Dr. Oliver Beren Kaul

Current virtual and augmented reality head-mounted displays usually include no or only a single vibration motor for haptic feedback and do not use it for guidance. We present HapticHead, a system utilizing multiple vibrotactile actuators distributed in three concentric ellipses around the head for intuitive haptic guidance through moving tactile cues. We conducted three experiments, which indicate that HapticHead vibrotactile feedback is both faster (2.6 s vs. 6.9 s) and more precise (96.4 % vs. 54.2 % success rate) than spatial audio (generic head-related transfer function) for finding visible virtual objects in 3D space around the user. The baseline of visual feedback is – as expected – more precise (99.7 % success rate) and faster (1.3 s) in comparison, but there are many applications in which visual feedback is not desirable or available due to lighting conditions, visual overload, or visual impairments. Mean final precision with HapticHead feedback on invisible targets is 2.3° compared to 0.8° with visual feedback. We successfully navigated blindfolded users to real household items at different heights using HapticHead vibrotactile feedback independently of a head-mounted display.

A high level of presence is an essential aspect of immersive virtual reality applications. However, presence is difficult to achieve as it depends on the system's user, immersion capabilities (visual, auditory, and tactile), and the concrete application. We use a vibrotactile grid around the head to further increase the level of presence users feel in virtual reality scenes. In a between-groups com-parison study, the vibrotactile group scored significantly higher in a standardized presence questionnaire than the baseline of no tactile feedback. Our study suggests the proposed prototype as an additional tool to increase the level of presence users feel in virtual reality scenes.

Creating tactile patterns on the body via a spatial arrangement of many tactile actuators offers many opportunities and presents a challenge, as the design space is enormous. This paper presents a VR interface that enables designers to rapidly prototype complex tactile interfaces. It allows for painting strokes on a modeled body part and translates these strokes into continuous tactile patterns using an interpolation algorithm. The presented VR approach avoids several problems of traditional 2D editors. It realizes spatial 3D input using VR controllers with natural mapping and intuitive spatial movements. To evaluate this approach in detail, we conducted a user study and iteratively improved the system. The study participants gave predominantly positive feedback on the presented VR interface (SUS score 79.7, AttrakDiff ``desirable''). The final system is released alongside this paper as an open-source Unity project for various tactile hardware.

Tactile patterns are a means to convey navigation instructions to pedestrians and are especially helpful for people with visual impairments. This article presents a concept to provide precise micro-navigation instructions through a tactile around-the-head display. Our system presents four tactile patterns for fundamental navigation instructions in conjunction with continuous directional guidance. We followed an iterative, user-centric approach to design the patterns for the fundamental navigation instructions, combined them with a continuous directional guidance stimulus, and tested our system with 13 sighted (blindfolded) and 2 blind participants in an obstacle course, including stairs. We optimized the patterns and validated the final prototype with another five blind participants in a follow-up study. The system steered our participants successfully with a 5.7 cm average absolute deviation from the optimal path. Our guidance is only a little less precise than the usual shoulder wobbling during normal walking and an order of magnitude more precise than previous tactile navigation systems. Our system allows various new use cases of micro-navigation for people with visual impairments, e.g., preventing collisions on a sidewalk or as an anti-veering tool. It also has applications in other areas, such as personnel working in low-vision environments (e.g., firefighters).

People with visual impairments face challenges in scene and object recognition, especially in unknown environments. We combined the mobile scene detection framework Apple ARKit with MobileNet-v2 and 3D spatial audio to provide an auditory scene description to people with visual impairments. The combination of ARKit and MobileNet allows keeping recognized objects in the scene even if the user turns away from the object. An object can thus serve as an auditory landmark. With a search function, the system can even guide the user to a particular item. The system also provides spatial audio warnings for nearby objects and walls to avoid collisions. We evaluated the implemented app in a preliminary user study. The results show that users can find items without visual feedback using the proposed application. The study also reveals that the range of local object detection through MobileNet-v2 was insufficient, which we aim to overcome using more accurate object detection frameworks in future work (YOLOv5x).

The vibrotactile funneling illusion is the sensation of a single (non-existing) stimulus somewhere in-between the actual stimulus locations. Its occurrence depends upon body location, the distance between the actuators, signal synchronization, and intensity. Related work has shown that the funneling illusion may occur on the forehead. We were able to reproduce these findings and explored five other regions to get a complete picture of the funneling illusion's occurrence on the head. Our study results (24 participants) show that the actuator distance, for which the funneling illusion occurs, strongly depends upon the head region. Moreover, we evaluated the centralizing bias (smaller perceived than actual actuator distances) for different head regions, which also showed widely varying characteristics. We computed a detailed heat map of vibrotactile localization accuracies on the head. The results inform the design of future tactile head-mounted displays that aim to support the funneling illusion.