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NASA NTRS2003

Ultra-Sensitive Magnetoresistive Displacement Sensing Device

An ultrasensitive displacement sensing device for use in accelerometers, pressure gauges, temperature transducers, and the like, comprises a sputter deposited, multilayer, magnetoresistive field sensor with a variable electrical resistance based on an imposed magnetic field. The device detects displacement by sensing changes in the local magnetic field about the magnetoresistive field sensor caused by the displacement of a hard magnetic film on a movable microstructure. The microstructure, which may be a cantilever, membrane, bridge, or other microelement, moves under the influence of an acceleration a known displacement predicted by the configuration and materials selected, and the resulting change in the electrical resistance of the MR sensor can be used to calculate the displacement. Using a micromachining approach, very thin silicon and silicon nitride membranes are fabricated in one preferred embodiment by means of anisotropic etching of silicon wafers. Other approaches include reactive ion etching of silicon on insulator (SOI), or Low Pressure Chemical Vapor Deposition of silicon nitride films over silicon substrates. The device is found to be improved with the use of giant magnetoresistive elements to detect changes in the local magnetic field.

Olivas, John D.↗

NASA NTRS1981

MAGSAT: Vector magnetometer absolute sensor alignment determination

A procedure is described for accurately determining the absolute alignment of the magnetic axes of a triaxial magnetometer sensor with respect to an external, fixed, reference coordinate system. The method does not require that the magnetic field vector orientation, as generated by a triaxial calibration coil system, be known to better than a few degrees from its true position, and minimizes the number of positions through which a sensor assembly must be rotated to obtain a solution. Computer simulations show that accuracies of better than 0.4 seconds of arc can be achieved under typical test conditions associated with existing magnetic test facilities. The basic approach is similar in nature to that presented by McPherron and Snare (1978) except that only three sensor positions are required and the system of equations to be solved is considerably simplified. Applications of the method to the case of the MAGSAT Vector Magnetometer are presented and the problems encountered discussed.

Acuna, M. H.↗

NASA NTRS2003

Magnetic Bearing Controller Improvements for High Speed Flywheel System

A magnetic bearing control system for a high-speed flywheel system is described. The flywheel utilizes a five axis active magnetic bearing system, using eddy current sensors for position feedback to the bearing controller. Magnetic bearing controller features designed to improve flywheel operation and testing are described. Operational improvements include feed forward control to compensate for rotor imbalance, moving notch filtering to compensate for synchronous and harmonic rotational noise, and fixed notching to prevent rotor bending mode excitation. Testing improvements include adding safe gain, bearing current hold, bearing current zero, and excitation input features. Performance and testing improvements provided by these features are measured and discussed.

Dever, Timothy P.↗

NASA NTRS2010

Wirelessly Interrogated Wear or Temperature Sensors

Sensors for monitoring surface wear and/or temperature without need for wire connections have been developed. Excitation and interrogation of these sensors are accomplished by means of a magnetic-field-response recorder. In a sensor of the present type as in the previously reported ones, the capacitance and, thus, the resonance frequency, varies as a known function of the quantity of interest that one seeks to determine. Hence, the resonance frequency is measured and used to calculate the quantity of interest.

Woodard, Stanley E.↗

NASA NTRS2014

Wireless Capacitive Pressure Sensor Operating up to 400 Celcius from 0 to 100 psi Utilizing Power Scavenging

In this paper, a wireless capacitive pressure sensor developed for the health monitoring of aircraft engines has been demonstrated. The sensing system is composed of a Clapp-type oscillator that operates at 131 MHz. The Clapp oscillator is fabricated on a alumina substrate and consists of a Cree SiC (silicon carbide) MESFET (Metal Semiconductor Field Effect Transistors), this film inductor, Compex chip capacitors and Sporian Microsystem capacitive pressure sensor. The resonant tank circuit within the oscillator is made up of the pressure sensor and a spiral thin film inductor, which is used to magnetically couple the wireless pressure sensor signal to a coil antenna placed over 1 meter away. 75% of the power used to bias the sensing system is generated from thermoelectric power modules. The wireless pressure sensor is operational at room temperature through 400 C from 0 to 100 psi and exhibits a frequency shift of over 600 kHz.

Scardelletti, Maximilian C.↗

NASA NTRSDate not supplied

Dione: A Pathfinder Mission for Understanding the Iono-sphere-Thermosphere Responses to Magnetospheric Forcing

Dione is a NASA small satellite prototype for future constellations that in different configurations will provide global and localized measurements of Ionosphere-Thermosphere responses to Magnetospheric energy input in a variety of scales, enabling their better forecast and prediction. This is done with a comprehensive sensor package which includes four instruments: a miniaturized fluxgate magnetometer providing magnetic field measurements with two sensor heads, an ion sensor that measures vector plasma drifts and deduce the in-situ electric fields, an electrostatic analyzer that measures precipitating electrons and up-going secondary electrons, and a neutral mass spectrometer measuring total neutral density and composition. Dione is 3-axis stabilized in a circular low-earth (400-600 km), high-inclination orbit, traversing the auroral precipitation and high latitude currents in every orbit. This paper focuses on the mission-level architecture, but provides contextual information on the science objectives, instruments, and space-craft.

Jaime Esper↗

NASA NTRS1992

Precision measurement of magnetic characteristics of an article with nullification of external magnetic fields

An apparatus for characterizing the magnetic field of a device under test is discussed. The apparatus is comprised of five separate devices: (1) a device for nullifying the ambient magnetic fields in a test environment area with a constant applied magnetic field; (2) a device for rotating the device under test in the test environment area; (3) a device for sensing the magnetic field (to obtain a profile of the magnetic field) at a sensor location which is along the circumference of rotation; (4) a memory for storing the profiles; and (5) a processor coupled to the memory for characterizing the magnetic field of the device from the magnetic field profiles thus obtained.

Honess, Shawn B.↗

NASA NTRS2014

Wireless Open-Circuit In-Plane Strain and Displacement Sensor Requiring No Electrical Connections

A wireless in-plane strain and displacement sensor includes an electrical conductor fixedly coupled to a substrate subject to strain conditions. The electrical conductor is shaped between its ends for storage of an electric field and a magnetic field, and remains electrically unconnected to define an unconnected open-circuit having inductance and capacitance. In the presence of a time-varying magnetic field, the electrical conductor so-shaped resonates to generate harmonic electric and magnetic field responses. The sensor also includes at least one electrically unconnected electrode having an end and a free portion extending from the end thereof. The end of each electrode is fixedly coupled to the substrate and the free portion thereof remains unencumbered and spaced apart from a portion of the electrical conductor so-shaped. More specifically, at least some of the free portion is disposed at a location lying within the magnetic field response generated by the electrical conductor. A motion guidance structure is slidingly engaged with each electrode's free portion in order to maintain each free portion parallel to the electrical conductor so-shaped.

Woodard, Stanley E.↗

NASA NTRS1977

Large, high resolution integrating TV sensor for astronomical appliations

A magnetically focused SEC tube developed for photometric applications is described. Efforts to design a 70 mm version of the tube which meets the ST f/24 camera requirements of the space telescope are discussed. The photometric accuracy of the 70 mm tube is executed to equal that of the previously developed 35 mm tube. The tube meets the criterion of 50 percent response at 20 cycles/mm in the central region of the format, and, with the removal of the remaining magnetic parts, this spatial frequency is expected over almost all of the format. Since the ST f/24 camera requires sensitivity in the red as well as the ultraviolet and visible spectra, attempts were made to develop tubes with this ability. It was found that it may be necessary to choose between red and u.v. sensitivity and tradeoff red sensitivity for low background. Results of environmental tests indicate no substantive problems in utilizing it in a flight camera system that will meet the space shuttle launch requirements.

Spitzer, L. J.↗

NASA NTRS2017

Preliminary GN&C Design for the On-Orbit Autonomous Assembly of Nanosatellite Demonstration Mission

Small spacecraft autonomous rendezvous and docking (ARD) is an essential technology for future space structure assembly missions. The On-orbit Autonomous Assembly of Nanosatellites (OAAN) team at NASA Langley Research Center (LaRC) intends to demonstrate the technology to autonomously dock two nanosatellites to form an integrated system. The team has developed a novel magnetic capture and latching mechanism that allows for docking of two CubeSats without precise sensors and actuators. The proposed magnetic docking hardware not only provides the means to latch the CubeSats, but it also significantly increases the likelihood of successful docking in the presence of relative attitude and position errors. The simplicity of the design allows it to be implemented on many CubeSat rendezvous missions. Prior to demonstrating the docking subsystem capabilities on orbit, the GN&C subsystem should have a robust design such that it is capable of bringing the CubeSats from an arbitrary initial separation distance of as many as a few thousand kilometers down to a few meters. The main OAAN Mission can be separated into the following phases: 1) Launch, checkout, and drift, 2) Far-Field Rendezvous or Drift Recovery, 3) Proximity Operations, 4) Docking. This paper discusses the preliminary GN&C design and simulation results for each phase of the mission.

Pei, Jing↗

NASA NTRS2015

Relativistic Electron Response to the Combined Magnetospheric Impact of a Coronal Mass Ejection Overlapping with a High-Speed Stream: Van Allen Probes Observations

During early November 2013, the magnetosphere experienced concurrent driving by a coronal mass ejection (CME) during an ongoing high-speed stream (HSS) event. The relativistic electron response to these two kinds of drivers, i.e., HSS and CME, is typically different, with the former often leading to a slower buildup of electrons at larger radial distances, while the latter energizing electrons rapidly with flux enhancements occurring closer to the Earth. We present a detailed analysis of the relativistic electron response including radial profiles of phase space density as observed by both Magnetic Electron and Ion Sensor (MagEIS) and Relativistic Electron Proton Telescope instruments on the Van Allen Probes mission. Data from the MagEIS instrument establish the behavior of lower energy (<1 MeV) electrons which span both intermediary and seed populations during electron energization. Measurements characterizing the plasma waves and magnetospheric electric and magnetic fields during this period are obtained by the Electric and Magnetic Field Instrument Suite and Integrated Science instrument on board Van Allen Probes, Search Coil Magnetometer and Flux Gate Magnetometer instruments on board Time History of Events and Macroscale Interactions during Substorms, and the low-altitude Polar-orbiting Operational Environmental Satellites. These observations suggest that during this time period, both radial transport and local in situ processes are involved in the energization of electrons. The energization attributable to radial diffusion is most clearly evident for the lower energy (<1 MeV) electrons, while the effects of in situ energization by interaction of chorus waves are prominent in the higher-energy electrons.

Magnetosphere↗

NASA NTRS1981

Attitude measurement: Principles and sensors

Tools used in the measurement of satellite attitude are described. Attention is given to the elements that characterize an attitude sensor, the references employed (stars, moon, Sun, Earth, magnetic fields, etc.), and the detectors (optical, magnetic, and inertial). Several examples of attitude sensors are described, including sun sensors, star sensors, earth sensors, triaxial magnetometers, and gyrometers. Finally, sensor combinations that make it possible to determine a complete attitude are considered; the SPOT attitude measurement system and a combined CCD star sensor-gyrometer system are discussed.

Duchon, P.↗

NASA NTRS1981

Design, development, and field demonstration of a remotely deployable water quality monitoring system

A prototype water quality monitoring system is described which offers almost continuous in situ monitoring. The two-man portable system features: (1) a microprocessor controlled central processing unit which allows preprogrammed sampling schedules and reprogramming in situ; (2) a subsurface unit for multiple depth capability and security from vandalism; (3) an acoustic data link for communications between the subsurface unit and the surface control unit; (4) eight water quality parameter sensors; (5) a nonvolatile magnetic bubble memory which prevents data loss in the event of power interruption; (6) a rechargeable power supply sufficient for 2 weeks of unattended operation; (7) a water sampler which can collect samples for laboratory analysis; (8) data output in direct engineering units on printed tape or through a computer compatible link; (9) internal electronic calibration eliminating external sensor adjustment; and (10) acoustic location and recovery systems. Data obtained in Saginaw Bay, Lake Huron are tabulated.

Wallace, J. W.↗

NASA NTRS2017

Ground Demonstration on the Autonomous Docking of Two 3U CubeSats Using a Novel Permanent-Magnet Docking Mechanism

Small spacecraft autonomous rendezvous and docking is an essential technology for future space structure assembly missions. A novel magnetic capture and latching mechanism is analyzed that allows for docking of two CubeSats without precise sensors and actuators. The proposed magnetic docking hardware not only provides the means to latch the CubeSats but it also significantly increases the likelihood of successful docking in the presence of relative attitude and position errors. The simplicity of the design allows it to be implemented on many CubeSat rendezvous missions. A CubeSat 3-DOF ground demonstration effort is on-going at NASA Langley Research Center that enables hardware-in-the loop testing of the autonomous approach and docking of a follower CubeSat to an identical leader CubeSat. The test setup consists of a 3 meter by 4 meter granite table and two nearly frictionless air bearing systems that support the two CubeSats. Four cold-gas on-off thrusters are used to translate the follower towards the leader, while a single reaction wheel is used to control the attitude of each CubeSat. An innovative modified pseudo inverse control allocation scheme was developed to address interactions between control effectors. The docking procedure requires relatively high actuator precision, a novel minimal impulse bit mitigation algorithm was developed to minimize the undesirable deadzone effects of the thrusters. Simulation of the ground demonstration shows that the Guidance, Navigation, and Control system along with the docking subsystem leads to successful docking under 3-sigma dispersions for all key system parameters. Extensive simulation and ground testing will provide sufficient confidence that the proposed docking mechanism along with the choosen suite of sensors and actuators will perform successful docking in the space environment.

Pei, Jing↗

NASA NTRS2004

An Overview of Magnetic Bearing Technology for Gas Turbine Engines

The idea of the magnetic bearing and its use in exotic applications has been conceptualized for many years, over a century, in fact. Patented, passive systems using permanent magnets date back over 150 years. More recently, scientists of the 1930s began investigating active systems using electromagnets for high-speed ultracentrifuges. However, passive magnetic bearings are physically unstable and active systems only provide proper stiffness and damping through sophisticated controllers and algorithms. This is precisely why, until the last decade, magnetic bearings did not become a practical alternative to rolling element bearings. Today, magnetic bearing technology has become viable because of advances in micro-processing controllers that allow for confident and robust active control. Further advances in the following areas: rotor and stator materials and designs which maximize flux, minimize energy losses, and minimize stress limitations; wire materials and coatings for high temperature operation; high-speed micro processing for advanced controller designs and extremely robust capabilities; back-up bearing technology for providing a viable touchdown surface; and precision sensor technology; have put magnetic bearings on the forefront of advanced, lubrication free support systems. This paper will discuss a specific joint program for the advancement of gas turbine engines and how it implies the vitality of magnetic bearings, a brief comparison between magnetic bearings and other bearing technologies in both their advantages and limitations, and an examination of foreseeable solutions to historically perceived limitations to magnetic bearing.

Clark, Daniel J.↗

NASA NTRS1994

Non-volatile magnetic random access memory

Improvements are made in a non-volatile magnetic random access memory. Such a memory is comprised of an array of unit cells, each having a Hall-effect sensor and a thin-film magnetic element made of material having an in-plane, uniaxial anisotropy and in-plane, bipolar remanent magnetization states. The Hall-effect sensor is made more sensitive by using a 1 m thick molecular beam epitaxy grown InAs layer on a silicon substrate by employing a GaAs/AlGaAs/InAlAs superlattice buffering layer. One improvement avoids current shunting problems of matrix architecture. Another improvement reduces the required magnetizing current for the micromagnets. Another improvement relates to the use of GaAs technology wherein high electron-mobility GaAs MESFETs provide faster switching times. Still another improvement relates to a method for configuring the invention as a three-dimensional random access memory.

Katti, Romney R.↗

NASA NTRS2003

Performance Evaluation Modeling of Network Sensors

Substantial benefits are promised by operating many spatially separated sensors collectively. Such systems are envisioned to consist of sensor nodes that are connected by a communications network. A simulation tool is being developed to evaluate the performance of networked sensor systems, incorporating such metrics as target detection probabilities, false alarms rates, and classification confusion probabilities. The tool will be used to determine configuration impacts associated with such aspects as spatial laydown, and mixture of different types of sensors (acoustic, seismic, imaging, magnetic, RF, etc.), and fusion architecture. The QualNet discrete-event simulation environment serves as the underlying basis for model development and execution. This platform is recognized for its capabilities in efficiently simulating networking among mobile entities that communicate via wireless media. We are extending QualNet's communications modeling constructs to capture the sensing aspects of multi-target sensing (analogous to multiple access communications), unimodal multi-sensing (broadcast), and multi-modal sensing (multiple channels and correlated transmissions). Methods are also being developed for modeling the sensor signal sources (transmitters), signal propagation through the media, and sensors (receivers) that are consistent with the discrete event paradigm needed for performance determination of sensor network systems. This work is supported under the Microsensors Technical Area of the Army Research Laboratory (ARL) Advanced Sensors Collaborative Technology Alliance.

probability of detection↗

NASA NTRS2006

Galfenol Tactile Sensor Array and Visual Mapping System

The smart material, Galfenol, is being explored for its uses as a magnetostrictive material. This project seeks to determine if Galfenol can be used as a tactile sensor in a 2-D grid array, magnetic circuit system. When used within a magnetic circuit, Galfenol indicates induced stress and force as a change in flux, due to a change in permeability of the material. The change in flux is detected by Giant MagnetoResistive (GMR) Sensors, which produce a voltage change proportional to the field change. By using Galfenol in an array, this research attempts to create a sensory area. Galfenol is an alloy made of Iron and Gallium. FexGax, where 15 less than or equal to x less than or equal to 28, creates a material with useful mechanical and transduction attributes (Clark et al and Kell). Galfenol is also distinguished by the crystalline structure of the material. Two types currently exist: single crystal and polycrystalline. Single crystal has higher transduction coefficients than polycrystalline, but is more costly. Polycrystalline Galfenol is currently available as either production or research grade. The designations are related to the sample growth rate with the slower rate being the research grade. The slower growth rate more closely resembles the single crystal Galfenol properties. Galfenol 17.5- 18% research grade is used for this experiment, provided by Etrema Products Inc. The magnetic circuit and sensor array is first built at the macro scale so that the design can be verified. After the macro scale is proven, further development will move the system to the nano-level. Recent advances in nanofabrication have enabled Galfenol to be grown as nanowires. Using the nanowires, research will seek to create high resolution tactile sensors with spatial resolutions similar to human finger tips, but with greater force ranges and sensitivity capabilities (Flatau & Stadler). Possible uses of such systems include robotics and prosthetics.

Hale, Kathleen↗