# Shared eHMI: Bridging Human-Machine Understanding in Autonomous Wheelchair Navigation
## 3 Our Method
### On-Ground Projection-Based Shared eHMI for Autonomous Wheelchair  
To enhance the understanding of wheelchair users and other road users regarding the behavior of autonomous wheelchairs and promote transparent communication, thereby boosting their trust in autonomous wheelchairs and improving safe interaction during road-sharing, we propose a ground-projection-based eHMI approach. This method is designed for sharing the visualization of the movement status and intentions of autonomous wheelchairs. This innovation aims to transparently and distinctly convey the intentions of the wheelchair, ensuring a comprehensive understanding for both users and pedestrians, thereby enriching the interactive experience. A conceptual outline of this approach is presented in Figure 2.  
As these projections integrate real-time environmental changes and present a varied color and pattern spectrum, this augmented visual feedback significantly heightens visibility and paves the way for a symbiotic human-machine relationship [64; 65]. [PERSON]'s research introduced four conceptual themes pertinent to autonomous wheelchair users: type of information needed, interaction modality, interface location, and adaptable design [42]. Based on this, we are considering the types of information interfaces and interaction content to provide for autonomous wheelchair users. Moreover, it is imperative to consider the dynamics between autonomous wheelchairs and other road users. Pedestrians, as the most targeted type of road users [66], also need to access information from autonomous wheelchairs. The incorporation of \"status + intention eHMI\" augments the user experience, enhances perceived system intelligence, elevates transparency, and contributes to an enhanced perception of safety [16]. We referenced the foundational eHMI use cases framework designed for autonomous cars, where the main suggestions include communicating the vehicle's status, its intentions, and interactions with pedestrians. The first two employ non-specific strategies, while interactions with pedestrians are more targeted and preserve the negotiation of right-of-way between autonomous vehicles and pedestrians [6]. Based on this framework, we modified and meticulously designed an eHMI framework specific to wheelchair scenarios, incorporating more detailed elements. This new framework synergizes HMI and eHMI to achieve more comprehensive user scenarios. As shown in Table 1, it includes three categories of use cases: wheelchair's status for user, wheelchair's intent, and wheelchair-pedestrian interaction. Based on these use cases, we identified specific scenarios that cover the majority of travel situations. For each scenario, we determined the necessary information to visualize, focusing on the problems users need to solve and the goals they aim to achieve. Specifically, taking the most intuitive and clear navigation path in the interface as an example, it needs to be displayed in multiple scenarios within the intent communication. These scenarios include the wheelchair starting, driving, slowing down or stopping, and turning. This highlights its vital role in conveying real-time path changes, turning, and behavioral intentions of the wheelchair. This design framework focuses on not just conveying wheelchair status and intentions but also elevating the overall user experience. It incorporates human-in-the-loop considerations for situations like poor road conditions, advising on mode adjustments to align with user preferences. In line with the insights from [PERSON]'s design implications, the interface should be context-responsive, efficiently channel a broad information range, and preclude information saturation. It is paramount that this interface harmoniously integrates into societal settings, emphasizing user empathy and societal receptiveness, thereby nurturing open communication between users and pedestrians [42].