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2015 | Book

Spacecraft Momentum Control Systems

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About this book

The goal of this book is to serve both as a practical technical reference and a resource for gaining a fuller understanding of the state of the art of spacecraft momentum control systems, specifically looking at control moment gyroscopes (CMGs). As a result, the subject matter includes theory, technology, and systems engineering. The authors combine material on system-level architecture of spacecraft that feature momentum-control systems with material about the momentum-control hardware and software. This also encompasses material on the theoretical and algorithmic approaches to the control of space vehicles with CMGs. In essence, CMGs are the attitude-control actuators that make contemporary highly agile spacecraft possible. The rise of commercial Earth imaging, the advances in privately built spacecraft (including small satellites), and the growing popularity of the subject matter in academic circles over the past decade argues that now is the time for an in-depth treatment of the topic. CMGs are augmented by reaction wheels and related algorithms for steering all such actuators, which together comprise the field of spacecraft momentum control systems. The material is presented at a level suitable for practicing engineers and those with an undergraduate degree in mechanical, electrical, and/or aerospace engineering.

Table of Contents

Frontmatter
Chapter 1. Introduction
Abstract
This book provides a range of perspectives on spacecraft momentum actuators–spinning rotors and gimbaled devices–for use in attitude control of spacecraft. It combines diverse perspectives from government space systems (satellites for the Air Force, Navy, and NASA), the commercial space industry, and academia. The scope extends from electromechanical details of individual actuators to space-system architecture issues of interest in spacecraft concept development. The book treats foundational rigid- and flexible-body dynamics, the subtle mathematics of steering multiple devices within an array, and the applications of these technologies. The history of these devices is summarized. Also discussed are potential future applications: asteroid mining, in-orbit servicing and repair of satellites, and new human-space missions.
Frederick A. Leve, Brian J. Hamilton, Mason A. Peck
Chapter 2. Applications
Abstract
Virtually all spacecraft incorporate some form of momentum control. Even the simplest spin-stabilized spacecraft—nothing more than a rigid body stabilized by virtue of its own spin—might be considered to benefit from a form of momentum control. Dual-spin spacecraft incorporate a spinning “rotor” and a non-spinning “platform,” which achieves attitude stabilization through a similar but more versatile approach. Contemporary spacecraft use a wide range of momentum-control technologies—momentum wheels, reaction wheels, and several types of control-moment gyroscopes—with an ever-increasing number of applications. The applications discussed here focus on contemporary spacecraft, from small autonomous satellites to large human-space vehicles and earth-observation systems. However, the hardware and basic principles have found uses outside the field of aerospace engineering, largely in commercial applications. Examples include stabilization of trains, automobiles, and boats. As spinoffs from the high-tech, high-reliability world of aerospace make their way into other fields, one can expect to find reaction wheels and CMGs in even more surprising places.
Frederick A. Leve, Brian J. Hamilton, Mason A. Peck
Chapter 3. Requirements Development for Momentum Control Systems
Abstract
This chapter addresses the subject of how to flow spacecraft agility requirements down to an array of momentum devices and provides guidelines for choosing the appropriate technology. We shall see that the design trades in selecting and sizing momentum devices span orders of magnitude in performance, complexity, and cost. Therefore, to arrive at an efficient and cost-effective design, it is important not to over-specify the momentum-system requirements.
Frederick A. Leve, Brian J. Hamilton, Mason A. Peck
Chapter 4. Dynamics of Momentum-Control Systems
Abstract
It is not enough to treat the momentum system as a black box, simply receiving power and control signals and imparting torque or momentum, as if it were any other element in a feedback-control block diagram. A momentum system offers unique opportunities to achieve robust and lightweight spacecraft designs, but taking advantage of these opportunities requires careful attention to rigid- and flexible-body dynamics. This chapter provides the foundational equations of motion for spacecraft with momentum-control devices and summarizes important flexible effects that drive the design of spacecraft that incorporate these actuators.
Frederick A. Leve, Brian J. Hamilton, Mason A. Peck
Chapter 5. Singularities of Control Moment Gyroscopes
Abstract
A book on spacecraft momentum control systems would not be complete without a discussion of geometric singularities inherent in CMGs. Therefore, this chapter starts with a discussion of common singularities associated with DGCMGs (e.g., gimbal lock) and then moves on to the more troublesome singularities associated SGCMGs. The mathematical structure of these singularities and how it relates to difficulties in avoiding them is also discussed in a way made more accessible to the reader not familiar with the subject matter. Also discussed is the location of singularities associated with an array of CMGs by way of a three-dimensional surface in the momentum space. This chapter concludes with some brief discussion on techniques to perform zero-momentum spin up of an array of CMGs in the presence of singularities at zero momentum.
Frederick A. Leve, Brian J. Hamilton, Mason A. Peck
Chapter 6. Momentum-Control System Array Architectures
Abstract
This chapter provides the analysis tools and fundamental theory for the design of an array architecture consisting of momentum devices. First, the properties of the actuator alignments and their effect on shaping the performance envelope of the momentum-control system are discussed. A survey of common array types for RWA, CMG, and mixed arrays follows. A discussion of performance metrics and methods used to optimize the array architecture concludes the chapter.
Frederick A. Leve, Brian J. Hamilton, Mason A. Peck
Chapter 7. Steering Algorithms
Abstract
This chapter discusses the methods of CMG torque allocation—techniques for finding CMG gimbal rates to provide a commanded torque. The literature often refers to these allocation techniques as steering algorithms or steering laws, of which pseudoinverse solutions are the most commonly discussed. The chapter surveys many of the classes of steering algorithms, starting with pseudoinverse methods, continuing with the more conservative methods based on limited gimbal angles and angular momentum, and ending with the less conventional and state-of-the-art optimal methods.
Frederick A. Leve, Brian J. Hamilton, Mason A. Peck
Chapter 8. Inner-Loop Control of Momentum Devices
Abstract
Implicit in a discussion of how to command the devices in momentum control system is the assumption that the devices faithfully track those commands. And yet, momentum devices exhibit several significant nonlinearities and can experience significant disturbances and errors. For this reason, momentum devices almost always include “inner loops” applying feedback control to the quantities of interest to ensure that those commands are tracked.
Frederick A. Leve, Brian J. Hamilton, Mason A. Peck
Chapter 9. Motors in Space
Abstract
All momentum devices require a spin motor of some type to actuate the rotor spin axis. CMGs also require a motor on the gimbal axis. The torque and speed requirements for the gimbal motor design are typically much different from those for the rotor. These issues, among others, motivate the following discussion of motors commonly employed in spaceborne momentum devices. The objective of this chapter is to familiarize the reader with some of the key considerations with the goal of informing the analysis, implementation, and operation of momentum-control systems and the spacecraft that use them. Motor design is a broad specialty field that demands much more depth than offered here.
Frederick A. Leve, Brian J. Hamilton, Mason A. Peck
Chapter 10. Modeling Simulation and Test Beds
Abstract
Ground-based validation of spaceborne momentum control systems and the attitude control systems that depend upon them offers a unique set of challenges. Computer simulations must include a variety of nonlinear phenomena found in momentum devices, which fundamentally limits the way these simulations can be architected. And because momentum systems rely on the conservation of angular momentum for proper operation, hardware-in-the-loop test facilities must reproduce the dynamics of a free body with great precision.
Frederick A. Leve, Brian J. Hamilton, Mason A. Peck
Backmatter
Metadata
Title
Spacecraft Momentum Control Systems
Authors
Frederick A. Leve
Brian J. Hamilton
Mason A. Peck
Copyright Year
2015
Electronic ISBN
978-3-319-22563-0
Print ISBN
978-3-319-22562-3
DOI
https://doi.org/10.1007/978-3-319-22563-0

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