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At least 253 records · Page 14

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NASA NTRS1992

Rat soleus muscle fiber responses to 14 days of spaceflight and hindlimb suspension

Morphological and enzymatic responses in fibers of different types were studied in rats after 14 days of spaceflight onboard Cosmos 2044 or hindlimb suspension. Fibers were classified as fast-twitch, slow-twitch, or both fast- and slow-twitch on the basis of the type of myosin heavy chains (MHC). Data obtained indicate that during the 14 days of spaceflight or suspension the protein profiles of 9-14 percents of the slow-twitch fibers reconfigured from typical slow-twitch toward fast switch fibers, while all fibers were dramatically losing total protein. These results were consistent with the data obtained from Cosmos 1887 and Skylab 3. It is suggested that effects of spaceflight on skeletal muscle can be attributed to a dramatic reduction in the level and/or pattern of loading.

Ohira, Yoshi↗

NASA NTRS1992

Adaptation of fibers in fast-twitch muscles of rats to spaceflight and hindlimb suspension

The adaptation of single fibers in medial gastrocnemius (MG), a fast-twitch extensor, and in tibialis anterior (TA), a fast-twitch flexor, was studied after 14 days of spaceflight onboard Cosmos 2044 or hindlimb suspension. Quantitative myosin ATPase activities of single fibers were measured in flight and suspended rats. Each of the enzyme and size measurements were directly correlated within each fiber with respect to its qualitative myosin ATPase staining properties and its expression of fast, slow, or both myosin heavy chains (MHC). The percentage of slow- and fast-twitch fibers of the MG and TA were found to be unchanged. Mean fiber size of all fibers was unaffected after flight or suspension. The ATPase activity in the MG was higher in flight than in control or suspended rats. In comparison to Cosmos 1887 spaceflight, the adaptations in the muscle fibers of the MG were more moderate.

Jiang, Bian↗

NASA NTRS1992

Ventral horn cell responses to spaceflight and hindlimb suspension

Ventral horn cells of the lumbosacral enlargement of the spinal cord were studied focusing on the succinate dehydrogenase (SDH) activity and cross-sectional area of the soma of ventral horn cells which were measured using a computer-aided image-processing system. The relationships between the soma size and SDH activities of lumber ventral horn cells after 14 days of spaceflight (Cosmos 2044) or of hindlimb suspension are considered. Three groups of rats under consideration include control, 14-day spaceflight, and 14-day hindlimb suspension. Data obtained indicate that, compared to the control group, the population distribution of SDH activities in the flight rats shifted toward higher activities, whereas in the suspended rats the distribution shifted toward lower activities. The interactive effects within individual cells showed that there was a higher percentage of small cells with high SDH activities in the flight than in the control or suspended rats. It is suggested that changes in ventral horn cells were due to factors other than simply the absence of weight support.

Jiang, Bian↗

NASA NTRS1993

Magnetic Suspension Technology Workshop

In order to identify the state of magnetic suspension technology in such areas as rotating systems, pointing of experiments or subsystems, payload isolation, and superconducting materials, a workshop on Magnetic Suspension Technology was held at the Langley Research Center in Hampton, Virginia, on 2-4 Feb. 1988. The workshop included five technical sessions in which a total of 24 papers were presented. The technical sessions covered the areas of pointing, isolation, and measurement, rotating systems, modeling and control, and superconductors. A list of attendees is provided.

Keckler, Claude R.↗

NASA NTRS1993

Magnetic suspension actuator concepts and applications

The fundamental aspect which makes magnetic suspension systems possible is the magnetic phenomena by which significant forces can be generated. Each of these force-producing phenomena has unique characteristics and is implementable in a unique fashion, such that each performs the magnetic suspension task differently than the others. A practical overview of the force-producing concepts, their unique characteristics, and their typical methods of application is provided.

Kroeger, John↗

NASA NTRS1993

A decoupled control approach for magnetic suspension systems using electromagnets mounted in a planar array

A decoupled control approach for a Large Gap Magnetic Suspension System (LGMSS) is presented. The control approach is developed for an LGMSS which provides five degree-of-freedom control of a cylindrical suspended element that contains a core composed of permanent magnet material. The suspended element is levitated above five electromagnets mounted in a planar array. Numerical results are obtained by using the parameters of the Large Angle Magnetic Suspension Test Fixture (LAMSTF) which is a small scale laboratory model LGMSS.

Groom, Nelson J.↗

NASA NTRS1991

Optical position measurement for a Large Gap Magnetic Suspension System

This paper describes the design of an optical position measurement system which is being built as part of the NASA Langley Large Gap Magnetic Suspension System (LGMSS). The LGMSS is a five degree-of-freedom, large-gap magnetic suspension system which is being built for Langley Research Center as part of the Advanced Controls Test Facility (ACTF). The LGMSS consists of a planar array of electromagnets which levitate and position a cylindrically shaped model containing a permanent magnet core. The optical position measurement system provides information on the location and orientation of the model to the LGMSS control system to stabilize levitation of the model.

Welch, Sharon S.↗

NASA NTRS1993

A magnetic suspension system with a large angular range

The paper describes a small-scale laboratory system, called the Large-Angle Magnetic Suspension Test Fixture (LAMSTF), constructed at NASA Langley Research Center in order to explore and develop technology required for the magnetic suspension of objects over large ranges of orientation. The LAMSTF hardware comprises five electromagnets in a circular arrangement, each driven from a separate bipolar power amplifier. The suspended element is a cylindrical axially magnetized permanent magnet core, within an aluminum tube. The element, which is 'levitated' by repulsive forces, is stabilized in five degrees-of-freedom, with rotation about the cylinder axis not controlled. The controller accommodates the changes in magnetic coupling between the electromagnets and the suspended element by real-time adaptation of a decoupling matrix. The paper presents performance measurements demonstrating that the major design objective of the 360 deg rotation was accomplished.

Britcher, Colin P.↗

NASA NTRS1994

Suspension System Provides Independent Translation And Rotation

Spring suspension provides one translational and one rotational degree of freedom. Suspension used to provide for pitching and plunging movements of airfoil in wind tunnel. Translational freedom provided by two thin, flat steel spring tines, clamped at one end to stationary block fixed to ceiling of wind tunnel, and clamped to movable block at other end.

Heeg, Jennifer↗

NASA NTRS1994

System concept definition of the Grumman superconducting Electromagnetic Suspension (EMS) Maglev design

Grumman, under contract to the Army Corps of Engineers, completed a System Concept Definition (SCD) study to design a high-speed 134 m/s (300 m.p.h.) magnetically levitated (Maglev) transportation system. The primary development goals were to design a Maglev that is safe, reliable, environmentally acceptable, and low-cost. The cost issue was a predominant one, since previous studies have shown that an economically viable Maglev system (one that is attractive to investors for future models of passenger and/or freight transportation) requires a cost that is about $12.4 M/km ($20 Million per mile). The design is based on the electromagnetic suspension (EMS) system using superconducting iron-core magnets mounted along both sides of the vehicle. The EMS system has several advantages compared to the electrodynamic suspension (EDS) Maglev systems such as low stray magnetic fields in the passenger cabin and the surrounding areas, uniform load distribution along the full length of the vehicle, and small pole pitch for smoother propulsion and ride comfort. It is also levitated at all speeds and incorporates a wrap-around design of safer operation. The Grumman design has all the advantages of an EMS system identified above, while eliminating (or significantly improving) drawbacks associated with normal magnet powered EMS systems. Improvements include larger gap clearance, lighter weight, lower number of control servos, and higher off line switching speeds. The design also incorporates vehicle tilt (plus or minus 9 deg) for higher coordinated turn and turn out speed capability.

Proise, M.↗

NASA NTRS1994

Implementation of a decoupled controller for a magnetic suspension system using electromagnets mounted in a planar array

An implementation of a decoupled, single-input/single-output control approach for a large angle magnetic suspension test fixture is described. Numerical and experimental results are presented. The experimental system is a laboratory model large gap magnetic suspension system which provides five degree-of-freedom control of a cylindrical suspended element. The suspended element contains a core composed of permanent magnet material and is levitated above five electromagnets mounted in a planar array.

Cox, D. E.↗

NASA NTRS1994

Some further developments in the dynamic modelling and control of the large angle magnetic suspension test fixture

A small-scale laboratory magnetic suspension system, the Large Angle Magnetic Suspension Test Fixture (LAMSTF) has been constructed at NASA Langley Research Center. This paper first presents some recent developments in the mathematical modelling of the system, particularly in the area of eddy current effects. It is shown that these effects are significant, but may be amenable to modelling and measurement. Next, a theoretical framework is presented, together with a comparison of computed and experimental data. Finally, some control aspects are discussed, together with illustration that the major design objective of LAMSTF - a controlled 360 deg rotation about the vertical axis, has been accomplished.

Britcher, Colin P.↗

NASA NTRS1994

Nonlinear feedback model attitude control using CCD in magnetic suspension system

A model attitude control system for a CCD camera magnetic suspension system is studied in this paper. In a recent work, a position and attitude sensing method was proposed. From this result, model position and attitude of a magnetic suspension system can be detected by generating digital outputs. Based on this achievement, a control system design using nonlinear feedback techniques for magnetic suspended model attitude control is proposed.

Lin, CHIN-E.↗

NASA NTRS1993

Annular suspension and pointing system with controlled DC electromagnets

The Annular Suspension and Pointing System (ASPS) developed by the Flight System division of Sperry Corporation is a six-degree of freedom payload pointing system designed for use with the space shuttle. This magnetic suspension and pointing system provides precise controlled pointing in six-degrees of freedom, isolation of payload-carrier disturbances, and end mount controlled pointing. Those are great advantages over the traditional mechanical joints for space applications. In this design, we first analyzed the assumed model of the single degree ASPS bearing actuator and obtained the plant dynamics equations. By linearizing the plant dynamics equations, we designed the cascade and feedback compensators such that a stable and satisfied result was obtained. The specified feedback compensator was computer simulated with the nonlinearized plant dynamics equations. The results indicated that an unstable output occurred. In other words, the designed feedback compensator failed. The failure of the design is due to the Taylor's series expansion not converging.

Vu, Josephine Lynn↗

NASA NTRS1994

Modelling of eddy currents related to large angle magnetic suspension test fixture

This report presents a preliminary analysis of the mathematical modelling of eddy current effects in a large-gap magnetic suspension system. It is shown that eddy currents can significantly affect the dynamic behavior and control of these systems, but are amenable to measurement and modelling. A theoretical framework is presented, together with a comparison of computed and experimental data related to the Large Angle Magnetic Suspension Test Fixture at NASA Langley Research Center.

Britcher, Colin P.↗

NASA NTRS1996

Third International Symposium on Magnetic Suspension Technology

In order to examine the state of technology of all areas of magnetic suspension and to review recent developments in sensors, controls, superconducting magnet technology, and design/implementation practices, the Third International Symposium on Magnetic Suspension Technology was held at the Holiday Inn Capital Plaza in Tallahassee, Florida on 13-15 Dec. 1995. The symposium included 19 sessions in which a total of 55 papers were presented. The technical sessions covered the areas of bearings, superconductivity, vibration isolation, maglev, controls, space applications, general applications, bearing/actuator design, modeling, precision applications, electromagnetic launch and hypersonic maglev, applications of superconductivity, and sensors.

Groom, Nelson J.↗

NASA NTRS1996

A Digital Control Algorithm for Magnetic Suspension Systems

An ongoing program exists to investigate and develop magnetic suspension technologies and modelling techniques at NASA Langley Research Center. Presently, there is a laboratory-scale large air-gap suspension system capable of five degree-of-freedom (DOF) control that is operational and a six DOF system that is under development. Those systems levitate a cylindrical element containing a permanent magnet core above a planar array of electromagnets, which are used for levitation and control purposes. In order to evaluate various control approaches with those systems, the Generic Real-Time State-Space Controller (GRTSSC) software package was developed. That control software package allows the user to implement multiple control methods and allows for varied input/output commands. The development of the control algorithm is presented. The desired functionality of the software is discussed, including the ability to inject noise on sensor inputs and/or actuator outputs. Various limitations, common issues, and trade-offs are discussed including data format precision; the drawbacks of using either Direct Memory Access (DMA), interrupts, or program control techniques for data acquisition; and platform dependent concerns related to the portability of the software, such as memory addressing formats. Efforts to minimize overall controller loop-rate and a comparison of achievable controller sample rates are discussed. The implementation of a modular code structure is presented. The format for the controller input data file and the noise information file is presented. Controller input vector information is available for post-processing by mathematical analysis software such as MATLAB1.

Britton, Thomas C.↗

NASA NTRS1996

Third International Symposium on Magnetic Suspension Technology

Groom, Nelson J.↗