Perceiving virtual geographic slant: action influences perception

technical reportFour experiments varied the extent and nature of observer movement in a virtual environment to examine the influence of action on estimates of geographical slant. Previous slant studies demonstrated that people consciously overestimate hill slant but can still accurately guide an action toward the hill (Proffitt, Bhalla, Gossweiler & Midget, 1995). Related studies (Bhalla & Proffitt, 1999) suggest that one s potential to act may influence perception of slant and that distinct representations may independently inform perceptual and motoric responses. We found that in all conditions, perceptual judgments were overestimated and motoric adjustments were more accurate. The virtual environment allowed manipulation of the effort required to walk up simulated hills. Walking with the effort appropriate to the visual slant led to increased perceptual overestimation of slant compared to active walking with effort appropriate to level ground, while visually guided actions remained accurate

Locomotion in virtual environments and analysis of a new virtual walking device

This thesis investigates user interfaces for locomotion in virtual environments (VEs). It looks initially at virtual environments and user interfaces, then concentrates on locomotion interfaces, specifically on the Omni-Directional Treadmill (ODT) (Darken and Cockayne, 1997) and a new virtual walking device, LocoX, which was developed at the MOVES Institute, Naval Postgraduate School. It analyzes and compares the ODT and LocoX in terms of the application of human ability requirements (HARs). Afterwards, it compares the results of the analysis of the ODT and LocoX to real-world locomotion. The analysis indicates that LocoX, a new way of exploring virtual environments (VEs), provides a close match to real locomotion on some subtasks in VEs-- compared to the ODT--and produces relatively closer representation on some subtasks of real world locomotion. This thesis concludes that LocoX has great potential and that the locomotion provided is realistic enough to simulate certain kinds of movements inherent to real-world locomotion. LocoX still requires maturation and development, but is nonetheless a viable locomotion technique for VEs and future game-based simulations.http://archive.org/details/locomotioninvirt109452226Lieutenant Junior Grade, Turkish NavyApproved for public release; distribution is unlimited

Expanding the usable workspace of a haptic device by placing it on a moving base

The goal of this research is to expand the reachable workspace of a haptic device when used in a projection screen virtual environment. The proposed method includes supplementing the haptic device with a redundant degree of freedom to provide motion of the base. The key research challenge is to develop controls for the mobile base that will keep the haptic end-effector in the usable haptic workspace at all times. An experimental set up consisting of an Omni haptic device and a XY motorized table was used in the development of the control algorithms. Tests were conducted which demonstrate that the force felt by the user when touching a virtual wall remains constant even when the mobile base is moving to re-center the haptic device in the usable haptic workspace

Reliability of a feedback-controlled treadmill algorithm dependent on the user\u27s behavior

he reliability of the treadmill belt speed using a feedback-controlled treadmill algorithm was analyzed in this study. Using biomechanical factors of the participant\u27s walking behavior, an estimated walking speed was calculated and used to adjust the speed of the treadmill. Our proposed algorithm expands on the current hypotheses of feedback-controlled treadmill algorithms and is presented below. Nine healthy, young adults walked on a treadmill controlled by the algorithm for three trials over two days. Each participant walked on the feedback-controlled treadmill for one 16-minute and one five-minute trial during day one and one 16-minute trial during day two. Mean, standard deviation, interclass correlation coefficient (ICC), and standard error of measurement (SEM) were analyzed on the treadmill belt speed mean, standard deviation, and coefficient of variation. There were significantly high ICC for mean treadmill speed within- and between-days. Treadmill speed standard deviation and coefficient of variation were significantly reliable within-day. These results suggest the algorithm will reliably produce the same treadmill belt speed mean, but may only produce a similar treadmill belt speed standard deviation and coefficient of variation if the trials are performed in the same day. A feedback-controlled treadmill algorithm that accounts for the user\u27s behavior provides a greater level of control and minimizes any possible constraints of walking on a conventional treadmill

Emulating constant acceleration locomotion mechanics on a treadmill

Locomotion on an accelerating treadmill belt is not dynamically similar to overground acceleration. The purpose of this study was to test if providing an external force to compensate for inertial forces during locomotion on an accelerating treadmill belt could induce locomotor dynamics similar to real accelerations. Nine males (mean±sd age=26±4 years, mass=81±9 kg, height=1.8±0.05 m) began walking and transitioned to running on an accelerating instrumented treadmill belt at three accelerations (0.27 m s, 0.42 m s, 0.76 m s). Half the trials were typical treadmill locomotion (TT) and half were emulated acceleration (EA), where elastic tubing harnessed to the participant provided a horizontal force equal to mass multiplied by acceleration. Net mechanical work (W) and ground reaction force impulses (I) were calculated for individual steps and a linear regression was performed with these experimental measures as independent variables and theoretically derived values of work and impulse as predictor variables. For EA, linear fits were significant for W (y=1.19x+10.5,

Inattentional Blindness for Redirected Walking Using Dynamic Foveated Rendering

Redirected walking is a Virtual Reality(VR) locomotion technique which enables users to navigate virtual environments (VEs) that are spatially larger than the available physical tracked space. In this work we present a novel technique for redirected walking in VR based on the psychological phenomenon of inattentional blindness. Based on the user's visual fixation points we divide the user's view into zones. Spatially-varying rotations are applied according to the zone's importance and are rendered using foveated rendering. Our technique is real-time and applicable to small and large physical spaces. Furthermore, the proposed technique does not require the use of stimulated saccades but rather takes advantage of naturally occurring saccades and blinks for a complete refresh of the framebuffer. We performed extensive testing and present the analysis of the results of three user studies conducted for the evaluation

Walking speed and spatiotemporal step mean measures are reliable during feedback-controlled treadmill walking; however, spatiotemporal step variability is not reliable

The purpose of the study was to compare the effects of a feedback-controlled treadmill (FeedbackTM) to a traditional fixed-speed treadmill (FixedTM) on spatiotemporal gait means, variability, and dynamics. The study also examined inter-session reliability when using the FeedbackTM. Ten young adults walked on the FeedbackTM for a 5-minute familiarization followed by a 16-minute experimental trial. They returned within one week and completed a 5-minute familiarization followed by a 16-minute experimental trial each for FeedbackTM and FixedTM conditions. Mean walking speed and step time, length, width, and speed means and coefficient of variation were calculated from all experimental conditions. Step time, length, width, and speed gait dynamics were analyzed using detrended fluctuation analysis. Mean differences between experimental trials were determined using ANOVAs and reliability between FeedbackTM sessions was determined by intraclass correlation coefficient. No difference was found in mean walking speed nor spatiotemporal variables, with the exception of step width, between the experimental trials. All mean spatiotemporal variables demonstrated good to excellent reliability between sessions, while coefficient of variation was not reliable. Gait dynamics of step time, length, width, and speed were significantly more persistent during the FeedbackTM condition compared to FixedTM, especially step speed. However, gait dynamics demonstrated fair to poor reliability between FeedbackTM sessions. When walking on the FeedbackTM, users maintain a consistent set point, yet the gait dynamics around the mean are different when compared to walking on a FixedTM. In addition, spatiotemporal gait dynamics and variability may not be consistent across separate days when using the FeedbackTM

Investigating the Effectiveness of a Haptic Feedback System to Improve the Gait Speed of Older Adults in Overground Walking

While the use of tactile feedback for modifying gait has recently shown promising results in a number of research studies, there has been little attention given to its ability to effect change in the gait of older adults nor has the effect of the frequency of this feedback been examined. Given the important associations of walking speed with the health of older adults, the goal of this study was to determine if a recently developed haptic feedback system could increase the walking speed of older adults and whether the frequency at which this feedback was provided would have an impact on the results. In order to achieve a faster walking speed, peak thigh extension was selected as a biomechanical surrogate for stride length with vibrotactile haptic feedback being provided to the thighs to increase that parameter and, consequently, increase speed. Further, the influence of the frequency of the feedback on several other gait parameters was also investigated. Ten healthy older adults (68.4 ± 4.1 years) were recruited for this study, in which their peak thigh extension, cadence, normalized stride length, and normalized stride velocity, as well as their coefficients of variation (COV), were compared among six different experimental conditions. The study’s findings demonstrated that when compared to their pretest values, older people using the haptic feedback device had considerably longer peak thigh extensions during both post-tests and feedback walking conditions. The longer stride length made possible by this more extended thigh angle allowed for a corresponding rise in walking velocity. Surprisingly, none of the gait metrics examined were substantially impacted by the feedback’s frequency. In other words, regardless of how frequently the input was given, the haptic feedback device was successful in improving elderly people’s walking abilities. These results indicate the haptic feedback device has the potential to enhance gait speed, stride length, and stride velocity, which are essential elements involved with keeping independence and mobility in older people