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NASA NTRS1994

ARK: Autonomous mobile robot in an industrial environment

This paper describes research on the ARK (Autonomous Mobile Robot in a Known Environment) project. The technical objective of the project is to build a robot that can navigate in a complex industrial environment using maps with permanent structures. The environment is not altered in any way by adding easily identifiable beacons and the robot relies on naturally occurring objects to use as visual landmarks for navigation. The robot is equipped with various sensors that can detect unmapped obstacles, landmarks and objects. In this paper we describe the robot's industrial environment, it's architecture, a novel combined range and vision sensor and our recent results in controlling the robot in the real-time detection of objects using their color and in the processing of the robot's range and vision sensor data for navigation.

Nickerson, S. B.↗
NASA NTRS1994

Vision based object pose estimation for mobile robots

Mobile robot navigation using visual sensors requires that a robot be able to detect landmarks and obtain pose information from a camera image. This paper presents a vision system for finding man-made markers of known size and calculating the pose of these markers. The algorithm detects and identifies the markers using a weighted pattern matching template. Geometric constraints are then used to calculate the position of the markers relative to the robot. The selection of geometric constraints comes from the typical pose of most man-made signs, such as the sign standing vertical and the dimensions of known size. This system has been tested successfully on a wide range of real images. Marker detection is reliable, even in cluttered environments, and under certain marker orientations, estimation of the orientation has proven accurate to within 2 degrees, and distance estimation to within 0.3 meters.

Wu, Annie↗
NASA NTRS1994

Total hydrocarbon analysis by ion mobility spectrometry

Astronauts must be alerted quickly to chemical leaks that compromise their health and the success of their missions. An ideal leak detector would be equally sensitive to all compounds that might constitute a hazard and insensitive to nontoxic compounds. No ideal sensor exists; thus, selection of a methodology is a series of compromises. The commonly used methods are either insensitive at the low exposure levels set by OSHA, NASA, and other organizations or are selectively insensitive to important classes of chemicals such as Freons. After extensive study and experience, the Toxicology Group at JSC has selected ion mobility spectrometry (IMS) for development into a broad range, sensitive detector. In addition to the sensing method, signal processing is important leak detection because a background signal can be expected at all times. The leak-detecting instrument must be programmed to discriminate between authentic leaks and background fluctuations caused by routine operations. The results of an evaluation of the prototype THA is presented in terms related to spacecraft operations. The evaluation included determination of instrumental parameters such as stability and response times. We also included responses to some common components of spacecraft atmospheres in pure form and in binary and ternary mixtures. The output of the four algorithms to the mixtures was found to be noticeably different. These responses are compared on the basis of their utility for signaling a chemical leak. As a means of evaluating its resistance to a falsely positive response, the THA was challenged with carbon dioxide and methane, compounds whose concentrations normally increase in spacecraft air during human habitation. The instrument showed virtually no response to these interferences. Although the prototype THA is designed for space flight, this detector is expected to be useful for field screening at chemical waste dumps and other environmentally sensitive locations.

Cross, John H.↗
NASA NTRS1993

Advanced communication satellites worldwide - Satellites of opportunity for the ACTS mobile terminal

Space agencies worldwide are involved in advanced satellite communication systems. This paper presents an overview of these satellites and related technologies in the U.S., Europe, and Japan. They are geostationary satellites using high frequency bands such as K/Ka (20/30 GHz) and O-band (millimeter wave), as well as optical frequencies. The similarity of these programs demonstrate a common interest to develop large capacity satellite communication systems, and shows that closer international cooperation could be set up. The ACTS Mobile Terminal (AMT) project discussed here is such an example. The AMT's compatibility with satellites other than ACTS has been studied, and a proposed common experiment is presented here. The Japanese Engineering Test Satellite ETS-VI has been identified as the best initial 'satellite of opportunity' for AMT in this preliminary assessment.

Girardey, Catherine C.↗
NASA NTRS1994

Integration for navigation on the UMASS mobile perception lab

Integration of real-time visual procedures for use on the Mobile Perception Lab (MPL) was presented. The MPL is an autonomous vehicle designed for testing visually guided behavior. Two critical areas of focus in the system design were data storage/exchange and process control. The Intermediate Symbolic Representation (ISR3) supported data storage and exchange, and the MPL script monitor provided process control. Resource allocation, inter-process communication, and real-time control are difficult problems which must be solved in order to construct strong autonomous systems.

Draper, Bruce↗
NASA NTRS1994

ACTS mobile propagation campaign

Preliminary results are presented for three propagation measurement campaigns involving a mobile receiving laboratory and 20 GHz transmissions from the Advanced Communications Technology Satellite (ACTS). Four 1994 campaigns were executed during weekly periods in and around Austin, Texas in February and May, in Central Maryland during March, and in Fairbanks, Alaska and environs in June. Measurements tested the following effects at 20 GHz: (1) attenuation due to roadside trees with and without foliage, (2) multipath effects for scenarios in which line-of-sight paths were unshadowed, (3) fades due to terrain and roadside obstacles, (4) fades due to structures in urban environs, (5) single tree attenuation, and (6) effects of fading at low elevation angles (8 deg in Fairbanks, Alaska) and high elevation angles (55 deg in Austin, Texas). Results presented here cover sampled measurements in Austin, Texas for foliage and non-foliage cases and in Central Maryland for non-foliage runs.

Goldhirsh, Julius↗
NASA NTRS1994

Photogrammetric mobile satellite service prediction

Photographic images of the sky were taken with a camera through a fisheye lens with a 180 deg field-of-view. The images of rural, suburban, and urban scenes were analyzed on a computer to derive quantitative information about the elevation angles at which the sky becomes visible. Such knowledge is needed by designers of mobile and personal satellite communications systems and is desired by customers of these systems. The 90th percentile elevation angle of the skyline was found to be 10 deg, 17 deg, and 51 deg in the three environments. At 8 deg, 75 percent, 75 percent, and 35 percent of the sky was visible, respectively. The elevation autocorrelation fell to zero with a 72 deg lag in the rural and urban environment and a 40 deg lag in the suburb. Mean estimation errors are below 4 deg.

Akturan, Riza↗
NASA NTRS1995

A satellite-tracking millimeter-wave reflector antenna system for mobile satellite-tracking

A miniature dual-band two-way mobile satellite tracking antenna system mounted on a movable ground vehicle includes a miniature parabolic reflector dish having an elliptical aperture with major and minor elliptical axes aligned horizontally and vertically, respectively, to maximize azimuthal directionality and minimize elevational directionality to an extent corresponding to expected pitch excursions of the movable ground vehicle. A feed-horn has a back end and an open front end facing the reflector dish and has vertical side walls opening out from the back end to the front end at a lesser horn angle and horizontal top and bottom walls opening out from the back end to the front end at a greater horn angle. An RF circuit couples two different signal bands between the feed-horn and the user. An antenna attitude controller maintains an antenna azimuth direction relative to the satellite by rotating it in azimuth in response to sensed yaw motions of the movable ground vehicle so as to compensate for the yaw motions to within a pointing error angle. The controller sinusoidally dithers the antenna through a small azimuth dither angle greater than the pointing error angle while sensing a signal from the satellite received at the reflector dish, and deduces the pointing angle error from dither-induced fluctuations in the received signal.

Densmore, Arthur C.↗
NASA NTRS1995

The use of ion mobility spectrometry and gas chromatography/mass spectrometry for the detection of illicit drugs on clandestine records

Illicit drug distribution has over the past decade grown tremendously from simple 'drug pushing' where drugs were distributed from poorly organized individuals to today's well organized and well financed drug cartels. This change to a more 'corporate-like' atmosphere has resulted in a greater use of record keeping to monitor the profits generated. The use of record keeping by drug distributors is not restricted to high level drug smugglers but is used at all levels within the distribution network. Dealers at all levels including street dealers are generally 'fronted', given on consignment quantities of drugs that they in turn sell to customers, thereby requiring the need for records to keep track of drug sales versus liabilities. These records because of their illicit nature are often encrypted to hide the fact that they are indeed records of drug transactions. The creation of a handwritten notation concerning a drug transaction is normally brought on because of a purchase or sale. In a sale, this is commonly accomplished through a consignment, or the designation of a quantity to a customer to whom that amount has been 'fronted'. Because this activity generates a debt, it follows that an accounting for payments made, as well as new transactions completed, is only logical. One of the most common means of representing these is through an 'accounting flow', in which payments are subtracted from a running balance while new sales are added to it. The examination of illicit drug records has been the key to the prosecution of numerous federal, state, and local drug cases for a number of years. The Document Section of the FBI Laboratory, through its Racketeering Records Analysis Unit (RRAU), has been involved in such analytical efforts since 1983. Detailed analytical research brought about an evolution in the systematic approach utilized in the RRAU since that time. The close proximity of the drugs to the records often results in trace drug evidence being transferred to the records. The detection of trace drug residue on surfaces by ion mobility spectrometry (IMS) is well documented in literature. The following procedure will deal primarily with the newer techniques of trace drug analysis and drug record analysis developed by the Chemistry/Toxicology Unit of the FBI Laboratory since the more traditional techniques of latent finger print analysis and document analysis are well known.

Donnelly, Brian↗
NASA NTRS1995

Hand-portable gas chromatography-ion mobility spectrometer for the determination of the freshness of fish

A hand-held, portable gas chromatography-ion mobility spectrometer (GC-IMS) device was used to detect the presence of volatile amine compounds in the headspace of decomposing fish. The Food and Drug Administration (FDA) largely relies on olfactory discrimination with respect to fresh and spoiled, frozen and unfrozen fish. The fish are delivered at ship docks on pallets, and each pallet of fish can range from 30-40 thousand dollars in value. Fresh fish were placed in a teflon bag and the direct headspace was interrogated. In the first three days, only low molecular weight volatile amines were detected. On the fourth day, a number of spectral signatures were observed which indicated the presence of 1,5-diaminopentane, cadaverine. Analyses typically took from 0.5-1 minute.

Snyder, A. Peter↗
NASA NTRS1995

Gas chromatography/ion mobility spectrometry as a hyphenated technique for improved explosives detection and analysis

Ion Mobility Spectrometry (IMS) is currently being successfully applied to the problem of on-line trace detection of plastic and other explosives in airports and other facilities. The methods of sample retrieval primarily consist of batch sampling for particulate residue on a filter card for introduction into the IMS. The sample is desorbed into the IMS using air as the carrier and negative ions of the explosives are detected, some as an adduct with a reagent ion such as Cl(-). Based on studies and tests conducted by different airport authorities, this method seems to work well for low vapor pressure explosives such as RDX and PETN, as well as TNT that are highly adsorptive and can be found in nanogram quantities on contaminated surfaces. Recently, the changing terrorist threat and the adoption of new marking agents for plastic explosives has meant that the sample introduction and analysis capabilities of the IMS must be enhanced in order to keep up with other detector developments. The IMS has sufficient analytical resolution for a few threat compounds but the IMS Plasmogram becomes increasingly more difficult to interpret when the sample mixture gets more complex.

Mercado, AL↗
NASA NTRS1995

Application of Ion Mobility Spectrometry (IMS) in forensic chemistry and toxicology with focus on biological matrices

The IMS (Ion Mobility Spectroscopy) instrument 'Ionscan' takes advantage of the fact that trace quantities of illicit drugs are adsorbed on dust particles on clothes, in cars and on other items of evidence. The dust particles are collected on a membrane filter by a special attachment on a vacuum cleaner. The sample is then directly inserted into the spectrometer and can be analyzed immediately. We show casework applications of a forensic chemistry and toxicology laboratory. One new application of IMS in forensic chemistry is the detection of psilocybin in dried mushrooms without any further sample preparation.

Bernhard, Werner↗
NASA NTRS1995

Signal processing for ION mobility spectrometers

Signal processing techniques for systems based upon Ion Mobility Spectrometry will be discussed in the light of 10 years of experience in the design of real-time IMS. Among the topics to be covered are compensation techniques for variations in the number density of the gas - the use of an internal standard (a reference peak) or pressure and temperature sensors. Sources of noise and methods for noise reduction will be discussed together with resolution limitations and the ability of deconvolution techniques to improve resolving power. The use of neural networks (either by themselves or as a component part of a processing system) will be reviewed.

Taylor, S.↗
NASA NTRS1995

Quantitative analysis of volatile organic compounds using ion mobility spectra and cascade correlation neural networks

Ion Mobility Spectrometry (IMS) is a powerful technique for trace organic analysis in the gas phase. Quantitative measurements are difficult, because IMS has a limited linear range. Factors that may affect the instrument response are pressure, temperature, and humidity. Nonlinear calibration methods, such as neural networks, may be ideally suited for IMS. Neural networks have the capability of modeling complex systems. Many neural networks suffer from long training times and overfitting. Cascade correlation neural networks train at very fast rates. They also build their own topology, that is a number of layers and number of units in each layer. By controlling the decay parameter in training neural networks, reproducible and general models may be obtained.

Harrington, Peter DEB.↗
NASA NTRS1994

Linear stability of a layered fluid with mobile surface plates

We develop a general method of calculating the linear stability of a fluid with homogeneous layers that is heated from below. The method employs a propagator technique to obtain expressions for the fluid velocity, stress, and temperature. The principal advantage of the method is the ease with which solutions are adapted to a wide variety of boundary conditions and fluid properties. We demonstrate the utility of the method using three examples which quantify the effects of (1) rheological layering, (2) mobile plates at the surface, and (3) multiple phase transitions. Each example is presented in the context of Earth's mantle. In the first example, we predict that convection becomes confined to the upper mantle once the viscosity increase between the upper and lower mantle exceeds a factor of 2000, consistent with the nonlinear calculations of Davies (1977). In the second example we find that the heat flux variations in a convecting fluid with variably sized, surface plates can be attributed, in part, to changes in the critical Rayleigh number. The linear stability of a fluid with multiple phase transitions is significantly affects by the locations of the transitions. We find that phase transitions have their largest effect when they are located at the center of the fluid layer and become much less important when they are located near the exterior boundaries.

Buffett, B. A.↗
NASA NTRS1995

Extended Empirical Roadside Shadowing model from ACTS mobile measurements

Employing multiple data bases derived from land-mobile satellite measurements using the Advanced Communications Technology Satellite (ACTS) at 20 GHz, MARECS B-2 at 1.5 GHz, and helicopter measurements at 870 MHz and 1.5 GHz, the Empirical Road Side Shadowing Model (ERS) has been extended. The new model (Extended Empirical Roadside Shadowing Model, EERS) may now be employed at frequencies from UHF to 20 GHz, at elevation angles from 7 to 60 deg and at percentages from 1 to 80 percent (0 dB fade). The EERS distributions are validated against measured ones and fade deviations associated with the model are assessed. A model is also presented for estimating the effects of foliage (or non-foliage) on 20 GHz distributions, given distributions from deciduous trees devoid of leaves (or in full foliage).

Goldhirsh, Julius↗
NASA NTRS1995

Emergency response mobile robot for operations in combustible atmospheres

A mobile, self-powered, self-contained, and remote-controlled robot is presented. The robot is capable of safely operating in a combustible atmosphere and providing information about the atmosphere to the operator. The robot includes non-sparking and non-arcing electro-mechanical and electronic components designed to prevent the robot from igniting the combustible atmosphere. The robot also includes positively pressurized enclosures that house the electromechanical and electronic components of the robot and prevent intrusion of the combustible atmosphere into the enclosures. The enclosures are interconnected such that a pressurized gas injected into any one of the enclosures is routed to all the other enclosures through the interconnections. It is preferred that one or more sealed internal channels through structures intervening between the enclosures be employed. Pressure transducers for detecting if the pressure within the enclosures falls below a predetermined level are included. The robot also has a sensing device for determining the types of combustible substances in the surrounding atmosphere, as well as the concentrations of each type of substance relative to a pre-determined lower explosive limit (LEL). In addition, the sensing device can determine the percent level of oxygen present in the surrounding atmosphere.

Stone, Henry W.↗