# Shared eHMI: Bridging Human-Machine Understanding in Autonomous Wheelchair Navigation
## 3 Our Method
### Pilot Study via Video-Based Experiments and Interviews  
In the pilot study, we implemented video-based experiments with our autonomous wheelchair simulation platform [68, 69]. Participants engaged with the experiments by watching videos, immersing themselves in first-person perspective scenarios, and were also presented with third-person perspectives for holistic scene comprehension. Following the video presentations, participants were invited to complete questionnaires and partake in interviews for further insights.  
1. Experiment 1: Viewpoints of Wheelchair Users  
The aim of Experiment 1 was to showcase typical user scenarios of the autonomous wheelchair with the proposed shared eHMI, delineating wheelchair behaviors and interactions with pedestrians. Two distinct experimental routes, as depicted in Figure 6, were chosen to test varied wheelchair behaviors, offering a comprehensive overview of the user interface and interaction designs. In Route 1, two obstacles were placed: a curb to simulate the road's bend and a general route obstacle to represent unexpected impediments encountered during typical navigational routes. These obstacles disrupted the autonomous navigation, necessitating the autonomous wheelchair to execute tasks like moving straight, turning, and obstacle avoidance. Route 2 was designed to simulate scenarios of coexistence between wheelchairs and pedestrians, incorporating both stationary and moving pedestrian behaviors, to assess the wheelchair's behaviors in circumventing and yielding to different pedestrian conditions.  
Figure 5: Construction of the autonomous wheelchair simulation platform, illustrating the hardware components utilized.  
Experiment 1 focused on the assessment of on-ground projection interactions within the realm of autonomous driving, alongside gauging user attitudes and experiential metrics. Initially, participants were familiarized with the components of the projection interface, aiding their comprehension of user interface information. Following this, a 5.5 min video was shown to the participants, integrating visual and auditory components. This video, which was segmented into three distinct parts, immersed the participants in the first-person perspective of a user interacting with the autonomous wheelchair. The first segment of the video depicted the autonomous wheelchair navigating along Route 1 without the on-ground projection interaction. The following segments sequentially presented the wheelchair's navigation on Route 1 and then Route 2 with the projection feature engaged.  
2. Experiment 2: Viewpoints of pedestrians  
The purpose of Experiment 2 was to assess the acceptance of pedestrians when interacting with an autonomous wheelchair equipped with on-ground projection technology. This experiment involved a larger number of participants who were invited to engage from the first-person perspective of both stationary and moving pedestrians interacting with an autonomous wheelchair.  
The video shown to participants was segmented into two distinct parts: In the first segment, participants were shown sequentially embodying the roles of stationary and moving pedestrians as they interacted with an autonomous wheelchair without projection interaction. The second segment presented interactions between pedestrians and the autonomous wheelchair with the projection feature engaged. The video for Experiment 2 corresponded to the pedestrian perspective depicted in the third segment of Experiment 1. Following the viewing, participants were invited to complete a questionnaire too.