집중 배열 초음파를 이용한 반고리관 가상 가속도 감각의 개념 및 수치 해석 모델링

Abstract

Virtual reality allows people to experience a groundbreaking sense of interactive 3D digital environment. However, virtual reality head-mounted displays include several problems, which threaten the nessicity. New environment bring unexperienced pleasure to users, but they also accompany undesirable discomport such as nausea, fatigue and dizziness. According to the cue conflict theory, the phenomena occur when correlation between visual and vestibular proprioceptive systems is mismatched. The absence of body movement in virtual environment implies mismatch of the vestibular-ocular system leading motion sickness. This paper proposes a concept of ultrasonic vestibular stimulation producing virtual acceleration sense to expand the applicability of head-mounted displays. The membranous labyrinth of semicircular canal in the human inner ear consists of endolymph. Rotation of the semicircular canal generates inertial force and drag force in endolymph inducing deformation of cupula, which transfers the orientation signals to the brain. Using the acoustic streaming phenomena, which is the fluid manipulation technique, we control the flow of the endolymph. To verify the influence of ultrasonic stimulation, we simulated and analyzed the deformation of cupula in both real rotation and virtual rotation environment. The two rotation model is constructed with finite element method and arbitrary Lagrangian Eulerian method. Our simulation was performed using simulation package, COMSOL5.5. The program enables us to estimate and compare the two different circumstances; real rotation and virtual rotation. The model representing real rotation is analyzed by fully-coupled fluid structure interaction between fluid velocity and solid displacement. For inducing the virtual sense of rotation to human, we utilized acoustic structure interaction which analyze both acoustic pressure and solid deformation. Although galvanic vestibular stimulation has been developed for decades, the electrical system has fatal disadvantages such as weight of the circuit, low resolution, and ambiguity as an input source. Furthermore, its fundamental effects on the neural activities are still elusive, such as the dominant parameters. Even though the ultrasonic vestibular stimulation is an undeveloped territory, the advantages such as resolution, non-invasive, high speed, and lightness can be expected. Throughout these investigations about virtual sense of rotation, the critical defects of virtual reality head mounted-displays related to the vestibular-ocular system can be resolved. In addition, further 3D real experiences can provided to user.