189 research outputs found
Integrated Magnetic Management of Stored Angular Momentum in Autonomous Attitude Control Systems
No full textAutonomous spacecraft operations are at the front end of modern research interests, because they enable space missions that would not be viable only with ground control. The possibility to exploit onboard autonomy to deal with platform management and nominal housekeeping is thus beneficial to realize complex space missions, which could then rely on ground support only for the mission-critical phases. One routine operation that most spacecraft must perform is stored angular momentum management to maintain fully usable momentum exchange actuators. The execution of this activity may be scheduled, commanded from the ground, or automatically triggered when certain thresholds are reached. However, autonomous angular momentum management may interfere with other primary spacecraft operations if executed with a dedicated and separate system mode. This paper presents the magnetic management of stored angular momentum, integrated with the main attitude control system. The system design and implementation are intended for autonomous spacecraft, and it can be operated without significant ground support. The paper describes the system architecture and the attitude control laws integrated with the magnetic angular momentum management. Specifically, the capability of the autonomous system to keep the internal angular momentum far from the saturation and far from the zero-crossing levels is highlighted. The performance of an example attitude control system with four reaction wheels and three magnetic torquers is presented and discussed, with the simulation results at model-in-the-loop (MIL) level
Orbital dynamics
No full textThe following chapter gives an overview on modern techniques for Guidance, Navigation, and Control (GNC). In particular, an overview of Artificial Intelligence (AI) techniques is provided in light of a tailored application to the Space domain. Thanks to their enormous success in a great variety of applications and fields, modern AI techniques can be found in almost every aspect of science and engineering as well as everyday life. AI enables the automation of tasks previously limited to humans, even surpassing human performance on many tasks. Consequently, the terms AI, machine learning, and deep learning are nowadays ubiquitous and are often used interchangeably to describe computer systems which are designed to act in an intelligent way. Among the modern applications, a thorough description of innovative methods for GNC FDIR is presented, highlighting the latest novelties. Finally, the emerging topic of CubeSats and nanosatellites in general is treated by underlining the peculiar challenges that such missions pose
Mathematical and geometrical rules
No full textMathematical and geometrical rules are the underlying basis for any engineering application. This section summarizes and reports some of the most useful mathematical and geometrical rules for guidance, navigation, and control applications. In particular, matrix, vector, and quaternion algebra are discussed, together with some basic concepts of statistics. Finally, the expressions of the matrices to perform the rotation from the Earth-centered inertial to the Earth-centered Earth-fixed are reported
The space environment
No full textThis chapter explains the concept of perturbation, discussing the major external and internal perturbations sources. External perturbations are those properly related with the surrounding space environment, while internal perturbations are related with the elements inside the spacecraft, which anyway influences the satellite dynamics. The combination of the two composes the complete space environment. As a matter of fact, the internal perturbation sources are characterized by the fact the satellite is in space and not on ground. The main guidelines to model the external and internal perturbations and their influence on the guidance, navigation, and control chain are carefully explained in this chapter
Reference systems and planetary models
No full textThis chapter presents the models to describe planetary geometry, with focus on the Earth's ellipsoid and geoid. It also includes a brief introduction to position representation methods for objects on and above the planetary surface. An introduction to the most relevant coordinate reference systems is presented, together with the methods to transform the coordinates from one reference system to another one. The most useful time systems used in Guidance, Navigation and Control (GNC) applications are listed as well
FDIR development approaches in space systems
No full textThis chapter presents technical solutions and industrial processes used by the Space Industry to design, develop, test, and operate health (or failure) management systems, which are needed to devise and implement space missions with the required levels of dependability and safety. The overall chapter is inspired by Failure (or Fault) Detection, Isolation and Recovery (FDIR) systems designed for European Space Agency missions; however, the presentation is maintained at a proper level of detail so that its contents are in line with the FDIR practices adopted by other space agencies
Fully magnetic attitude control subsystem for picosat platforms
No full textIn this paper, the design of a fully magnetic attitude control subsystem for a picosat platform is discussed. The developed control law is based on a simple and reliable architecture, which can be easily implemented on small spacecrafts for de-tumbling and three-axis stabilization purposes. The subsystem design follows a practical engineering approach, exploiting global optimization methods, which lead to an integral actuation compliant with typical pointing accuracy requirements for picosat missions. Performance of the proposed attitude control subsystem is demonstrated by numerical simulations
Preliminary Results on the Dynamics of Large and Flexible Space Structures in Halo Orbits
No full textThe global exploration roadmap suggests, among other ambitious future space programmes, a possible manned outpost in lunar vicinity, to support surface operations and further astronaut training for longer and deeper space missions and transfers. In particular, a Lagrangian point orbit location - in the Earth-Moon system - is suggested for a manned cis-lunar infrastructure; proposal which opens an interesting field of study from the astrodynamics perspective. Literature offers a wide set of scientific research done on orbital dynamics under the Three-Body Problem modelling approach, while less of it includes the attitude dynamics modelling as well. However, whenever a large space structure (ISS-like) is considered, not only the coupled orbit-attitude dynamics should be modelled to run more accurate analyses, but the structural flexibility should be included too. The paper, starting from the well-known Circular Restricted Three-Body Problem formulation, presents some preliminary results obtained by adding a coupled orbit-attitude dynamical model and the effects due to the large structure flexibility. In addition, the most relevant perturbing phenomena, such as the Solar Radiation Pressure and the fourth-body (Sun) gravity, are included in the model as well. A multi-body approach has been preferred to represent possible configurations of the large cis-lunar infrastructure: interconnected simple structural elements - such as beams, rods or lumped masses linked by springs and dampers - build up the space segment. To better investigate the relevance of the flexibility effects, the lumped parameters approach is compared with a distributed parameters semi-analytical technique. A sensitivity analysis of system dynamics, with respect to different configurations and mechanical properties of the extended structure, is also presented, in order to highlight drivers for the lunar outpost design and station-keeping manoeuvres minimisation. Furthermore, a case study for a large and flexible space structure on Halo orbits around one of the Earth-Moon collinear Lagrangian points, L1 or L2, is discussed to point out some relevant outcomes for the potential implementation of such a mission
Actuators
No full textThis chapter is dedicated to briefly present all the major actuator typologies for spacecraft guidance, navigation, and control (GNC) applications, to discuss their operating principles, to highlight their peculiarities, strengths, and weaknesses, to categorize the available components according to their performances, and to discuss the most relevant modeling techniques and rules. The actuator modeling techniques are presented, discussing the main implementation principles of the most common numerical models to include the actuators behavior in the GNC design, analysis, verification, and validation phases. The principles of errors modeling and the most common actuator faults are also introduced. Dedicated sections on thrusters, reaction wheels, control moment gyros, and magnetorquers are present, discussing their primary operating principles, outlining the fundamental characteristics and comparing the available performance
Attitude dynamics
No full textMathematical and geometrical rules are the underlying basis for any engineering application. This section summarizes and reports some of the most useful mathematical and geometrical rules for guidance, navigation, and control applications. In particular, matrix, vector, and quaternion algebra are discussed, together with some basic concepts of statistics. Finally, the expressions of the matrices to perform the rotation from the Earth-centered inertial to the Earth-centered Earth-fixed are reported
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