Search NASA⌕ Search

SEARCH · Search NASA

Results for “Determination and Control”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Results of an investigation of hypersonic viscous interaction effects on and 0.01 scale Space Shuttle Orbiter 51-0 model in the AEDC-VKF Hypervelocity Wind Tunnel (0A81)

The major hypersonic aerodynamic results obtained experimentally from the 0.010-scale (51-0) 140A/B orbiter vehicle are presented. The test was conducted over an angle-of-attack range from 20 to 35 degrees for nominal Mach numbers of 16 and 20. The Mach 16 data were obtained at Reynolds numbers, based on model length, of nominally 0.54 x 106 and 1.18 x 106. The Mach number 20 data were obtained at nominal Reynolds numbers of 0.08 x 106 and 0.27 x 106. Various elevon deflections and body flap deflections were tested for determination of control effectiveness. The test objectives were: (1) verify December 1973 aerodynamic Design Data Book estimates for Mach number greater than 10; (2) determine configuration forward and aft trim boundaries and control characteristics; (3) determine high Mach number - low Reynolds number effects; (4) determine if positive control surface flow separation is present and magnitude of separation effects.

Elder, D. J.↗
NASA NTRS1991

Fixed-order multi-model estimation and control

The problems of determining a feedback controller or estimator that optimizes an H2 performance criterion involving a collection of plant models is considered. The approach is based upon fixed-structure optimization in which the estimator or controller order is fixed prior to the development of optimality conditions. The question of maximal controller order is also investigated.

Macmartin, Douglas G.↗
NASA NTRS2003

Structured Uncertainty Bound Determination From Data for Control and Performance Validation

This report attempts to document the broad scope of issues that must be satisfactorily resolved before one can expect to methodically obtain, with a reasonable confidence, a near-optimal robust closed loop performance in physical applications. These include elements of signal processing, noise identification, system identification, model validation, and uncertainty modeling. Based on a recently developed methodology involving a parameterization of all model validating uncertainty sets for a given linear fractional transformation (LFT) structure and noise allowance, a new software, Uncertainty Bound Identification (UBID) toolbox, which conveniently executes model validation tests and determine uncertainty bounds from data, has been designed and is currently available. This toolbox also serves to benchmark the current state-of-the-art in uncertainty bound determination and in turn facilitate benchmarking of robust control technology. To help clarify the methodology and use of the new software, two tutorial examples are provided. The first involves the uncertainty characterization of a flexible structure dynamics, and the second example involves a closed loop performance validation of a ducted fan based on an uncertainty bound from data. These examples, along with other simulation and experimental results, also help describe the many factors and assumptions that determine the degree of success in applying robust control theory to practical problems.

Lim, Kyong B.↗
NASA NTRS2005

Up, Up and Away: Arc Minute Pointing at 130,000 Feet

The InFOC-S X-ray telescope was launched September 16, 2004 aboard a 40 million cubic foot zero pressure high altitude balloon. Its primary objective was to demonstrate advances in hard X-ray focusing optics technology by flying an incident grazing mirror developed in cooperation between NASA Goddard Space Flight Center and Nagoya University, Japan. Launched from Ft. Sumner, NM and recovered near Wickenburg, AZ, the payload successfully collected photons from several X-ray sources during its 27 hour flight at a float altitude of 130,000 feet. To accommodate the instrument's narrow field of view, a precision arc-minute attitude determination and control systems was flown. This paper describes the application of a traditional spacecraft star tracker gyro based attitude determination and control system to the balloon problem. The control system architecture is presented, hardware identified, and software outlined. Simulated results are compared against actual flight data, with recommendations for enhanced performance identified.

Freesland, Doug↗
NASA NTRS1978

Optimal regulator or conventional? Setup techniques for a model following simulator control system

Optimal regulator technique was compared for determining simulator control system gains with the conventional servo analysis approach. Practical considerations, associated with airborne motion simulation using a model-following system, provided the basis for comparison. The simulation fidelity specifications selected were important in evaluating the relative advantages of the two methods. Frequency responses for a JetStar aircraft following a roll mode model were calculated digitally to illustrate the various cases. A technique for generating forward loop lead in the optimal regulator model-following problem was developed which increases the flexibility of that approach. It appeared to be the only way in which the optimal regulator method could meet the fidelity specifications.

Deets, D. A.↗
NASA NTRS2004

Optimum Actuator Selection with a Genetic Algorithm for Aircraft Control

The placement of actuators on a wing determines the control effectiveness of the airplane. One approach to placement maximizes the moments about the pitch, roll, and yaw axes, while minimizing the coupling. For example, the desired actuators produce a pure roll moment without at the same time causing much pitch or yaw. For a typical wing, there is a large set of candidate locations for placing actuators, resulting in a substantially larger number of combinations to examine in order to find an optimum placement satisfying the mission requirements and mission constraints. A genetic algorithm has been developed for finding the best placement for four actuators to produce an uncoupled pitch moment. The genetic algorithm has been extended to find the minimum number of actuators required to provide uncoupled pitch, roll, and yaw control. A simplified, untapered, unswept wing is the model for each application.

Rogers, James L.↗
NASA NTRS1965

Combined optimal control and estimation.

Combined optimization problem, equivalent to dual control problem, considering determination of optimal control policies for plant under random disturbances, using iterative equations

CONTROL SYSTEM↗
NASA NTRS1969

On adaptive manual control.

Adaptive manual control rapid variation determined by input, controlled element, task and programmed adaptation systems, discussing human strategy changes

Young, L. R.↗
NASA NTRS1978

Creep of oxide dispersion strengthened materials (with special reference to TD nichrome)

It was shown that the creep behavior of oxide dispersion strengthened (ODS) alloys is controlled principally by the creep properties of the matrix of the alloy devoid of particles. Thus, diffusion controlled slip process determine the rate controlling step in such materials. The role of the particles is to stabilize a fine substructure which is invariant with the creep stress over a wide range of stress. This characteristic leads to negligible strain hardening during creep and suggests that creep relations developed for pure metals and many solid solution alloys at constant structure should be used to describe the creep of ODS alloys. A second characteristics of the ODS alloys is that a stress may exist below which creep will not occur (threshold stress).

Lin, J.↗
NASA NTRS1991

The control network of Mercury: April 1991

Features identified on Mariner 10 high resolution images of Mercury, acquired during three flybys between 1974 and 1975, form the basis of Mercury's planetwide control network. Although images from all three flybys are used in the net, the large amount of contiguous coverage from the second flyby, a southern bright-side pass, make these images the strongest contributors to the control net. Mercury is in synchronous rotation with a period of 58.6462 days and its spin axis is approximately normal to the equatorial plane. The 20 degree meridian is defined by the crater Hun Kal, located just south of the equator. The control network computations involve the photogrammetric determination of control point coordinates and an analytical triangulation solution. The current control network computations for Mercury are performed in the J2000 coordinate system according to the International Astronomical Union (IAU) convention. In recent years, updates to the control network have included improved trajectory solutions and modification of the standard radii (2439) at several points based on Earth-based radar altimetry data. The current status of the control network calculations is presented. Improvements were made to existing control points and new control points were added to the net to strengthen the overall network and improve the standard error of measurement.

Davies, Merton E.↗
NASA NTRS1993

The Cassini spacecraft: Object oriented flight control software

The Cassini Attitude and Articulation Control Subsystem (AACS) is responsible for determining and controlling the spacecraft attitude including instrument pointing, antenna pointing, and thrust vector pointing during velocity change maneuvers. The 12 year mission life, long round-trip light time, and extended periods of coast without continuous ground control drive the AACS flight software design in the directions of autonomy, fault tolerance, and modularity to accommodate planned upgrades in flight. The Cassini AACS Flight Software is depicted in increasing levels of detail using a Context Diagram, Architecture Diagrams (i.e., Dependency Diagrams), an Object Diagram for each object, and a Statechart (i.e., State Transition Diagram) for each object. The detail contained in the diagrams is enhanced and refined during the Requirements and Design Phases of both Subsystem and Software Development. Examples of all the diagrams as well as the criteria for object selection, the advantages of statecharts, and the ease of modifying the design to accommodate changes in scope are described.

Hackney, John C.↗
NASA NTRS1997

HARV ANSER Flight Test Data Retrieval and Processing Procedures

Under the NASA High-Alpha Technology Program the High Alpha Research Vehicle (HARV) was used to conduct flight tests of advanced control effectors, advanced control laws, and high-alpha design guidelines for future super-maneuverable fighters. The High-Alpha Research Vehicle is a pre-production F/A-18 airplane modified with a multi-axis thrust-vectoring system for augmented pitch and yaw control power and Actuated Nose Strakes for Enhanced Rolling (ANSER) to augment body-axis yaw control power. Flight testing at the Dryden Flight Research Center (DFRC) began in July 1995 and continued until May 1996. Flight data will be utilized to evaluate control law performance and aircraft dynamics, determine aircraft control and stability derivatives using parameter identification techniques, and validate design guidelines. To accomplish these purposes, essential flight data parameters were retrieved from the DFRC data system and stored on the Dynamics and Control Branch (DCB) computer complex at Langley. This report describes the multi-step task used to retrieve and process this data and documents the results of these tasks. Documentation includes software listings, flight information, maneuver information, time intervals for which data were retrieved, lists of data parameters and definitions, and example data plots.

Yeager, Jessie C.↗
NASA NTRS1985

A design technique for determining actuator gains in spacecraft vibration control

A design procedure is described which determines the gains of a diagonal damping matrix to control the vibrations of a flexible structure with application to orbiting spacecraft. The procedure is based on minimizing the energy dissipated by control actuators using nonlinear mathematical programming. Each damping gain is assumed to be an active viscous damper and the design process is formulated so that the force or torque output of the actuator does not exceed a specified value. The response of the structure at some specified time after the termination of the disturbance is constrained to be less than some prescribed value based upon spacecraft mission performance requirements. A grillage example is used to demonstrate the design process for determining gains for two representative cases. Resulting designs are verified by a finite element analysis of the structure augmented by the control actuators.

Horner, G. C.↗
NASA NTRS1971

Flight-determined aerodynamic stability and control derivatives of the M2-F2 lifting body vehicle at subsonic speeds

Aerodynamic derivatives were obtained for the M2-F2 lifting body flight vehicle in the subsonic flight region between Mach numbers of 0.41 and 0.64 and altitudes of 7000 feet to 45,000 feet. The derivatives were determined by a flight time history curve-fitting process utilizing a hybrid computer. The flight-determined derivatives are compared with wind-tunnel and predicted values. Modal-response characteristics, calculated from the flight derivatives, are presented.

Kempel, R. W.↗
NASA NTRS1978

Optimal guidance and control for investigating aircraft noise-impact reduction

A methodology for investigating the reduction of community noise impact is reported. This report is concerned with the development of two models to provide data: a guidance generator and an aircraft control generator suitable for various current and advanced types of aircraft. The guidance generator produces the commanded path information from inputs chosen by an operator from a graphic scope display of a land-use map of the terminal area. The guidance generator also produces smoothing at the junctions of straight-line paths.The aircraft control generator determines the optimal set of the available controls such that the aircraft will follow the commanded path. The solutions for the control functions are given and shown to be dependent on the class of aircraft to be considered, that is, whether the thrust vector is rotatable and whether the thrust vector affects the aerodynamic forces. For the class of aircraft possessing a rotatable thrust vector, the solution is redundant; this redundancy is removed by the additional condition that the noise inpact be minimized. Information from both the guidance generator and the aircraft control generator is used by the footprint program to construct the noise footprint.

Stewart, E. C.↗
NASA NTRS1981

Transient upsets in microprocessor controllers

The modeling and analysis of transient faults in microprocessor based controllers are discussed. Such controllers typically consist of a microprocessor, read only memory storing and application program, random access memory for data storage, and input/output devices for external communications. The effects of transient faults on the performance of the controller are reviewed. An instruction level perspective of performance is taken which is the basis of a useful high level program state description of the microprocessor controller. A transition matrix is defined which determines the controller's response to transient fault arrivals.

Glaser, R. E.↗
NASA NTRS1988

Control law parameterization for an aeroelastic wind-tunnel model equipped with an active roll control system and comparison with experiment

Nominal roll control laws were designed, implemented, and tested on an aeroelastically-scaled free-to-roll wind-tunnel model of an advanced fighter configuration. The tests were performed in the NASA Langley Transonic Dynamics Tunnel. A parametric study of the nominal roll control system was conducted. This parametric study determined possible control system gain variations which yielded identical closed-loop stability (roll mode pole location) and identical roll response but different maximum control-surface deflections. Comparison of analytical predictions with wind-tunnel results was generally very good.

Perry, Boyd, III↗