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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Status of the Mast experiment

Many sophisticated mathematical control techniques for flexible structures have been devised. The basic problem is that most of them require a relatively accurate mathematical model of the system under control including the dynamics of both the structure and the control system components. Obtaining such a model for either subsystem traditionally has required great effort including a significant validation step based on test data. Because of the quantum increase in complexity over proven methods, promising techniques for the control of flexible structures must be validated in actual hardware experiments before committing to their use in actual spacecraft missions. The Mast experiment system serves as a focus for such validation. It is the first in a series of experiments under the Control of Flexible Structures (COFS) Program at the NASA Langley Research Center. The Mast experiment is a combination of ground tests, orbital flight test, and analysis of a deployable beam under the COFS program. It provides a vehicle for research in structures, structural dynamics, and control issues.

Hanks, Brantley R.↗
NASA NTRS1997

Direct Adaptive Aircraft Control Using Dynamic Cell Structure Neural Networks

A Dynamic Cell Structure (DCS) Neural Network was developed which learns topology representing networks (TRNS) of F-15 aircraft aerodynamic stability and control derivatives. The network is integrated into a direct adaptive tracking controller. The combination produces a robust adaptive architecture capable of handling multiple accident and off- nominal flight scenarios. This paper describes the DCS network and modifications to the parameter estimation procedure. The work represents one step towards an integrated real-time reconfiguration control architecture for rapid prototyping of new aircraft designs. Performance was evaluated using three off-line benchmarks and on-line nonlinear Virtual Reality simulation. Flight control was evaluated under scenarios including differential stabilator lock, soft sensor failure, control and stability derivative variations, and air turbulence.

Jorgensen, Charles C.↗
NASA NTRS1998

Feedback Linearized Aircraft Control Using Dynamic Cell Structure

A Dynamic Cell Structure (DCS ) Neural Network was developed which learns a topology representing network (TRN) of F-15 aircraft aerodynamic stability and control derivatives. The network is combined with a feedback linearized tracking controller to produce a robust control architecture capable of handling multiple accident and off-nominal flight scenarios. This paper describes network and its performance for accident scenarios including differential stabilator lock, soft sensor failure, control, stability derivative variation, and turbulence.

Jorgensen, C. C.↗
NASA NTRS1989

Computational methods and software systems for dynamics and control of large space structures

The deployment, assembly and mission-oriented maneuvering of space structures in orbit will trigger large motions of flexible, truss-type structures. In addition, the presence of on-board controls both for attitude stabilization and specified vibration tolerance requirements may further complicate the dynamic behavior of the orbiting structures. Because of safety and cost considerations, the dynamic response of the combined structural and control systems must be predicted reliably. This need can only be met through the development of reliable and efficient simulation capabilities, since there is general agreement that on-orbit experiments should be limited because of cost, time and facility constraints. The long-term objective of this research effort is to develop a next-generation computer simulator for the dynamics and control of large space structures. The simulator will be based on integrating four research thrusts: a new multibody dynamics formulation methodology, modeling capabilities in long/slender truss-beam components with realistic joints, efficient computational procedures that can be implemented either in sequential or concurrent computers, and prototype simulation modules that can be easily processed into a modern large-scale engineering software system such as the NASA/Computational Structural Mechanics (CSM) testbed.

Park, K. C.↗
NASA NTRS1987

Structural dynamics and attitude control study of early manned capability space station configurations

A study was performed to determine the vibration and attitude control characteristics of critical space station configurations featuring early manned capability during buildup from initial user support through the operations capability reference station. Five configurations were selected and were examined thus determining the changes that are likely to occur in the characteristics of the system as the station progresses from a single boom structure to a mature, dual keel, operations capability reference station. Both 9 foot and 5 meter truss bay sizes were investigated. All configurations analyzed were stable; however, the 5 meter truss bay size structure exhibited superior stability characteristics.

Ayers, J. Kirk↗
NASA NTRS1976

Structural dynamics, stability, and control of helicopters

The dynamic synthesis of a helicopter is reported. The method of approach is a variation of the component mode synthesis in the sense that it regards the aircraft as an assemblage of interconnected substructures. The equations of motion are derived in general form by means of the Lagrangian formulation in conjunction with an orderly kinematical procedure that takes into account the superposition of motion of various substructures, thus circumventing constraint problems.

Meirovitch, L.↗
NASA NTRS1985

Space Technology Experiments Platform (STEP) Status: an In-space Test Facility

Designed for utilization of the space transportation system for technology experiments in space, the space technology experiment platform (STEP) is a shuttle-borne experiment support facility for use primarily for structures, structural dynamics, and control flexible structures technology flight experiments. The STEP concept is discussed as well as shows its relationship to broad NASA goals and objectives. The development chronology is presented and the current system capability in block diagram format is described. The STEP development schedule is included.

Harris, J. E.↗
NASA NTRS1988

Emulating a flexible space structure: Modeling

Control Dynamics, in conjunction with Marshall Space Flight Center, has participated in the modeling and testing of Flexible Space Structures. Through the series of configurations tested and the many techniques used for collecting, analyzing, and modeling the data, many valuable insights have been gained and important lessons learned. This paper discusses the background of the Large Space Structure program, Control Dynamics' involvement in testing and modeling of the configurations (especially the Active Control Technique Evaluation for Spacecraft (ACES) configuration), the results from these two processes, and insights gained from this work.

Waites, H. B.↗
NASA NTRS1985

Identification and control of structures in space

Work during the period July 1 - December 31, 1985, has concentrated on the application of the equations derived in the preceding period to the maneuvering and vibration suppression of the Spacecraft Control Laboratory Experiment (SCOLE) model. Two different situations have been considered: (1) a space environment and (2) a laboratory environment. This report covers the first case and consists of a paper entitled Maneuvering and Vibration Control of Flexible Spacecraft, presented at the Workshop on Structural Dynamics and Control Interaction of Flexible Structures, Marshall Space flight Center, Huntsville, AL, April 22 to 24, 1986. The second case will be covered in the report for the next period.

Meirovitch, L.↗
NASA NTRS1991

PDEMOD: Software for control/structures optimization

Because of the possibility of adverse interaction between the control system and the structural dynamics of large, flexible spacecraft, great care must be taken to ensure stability and system performance. Because of the high cost of insertion of mass into low earth orbit, it is prudent to optimize the roles of structure and control systems simultaneously. Because of the difficulty and the computational burden in modeling and analyzing the control structure system dynamics, the total problem is often split and treated iteratively. It would aid design if the control structure system dynamics could be represented in a single system of equations. With the use of the software PDEMOD (Partial Differential Equation Model), it is now possible to optimize structure and control systems simultaneously. The distributed parameter modeling approach enables embedding the control system dynamics into the same equations for the structural dynamics model. By doing this, the current difficulties involved in model order reduction are avoided. The NASA Mini-MAST truss is used an an example for studying integrated control structure design.

Taylor, Lawrence W., Jr.↗
NASA NTRS1992

Dynamics and control of coherent structure in turbulent jets

Current understanding of coherent structure dynamics in incompressible turbulent jets as explained by the nonlinear stability theory is reviewed, focusing on nonswirling turbulent jets. Topics addressed include hydrodynamic stability theory and coherent structures; dynamics of energy transfers among different scales of motion; nonlinear development of amplitude; development of single-frequency coherent mode; fundamental-subharmonic interaction and vortex pairing; and reversal of Reynolds stresses. Attention is also given to the effect of initial phase-difference angle between fundamental and subharmonic, conditions for resonance interaction, modulation of spreading rate by controlling coherent structure, turbulence enhancement or suppression due to excitation, 3D effects, jet noise, and swirling jets.

Mankbadi, Reda R.↗
NASA NTRS1990

Computational methods and software systems for dynamics and control of large space structures

This final report on computational methods and software systems for dynamics and control of large space structures covers progress to date, projected developments in the final months of the grant, and conclusions. Pertinent reports and papers that have not appeared in scientific journals (or have not yet appeared in final form) are enclosed. The grant has supported research in two key areas of crucial importance to the computer-based simulation of large space structure. The first area involves multibody dynamics (MBD) of flexible space structures, with applications directed to deployment, construction, and maneuvering. The second area deals with advanced software systems, with emphasis on parallel processing. The latest research thrust in the second area, as reported here, involves massively parallel computers.

Park, K. C.↗
NASA NTRS1985

AFWAL space control technology program

An overview of space oriented control technology programs which are applicable to flexible large space structures is presented. The spacecraft control activity is interdisciplinary with activities in structures, structural dynamics and control brought together. The large flexible structures to be controlled have many physical factors that influence the final controllability of the vehicle. Factors are studied such as rigidity of both structural elements and joints, damping inherent in both material as well as discrete dampers located throughout the structure, and the bandwidth of both sensors and actuators used to sense motion and control it. Descriptions of programs both in-house and contracted are given.

Hoehne, V. O.↗
NASA NTRS1985

AFWAL control technology programs

An overview of space oriented control technology programs which are applicable to flexible large space structures is presented. The spacecraft control activity is interdisciplinary with activities in structures, structural dynamics and control brought together. The large flexible structures to be controlled have many physical factors that influence the final controllability of the vehicle. Factors are studied such as rigidity of both structural elements and joints, damping inherent in both material and discrete dampers located throughout the structure, and the bandwidth of both sensors and actuators used to sense motion and control are the physical factors that are interdisciplinary and influence control.

Hoehne, V. O.↗
NASA NTRS1986

COFS 1: Beam dynamics and control technology overview

The Control of Flexible Structures (COFS) 1 Project provides the invaluable opportunity to test, validate, and measure the effectiveness of theories, structural concepts, control systems, and flight certification processes for future missions through a research program focusing on multiple issues in large flexible structures, dynamics, and controls. The COFS 1 Project consists of a series of ground and flight activities building progressively from modeling and dynamic characterization of large space systems to the more complex issues of flexible-body control. The program objectives are to: determine the degree to which theory and ground testing can predict flight performance of next-generation low-frequency structures; evaluate structural fidelity of representative next-generation large deployable precision structure; assess math modeling requirements for large lightweight complex systems on which ground test results are questionable; determine degree to which scale model analysis and tests can be correlated to full-scale performance; evaluate system identification and state estimation algorithms on complex lightweight structures in the space environment; evaluate and verify controls/structures modeling capability; evaluate control laws and control systems; and evaluate damping effects in micro-g environment.

Allen, John L.↗
NASA NTRS1984

An on-orbit experiment for dynamics and control of large structures

Attention is given to the definition of the on-orbit dynamic testing that is currently being planned for the flight of a large solar array test article, the Solar Array Flight Experiment (SAFE 1), which consists of a coilable longeron mast that deploys a large solar array blanket. Also discussed is the design of an additional experiment employing this structure in conjunction with a two- or three-axis gimbal system, in order to demonstrate control techniques applicable to such large structures. SAFE 1 experiment objectives, hardware, software, and the experimental operations foreseen are discussed.

Buchanan, H. J.↗