Engineering topics

Null, Cynthia H.

Publications and source records attributed to Null, Cynthia H..

At least 37 records · Page 2

NASA NTRS1998

Masking by Gratings Predicted by an Image Sequence Discriminating Model: Testing Models for Perceptual Discrimination Using Repeatable Noise

Adding noise to stimuli to be discriminated allows estimation of observer classification functions based on the correlation between observer responses and relevant features of the noisy stimuli. Examples will be presented of stimulus features that are found in auditory tone detection and visual vernier acuity. using the standard signal detection model (Thurstone scaling), we derive formulas to estimate the proportion of the observers decision variable variance that is controlled by the added noise. one is based on the probability of agreement of the observer with him/herself on trials with the same noise sample. Another is based on the relative performance of the observer and the model. When these do not agree, the model can be rejected. A second derivation gives the probability of agreement of observer and model when the observer follows the model except for internal noise. Agreement significantly less than this amount allows rejection of the model.

Ahumada, Albert J., Jr.↗

NASA NTRS1998

Cockpit Interruptions and Distractions: Effective Management Requires a Careful Balancing Act

Managing several tasks concurrently is an everyday part of cockpit operations. For the most part, crews handle concurrent task demands efficiently, yet crew preoccupation with one task to the detriment of performing other tasks is one of the more common forms of error in the cockpit. Most pilots are familiar with the December 1972 L1011 crash that occurred when the crew became preoccupied with a landing gear light malfunction and failed to notice that someone had inadvertently bumped off the autopilot. More recently a DC-9 landed gear-up in Houston when the crew, preoccupied with an stabilized approach, failed to recognize that the gear was not down because they had not switched the hydraulic pumps to high. We have recently started a research project to study why crews are vulnerable to these sorts of errors. As part of that project we reviewed NTSB reports of accidents attributed to crew error; we concluded that nearly half of these accidents involved lapses of attention associated with interruptions, distractions, or preoccupation with one task to the exclusion of another task. We have also analyzed 107 ASRS reports involving competing tasks; we present here some of our conclusions from those ASRS reports. These 107 reports involved 21 different types of routine tasks crews neglected at a critical moment while attending to another task. Sixty-nine percent of the neglected tasks involved either failure to monitor the current status or position of the aircraft or failure to monitor the actions of the pilot flying or taxiing. Thirty-four different types of competing activities distracted or preoccupied the pilots. Ninety percent of these competing activities fell into one of four broad categories: communication (e.g., discussion among crew or radio communication), heads-down work (e.g., programming the FMS or reviewing approach plates), responding to abnormals, or searching for VMC traffic. We will discuss examples of each of these four categories and suggest things crews can do to reduce their vulnerability to these and similar situations.

Dismukes, R. K.↗

NASA NTRS1998

Errors in Aviation Decision Making: Bad Decisions or Bad Luck?

Despite efforts to design systems and procedures to support 'correct' and safe operations in aviation, errors in human judgment still occur and contribute to accidents. In this paper we examine how an NDM (naturalistic decision making) approach might help us to understand the role of decision processes in negative outcomes. Our strategy was to examine a collection of identified decision errors through the lens of an aviation decision process model and to search for common patterns. The second, and more difficult, task was to determine what might account for those patterns. The corpus we analyzed consisted of tactical decision errors identified by the NTSB (National Transportation Safety Board) from a set of accidents in which crew behavior contributed to the accident. A common pattern emerged: about three quarters of the errors represented plan-continuation errors, that is, a decision to continue with the original plan despite cues that suggested changing the course of action. Features in the context that might contribute to these errors were identified: (a) ambiguous dynamic conditions and (b) organizational and socially-induced goal conflicts. We hypothesize that 'errors' are mediated by underestimation of risk and failure to analyze the potential consequences of continuing with the initial plan. Stressors may further contribute to these effects. Suggestions for improving performance in these error-inducing contexts are discussed.

Orasanu, Judith↗

NASA NTRS1998

Operator Localization of Virtual Objects

Errors in the localization of nearby virtual objects presented via see-through, helmet mounted displays are examined as a function of viewing conditions and scene content. Monocular, biocular or stereoscopic presentation of the virtual objects, accommodation (required focus), subjects'age, and the position of physical surfaces are examined. Nearby physical surfaces are found to introduce localization errors that differ depending upon the other experimental factors. The apparent physical size and transparency of the virtual objects and physical surfaces respectively are also influenced by their relative position when superimposed. Design implications are discussed.

Ellis, Stephen R.↗

NASA NTRS1998

Pursuit Eye Movements

When viewing objects, primates use a combination of saccadic and pursuit eye movements to stabilize the retinal image of the object of regard within the high-acuity region near the fovea. Although these movements involve widespread regions of the nervous system, they mix seamlessly in normal behavior. Saccades are discrete movements that quickly direct the eyes toward a visual target, thereby translating the image of the target from an eccentric retinal location to the fovea. In contrast, pursuit is a continuous movement that slowly rotates the eyes to compensate for the motion of the visual target, minimizing the blur that can compromise visual acuity. While other mammalian species can generate smooth optokinetic eye movements - which track the motion of the entire visual surround - only primates can smoothly pursue a single small element within a complex visual scene, regardless of the motion elsewhere on the retina. This ability likely reflects the greater ability of primates to segment the visual scene, to identify individual visual objects, and to select a target of interest.

Krauzlis, Rich↗

NASA NTRS1998

Challenges Facing 3-D Audio Display Design for Multimedia

The challenges facing successful multimedia presentation depend largely on the expectations of the designer and end user for a given application. Perceptual limitations in distance, elevation and azimuth sound source simulation differ significantly between headphone and cross-talk cancellation loudspeaker listening and therefore must be considered. Simulation of an environmental context is desirable but the quality depends on processing resources and lack of interaction with the host acoustical environment. While techniques such as data reduction of head-related transfer functions have been used widely to improve simulation fidelity, another approach involves determining thresholds for environmental acoustic events. Psychoacoustic studies relevant to this approach are reviewed in consideration of multimedia applications

Begault, Durand R.↗

NASA NTRS1998

Joint ASRS and NASA Callback on FANS-1 Datalink Operational Incidents

The recent certification and implementation of the Future Air Navigation System (FANS- 1) was based on the benefits of reduced separation minima, ability to optimize flight plans enroute, and the prompt transmission and reception of messages between oceanic controllers and 747-400 aircraft transiting the Pacific. In addition, FANS was intended to supersede High Frequency (HF) radio which has been the staple, yet problematic, long distance communication link for years. However, in the three initial years of operation, FANS has revealed its own unique operational issues. Although some technical and engineering problems have been studied and addressed, little research has been conducted on human factors issues associated with the use of FANS on the flight deck. This lack of prior data on the operational use of FANS prompted a joint NASA/Aviation Safety Reporting System (ASRS) inquiry into FANS datalink. In addition, two foreign air carriers and their respective safety agencies were recruited to participate. This international FANS research effort consisting of three aviation safety agencies and three international commercial air-carriers has provided a unique opportunity for conducting human factors research in an operational environment. An ASRS 'callback' format was chosen for the study as a practical and viable method for capturing FANS events on the flight deck. Initially, 747-400 pilots were encouraged to submit reports to their respective safety agencies if they had experienced any positive or negative incidents with the use of FANS. Upon receipt of a report, it was evaluated and if deemed pertinent to the study, a telephone interview or 'callback' was conducted on the FANS incident to elicit further details, capture the key events, and gather contextual information. Once the operational data collection phase was completed, the reports and interviews were analyzed with two purposes in mind: primarily to identify and address problematic human factors issues with current FANS technology, and, secondarily, to provide 'lessons learned' for future datalink systems and implementation.

Moses, John↗

NASA NTRS1998

Minimization of Retinal Slip Cannot Explain Human Smooth-Pursuit Eye Movements

Existing models assume that pursuit attempts a direct minimization of retinal image motion or "slip" (e.g. Robinson et al., 1986; Krauzlis & Weisberger, 1989). Using occluded line-figure stimuli, we have previously shown that humans can accurately pursue stimuli for which perfect tracking does not zero retinal slip (Neurologic ARCO). These findings are inconsistent with the standard control strategy of matching eye motion to a target-motion signal reconstructed by adding retinal slip and eye motion, but consistent with a visual front-end which estimates target motion via a global spatio-temporal integration for pursuit and perception. Another possible explanation is that pursuit simply attempts to minimize slip perpendicular to the segments (and neglects parallel "sliding" motion). To resolve this, 4 observers (3 naive) were asked to pursue the center of 2 types of stimuli with identical velocity-space descriptions and matched motion energy. The line-figure "diamond" stimulus was viewed through 2 invisible 3 deg-wide vertical apertures (38 cd/m2 equal to background) such that only the sinusoidal motion of 4 oblique line segments (44 cd/m2 was visible. The "cross" was identical except that the segments exchanged positions. Two trajectories (8's and infinity's) with 4 possible initial directions were randomly interleaved (1.25 cycles, 2.5s period, Ax = Ay = 1.4 deg). In 91% of trials, the diamond appeared rigid. Correspondingly, pursuit was vigorous (mean Again: 0.74) with a V/H aspect ratio approx. 1 (mean: 0.9). Despite a valid rigid solution, the cross however appeared rigid in 8% of trials. Correspondingly, pursuit was weaker (mean Hgain: 0.38) with an incorrect aspect ratio (mean: 1.5). If pursuit were just minimizing perpendicular slip, performance would be the same in both conditions.

Stone, Leland S.↗

NASA NTRS1998

Why is it Doing That? - Assumptions about the FMS

In the glass cockpit, it's not uncommon to hear exclamations such as "why is it doing that?". Sometimes pilots ask "what were they thinking when they set it this way?" or "why doesn't it tell me what it's going to do next?". Pilots may hold a conceptual model of the automation that is the result of fleet lore, which may or may not be consistent with what the engineers had in mind. But what did the engineers have in mind? In this study, we present some of the underlying assumptions surrounding the glass cockpit. Engineers and designers make assumptions about the nature of the flight task; at the other end, instructor and line pilots make assumptions about how the automation works and how it was intended to be used. These underlying assumptions are seldom recognized or acknowledged, This study is an attempt to explicitly arti culate such assumptions to better inform design and training developments. This work is part of a larger project to support training strategies for automation.

Feary, Michael↗

NASA NTRS1998

Analysis of Autopilot Behavior

Aviation and cognitive science researchers have identified situations in which the pilot's expectations for behavior of autopilot avionics are not matched by the actual behavior of the avionics. These "automation surprises" have been attributed to differences between the pilot's model of the behavior of the avionics and the actual behavior encoded in the avionics software. A formal technique is described for the analysis and measurement of the behavior of the cruise pitch modes of a modern Autopilot. The analysis characterizes the behavior of the Autopilot as situation-action rules. The behavior of the cruise pitch mode logic for a contemporary modern Autopilot was found to include 177 rules, including Level Change (23), Vertical Speed (16), Altitude Capture (50), and Altitude Hold (88). These rules are determined based on the values of 62 inputs. Analysis of the rule-based model also shed light on the factors cited in the literature as contributors to "automation surprises."

Sherry, Lance↗

NASA NTRS1998

A Survey of Flight Crew Experience with FANS-1 ATC Datalink

A survey was used to collect data from Boeing 747-400 pilots who fly with three international carriers about their operational experience using FANS-1 CPDLC (controller-pilot datalink communication) for oceanic communication with air traffic control (ATC). The survey provides data characterizing the operators' experiences performing all routine datalink communication tasks, with the goal of determining how well the FANS-1 CPDLC system supports task performance, the problems flight crews experience when using the system, and the possible operational consequences of those problems. Survey questions were developed from an analysis of activities performed by pilots when using FANS-1 CPDLC. Seven routine tasks were identified: (1) preflight initialization; (2) ATC facility logon; (3) monitoring ATC facility handoffs; (4) monitoring integrity of FANS- 1 CPDLC connection; (5) responding to ATC communications; (6) sending ATC requests; and (7) sending ATC position reports. A decomposition of each task described its information requirements, task timing requirements, user interface actions, company procedures and documentation, and the available cues and feedback provided by the interface. This analysis was used to determine where the system might provide poor support for task performance, and survey questions were developed to determine whether operator experience reflected problems in these areas.

Smith, Nancy↗

NASA NTRS1997

Virtual Acoustics: Evaluation of Psychoacoustic Parameters

Current virtual acoustic displays for teleconferencing and virtual reality are usually limited to very simple or non-existent renderings of reverberation, a fundamental part of the acoustic environmental context that is encountered in day-to-day hearing. Several research efforts have produced results that suggest that environmental cues dramatically improve perceptual performance within virtual acoustic displays, and that is possible to manipulate signal processing parameters to effectively reproduce important aspects of virtual acoustic perception in real-time. However, the computational resources for rendering reverberation remain formidable. Our efforts at NASA Ames have been focused using a several perceptual threshold metrics, to determine how various "trade-offs" might be made in real-time acoustic rendering. This includes both original work and confirmation of existing data that was obtained in real rather than virtual environments. The talk will consider the importance of using individualized versus generalized pinnae cues (the "Head-Related Transfer Function"); the use of head movement cues; threshold data for early reflections and late reverberation; and consideration of the necessary accuracy for measuring and rendering octave-band absorption characteristics of various wall surfaces. In addition, a consideration of the analysis-synthesis of the reverberation within "everyday spaces" (offices, conference rooms) will be contrasted to the commonly used paradigm of concert hall spaces.

Begault, Durand R.↗

NASA NTRS1997

An Introduction to 3-D Sound

This talk will overview the basic technologies related to the creation of virtual acoustic images, and the potential of including spatial auditory displays in human-machine interfaces. Research into the perceptual error inherent in both natural and virtual spatial hearing is reviewed, since the formation of improved technologies is tied to psychoacoustic research. This includes a discussion of Head Related Transfer Function (HRTF) measurement techniques (the HRTF provides important perceptual cues within a virtual acoustic display). Many commercial applications of virtual acoustics have so far focused on games and entertainment ; in this review, other types of applications are examined, including aeronautic safety, voice communications, virtual reality, and room acoustic simulation. In particular, the notion that realistic simulation is optimized within a virtual acoustic display when head motion and reverberation cues are included within a perceptual model.

Begault, Durand R.↗

NASA NTRS1997

Eye Movement Latencies to Direction Change for Different Classes of Motion

In the analysis of visual motion, local features such as orientation are analyzed early in the cortical processing stream (V1), while integration across orientation and space is thought to occur in higher cortical areas such as MT, MST, etc. If all areas provide inputs to eye movement control centers, we would expect that local properties would drive eye movements with relatively short latencies, while global properties would require longer latencies. When such latencies are observed, they can provide information about when (and where?) various stimulus properties are analyzed. To this end, a stimulus was employed in which local and global properties determining perceived direction-of-motion could be manipulated independently: an elliptical Gabor patch with a drifting carrier, with variable orientation of the carrier grating and the contrast window. We have previously demonstrated that the directional percepts evoked by this stimulus vary between the "grating direction" (the normal to the grating's orientation) and the "window direction" (ARVO 91, 94), and that similar effects can be observed in reflexive eye movements (ARVO 95). Subjects viewed such a stimulus while attempting to maintain steady fixation on the center of the pattern, and the small reflexive eye movements ("stare OKN") were recorded. In the middle of the trial, the orientation of either the grating or the window was rotated smoothly by 30 degrees. Responses to the shift of both grating orientation and window orientation are seen in the average OKN slow phase velocity. Grating rotations produce a rapid OKN rotation to the grating direction (100 ms latency, 300 ms time constant), followed by a slower rebound to the steady state perceived direction midway between the grating and window directions. Window rotations, on the other hand, evoke a slower response (200 ms latency, 500 ms time constant). The results demonstrate multiple cortical inputs to eye movement control: a taste early input driven by orientation, and a slower input from higher areas sensitive to global stimulus properties.

Mulligan, Jeffrey B.↗

NASA NTRS1997

Digital Images and Human Vision

Processing of digital images destined for visual consumption raises many interesting questions regarding human visual sensitivity. This talk will survey some of these questions, including some that have been answered and some that have not. There will be an emphasis upon visual masking, and a distinction will be drawn between masking due to contrast gain control processes, and due to processes such as hypothesis testing, pattern recognition, and visual search.

Watson, Andrew B.↗

NASA NTRS1997

DCTune Perceptual Optimization of Compressed Dental X-Rays

In current dental practice, x-rays of completed dental work are often sent to the insurer for verification. It is faster and cheaper to transmit instead digital scans of the x-rays. Further economies result if the images are sent in compressed form. DCtune is a technology for optimizing DCT quantization matrices to yield maximum perceptual quality for a given bit-rate, or minimum bit-rate for a given perceptual quality. In addition, the technology provides a means of setting the perceptual quality of compressed imagery in a systematic way. The purpose of this research was, with respect to dental x-rays: (1) to verify the advantage of DCTune over standard JPEG; (2) to verify the quality control feature of DCTune; and (3) to discover regularities in the optimized matrices of a set of images. Additional information is contained in the original extended abstract.

Watson, Andrew B.↗

NASA NTRS1996

Guidance of Nonlinear Systems

The paper describes a method for guiding a dynamic system through a given set of points. The paradigm is a fully automatic aircraft subject to air traffic control (ATC). The ATC provides a sequence of way points through which the aircraft trajectory must pass. The way points typically specify time, position, and velocity. The guidance problem is to synthesize a system state trajectory which satisfies both the ATC and aircraft constraints. Complications arise because the controlled process is multi-dimensional, multi-axis, nonlinear, highly coupled, and the state space is not flat. In addition, there is a multitude of possible operating modes, which may number in the hundreds. Each such mode defines a distinct state space model of the process by specifying the state space coordination, the partition of the controls into active controls and configuration controls, and the output map. Furthermore, mode transitions must be smooth. The guidance algorithm is based on the inversion of the pure feedback approximations, which is followed by iterative corrections for the effects of zero dynamics. The paper describes the structure and modules of the algorithm, and the performance is illustrated by several example aircraft maneuvers.

Meyer, George↗

NASA NTRS1996

Quantifying the Correlation Between Eye-Movement and Perceptual Responses to Moving Plaids

To determine the extent to which the pursuit eye-movement and perceptual systems share a common neural motion-processing pathway, we simultaneously measure the psychophysical and eye-movement responses to drifting plaids in a direction-discrimination task. Correlation between the noise in the eye movements and percepts would suggest a shared neural substrate. Three observers were asked to track a plaid (Type I 90 deg; TF = 4 Hz, SF = 0.6 c/d; direction = -2, 0, or 2 deg), and to respond whether the motion was to the right or left of vertical. The eye-movement direction is computed from the initial 300 ms of saccade-free tracking (near open-loop). On each trial, we use the eye-movement direction to predict the perceptual response. We then compute the probability of successfully predicting the observer's response. We also use SOC analysis as an alternate measure of the correlation. We compare the data from both these analyses to the predictions of two models in which the eye movements and the percept are driven by either a common noisy signal (correlated model) or by two separate noisy signals (uncorrelated model). We also allow for the fact that our measured eye movements are degraded by eye-tracker noise. This noise causes our measured correlation to be lower than the actual biological correlation. The correlations in our data are higher than those predicted by the uncorrelated model, and are similar to the predictions of the correlated model. The proportion of perceptual responses correctly predicted by the eye movements were 0.66, 0.60, 0.73 for the -2, 0, 2 deg stimuli respectively (correlated model 0.65, 0.60, 0.70; uncorrelated model 0.58, 0.51, 0.60).The SOC proportions were 0.71, 0.64, 0.72 (correlated model 0.66, 0.64, 0.69; uncorrelated model 0.5, 0.5, 0.5). These results show that the oculomotor and perceptual system share a performance-limiting noise source and provide strong evidence that a common neural mechanism (perhaps MT or MST) drives both perception and smooth eye movements.

Beutter, Brent R.↗