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At least 325 records · Page 18

Studies of the Interactions Between Vestibular Function and Tactual Orientation Display Systems

When humans experience conditions in which internal vestibular cues to movement or spatial location are challenged or contradicted by external visual information, the result can be spatial disorientation, often leading to motion sickness. Spatial disorientation can occur in any situation in which the individual is passively moved in the environment, but is most common in automotive, aircraft, or undersea travel. Significantly, the incidence of motion sickness in space travel is great: The majority of individuals in Shuttle operations suffer from the syndrome. Even after the space-sickness-producing influences of spatial disorientation dissipate, usually within several days, there are other situations in which, because of the absence of reliable or familiar vestibular cues, individuals in space still experience disorientation, resulting in a reliance on the already preoccupied sense of vision. One possible technique to minimize the deleterious effects of spatial disorientation might be to present attitude information (including orientation, direction, and motion) through another less-used sensory modality - the sense of touch. Data from experiences with deaf and blind persons indicate that this channel can provide useful communication and mobility information on a real-time basis. More recently, technologies have developed to present effective attitude information to pilots in situations in which dangerously ambiguous and conflicting visual and vestibular sensations occur. This summers project at NASA-Johnson Space Center will evaluate the influence of motion-based spatial disorientation on the perception of tactual stimuli representing veridical position and orientation information, presented by new dynamic vibrotactile array display technologies. In addition, the possibility will be explored that tactile presentations of motion and direction from this alternative modality might be useful in mitigating or alleviating spatial disorientation produced by multi-axis rotatory systems, monitored by physiological recording techniques developed at JSC.

Cholewiak, Roger W.↗

Terrain Portrayal for Synthetic Vision Systems Head-Down Displays Evaluation Results

A critical component of SVS displays is the appropriate presentation of terrain to the pilot. At the time of this study, the relationship between the complexity of the terrain presentation and resulting enhancements of pilot SA and pilot performance had been largely undefined. The terrain portrayal for SVS head-down displays (TP-HDD) simulation examined the effects of two primary elements of terrain portrayal on the primary flight display (PFD): variations of digital elevation model (DEM) resolution and terrain texturing. Variations in DEM resolution ranged from sparsely spaced (30 arc-sec) to very closely spaced data (1 arc-sec). Variations in texture involved three primary methods: constant color, elevation-based generic, and photo-realistic, along with a secondary depth cue enhancer in the form of a fishnet grid overlay.

Hughes, Monica F.↗

Synthetic Vision for Lunar and Planetary Landing Vehicles

The Crew Vehicle Interface (CVI) group of the Integrated Intelligent Flight Deck Technologies (IIFDT) has done extensive research in the area of Synthetic Vision (SV), and has shown that SV technology can substantially enhance flight crew situation awareness, reduce pilot workload, promote flight path control precision and improve aviation safety. SV technology is being extended to evaluate its utility for lunar and planetary exploration vehicles. SV may hold significant potential for many lunar and planetary missions since the SV presentation provides a computer-generated view of the terrain and other significant environment characteristics independent of the outside visibility conditions, window locations, or vehicle attributes. SV allows unconstrained control of the computer-generated scene lighting, terrain coloring, and virtual camera angles which may provide invaluable visual cues to pilots/astronauts and in addition, important vehicle state information may be conformally displayed on the view such as forward and down velocities, altitude, and fuel remaining to enhance trajectory control and vehicle system status. This paper discusses preliminary SV concepts for tactical and strategic displays for a lunar landing vehicle. The technical challenges and potential solutions to SV applications for the lunar landing mission are explored, including the requirements for high resolution terrain lunar maps and an accurate position and orientation of the vehicle that is essential in providing lunar Synthetic Vision System (SVS) cockpit displays. The paper also discusses the technical challenge of creating an accurate synthetic terrain portrayal using an ellipsoid lunar digital elevation model which eliminates projection errors and can be efficiently rendered in real-time.

Williams, Steven P.↗

Methods to Reduce Communication Workload for UAM Operations

Implementation of Urban Air Mobility (UAM) operations, or air passenger transportation systems within densely populated metropolitan areas, seeks to mitigate increasing traffic congestion. However, the development and integration of UAM operations into the national airspace system comes with its own unique challenges, such as vehicle requirements, flight planning and scheduling, and coordination between UAM flights and air traffic controllers. In particular, verbal coordination will play an integral part in the determined success of UAM operations and its ability to meet projected high consumer demands. In order to meet demands and higher traffic volumes on UAM routes, verbal communication between the UAM pilot and controller must be streamlined to reduce the controller's workload while helping to maintain safety within a given airspace. One method of reducing verbal workload are Letters Of Agreement (LOAs) that outline responsibilities and procedures for operations in an airspace. These LOAs will specify the operations, procedures, and routes for UAM flights. The proposed study will examine the usability of two route formatting styles for LOAs; (i) Verbal route descriptions and (ii) Tower En Route Control (TECs) routes. Verbal route descriptions will include the route name and associated visual cues on the route. The TEC route versions will include relevant waypoints and charts outlining the route with waypoints marked. The study will be part of a UAM X1 human in the loop (HITL) simulation. Controller participants will handle traditional air traffic including moderate levels of UAM traffic on current and modified helicopter routes within the Dallas Fort-Worth area. Scenarios will be counterbalanced and repeated to test both route formatting versions. After each trial, participants will rate the usability of the LOA used in the previous trial via a subjective questionnaire. We expect that controllers will prefer the LOA with TEC routes due to simplicity and visual elements available.

aerospace human factors↗

Synthetic Vision Displays for Planetary and Lunar Lander Vehicles

Aviation research has demonstrated that Synthetic Vision (SV) technology can substantially enhance situation awareness, reduce pilot workload, improve aviation safety, and promote flight path control precision. SV, and related flight deck technologies are currently being extended for application in planetary exploration vehicles. SV, in particular, holds significant potential for many planetary missions since the SV presentation provides a computer-generated view for the flight crew of the terrain and other significant environmental characteristics independent of the outside visibility conditions, window locations, or vehicle attributes. SV allows unconstrained control of the computer-generated scene lighting, terrain coloring, and virtual camera angles which may provide invaluable visual cues to pilots/astronauts, not available from other vision technologies. In addition, important vehicle state information may be conformally displayed on the view such as forward and down velocities, altitude, and fuel remaining to enhance trajectory control and vehicle system status. The paper accompanies a conference demonstration that introduced a prototype NASA Synthetic Vision system for lunar lander spacecraft. The paper will describe technical challenges and potential solutions to SV applications for the lunar landing mission, including the requirements for high-resolution lunar terrain maps, accurate positioning and orientation, and lunar cockpit display concepts to support projected mission challenges.

Arthur, Jarvis J., III↗

Relationships Between Vestibular Measures as Potential Predictors for Spaceflight Sensorimotor Adaptation

Introduction: During space exploration missions astronauts are exposed to a series of novel sensorimotor environments, requiring sensorimotor adaptation. Until adaptation is complete, sensorimotor decrements occur, affecting critical tasks such as piloted landing or docking. Of particularly interest are locomotion tasks such as emergency vehicle egress or extra-vehicular activity. While nearly all astronauts eventually adapt sufficiently, it appears there are substantial individual differences in how quickly and effectively this adaptation occurs. These individual differences in capacity for sensorimotor adaptation are poorly understood. Broadly, we aim to identify measures that may serve as pre-flight predictors of and individual's adaptation capacity to spaceflight-induced sensorimotor changes. As a first step, since spaceflight is thought to involve a reinterpretation of graviceptor cues (e.g. otolith cues from the vestibular system) we investigate the relationships between various measures of vestibular function in humans. Methods: In a set of 15 ground-based control subjects, we quantified individual differences in vestibular function using three measures: 1) ocular vestibular evoked myogenic potential (oVEMP), 2) computerized dynamic posturography and 3) vestibular perceptual thresholds. oVEMP responses are elicited using a mechanical stimuli approach. Computerized dynamic posturography was used to quantify Sensory Organization Tests (SOTs), including SOT5M which involved performing pitching head movements while balancing on a sway-reference support surface with eyes closed. We implemented a vestibular perceptual threshold task using the tilt capabilities of the Tilt-Translation Sled (TTS) at JSC. On each trial, the subject was passively roll-tilted left ear down or right ear down in the dark and verbally provided a forced-choice response regarding which direction they felt tilted. The motion profile was a single-cycle sinusoid of angular acceleration with a duration of 5 seconds (frequency of 0.2 Hz), which was selected as it requires sensory integration of otolith and semicircular canal cues. Stimuli direction was randomized and magnitude was determined using an adaptive sampling procedure. One hundred trials were provided and each subject's responses were fit with a psychometric curve to estimate the subject's threshold. Results: Roll tilt perceptual thresholds at 0.2 Hz ranged from 0.5 degrees to 1.82 degrees across the 15 subjects (geometric mean of 1.04 degrees), consistent with previous studies. The inter-individual variability in thresholds may be able to help explain individual differences observed in sensorimotor adaptation to spaceflight. Analysis is ongoing for the oVEMPS and computerized dynamic posturography to identify relationships between the various vestibular measures. Discussion: Predicting individual differences in sensorimotor adaptation is critical both for the development of personalized countermeasures and mission planning. Here we aim to develop a basis of vestibular tests and parameters which may serve as predictors of individual differences in sensorimotor adaptability through studying the relationship between these measures.

Clark, T. K.↗

Evaluation of several secondary tasks in the determination of permissible time delays in simulator visual and motion cues

The effect of secondary tasks in determining permissible time delays in visual-motion simulation of a pursuit tracking task was examined. A single subject, a single set of aircraft handling qualities, and a single motion condition in tracking a target aircraft that oscillates sinusoidally in altitude were used. In addition to the basic simulator delays the results indicate that the permissible time delay is about 250 msec for either a tapping task, an adding task, or an audio task and is approximately 125 msec less than when no secondary task is involved. The magnitudes of the primary task performance measures, however, differ only for the tapping task. A power spectraldensity analysis basically confirms the result by comparing the root-mean-square performance measures. For all three secondary tasks, the total pilot workload was quite high.

Miller, G. K., Jr.↗

Simulator evaluation of a perspective clipped-pole display and a thrust-vector controller for VTOL zero-zero landings

Five pilots participated in a simulator study to evaluate design features of a perspective clipped pole display and a side arm thrust vector controller for potential applications to VTOL zero visibility landings. Analyses of objective measures by a t test for related means showed significant learning effects, but did not show significant performance differences among display conditions. A mean longitudinal touchdown velocity of less than 4 knots, a mean vertical touchdown velocity of less than 1.22m/sec, and a mean longitudinal position error of approximately 15.24 m were attained during the final 10 trials of the experiment. The conclusion that adequate airspeed and altitude cues could be obtained from the glideslope and runway poles is supported by the absence of significant performance differences among display conditions.

Murphy, M. R.↗

Improved Lunar Lander Handling Qualities Through Control Response Type and Display Enhancements

A piloted simulation that studied the handling qualities for a precision lunar landing task from final approach to touchdown is presented. A vehicle model based on NASA's Altair Lunar Lander was used to explore the design space around the nominal vehicle configuration to determine which combination of factors provides satisfactory pilot-vehicle performance and workload; details of the control and propulsion systems not available for that vehicle were derived from Apollo Lunar Module data. The experiment was conducted on a large motion base simulator. Eight Space Shuttle and Apollo pilot astronauts and three NASA test pilots served as evaluation pilots, providing Cooper-Harper ratings, Task Load Index ratings and qualitative comments. Each pilot flew seven combinations of control response types and three sets of displays, including two varieties of guidance and a nonguided approach. The response types included Rate Command with Attitude Hold, which was used in the original Apollo Moon landings, a Velocity Increment Command response type designed for up-and-away flight, three response types designed specifically for the vertical descent portion of the trajectory, and combinations of these. It was found that Velocity Increment Command significantly improved handling qualities when compared with the baseline Apollo design, receiving predominantly Level 1 ratings. This response type could be flown with or without explicit guidance cues, something that was very difficult with the baseline design, and resulted in approximately equivalent touchdown accuracies and propellant burn as the baseline response type. The response types designed to be used exclusively in the vertical descent portion of the trajectory did not improve handling qualities.

Mueller, Eric Richard↗

Visual and motion cueing in helicopter simulation

The visual cues presented in the simulator are compared with those of flight in an attempt to identify deficiencies. For the low-amplitude maneuvering tasks normally associated with the hover mode, the unique motion capabilities of the Vertical Motion Simulator (VMS) at Ames Research Center permit nearly a full representation of vehicle motion. Especially appreciated in these tasks are the vertical-acceleration responses to collective control. For larger-amplitude maneuvering, motion fidelity must suffer diminution through direct attenuation through high-pass filtering washout of the computer cockpit accelerations or both. Experiments were conducted in an attempt to determine the effects of these distortions on pilot performance of height-control tasks.

Bray, Richard S.↗

Verifying Implementation of the Dryden Turbulence Model and MIL-F-8785 Gust Gradient

Turbulence modeling in human-in-the-loop simulation is important to assessing aircraft handling qualities and pilot performance and to provide additional realism for pilot training. In the simulation community, the Dryden turbulence spectra is a popular choice for modeling the linear turbulent gusts because its rational form is efficiently reproduced by passing white noise through linear filters. The MIL-F-8785 gust gradients similarly use additional linear filters to model the gradient of the turbulent gust over the wing, and it represents the gust gradients as perturbations to the air-relative rotational rates. The Cockpit Motion Facility at NASA Langley Research Center (LaRC) models continuous random turbulence using the Dryden one-dimensional spectra and MIL-F-8785 gust gradient. The facility recently reviewed and updated its verification of these models as part of an initiative to improve motion cueing under turbulence. This exercise introduced improved methods for verifying the turbulence models and led to rediscovery of model assumptions that informed improvements to implementation.

Madden, Michael M.↗

Low-visibility visual simulation with real fog

An environmental fog simulation (EFS) attachment was developed to aid in the study of natural low-visibility visual cues and subsequently used to examine the realism effect upon the aircraft simulator visual scene. A review of the basic fog equations indicated that two major factors must be accounted for in the simulation of low visibility - one due to atmospheric attenuation and one due to veiling luminance. These factors are compared systematically by (1) comparing actual measurements to those computed from the fog equations, and (2) comparing runway-visual-range-related visual-scene contrast values with the calculated values. These values are also compared with the simulated equivalent equations and with contrast measurements obtained from a current electronic fog synthesizer to help identify areas in which improvements are needed. These differences in technique, the measured values, the features of both systems, a pilot opinion survey of the EFS fog, and improvements (by combining features of both systems) that are expected to significantly increase the potential as well as flexibility for producing a very high-fidelity low-visibility visual simulation are discussed.

Chase, W. D.↗

Low-Visibility Visual Simulation with Real Fog

An environmental fog simulation (EFS) attachment was developed to aid in the study of natural low-visibility visual cues and subsequently used to examine the realism effect upon the aircraft simulator visual scene. A review of the basic fog equations indicated that the two major factors must be accounted for in the simulation of low visibility-one due to atmospheric attenuation and one due to veiling luminance. These factors are compared systematically by: comparing actual measurements lo those computed from the Fog equations, and comparing runway-visual-range-related visual-scene contrast values with the calculated values. These values are also compared with the simulated equivalent equations and with contrast measurements obtained from a current electronic fog synthesizer to help identify areas in which improvements are needed. These differences in technique, the measured values, the Features of both systems, a pilot opinion survey of the EFS fog, and improvements (by combining features of both systems) that are expected to significantly increase the potential as well as flexibility for producing a very high-fidelity, low-visibility visual simulation are discussed.

Chase, Wendell D.↗

Motion-Base Simulator Evaluation of an Aircraft Using an External Vision System

Twelve air transport-rated pilots participated as subjects in a motion-base simulation experiment to evaluate the use of eXternal Vision Systems (XVS) as enabling technologies for future supersonic aircraft without forward facing windows. Three head-up flight display concepts were evaluated -a monochromatic, collimated Head-up Display (HUD) and a color, non-collimated XVS display with a field-of-view (FOV) equal to and also, one significantly larger than the collimated HUD. Approach, landing, departure, and surface operations were conducted. Additionally, the apparent angle-of-attack (AOA) was varied (high/low) to investigate the vertical field-of-view display requirements and peripheral, side window visibility was experimentally varied. The data showed that lateral approach tracking performance and lateral landing position were excellent regardless of AOA, display FOV, display collimation or whether peripheral cues were present. However, the data showed glide slope approach tracking appears to be affected by display size (i.e., FOV) and collimation. The monochrome, collimated HUD and color, uncollimated XVS with Full FOV display had (statistically equivalent) glide path performance improvements over the XVS with HUD FOV display. Approach path performance results indicated that collimation may not be a requirement for an XVS display if the XVS display is large enough and employs color. Subjective assessments of mental workload and situation awareness also indicated that an uncollimated XVS display may be feasible. Motion cueing appears to have improved localizer tracking and touchdown sink rate across all displays.

Kramer, Lynda J.↗

Simulation System Fidelity Assessment at the Vertical Motion Simulator

Fidelity is a word that is often used but rarely understood when talking about groundbased simulation. Assessing the cueing fidelity of a ground based flight simulator requires a comparison to actual flight data either directly or indirectly. Two experiments were conducted at the Vertical Motion Simulator using the GenHel UH-60A Black Hawk helicopter math model that was directly compared to flight data. Prior to the experiment the simulator s motion and visual system frequency responses were measured, the aircraft math model was adjusted to account for the simulator motion system delays, and the motion system gains and washouts were tuned for the individual tasks. The tuned motion system fidelity was then assessed against the modified Sinacori criteria. The first experiments showed similar handling qualities ratings (HQRs) to actual flight for a bob-up and sidestep maneuvers. The second experiment showed equivalent HQRs between flight and simulation for the ADS33 slalom maneuver for the two pilot participants. The ADS33 vertical maneuver HQRs were mixed with one pilot rating the flight and simulation the same while the second pilot rated the simulation worse. In addition to recording HQRs on the second experiment, an experimental Simulation Fidelity Rating (SFR) scale developed by the University of Liverpool was tested for applicability to engineering simulators. A discussion of the SFR scale for use on the Vertical Motion Simulator is included in this paper.

Beard, Steven D.↗

Evaluation of Equivalent Vision Technologies for Supersonic Aircraft Operations

Twenty-four air transport-rated pilots participated as subjects in a fixed-based simulation experiment to evaluate the use of Synthetic/Enhanced Vision (S/EV) and eXternal Vision System (XVS) technologies as enabling technologies for future all-weather operations. Three head-up flight display concepts were evaluated a monochromatic, collimated Head-up Display (HUD) and a color, non-collimated XVS display with a field-of-view (FOV) equal to and also, one significantly larger than the collimated HUD. Approach, landing, departure, and surface operations were conducted. Additionally, the apparent angle-of-attack (AOA) was varied (high/low) to investigate the vertical field-of-view display requirements and peripheral, side window visibility was experimentally varied. The data showed that lateral approach tracking performance and lateral landing position were excellent regardless of the display type and AOA condition being evaluated or whether or not there were peripheral cues in the side windows. Longitudinal touchdown and glideslope tracking were affected by the display concepts. Larger FOV display concepts showed improved longitudinal touchdown control, superior glideslope tracking, significant situation awareness improvements and workload reductions compared to smaller FOV display concepts.

Kramer, Lynda J.↗

Sensitive Quantitative Assessment of Balance Disorders

Computerized dynamic posturography (CDP) has become a standard technique for objectively quantifying balance control performance, diagnosing the nature of functional impairments underlying balance disorders, and monitoring clinical treatment outcomes. We have long used CDP protocols to assess recovery of sensory-motor function in astronauts following space flight. The most reliable indicators of post-flight crew performance are the sensory organization tests (SOTs), particularly SOTs 5 and 6, which are sensitive to changes in availability and/or utilization of vestibular cues. We have noted, however, that some astronauts exhibiting obvious signs of balance impairment after flight are able to score within clinical norms on these tests, perhaps as a result of adopting competitive strategies or by their natural skills at substituting alternate sensory information sources. This insensitivity of the CDP protocol could underestimate of the degree of impairment and, perhaps, lead to premature release of those crewmembers to normal duties. To improve the sensitivity of the CDP protocol we have introduced static and dynamic head tilt SOT trials into our protocol. The pattern of postflight recovery quantified by the enhanced CDP protocol appears to more aptly track the re-integration of sensory-motor function, with recovery time increasing as the complexity of sensory-motor/biomechanical task increases. The new CDP protocol therefore seems more suitable for monitoring post-flight sensory-motor recovery and for indicating to crewmembers and flight surgeons fitness for return to duty and/or activities of daily living. There may be classes of patients (e.g., athletes, pilots) having motivation and/or performance characteristics similar to astronauts whose sensory-motor treatment outcomes would also be more accurately monitored using the enhanced CDP protocol. Furthermore, the enhanced protocol may be useful in early detection of age-related balance disorders.

Paloski, Willilam H.↗

Context-Specific Adaptation of Gravity-Dependent Vestibular Reflex Responses

Stabilization of the eyes and head during body movements is important for maintaining balance and keeping the images of objects stationary on our retinas. Impairment of this ability can lead to disorientation and reduced performance in sensorimotor tasks such as piloting of spacecraft. In the absence of a normal earth gravity field, the dynamics of head stabilization, and the interpretation of vestibular signals that sense gravity and linear acceleration, are subject to change. Transitions between different gravitoinertial force environments - as during different phases of space flight - provide an extreme test of the adaptive mechanisms that maintain these reflexive abilities. It is vitally important to determine human adaptive capabilities in such a circumstance, so that we can know to what extent the sensorimotor skills acquired in one gravity environment will transfer to others. Our work lays the foundation for understanding these capabilities, and for determining how we can aid the processes of adaptation and readaptation. An integrated set of experiments addresses this issue. We use the general approach of adapting some type of reflexive eye movement (saccades, the angular vestibulo-ocular reflex (AVOR), the linear vestibulo-ocular reflex (LVOR)), or the vestibulo-collic reflex (VCR), to a particular change in gain or phase in one condition of gravitoiner-tial force, and adapting to a different gain or phase (or asking for no change) in a second gravitoinertial force condition, and then seeing if the gravitoinertial force itself - the context cue - can recall the previously learned adapted responses. The majority of the experiments in the laboratory use the direction of vertical gaze or the direction of gravity (head tilt) as the context cue. This allows us to study context-specificity in a ground-based setting. One set of experiments, to be performed in parabolic flight, specifically uses the magnitude of gravitoinertial force as a context cue. This is a much better analog of the situation encountered in space flight. Various experiments investigate the behavioral properties, neurophysiological basis, and anatomical substrate of context-specific learning mechanisms. We use otolith (gravity) signals as the contextual cue for switching between adapted states of the saccadic system, the angular and linear vestibulo-ocular reflexes, and the VCR. (By LVOR we mean the oculomotor response - horizontal, vertical, and torsional - to linear translation of the head and body.) We are studying the effect of context on adaptation of saccade gain, phase and gain of the AVOR and LVOR, on ocular counterrolling (OCR) in response to static head tilt, and on head/neck reflexes (VCR) in response to rotation in different orientations. Such research is particularly germane to potential problems of postural and oculomotor control upon exposure to different gravitational environments.

Shelhamer, Mark J.↗