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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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At least 1,297 records · Page 72

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NASA NTRS1992

Geometric modeling for computer aided design

The goal was the design and implementation of software to be used in the conceptual design of aerospace vehicles. Several packages and design studies were completed, including two software tools currently used in the conceptual level design of aerospace vehicles. These tools are the Solid Modeling Aerospace Research Tool (SMART) and the Environment for Software Integration and Execution (EASIE). SMART provides conceptual designers with a rapid prototyping capability and additionally provides initial mass property analysis. EASIE provides a set of interactive utilities that simplify the task of building and executing computer aided design systems consisting of diverse, stand alone analysis codes that result in the streamlining of the exchange of data between programs, reducing errors and improving efficiency.

Schwing, James L.↗

NASA NTRS1992

Surface generation and editing operations applied to structural support of aerospace vehicle fuselages

The Solid Modeling Aerospace Research Tool (SMART) is a computer aided design tool used in aerospace vehicle design. Modeling of structural components using SMART includes the representation of the transverse or cross-wise elements of a vehicle's fuselage, ringframes, and bulkheads. Ringframes are placed along a vehicle's fuselage to provide structural support and maintain the shape of the fuselage. Bulkheads are also used to maintain shape, but are placed at locations where substantial structural support is required. Given a Bezier curve representation of a cross sectional cut through a vehicle's fuselage and/or an internal tank, this project produces a first-guess Bezier patch representation of a ringframe or bulkhead at the cross-sectional position. The grid produced is later used in the structural analysis of the vehicle. The graphical display of the generated patches allows the user to edit patch control points in real time. Constraints considered in the patch generation include maintaining 'square-like' patches and placement of longitudinal, or lengthwise along the fuselage, structural elements called longerons.

Schwartz, Susan K.↗

NASA NTRS1991

Real-time in situ sensors and control integration for life support systems

The limitations of the state-of-the-art for in situ sensors are discussed and a program of adaptation and enhancement of off-the-shelf sensor technologies and of innovation and research to develop more appropriate sensor technologies for life support systems is offered. By critically assessing the state-of-the-art in multifunctional sensors and smart sensors, research and development requirements for life support systems can be defined. Consideration is given to the desirable characteristics of smart sensors for life support applications, and some preliminary concepts for hierarchical integration of in situ sensors and control elements are presented.

Voecks, G. E.↗

NASA NTRS1990

On-orbit structural health monitoring

On-orbit structural health monitoring aboard space platforms requires the development of sensor systems for assessing impact damage from particles and debris, the effects of atomic oxygen erosion, and the integrity of power systems, storage tanks, pressure vessels, and major structural elements. The task of implementing such a smart structure diagnostic system during the initial phase of the NASA Space Station Freedom is evaluated, with a view to more complete smart structures implementation in the course of station evolution. The data processing/cataloguing task may ultimately require AI and neural networks.

Rogowski, Robert S.↗

NASA NTRS1991

Joint U.S./Japan Conference on Adaptive Structures, 1st, Maui, HI, Nov. 13-15, 1990, Proceedings

The present volume of adaptive structures discusses the development of control laws for an orbiting tethered antenna/reflector system test scale model, the sizing of active piezoelectric struts for vibration suppression on a space-based interferometer, the control design of a space station mobile transporter with multiple constraints, and optimum configuration control of an intelligent truss structure. Attention is given to the formulation of full state feedback for infinite order structural systems, robustness issues in the design of smart structures, passive piezoelectric vibration damping, shape control experiments with a functional model for large optical reflectors, and a mathematical basis for the design optimization of adaptive trusses in precision control. Topics addressed include approaches to the optimal adaptive geometries of intelligent truss structures, the design of an automated manufacturing system for tubular smart structures, the Sandia structural control experiments, and the zero-gravity dynamics of space structures in parabolic aircraft flight.

Wada, Ben K.↗

NASA NTRS1992

An Embedded Rule-Based Diagnostic Expert System in Ada

Ada is becoming an increasingly popular programming language for large Government-funded software projects. Ada with it portability, transportability, and maintainability lends itself well to today's complex programming environment. In addition, expert systems have also assumed a growing role in providing human-like reasoning capability expertise for computer systems. The integration is discussed of expert system technology with Ada programming language, especially a rule-based expert system using an ART-Ada (Automated Reasoning Tool for Ada) system shell. NASA Lewis was chosen as a beta test site for ART-Ada. The test was conducted by implementing the existing Autonomous Power EXpert System (APEX), a Lisp-based power expert system, in ART-Ada. Three components, the rule-based expert systems, a graphics user interface, and communications software make up SMART-Ada (Systems fault Management with ART-Ada). The rules were written in the ART-Ada development environment and converted to Ada source code. The graphics interface was developed with the Transportable Application Environment (TAE) Plus, which generates Ada source code to control graphics images. SMART-Ada communicates with a remote host to obtain either simulated or real data. The Ada source code generated with ART-Ada, TAE Plus, and communications code was incorporated into an Ada expert system that reads the data from a power distribution test bed, applies the rule to determine a fault, if one exists, and graphically displays it on the screen. The main objective, to conduct a beta test on the ART-Ada rule-based expert system shell, was achieved. The system is operational. New Ada tools will assist in future successful projects. ART-Ada is one such tool and is a viable alternative to the straight Ada code when an application requires a rule-based or knowledge-based approach.

Jones, Robert E.↗

NASA NTRS1992

An 8-DOF dual-arm system for advanced teleoperation performance experiments

This paper describes the electro-mechanical and control features of an 8-DOF manipulator manufactured by AAI Corporation and installed at the Jet Propulsion Lab. (JPL) in a dual-arm setting. The 8-DOF arm incorporates a variety of features not found in other lab or industrial manipulators. Some of the unique features are: 8-DOF revolute configuration with no lateral offsets at joint axes; 1 to 5 payload to weight ratio with 20 kg (44 lb) payload at a 1.75 m (68.5 in.) reach; joint position measurement with dual relative encoders and potentiometer; infinite roll of joint 8 with electrical and fiber optic slip rings; internal fiber optic link of 'smart' end effectors; four-axis wrist; graphite epoxy links; high link and joint stiffness; use of an upgraded JPL Universal Motor Controller (UMC) capable of driving up to 16 joints. The 8-DOF arm is equipped with a 'smart' end effector which incorporates a 6-DOF forcemoment sensor at the end effector base and grasp force sensors at the base of the parallel jaws. The 8-DOF arm is interfaced to a 6 DOF force reflecting hand controller. The same system is duplicated for and installed at NASA-Langley.

Bejczy, Antal K.↗

NASA NTRS1993

A semiconductor bridge ignited hot gas piston ejector

The topics are presented in viewgraph form and include the following: semiconductor bridge technology (SCB); SCB philosophy; technology transfer; simplified sketch of SCB; SCB processing; SCB design; SCB test assembly; 5 mJ SCB burst based on a polaroid photograph; micro-convective heat transfer hypothesis; SCB fire set; comparison of SCB and hot-wire actuators; satellite firing sets; logic fire set; SCB smart component; SCB smart firing set; semiconductor design considerations; and the adjustable actuator system.

Grubelich, M. C.↗

NASA NTRS1990

Growing the Space Station's electrical power plant

For over a decade NASA LeRC has been defining, demonstrating, and evaluating power electronic components and multi-kilowatt, multiply redundant, electrical power systems as part of OAST charter. Whether one considers aircraft (commercial transport/military), Space Station Freedom, growth station, launch vehicles, or the new Human Exploration Initiative, the conclusions remain the same: high frequency AC power distribution and control is superior to all other approaches for achieving a fast, smart, safe, versatile, and growable electrical power system that will meet a wide range of mission options. To meet the cost and operability goals of future aerospace missions that require significantly higher electrical power and longer durations, we must learn to integrate multiple technologies in ways that enhance overall system synergisms. The way NASA is doing business in space electric power is challenged and some approaches for evolving large space vehicles and platforms in well constructed steps to provide safe, ground testable, growable, smart systems that provide simple, replicative logic structures, which enable hardware and software verification, validation, and implementation are proposed. Viewgraphs are included.

Sundberg, Gale R.↗

NASA NTRS1993

Probabilistically configured adaptive composite structures

A composite wing with spars, bulkheads and built-in sensor/control devices is probabilistically configured with a methodology for the probabilistic assessment of smart composite structures. Structural responses such as changes in angle of attack, vertical displacements and stresses in the non-control and control plies are probabilistically assessed to quantify their respective scatter ranges. Sensitivity factors are evaluated to identify those parameters that have the greatest influence on a specific structural response. Results show that smart composite structures can be configured to control distortions and ply stresses, and to have specified scatter ranges in the frequencies, buckling loads in the presence of defects to satisfy specified design requirements.

Shiao, Michael C.↗

NASA NTRS1993

A piezoelectric transformer

This work describes a modeling and design method whereby a piezoelectric system is formulated by two sets of second-order equations, one for the mechanical system, and the other for the electrical system, coupled through the piezoelectric effect. The solution to this electromechanical coupled system gives a physical interpretation of the piezoelectric effect as a piezoelectric transformer that is a part of the piezoelectric system, which transfers the applied mechanical force into a force-controlled current source, and short circuit mechanical compliance into capacitance. It also transfers the voltage source into a voltage-controlled relative velocity input, and free motional capacitance into mechanical compliance. The formulation and interpretation simplify the modeling of smart structures and lead to physical insight that aids the designer. Due to its physical realization, the smart structural system can be unconditional stable and effectively control responses. This new concept has been demonstrated in three numerical examples for a simple piezoelectric system.

Won, C. C.↗

NASA NTRS1996

Spline Approximation of Thin Shell Dynamics

A spline-based method for approximating thin shell dynamics is presented here. While the method is developed in the context of the Donnell-Mushtari thin shell equations, it can be easily extended to the Byrne-Flugge-Lur'ye equations or other models for shells of revolution as warranted by applications. The primary requirements for the method include accuracy, flexibility and efficiency in smart material applications. To accomplish this, the method was designed to be flexible with regard to boundary conditions, material nonhomogeneities due to sensors and actuators, and inputs from smart material actuators such as piezoceramic patches. The accuracy of the method was also of primary concern, both to guarantee full resolution of structural dynamics and to facilitate the development of PDE-based controllers which ultimately require real-time implementation. Several numerical examples provide initial evidence demonstrating the efficacy of the method.

delRosario, R. C. H.↗

NASA NTRS1996

Layerwise mechanics and finite element for the dynamic analysis of piezoelectric composite plates

Laminate and structural mechanics for the analysis of laminated composite plate structures with piezoelectric actuators and sensors are presented. The theories implement layerwise representations of displacements and electric potential, and can model both the global and local electromechanical response of smart composite laminates. Finite-element formulations are developed for the quasi-static and dynamic analysis of smart composite structures containing piezoelectric layers. Comparisons with an exact solution illustrate the accuracy, robustness and capability of the developed mechanics to capture the global and local response of thin and/or thick laminated piezoelectric plates. Additional correlations and numerical applications demonstrate the unique capabilities of the mechanics in analyzing the static and free-vibration response of composite plates with distributed piezoelectric actuators and sensors.

Saravanos, Dimitris A.↗

NASA NTRS1996

Active Control of Noise Using Actuator/Sensor Arrays

Current research in smart structures is directed toward the integration of many actuators and sensors into a material. In this paper we investigate the possibility of using this instrumentation for active noise control from a vibrating structures. Current technology for reducing radiated sound is limited by the instrumentation for the control system. These control systems employ relatively small numbers of sensors and actuators. Hence, these control systems must rely on a model of the structure to estimate and control the global vibrations that contribute to the far field pressure. For complex, realistic structures the development of such a model is a formidable task. The model is a limiting factor in the continuing development of structural acoustics. In this paper we propose to increase the number of actuators and sensors of a smart material to offset the complexity of the model used for control design. The sensor arrays will be used to directly sense the shape of the structure rather than using a model of the structures to indirectly sense the shape of the structure. The actuator array is used to apply distributed forces to the structure, rather than using the structure itself as a load path. A control system for the active cancellation of sound is derived from standard control system methodologies.

Lindner, Douglas K.↗

NASA NTRS1996

Performance of Integrated Fiber Optic, Piezoelectric, and Shape Memory Alloy Actuators/Sensors in Thermoset Composites

Recently, scientists and engineers have investigated the advantages of smart materials and structures by including actuators in material systems for controlling and altering the response of structural environments. Applications of these materials systems include vibration suppression/isolation, precision positioning, damage detection and tunable devices. Some of the embedded materials being investigated for accomplishing these tasks include piezoelectric ceramics, shape memory alloys, and fiber optics. These materials have some benefits and some shortcomings; each is being studied for use in active material design in the SPICES (Synthesis and Processing of Intelligent Cost Effective Structures) Consortium. The focus of this paper concerns the manufacturing aspects of smart structures by incorporating piezoelectric ceramics, shape memory alloys and fiber optics in a reinforced thermoset matrix via resin transfer molding (RTM).

Trottier, C. Michael↗

NASA NTRS1996

Mechanical Response of Elastomers to Magnetic Fields

Elastomeric materials represent an important class of engineering materials, which are widely used to make components of structures, machinery, and devices for vibration and noise control. Elastomeric material possessing conductive or magnetic properties have been widely used in applications such as conductive and magnetic tapes, sensors, flexible permanent magnets, etc. Our interest in these materials has focussed on understanding and controlling the magnitude and directionality of their response to applied magnetic fields. The effect of magnetic fields on the mechanical properties of these materials has not been the subject of many published studies. Our interest and expertise in controllable fluids have given us the foundation to make a transition to controllable elastomers. Controllable elastomers are materials that exhibit a change in mechanical properties upon application of an external stimuli, in this case a magnetic field. Controllable elastomers promise to have more functionality than conventional elastomers and therefore could share the broad industrial application base with conventional elastomers. As such, these materials represent an attractive class of smart materials, and may well be a link that brings the applications of modern control technologies, intelligent structures and smart materials to a very broad industrial area. This presentation will cover our research work in the area of controllable elastomers at the Thomas Lord Research Center. More specifically, the presentation will discuss the control of mechanical properties and mathematical modeling of the new materials prepared in our laboratories along with experiments to achieve adaptive vibration control using the new materials.

Munoz, B. C.↗

NASA NTRS1995

Advancing MEMS Technology Usage through the MUMPS (Multi-User MEMS Processes) Program

In order to help provide access to advanced micro-electro-mechanical systems (MEMS) technologies and lower the barriers for both industry and academia, the Microelectronic Center of North Carolina (MCNC) and ARPA have developed a program which provides users with access to both MEMS processes and advanced electronic integration techniques. The four distinct aspects of this program, the multi-user MEMS processes (MUMP's), the consolidated micro-mechanical element library, smart MEMS, and the MEMS technology network are described in this paper. MUMP's is an ARPA-supported program created to provide inexpensive access to MEMS technology in a multi-user environment. It is both a proof-of-concept and educational tool that aids in the development of MEMS in the domestic community. MUMP's technologies currently include a 3-layer poly-silicon surface micromachining process and LIGA (lithography, electroforming, and injection molding) processes that provide reasonable design flexibility within set guidelines. The consolidated micromechanical element library (CaMEL) is a library of active and passive MEMS structures that can be downloaded by the MEMS community via the internet. Smart MEMS is the development of advanced electronics integration techniques for MEMS through the application of flip chip technology. The MEMS technology network (TechNet) is a menu of standard substrates and MEMS fabrication processes that can be purchased and combined to create unique process flows. TechNet provides the MEMS community greater flexibility and enhanced technology accessibility.

Koester, D. A.↗

NASA NTRS1995

System Construction for the Measurement of Bragg Grating Characteristics in Optical Fibers

Bragg gratings are used to measure strain in optical fibers. To measure strain they are sometimes used as a smart structure. They must be characterized after they are written to determine their spectral response. This paper deals with the test setup to characterize Bragg grating spectral responses.Bragg gratings are a photo-induced phenomena in optical fibers. The gratings can be used to measure strain by measuring the shift in wavelength. They placed the fibers into a smart structure to measure the stress and strain produced on support columns placed in bridges. As the cable is subjected to strain the grating causes a shift to a longer wavelength if the fiber is stretched and a shift to a shorter wavelength shift if the fiber is compacted. Our applications involve using the fibers to measure stress and strain on airborne systems. There are many ways to write Bragg gratings into optical fibers. Our focus is on side writing the grating. Our capabilities are limited in the production rate of the gratings. The Bragg grating is written into a fiber and becomes a permanent fixture. We are writing the grating to be centered at 1300 nm because that is the standard phase mask wavelength.

West, Douglas P.↗