Engineering topics

Stuart, Mark A.

Publications and source records attributed to Stuart, Mark A..

At least 19 records

NASA NTRS1995

Evaluation of restraint system concepts for the Japanese Experiment Module flight demonstration

The current International Space Station configuration includes a Japanese Experiment Module which relies on a large manipulator and a smaller dexterous manipulator to operate outside the pressurized environment of the experiment module. The module's flight demonstration is a payload that will be mounted in the aft flight deck on STS-87 to evaluate a prototype of the dexterous manipulator. Since the payload operations entail two 8-hour scenarios on consecutive days, adequate operator restraint at the workstation will be critical to the perceived success or failure of the payload. Simulations in reduced gravity environment on the KC-135A were the only way to evaluate the restraint systems and workstation configuration. Two astronaut and two non-astronaut operators evaluated the Advanced Lower Body Extremities Restraint Test and a foot loop restraint system by performing representative tasks at the workstation in each of the two restraint systems; at the end of each flight they gave their impressions of each system and the workstation. Results indicated that access to the workstation switch panels was difficult and manipulation of the hand controllers forced operators too low for optimal viewing of the aft flight deck monitors. The workstation panel should be angled for better visibility, and infrequently used switches should be on the aft flight deck panel. Pitch angle and placement of the hand controllers should optimize the operator's eye position with respect to the monitors. The lower body restraint was preferred over the foot loops because it allowed operators to maintain a more relaxed posture during long-duration tasks, its height adjustability allowed better viewing of aft flight deck monitors, and it provided better restraint for reacting forces imparted on the operator at the workstation. The foot loops provide adequate restraint for the flight demonstration tasks identified. Since results will impact the design of the workstation, both restraints should be flown and used during operation of the flight demonstration payload to evaluate the effect of restraint during long-duration tasks.

Sampaio, Carlos E.↗

NASA NTRS1993

Hand controller commonality evaluation process

Hand controller selection for NASA's Orbiter and Space Station Freedom is an important area of human-telerobot interface design and evaluation. These input devices will control remotely operated systems that include large crane-like manipulators (e.g., Remote Manipulator System or RMS), smaller, more dexterous manipulators (e.g., Flight Telerobotic Servicer or FTS), and free flyers (e.g., Orbital Maneuvering Vehicle or OMV). Candidate hand controller configurations for these systems vary in many ways: shape, size, number of degrees-of-freedom (DOF), operating modes, provision of force reflection, range of movement, and 'naturalness' of use. Unresolved design implementation issues remain, including such topics as how the current Orbiter RMS rotational and translational rate hand controllers compare with the proposed Space Station Freedom hand controllers, the advantages that position hand controllers offer for these applications, and whether separate hand controller configurations are required for each application. Since previous studies contain little empirical hand controller task performance data, a controlled study is needed that tests Space Station Freedom candidate hand controllers during representative tasks. This study also needs to include anthropometric and biomechanical considerations.

Stuart, Mark A.↗

NASA NTRS1993

Programmable display pushbuttons on the Space Station's telerobot control panel

The Man-Systems Telerobotics Laboratory at NASA's Johnson Space Center and supported by Lockheed, is working to ensure that the Flight Telerobotic Servicer (FTS) to be used on the Space Shuttle (Orbiter) and the Space Station has a well designed user interface from a Human Factors perspective. The FTS, which is a project led by NASA's Goddard Space Flight Center, will be a telerobot used for Space Station construction, maintenance, and satellite repair. It will be directly controlled from workstations on the Orbiter and the Space Station and monitored from a ground workstation. The FTS will eventually evolve into a more autonomous system, but in the short-term the system will be manually operated (teleoperated) for many tasks. This emphasizes the importance of the human/telerobot interface on this system. This phase of the FTS workstation evaluation covers a preliminary study of programmable display pushbuttons (PDP's). The PDP is constructed of a matrix of directly addressable electroluminescent (EL) pixels which can be used to form dot-matrix characters. PDP's can be used to display more than one message and to control more than one function. Since the PDP's have these features, then a single PDP may possibly replace the use of many single-function pushbuttons, rotary switches, and toggle switches, thus using less panel space. It is of interest to determine if PDP's can be used to adequately perform complex hierarchically structured task sequences. The objective of this investigation was to compare the performance of experienced and inexperienced Remote Manipulator System (RMS) operators while performing an RMS like task on simulated PDP and non-PDP computer prototypes so that guidelines governing the use of programmable display pushbuttons on the FTS workstation could be created. The functionality of the RMS on the Orbiter was used as a model for this evaluation since the functionality of the FTS at the time of this writing has not been solidified.

Stuart, Mark A.↗

NASA NTRS1993

Speech versus manual control of camera functions during a telerobotic task

This investigation has evaluated the voice-commanded camera control concept. For this particular task, total voice control of continuous and discrete camera functions was significantly slower than manual control. There was no significant difference between voice and manual input for several types of errors. There was not a clear trend in subjective preference of camera command input modality. Task performance, in terms of both accuracy and speed, was very similar across both levels of experience.

Bierschwale, John M.↗

NASA NTRS1993

Space Station Freedom coupling tasks: An evaluation of their telerobotic and EVA compatibility

Of the couplings included in this study, several design components were found to be of interest. With respect to the operation of the couplings, the various concepts resulted in differing reactions from the four subjects who participated in this study. The purpose of this study was not to conceive the final coupling design. Rather, it was intended as a step along an interactive process. The newly modified coupling will be included in a series of further controlled, as well as subjective, evaluations. This part of the ongoing work in the Remote Operator Interaction Laboratory (ROIL) designed to enhance the overall interface by improving design at both the teleoperator and telerobot ends of the system.

Sampaio, Carlos E.↗

NASA NTRS1993

The effects of spatially displaced visual feedback on remote manipulator performance

The results of this evaluation have important implications for the arrangement of remote manipulation worksites and the design of workstations for telerobot operations. This study clearly illustrates the deleterious effects that can accompany the performance of remote manipulator tasks when viewing conditions are less than optimal. Future evaluations should emphasize telerobot camera locations and the use of image/graphical enhancement techniques in an attempt to lessen the adverse effects of displaced visual feedback. An important finding in this evaluation is the extent to which results from previously performed direct manipulation studies can be generalized to remote manipulation studies. Even though the results obtained were very similar to those of the direct manipulation evaluations, there were differences as well. This evaluation has demonstrated that generalizations to remote manipulation applications based upon the results of direct manipulation studies are quite useful, but they should be made cautiously.

Smith, Randy L.↗

NASA NTRS1993

Simulation of the human-telerobot interface on the Space Station

Many issues remain unresolved concerning the components of the human-telerobot interface presented in this work. It is critical that these components be optimally designed and arranged to ensure, not only that the overall system's goals are met, but but that the intended end-user has been optimally accommodated. With sufficient testing and evaluation throughout the development cycle, the selection of the components to use in the final telerobotic system can promote efficient, error-free performance. It is recommended that whole-system simulation with full-scale mockups be used to help design the human-telerobot interface. It is contended that the use of simulation can facilitate this design and evaluation process.

Stuart, Mark A.↗

NASA NTRS1992

Methodology issues concerning the accuracy of kinematic data collection and analysis using the ariel performance analysis system

Kinematics, the study of motion exclusive of the influences of mass and force, is one of the primary methods used for the analysis of human biomechanical systems as well as other types of mechanical systems. The Anthropometry and Biomechanics Laboratory (ABL) in the Crew Interface Analysis section of the Man-Systems Division performs both human body kinematics as well as mechanical system kinematics using the Ariel Performance Analysis System (APAS). The APAS supports both analysis of analog signals (e.g. force plate data collection) as well as digitization and analysis of video data. The current evaluations address several methodology issues concerning the accuracy of the kinematic data collection and analysis used in the ABL. This document describes a series of evaluations performed to gain quantitative data pertaining to position and constant angular velocity movements under several operating conditions. Two-dimensional as well as three-dimensional data collection and analyses were completed in a controlled laboratory environment using typical hardware setups. In addition, an evaluation was performed to evaluate the accuracy impact due to a single axis camera offset. Segment length and positional data exhibited errors within 3 percent when using three-dimensional analysis and yielded errors within 8 percent through two-dimensional analysis (Direct Linear Software). Peak angular velocities displayed errors within 6 percent through three-dimensional analyses and exhibited errors of 12 percent when using two-dimensional analysis (Direct Linear Software). The specific results from this series of evaluations and their impacts on the methodology issues of kinematic data collection and analyses are presented in detail. The accuracy levels observed in these evaluations are also presented.

Wilmington, R. P.↗

NASA NTRS1992

Evaluation of force-torque displays for use with space station telerobotic activities

Recent experiments which addressed Space Station remote manipulation tasks found that tactile force feedback (reflecting forces and torques encountered at the end-effector through the manipulator hand controller) does not improve performance significantly. Subjective response from astronaut and non-astronaut test subjects indicated that force information, provided visually, could be useful. No research exists which specifically investigates methods of presenting force-torque information visually. This experiment was designed to evaluate seven different visual force-torque displays which were found in an informal telephone survey. The displays were prototyped in the HyperCard programming environment. In a within-subjects experiment, 14 subjects nullified forces and torques presented statically, using response buttons located at the bottom of the screen. Dependent measures included questionnaire data, errors, and response time. Subjective data generally demonstrate that subjects rated variations of pseudo-perspective displays consistently better than bar graph and digital displays. Subjects commented that the bar graph and digital displays could be used, but were not compatible with using hand controllers. Quantitative data show similar trends to the subjective data, except that the bar graph and digital displays both provided good performance, perhaps do to the mapping of response buttons to display elements. Results indicate that for this set of displays, the pseudo-perspective displays generally represent a more intuitive format for presenting force-torque information.

Hendrich, Robert C.↗

NASA NTRS1992

A human factors evaluation of the robotic interface for Space Station Freedom orbital replaceable units

An orbital replaceable unit (ORU) is often defined as any orbital unit aboard Space Station with a wearout life of less than 30 years. The capability of successful changeout of these units by remote manipulation is critical to the ORU to telerobot interface design. A human factors evaluation of the selected interface showed certain inadequacies of the alignment target concept that was part of the interface package. Alternative target concepts which addressed these inadequacies were developed and are presented. Recommendations will be incorporated into NASA requirements documents which ORU suppliers and manufacturers must then build to.

Sampaio, Carlos E.↗

NASA NTRS1992

Effects of spatially displaced feedback on remote manipulation tasks

Several studies have been performed to determine the effects on computer and direct manipulation task performance when viewing conditions are spatially displaced. Whether results from these studies can be directly applied to remote manipulation tasks is quenstionable. The objective of this evaluation was to determine the effects of reversed, inverted, and inverted/reversed views on remote manipulation task performance using two 3-Degree of Freedom (DOF) hand controllers and a replica position hand controller. Results showed that trials using the inverted viewing condition showed the worst performance, followed by the inverted/reversed view and the reversed view when using the 2x3 DOF. However, these differences were not significant. The inverted and inverted/reversed viewing conditions were significantly worse than the normal and reversed viewing conditions when using the Kraft Replica. A second evaluation was conducted in which additional trials were performed with each viewing condition to determine the long term effects of spatially displaced views on task performance for the hand controllers. Results of the second evaluation indicated that there was more of a difference in performance between the perturbed viewing conditions and the normal viewing condition with the Kraft Replica than with the 2x3 DOF.

Manahan, Meera K.↗

NASA NTRS1991

Investigation of varying gray scale levels for remote manipulation

A study was conducted to investigate the effects of variant monitor gray scale levels and workplace illumination levels on operators' ability to discriminate between different colors on a monochrome monitor. It was determined that 8-gray scale viewing resulted in significantly worse discrimination performance compared to 16- and 32-gray scale viewing and that there was only a negligible difference found between 16 and 32 shades of gray. Therefore, it is recommended that monitors used while performing remote manipulation tasks have 16 or above shades of gray since this evaluation has found levels lower than this to be unacceptable for color discrimination task. There was no significant performance difference found between a high and a low workplace illumination condition. Further analysis was conducted to determine which specific combinations of colors can be used in conjunction with each other to ensure errorfree color coding/brightness discrimination performance while viewing a monochrome monitor. It was found that 92 three-color combination and 9 four-color combinations could be used with 100 percent accuracy. The results can help to determine which gray scale levels should be provided on monochrome monitors as well as which colors to use to ensure the maximal performance of remotely-viewed color discrimination/coding tasks.

Bierschwale, John M.↗

NASA NTRS1991

Space Station Freedom coupling tasks: An evaluation of their space operational compatibility

The development of the Space Station Freedom tasks that are compatible with both telerobotic as well as extravehicular activity is a necessary redundancy in order to insure successful day to day operation. One task to be routinely performed aboard Freedom will be the changeout of various quick disconnect fluid connectors. In an attempt to resolve these potentially contradictory issues of compatibility, mock-ups of couplings suitable to both extravehicular as well as telerobotic activity were designed and built. An evaluation performed at the Remote Operator Interaction Laboratory at NASA's Johnson Space Center is discussed, which assessed the prototype couplings as well as three standard coupling designs. Data collected during manual and telerobotic manipulation of the couplings indicated that the custom coupling was in fact shown to be faster to operate and generally preferred over the standard coupling designs.

Sampaio, Carlos E.↗

NASA NTRS1991

Adaptive strategies of remote systems operators exposed to perturbed camera-viewing conditions

This report describes a preliminary investigation of the use of perturbed visual feedback during the performance of simulated space-based remote manipulation tasks. The primary objective of this NASA evaluation was to determine to what extent operators exhibit adaptive strategies which allow them to perform these specific types of remote manipulation tasks more efficiently while exposed to perturbed visual feedback. A secondary objective of this evaluation was to establish a set of preliminary guidelines for enhancing remote manipulation performance and reducing the adverse effects. These objectives were accomplished by studying the remote manipulator performance of test subjects exposed to various perturbed camera-viewing conditions while performing a simulated space-based remote manipulation task. Statistical analysis of performance and subjective data revealed that remote manipulation performance was adversely affected by the use of perturbed visual feedback and performance tended to improve with successive trials in most perturbed viewing conditions.

Stuart, Mark A.↗

NASA NTRS1990

Telepresence for space: The state of the concept

The purpose here is to examine the concept of telepresence critically. To accomplish this goal, first, the assumptions that underlie telepresence and its applications are examined, and second, the issues raised by that examination are discussed. Also, these assumptions and issues are used as a means of shifting the focus in telepresence from development to user-based research. The most basic assumption of telepresence is that the information being provided to the human must be displayed in a natural fashion, i.e., the information should be displayed to the same human sensory modalities, and in the same fashion, as if the person where actually at the remote site. A further fundamental assumption for the functional use of telepresence is that a sense of being present in the work environment will produce superior performance. In other words, that sense of being there would allow the human operator of a distant machine to take greater advantage of his or her considerable perceptual, cognitive, and motor capabilities in the performance of a task than would more limited task-related feedback. Finally, a third fundamental assumption of functional telepresence is that the distant machine under the operator's control must substantially resemble a human in dexterity.

Smith, Randy L.↗

NASA NTRS1990

Hand controller commonality evaluation process

A hand controller evaluation process has been developed to determine the appropriate hand controller configurations for supporting remotely controlled devices. These devices include remote manipulator systems (RMS), dexterous robots, and remotely-piloted free flyers. Standard interfaces were developed to evaluate six different hand controllers in three test facilities including dynamic computer simulations, kinematic computer simulations, and physical simulations. The hand controllers under consideration were six degree-of-freedom (DOF) position and rate minimaster and joystick controllers, and three-DOF rate controllers. Task performance data, subjective comments, and anthropometric data obtained during tests were used for controller configuration recommendations to the SSF Program.

Stuart, Mark A.↗

NASA NTRS1989

The use of graphics in the design of the human-telerobot interface

The Man-Systems Telerobotics Laboratory (MSTL) of NASA's Johnson Space Center employs computer graphics tools in their design and evaluation of the Flight Telerobotic Servicer (FTS) human/telerobot interface on the Shuttle and on the Space Station. It has been determined by the MSTL that the use of computer graphics can promote more expedient and less costly design endeavors. Several specific examples of computer graphics applied to the FTS user interface by the MSTL are described.

Stuart, Mark A.↗

NASA NTRS1989

Speech versus manual control of camera functions during a telerobotic task

Voice input for control of camera functions was investigated in this study. Objective were to (1) assess the feasibility of a voice-commanded camera control system, and (2) identify factors that differ between voice and manual control of camera functions. Subjects participated in a remote manipulation task that required extensive camera-aided viewing. Each subject was exposed to two conditions, voice and manual input, with a counterbalanced administration order. Voice input was found to be significantly slower than manual input for this task. However, in terms of remote manipulator performance errors and subject preference, there was no difference between modalities. Voice control of continuous camera functions is not recommended. It is believed that the use of voice input for discrete functions, such as multiplexing or camera switching, could aid performance. Hybrid mixes of voice and manual input may provide the best use of both modalities. This report contributes to a better understanding of the issues that affect the design of an efficient human/telerobot interface.

Bierschwale, John M.↗