Approach to ease design criteria of a real-time model used in a VR training system considering constraints of human perception

Date
2012-07-23
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Abstract
Virtual reality (VR) systems have potential of contributing to the training of medical students in a variety of procedures. This thesis focuses on a design issue related to developing VR training systems for soft tissue (e.g., breast phantom) palpation. In such a VR system, it is paramount to provide a real-time model that simulates physical behavior of an actual breast phantom. However, it is difficult to design such a real-time model with high accuracy due to time and physical constraints. To mitigate this difficulty, I consider constraints of human perception which is insensitive to small discrepancies of objects during real-time interaction. Such consideration could aid to relax design criteria of the real-time model by achieving its accuracy at a certain degree while keeping human perception of object softness unchanged. Therefore, I take a two-step approach to determine visual and haptic (pertinent to force feedback) discrepancies tolerable for this human perception. In the first step, an evaluation method is developed to compute discrepancies of the real-time model for visual displacement and force feedback, compared to its finite element method counterpart featuring physical parameters of a breast phantom. The computation uses statistical analyses which like human perception are insensitive to small discrepancies of datasets. In the second step, two studies are performed to examine the constraints of human perception. The first study reexamined raw data from my MSc work to understand the effect of three popular alignments between a visual display and a haptic device on the human perception of object softness. This study serves to select an alignment producing the least perceptual illusion and physical workload for palpation. Using the evaluation method and the selected alignment, the second study investigates the effect of different discrepancies on the human perception of object softness. It is observed that this perception is insensitive to small discrepancies up to a threshold of 11.0% and 6.3% for visual displacement and force feedback, respectively. This indicates that a real-time model yielding discrepancies of visual displacement and force feedback below their respective thresholds could be sufficient for simulating a soft tissue (such as a breast phantom) during palpation.
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Engineering--Electronics and Electrical
Citation
Widmer, A. (2012). Approach to ease design criteria of a real-time model used in a VR training system considering constraints of human perception (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/24980