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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.

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NASA NTRS1990

Automatic Calibration Of Manual Machine Tools

Modified scheme uses data from multiple positions and eliminates tedious positioning. Modification of computer program adapts calibration system for convenient use with manually-controlled machine tools. Developed for use on computer-controlled tools. Option added to calibration program allows data on random tool-axis positions to be entered manually into computer for reduction. Instead of setting axis to predetermined positions, operator merely sets it at variety of arbitrary positions.

Gurney, Rex D.↗

NASA NTRS1990

Method For Model-Reference Adaptive Control

Relatively simple method of model-reference adaptive control (MRAC) developed from two prior classes of MRAC techniques: signal-synthesis method and parameter-adaption method. Incorporated into unified theory, which yields more general adaptation scheme.

Seraji, Homayoun↗

NASA NTRS1990

Forward Stochastic Nonlinear Adaptive Control Method

New method of computation for optimal stochastic nonlinear and adaptive control undergoing development. Solves systematically stochastic dynamic programming equations forward in time, using nested-stochastic-approximation technique. Main advantage, simplicity of programming and reduced complexity with clear performance/computation trade-offs.

Bayard, David S.↗

NASA NTRS1989

PACOSS program status and results

Future large space systems (LSS), both civilian and military, will have performance objectives which require stringent pointing accuracies, relatively fast retargeting times, short settling times, accurate dynamic shape requirements, or combinations thereof. Many of these structures will be large but lightweight and will exhibit a dense, low-frequency modal spectrum with significant content within the control bandwidth. Although it is possible in principle to achieve structural vibration control with purely active means, experience with complex structures has shown that the realities of plant model inaccuracies and real sensor and actuator dynamics frequently combine to produce disappointing results. It was shown that a combination of passive and active control will result in a simpler system which can be expected to be more reliable and less expensive than a corresponding system utilizing active control exclusively. The goals of the Passive and Active Control of Space Structures (PACOSS) program consist of a thorough investigation of the relative roles of passive active vibration control, and the development of validated means of vibration control. The program approach, representative system article, dynamic test article, and test status and results are outlined.

Richards, K. E., Jr.↗

NASA NTRS1990

Development of non-conventional control methods for high angle of attack flight using vortex manipulation

Methods of manipulating the forebody vortices on a generic fighter model to produce controlled yawing moments at high angles of attack were investigated. Forces and moments were measured on the complete configuration and on the isolated forebody. Two schemes for vortex control on the forebody were evaluated: individually-controlled tip strakes and individually-controlled blowing ports. The effectiveness of the forebody strakes in controlling forebody side forces was strongly dependent on the size and location of the strakes. A yawing moment can be produced by deploying the forebody strakes asymmetrically, or can be eliminated by deploying the strakes symmetrically. The most effective strake position was found to be near the primary separation point, between 105 and 120 deg from windward. Blowing on the surface of the model was also shown to have a strong effect on the yawing moment. Blowing either forward or aft tangential to the surface appears to be more effective than blowing normal to the surface. The most effective method to control the yawing moment on the forebody was to minimize the natural asymmetry with a pair of small symmetrically mounted tip strakes and to perturb the vortex system away from the symmetric condition with asymmetric blowing.

Malcolm, Gerald N.↗

NASA NTRS1989

Multiple cooperating manipulators: The case of kinematically redundant arms

Existing work concerning two or more manipulators simultaneously grasping and transferring a common load is continued and extended. Specifically considered is the case of one or more arms being kinematically redundant. Some existing results in the modeling and control of single redundant arms and multiple manipulators are reviewed. The cooperating situation is modeled in terms of a set of coordinates representing object motion and internal object squeezing. Nominal trajectories in these coordinates are produced via actuator load distribution algorithms introduced previously. A controller is developed to track these desired object trajectories while making use of the kinematic redundancy to additionally aid the cooperation and coordination of the system. It is shown how the existence of kinematic redundancy within the system may be used to enhance the degree of cooperation achievable.

Walker, Ian D.↗

NASA NTRS1989

The Crop Growth Research Chamber - A ground-based facility for CELSS research

Crop Growth Research Chambers (CGRCs) are being developed as CELSS research facilities for the NASA/Ames Research Center. The history of the CGRC project is reviewed, noting the applications of CGRC research for the development of the Space Station. The CGRCs are designed for CELSS research and development, system control and integration, and flight hardware design and experimentation. The atmospheric and hydroponic environments of the CGRC system are described and the science requirements for CGRC environmental control are listed.

Bubenheim, David L.↗

NASA NTRS1991

Estimating Atmospheric Turbulence From Flight Records

Method for estimation of atmospheric turbulence encountered by airplanes utilizes wealth of data captured by multichannel digital flight-data recorders and air-traffic-control radar. Developed as part of continuing effort to understand how airplanes respond to such potentially hazardous phenomena as: clear-air turbulence generated by destabilized wind-shear layers above mountains and thunderstorms, and microbursts (intense downdrafts striking ground), associated with thunderstorms. Reconstructed wind fields used to predict and avoid future hazards.

Wingrove, R. C.↗

NASA NTRS1991

The Langley Research Center CSI phase-0 evolutionary model testbed-design and experimental results

A testbed for the development of Controls Structures Interaction (CSI) technology is described. The design philosophy, capabilities, and early experimental results are presented to introduce some of the ongoing CSI research at NASA-Langley. The testbed, referred to as the Phase 0 version of the CSI Evolutionary model (CEM), is the first stage of model complexity designed to show the benefits of CSI technology and to identify weaknesses in current capabilities. Early closed loop test results have shown non-model based controllers can provide an order of magnitude increase in damping in the first few flexible vibration modes. Model based controllers for higher performance will need to be robust to model uncertainty as verified by System ID tests. Data are presented that show finite element model predictions of frequency differ from those obtained from tests. Plans are also presented for evolution of the CEM to study integrated controller and structure design as well as multiple payload dynamics.

Belvin, W. K.↗

NASA NTRS1990

Containerless processing of undercooled melts

All practical solidification processes involve some level of melt undercooling. Usually in bulk liquids crystallization is initiated at a heterogeneous nucleation site at low undercooling. The realization of appreciable levels of liquid undercooling requires some control over the kinetics of crystal nucleation. One level of control is available in containerless processing where the capability to melt and solidify samples without a container removes a major source of impurities and heterogeneous nucleation sites which can be effective in promoting large undercooling and in studying other potential nucleants. The microgravity environment offers a unique opportunity for containerless processing of large liquid samples with negligible melt disturbance and continuous temperature measurement throughout processing. Perhaps the most important potential for microgravity containerless processing lies in the significant structural control to develop distinct microstructures and metastable phases during solidification at high undercooling.

Perepezko, J. H.↗

NASA NTRS1991

Development of silicon carbide semiconductor devices for high temperature applications

The semiconducting properties of electronic grade silicon carbide crystals, such as wide energy bandgap, make it particularly attractive for high temperature applications. Applications for high temperature electronic devices include instrumentation for engines under development, engine control and condition monitoring systems, and power conditioning and control systems for space platforms and satellites. Discrete prototype SiC devices were fabricated and tested at elevated temperatures. Grown p-n junction diodes demonstrated very good rectification characteristics at 870 K. A depletion-mode metal-oxide-semiconductor field-effect transistor was also successfully fabricated and tested at 770 K. While optimization of SiC fabrication processes remain, it is believed that SiC is an enabling high temperature electronic technology.

Matus, Lawrence G.↗

NASA NTRS1992

Development Of Maneuvering Autopilot For Flight Tests

Report describes recent efforts to develop automatic control system operating under supervision of pilot and making airplane follow prescribed trajectories during flight tests. Report represents additional progress on this project. Gives background information on technology of control of test-flight trajectories; presents mathematical models of airframe, engine and command-augmentation system; focuses on mathematical modeling of maneuvers; addresses design of autopilots for maneuvers; discusses numerical simulation and evaluation of results of simulation of eight maneuvers under control of simulated autopilot; and presents summary and discussion of future work.

Menon, P. K. A.↗

NASA NTRS1991

Dynamics of low velocity collisions of ice particle, coated with frost

We continued our investigations of low velocity collisions of ice particles for velocities in range 10(exp -3) - 2 cm/s. The work focused on two effects: (1) the sticking forces for ice particles coated with CO2 frost, and (2) the completion of a 2-D pendulum system for glancing collisions. A new computer software was also developed to control and monitor the position of the 2-D pendulum.

Bridges, F.↗

NASA NTRS1991

Langley's CSI evolutionary model: Phase O

A testbed for the development of Controls Structures Interaction (CSI) technology to improve space science platform pointing is described. The evolutionary nature of the testbed will permit the study of global line-of-sight pointing in phases 0 and 1, whereas, multipayload pointing systems will be studied beginning with phase 2. The design, capabilities, and typical dynamic behavior of the phase 0 version of the CSI evolutionary model (CEM) is documented for investigator both internal and external to NASA. The model description includes line-of-sight pointing measurement, testbed structure, actuators, sensors, and real time computers, as well as finite element and state space models of major components.

Belvin, W. Keith↗

NASA NTRS1990

Reuse metrics and measurement: A framework

The lessons learned and experience gleaned are described by those who have started to implement the reuse metrics and measurement framework used in controlling the development of common avionics and software for its affiliated aircraft programs. The framework was developed to permit the measurement of the long term cost/benefits resulting from the creation and use of Reusable Software Objects (RSOs). The framework also monitors the efficiency and effectiveness of the Software Reuse Library (SRL). The metrics and measurement framework is defined which was established to allow some determinations and findings to be made relative to software reuse. Seven criteria are discussed which were used to guide the establishment of the proposed reuse framework. Object recapture and creation metrics are explained along with their normalized use in effort, productivity, and quality determination. A single and multiple reuse instance version of a popular cost model is presented which uses these metrics and the measurement scheme proposed to predict the software effort and duration under various reuse assumptions. Studies in using this model to predict actuals taken from the RCI data base of over 1000 completed projects is discussed.

Reifer, Donald J.↗

NASA NTRS1992

Measurement of vortex flow fields

A 3-D laser fluorescence anemometer (LFA) was designed, built, and demonstrated for use in the Langley 16 x 24 inch Water Tunnel. Innovative optical design flexibility combined with compact and portable data acquisition and control systems were incorporated into the instrument. This will allow its use by NASA in other test facilities. A versatile fiber optic system facilities normal and off-axis laser beam alignment, removes mirror losses and improves laser safety. This added optical flexibility will also enable simple adaptation for use in the adjacent jet facility. New proprietary concepts in transmitting color separation, light collection, and novel prism separation of the scattered light was also designed and built into the system. Off-axis beam traverse and alignment complexity led to the requirement for a specialized, programmable transverse controller, and the inclusion of an additional traverse for the off-axis arm. To meet this challenge, an 'in-house' prototype unit was designed and built and traverse control software developed specifically for the water tunnel traverse applications. A specialized data acquisition interface was also required. This was designed and built for the LFA system.

Mcdevitt, T. Kevin↗

NASA NTRS1992

The Lunar CELSS Test Module

The evolutionarily-developed Lunar Controlled Ecological Life Support System (CELSS) Test Module presented can address questions concerning long-term human presence-related issues both at LEO and in the lunar environment. By achieving well-defined research goals at each of numerous developmental stages (each economically modest), easily justifiable operations can be undertaken. Attention is given to the possibility of maximizing non-NASA involvement in these CELSS developmental efforts via the careful definability and modest risk of each developmental stage.

Hoehn, Alexander↗

NASA NTRS1992

The role of criteria in design and management of space systems

Explicit requirements and standards arising in connection with space systems management serve as a framework for technical management and furnish legally binding control of development, verification, and operations. As a project develops, additional requirements are derived which are unique to the system in question; these are designated 'derived requirements'. The reliability and cost-effectiveness of a space system are best ensured where a balance has arisen between formal (legally binding) and informal. Attention is presently given to the development of criteria consistent with total quality management.

Blair, J. C.↗

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