A feedback linearization approach to spacecraft control using momentum exchange devices

Recent developments in the area of nonlinear control theory have shown how coordiante changes in the state and input spaces can be used with nonlinear feedback to transform certain nonlinear ordinary differential equations into equivalent linear equations. These feedback linearization techniques are applied to resolve two problems arising in the control of spacecraft equipped with control moment gyroscopes (CMGs). The first application involves the computation of rate commands for the gimbals that rotate the individual gyroscopes to produce commanded torques on the spacecraft. The second application is to the long-term management of stored momentum in the system of control moment gyroscopes using environmental torques acting on the vehicle. An approach to distributing control effort among a group of redundant actuators is described that uses feedback linearization techniques to parameterize sets of controls which influence a specified subsystem in a desired way. The approach is adapted for use in spacecraft control with double-gimballed gyroscopes to produce an algorithm that avoids problematic gimbal configurations by approximating sets of gimbal rates that drive CMG rotors into desirable configurations. The momentum management problem is stated as a trajectory optimization problem with a nonlinear dynamical constraint. Feedback linearization and collocation are used to transform this problem into an unconstrainted nonlinear program. The approach to trajectory optimization is fast and robust. A number of examples are presented showing applications to the proposed NASA space station

An approach to CMG steering using feedback linearization

This paper presents an approach for controlling spacecraft equipped with control moment gyroscopes. A technique from feedback linearization theory is used to transform the original nonlinear problem to an equivalent linear form without approximating assumptions. In this form, the spacecraft dynamics appear linearly, and are decoupled from redundancy in the system of gyroscopes. A general approach to distributing control effort among the available actuators is described which includes provisions for redistribution of rotors, explicit bounds in gimbal rates, and guaranteed operation at or near singular configurations. A particular algorithm is developed for systems of double-gimbal devices, and demonstrated in two examples for which existing approaches fail to give adequate performance

Toward an Interoperability and Integration Framework to Enable Digital Thread

This article discusses ongoing research investigating the feasibility of supporting an interoperability and integration framework to enable the digital thread, or an authoritative source of truth with current technology. The question that initiated this exploratory research was, “Is there current technology that can enable cross-domain digital artifact data sharing needed for the digital thread?” A thorough review and investigation of current state-of-the-art model-based systems engineering was performed by reviewing literature and performing multiple site visits and interviews with organizations at the forefront of digital engineering. After this initial investigation and review, a Semantic Web-enabled framework that would allow data in the thread to be captured, stored, transferred, checked for completeness and consistency, and changed under revision change control management began to be formed. This framework has gone through revisions. This paper reflects the most current demonstration of the framework and its capability of acquiring digital data, and parsing and querying the data using Semantic Web technology to generate a decision table that allows the decision data to be visualized. The article concludes with future demonstrations of the framework to further advance toward a framework that can enable a digital thread in practice

H\u3csup\u3e∞\u3c/sup\u3e-Optimal control for a class of reaction–diffusion equations

This paper investigates the control of laminar combustion processes represented by a class of one–dimensional, non-linear, reaction–diffusion equations. The control objective is to regulate the spatial location of a propagating flame front dynamically by varying the fuel-air velocity. It is shown that when viewed from an input–output perspective, the problem is equivalent to the control of a system consisting of linear elements and a single time-varying non–linear element. The system is controlled using a linear compensator that is designed based on an H∞ (minimax) optimality criterion