Applications of artificial intelligence techniques to a spacecraft control problem
Artificial intelligence applied to spacecraft control problem
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Spacecraft Control Laboratory Experiment: Status report
The Spacecraft Control Laboratory Experiment (SCOLE) will allow direct experimental comparison of competing control schemes for large flexible spacecraft structures. The experiment was designed to emulate the essential characteristics of a mathematical model design challenge which represents a Space Shuttle with a flexible mast and antenna attached. This experiment represents the third in a series of three flexible structure control experiments used by the Flight Dynamics and Control Division at LaRC. The key problem addressed by the facility is that flexible motion of the mast and antenna must be considered in the slewing and pointing control problems.
Williams, J. P.↗
Method for spinning up a three-axis controlled spacecraft
A three-axis controlled spacecraft (1), typically a satellite, is spun up about its roll axis (20) prior to firing a motor (2), i.e., a perigee kick motor, to achieve the requisite degree of angular momentum stiffness. Thrusters (21) for imparting rotation about the roll axis (20) are activated in open-loop fashion, typically at less than full duty cycle. Cross-axis torques induced by this rotational motion are compensated for by means of closed control loops for each of the pitch and yaw axes (30, 40, respectively). Each closed control loop combines a prebias torque (72) with torques (75, 74) representative of position and rate feedback information, respectively. A deadband (52) within each closed control loop can be widened during the spinup, to conserve fuel. Position feedback information (75) in each of the control loops is disabled upon saturation of the gyroscope associated with the roll axis (20).
Vorlicek, Preston L.↗
The 5th Annual NASA Spacecraft Control Laboratory Experiment (SCOLE) Workshop, part 1
The modeling, systems identification, and control synthesis for the Spacecraft Control Laboratory Experiment (SCOLE) configuration are examined.
Taylor, Lawrence W., Jr.↗
The 5th Annual NASA Spacecraft Control Laboratory Experiment (SCOLE) Workshop, part 2
A collection of papers from the workshop are presented. The topics addressed include: the modeling, systems identification, and control synthesis for the Spacecraft Control Laboratory Experiment (SCOLE) configuration.
Taylor, Lawrence W., Jr.↗
Experience in distributed parameter modeling of the Spacecraft Control Laboratory Experiment (SCOLE) structure
The Spacecraft Control Laboratory Experiment (SCOLE) configuration is used to compare exact and approximate solutions of the partial differential equations which define its structural dynamics. The need for a proof model for evaluating competing control laws demands that solutions be generated which not only exhibit accurate modal characteristics, but precise static deflections as well. Because precise pointing is required, the motion of the end bodies of the Shuttle-attached antenna must be known with great accuracy. Modal models are attractive because of their stable solutions but require hundreds of modes to obtain a static deflection accuracy of only one percent. Although proportional damping in bending agrees well with experimental results using the SCOLE experimental apparatus, modes which involve both torsion and bending differ significantly from proportional damping. A lumped mass model is used to generate exact static deflections, but only approximate modal characteristics. Asymptotic solutions to the distributed parameter system approximate very accurately the modal characteristics at high mode numbers. Ways are examined for refining the approximate solutions by applying a first-order variation and by employing singular perturbation techniques which are usually limited to ordinary differential equations. The most accurate solutions of the distributed parameter model of SCOLE are obtained by combining exact and asymptotic solutions.
Taylor, L. W.↗
Study to develop the equations describing the characteristics of rate and attitude sensors associated with spacecraft control systems
Equations describing characteristics of rate and attitude sensors for spacecraft control systems
SENSOR↗
Ulysses spacecraft control and monitoring system
The baseline Ulysses spacecraft control and monitoring system (SCMS) concepts and the converted SCMS, residing on a DEC/VAX 8350 hardware, are considered. The main functions of the system include monitoring and displaying spacecraft telemetry, preparing spacecraft commands, producing hard copies of experimental data, and archiving spacecraft telemetry. The SCMS system comprises over 20 subsystems ranging from low-level utility routines to the major monitoring and control software. These in total consist of approximately 55,000 lines of FORTRAN source code and 100 VMS command files. The SCMS major software facilities are described, including database files, telemetry processing, telecommanding, archiving of data, and display of telemetry.
Hamer, P. A.↗
A new communication protocol family for a distributed spacecraft control system
In this paper we describe the concepts behind and architecture of a communication protocol family, which was designed to fulfill the communication requirements of ESOC's new distributed spacecraft control system SCOS 2. A distributed spacecraft control system needs a data delivery subsystem to be used for telemetry (TLM) distribution, telecommand (TLC) dispatch and inter-application communication, characterized by the following properties: reliability, so that any operational workstation is guaranteed to receive the data it needs to accomplish its role; efficiency, so that the telemetry distribution, even for missions with high telemetry rates, does not cause a degradation of the overall control system performance; scalability, so that the network is not the bottleneck both in terms of bandwidth and reconfiguration; flexibility, so that it can be efficiently used in many different situations. The new protocol family which satisfies the above requirements is built on top of widely used communication protocols (UDP and TCP), provides reliable point-to-point and broadcast communication (UDP+) and is implemented in C++. Reliability is achieved using a retransmission mechanism based on a sequence numbering scheme. Such a scheme allows to have cost-effective performances compared to the traditional protocols, because retransmission is only triggered by applications which explicitly need reliability. This flexibility enables applications with different profiles to take advantage of the available protocols, so that the best rate between sped and reliability can be achieved case by case.
Baldi, Andrea↗
Description of the Spacecraft Control Laboratory Experiment (SCOLE) facility
A laboratory facility for the study of control laws for large flexible spacecraft is described. The facility fulfills the requirements of the Spacecraft Control Laboratory Experiment (SCOLE) design challenge for laboratory experiments, which will allow slew maneuvers and pointing operations. The structural apparatus is described in detail sufficient for modelling purposes. The sensor and actuator types and characteristics are described so that identification and control algorithms may be designed. The control implementation computer and real-time subroutines are also described.
Williams, Jeffrey P.↗
Description of the Spacecraft Control Laboratory Experiment (SCOLE) facility
A laboratory facility for the study of control laws for large flexible spacecraft is described. The facility fulfills the requirements of the Spacecraft Control Laboratory Experiment (SCOLE) design challenge for a laboratory experiment, which will allow slew maneuvers and pointing operations. The structural apparatus is described in detail sufficient for modelling purposes. The sensor and actuator types and characteristics are described so that identification and control algorithms may be designed. The control implementation computer and real-time subroutines are also described.
Williams, Jeffrey P.↗
Slew maneuvers of Spacecraft Control Laboratory Experiment (SCOLE)
This is the final report on the dynamics and control of slew maneuvers of the Spacecraft Control Laboratory Experiment (SCOLE) test facility. The report documents the basic dynamical equation derivations for an arbitrary large angle slew maneuver as well as the basic decentralized slew maneuver control algorithm. The set of dynamical equations incorporate rigid body slew maneuver and three dimensional vibrations of the complete assembly comprising the rigid shuttle, the flexible beam, and the reflector with an offset mass. The analysis also includes kinematic nonlinearities of the entire assembly during the maneuver and the dynamics of the interactions between the rigid shuttle and the flexible appendage. The equations are simplified and evaluated numerically to include the first ten flexible modes to yield a model for designing control systems to perform slew maneuvers. The control problem incorporates the nonlinear dynamical equations and is expressed in terms of a two point boundary value problem.
Kakad, Yogendra P.↗
Motion-Based System Identification and Fault Detection and Isolation Technologies for Thruster Controlled Spacecraft
By analyzing the motions of a thruster-controlled spacecraft, it is possible to provide on-line (1) thruster fault detection and isolation (FDI), and (2) vehicle mass- and thruster-property identification (ID). Technologies developed recently at NASA Ames have significantly improved the speed and accuracy of these ID and FDI capabilities, making them feasible for application to a broad class of spacecraft. Since these technologies use existing sensors, the improved system robustness and performance that comes with the thruster fault tolerance and system ID can be achieved through a software-only implementation. This contrasts with the added cost, mass, and hardware complexity commonly required by FDI. Originally developed in partnership with NASA - Johnson Space Center to provide thruster FDI capability for the X-38 during re-entry, these technologies are most recently being applied to the MIT SPHERES experimental spacecraft to fly on the International Space Station in 2004. The model-based FDI uses a maximum-likelihood calculation at its core, while the ID is based upon recursive least squares estimation. Flight test results from the SPHERES implementation, as flown aboard the NASA KC-1 35A 0-g simulator aircraft in November 2003 are presented.
Wilson, Edward↗
A computational algorithm for spacecraft control and momentum management
Developments in the area of nonlinear control theory have shown how coordinate changes in the state and input spaces of a dynamical system can be used to transform certain nonlinear differential equations into equivalent linear equations. These techniques are applied to the control of a spacecraft equipped with momentum exchange devices. An optimal control problem is formulated that incorporates a nonlinear spacecraft model. An algorithm is developed for solving the optimization problem using feedback linearization to transform to an equivalent problem involving a linear dynamical constraint and a functional approximation technique to solve for the linear dynamics in terms of the control. The original problem is transformed into an unconstrained nonlinear quadratic program that yields an approximate solution to the original problem. Two examples are presented to illustrate the results.
Dzielski, John↗
Dynamics of spacecraft control laboratory experiment (SCOLE) slew maneuvers
This is the first of two reports on the dynamics and control of slewing maneuvers of the NASA Spacecraft Control Laboratory Experiment (SCOLE). In this report, the dynamics of slewing maneuvers of SCOLE are developed in terms of an arbitrary maneuver about any given axis. The set of dynamical equations incorporate rigid-body slew maneuver and three-dimensional vibrations of the complete assembly comprising the rigid shuttle, the flexible beam, and the reflector with an offset mass. The analysis also includes kinematic nonlinearities of the entire assembly during the maneuver and the dynamics of the interaction between the rigid shuttle and the flexible appendage. The final set of dynamical equations obtained for slewing maneuvers is highly nonlinear and coupled in terms of the flexible modes and the rigid-body modes. The equations are further simplified and evaluated numerically to include the first ten flexible modes and the SCOLE data to yield a model for designing control systems to perform slew maneuvers.
Kakad, Y. P.↗
A model for the three-dimensional spacecraft control laboratory experiment
A model for the three-dimensional Spacecraft Control Laboratory Experiment (SCOLE) is developed. The objective behind this method of modelling is to utilize the basic partial differential equations of motion for this distributed parameter system and not to use the modal expansion in developing the model. The final model obtained is in terms of a transfer function matrix which relates the flexible mast parameters like displacement, slope, shear stress, etc. to external forces and moments.
Kakad, Yogendra P.↗
Advanced avionics concepts: Autonomous spacecraft control
A large increase in space operations activities is expected because of Space Station Freedom (SSF) and long range Lunar base missions and Mars exploration. Space operations will also increase as a result of space commercialization (especially the increase in satellite networks). It is anticipated that the level of satellite servicing operations will grow tenfold from the current level within the next 20 years. This growth can be sustained only if the cost effectiveness of space operations is improved. Cost effectiveness is operational efficiency with proper effectiveness. A concept is presented of advanced avionics, autonomous spacecraft control, that will enable the desired growth, as well as maintain the cost effectiveness (operational efficiency) in satellite servicing operations. The concept of advanced avionics that allows autonomous spacecraft control is described along with a brief description of each component. Some of the benefits of autonomous operations are also described. A technology utilization breakdown is provided in terms of applications.
Source record↗
Spacecraft control section for the improved Small Astronomy Satellite (SAS)
The upgraded spacecraft control section for the Small Astronomy Satellite is able to point its thrust axis to any direction in space; it can also spin or slow its outer body rotation to zero for star-locked pointing of side viewing experiments. A programmable telemetry system and delayed command system enhance the inherent capability of a spacecraft designed to be used for a variety of experiments, each of which can be built independently and attached just prior to final acceptance testing and launch. The design of this new spacecraft, whose first launch is scheduled for 1975, is provided in sufficient detail to permit the reader to ascertain its suitability for specific experiments. A summary of the spacecraft characteristics, project reliability requirements, and environmental test conditions are included in the appendices.
Townsend, M. R.↗