Dynamic stability of VR headsets: the effect of contact area on displacement in user motion

Since the metaverse was introduced, virtual reality (VR) head-mounted displays (HMDs) are increasingly being used for VR gaming, sports and 3D films. Additionally, the Pancake optical module has made HMDs smaller and lighter, which greatly increased its comfortability. However, during real use, there will inevitably be a lot of user head mouvements, such as shaking, lowering and raising, etc., which will cause certain displacement of the HMDs due to its inertia. Then the relative displacement of HMDs may affect the pressure and pressure-bearing area of the head, which leads to user discomfort.Currently, the research on the comfort of HMDs primarily focuses on the static scenarios without mouvement. This paper investigated the relative displacement and user comfort of the HMDs in motion. The main purpose of this study is to determine the relationship between HMDs' displacement and the contact area in order to provide design guidances and insights for HMDs, particularly the binding area. This paper also proposed an effective experimental method for measuring the relative displacement of HMDs, which can be used to assess the dynamic stability.A simple VR environment was bulit to guide the participant’s head movements by moving circular lightened dots, for simulating the head mouvements in daily life. At the same time, a wearable ruler sticker was designed to measure the displacement of the HMDs relative to the head.The experimenter took measurements of participants’ heads and assisted them to get familiar with the HMDs, and then pasted ruler stickers on the participants’ faces. The participants put on the HMD and adjust it to a comfortable position. Then they completed the head movement under the guidance of the VR environment and repeated it for 5 times. The same procedure was repeated after changing the contact area of the binding with 40mm*40mm foam cotton pieces. The HMD’s position was recorded before and after the mouvement.The results shows that, the HMDs exhibit a significant displacement relative to the head, after performing typical head motions, which causes some slight discomfort. Meanwhile, after doing a data correlation with SPSS, it can be found that the contact area of the binding is one of the main reasons for HMDs’ displacement. And the displacement can be greatly reduced and the pressure comfort rarely changes when the contact area of the bindings is increased, which has a positive impact on the overall comfort evaluation. Besides, we believe that in addition to the contact area, the mass distribution, pressure, and materials also have an effect on the relative displacement of HMDs, which might be the focus of future research. In future, new prototypes will be developed to increase the accuracy of environmental variables control and the evaluation of different factors.