferometry
    Nature Communications, 2014
    Co-Authors: B. Soja, R. Heinkelmann, H. Schuh
    Abstract:

    Understanding and monitoring the solar corona and solar wind is important for many applications like telecommunications or geomagnetic studies. Coronal electron density models have been derived by various techniques over the last 45 years, principally by analysing the effect of the corona on Spacecraft Tracking. Here we show that recent observational data from very long baseline interferometry (VLBI), a radio technique crucial for astrophysics and geodesy, could be used to develop electron density models of the Sun’s corona. The VLBI results agree well with previous models from Spacecraft measurements. They also show that the simple spherical electron density model is violated by regional density variations and that on average the electron density in active regions is about three times that of low-density regions. Unlike Spacecraft Tracking, a VLBI campaign would be possible on a regular basis and would provide highly resolved spatial–temporal samplings over a complete solar cycle. Very long baseline interferometry is an astronomical technique that uses radio telescopes on Earth to observe extragalactic radio sources. Here, the authors show that it can be used to measure the electron density of the Sun’s corona and compare their findings to models from Spacecraft Tracking data.

  • Probing the solar corona with very long baseline interferometry.
    Nature communications, 2014
    Co-Authors: B. Soja, R. Heinkelmann, H. Schuh
    Abstract:

    Very long baseline interferometry is an astronomical technique that uses radio telescopes on Earth to observe extragalactic radio sources. Here, the authors show that it can be used to measure the electron density of the Sun’s corona and compare their findings to models from Spacecraft Tracking data.