Browsing by Author "Gellatly, Andrew William"

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    Effects of seated posture on static strength, lower-body isometric muscle contractions, and manual tracking performance
    Gellatly, Andrew William (Virginia Tech, 1995-05-05)
    This research evaluates the effects of seat back angle and armrest angle on performance of the following variables: (1) static force generation capabilities on an isometric force-stick; (2) lower-body isometric muscle contractions used in anti-gravity straining maneuvers (AGSMs); and (3) tracking performance for a manual tracking task. The purpose of this research is to determine if certain body postures significantly affect force generation, isometric muscle contractions, and tracking error. Subjects perform three different tasks over four experimental sessions. In the first session, subjects generate maximum force on a sidearm isometric force-stick at 18 seat back and armrest combinations (six seat back angles x three armrest angles) in two directions (roll left and roll right). In the next three sessions, subjects perform either a manual tracking task or a manual tracking task concurrent with lower-body isometric muscle contractions at each of the 18 seat back and armrest combinations. The dependent measures used to evaluate performance are stick force, blood pressure, and tracking error. The results indicate the following: (1) static force generation ability is significantly affected by gender, seat back angle, and direction in which the force is applied; (2) 1ower-body isometric muscle contractions used to elevate blood pressure are not significantly affected by seatback angle and armrest angle; and (3) tracking error is significantly affected by seatback angle. Some results are consistent with previous research that found force capabilities are affected by the direction in which force is applied, and that body posture does not affect isometric muscle contractions used to increase blood pressure. However, other results indicate the need for further research to determine the relationship of body posture to isometric muscle contraction used in AGSMs and manual tracking.
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    The Use of Speech Recognition Technology in Automotive Applications
    Gellatly, Andrew William (Virginia Tech, 1997-03-28)
    The research objectives were (1) to perform a detailed review of the literature on speech recognition technology and the attentional demands of driving; (2) to develop decision tools that assist designers of in-vehicle systems; (3) to experimentally examine automatic speech recognition (ASR) design parameters, input modalities, and driver ages; and (4) to provide human factors recommendations for the use of speech recognition technology in automotive applications. Two experiments were conducted to determine the effects of ASR design parameters, input modality, and age on driving performance, system usability, and driver preference/acceptance. Eye movement behavior, steering input behavior, speed maintenance behavior, reaction time to forward scene event, task completion time, and task completion errors when driving and performing in-vehicle tasks were measured. Driver preference/acceptance subjective data were also recorded. The results showed that ASR design parameters significantly affected measures of driving performance, system usability, and driver preference/acceptance. However, from a practical viewpoint, ASR design parameters had a nominal effect on driving performance. Differences measured in driving performance brought on by changes in ASR system design parameters were small enough that alternative ASR system designs could be considered without impacting driving performance. No benefits could be claimed for ASR systems improving driving safety/performance compared to current manual-control systems. Speech recognition system design demonstrated a moderate influence on the usability of in-vehicle tasks. Criteria such as task completion times and task completion errors were shown to be different between speech-input and manual-input control methods, and under different ASR design configurations. Therefore, trade-offs between ASR system designs, and between speech-input and manual-input systems, could be evaluated in terms of usability. Finally, ASR system design had a nominal effect on driver preference/acceptance. Further research is warranted to determine if long-term use of ASR systems with less than optimal design parameters would result in significantly lower values for driver preference/acceptance compared to data collected in this research effort. Human factors recommendations for the use of ASR technology in automotive applications are included. The recommendations are based on the empirical research and the literature review on speech recognition technology and the attentional demands of driving.