## 3 Results and Discussion  
### Survey Results of Workers Collaborating with Quadruped Robots  
A survey of 93 workers with experience in quadruped robot collaboration was conducted to identify initial risk factors. Table 2 summarizes the identified risk factors and their frequencies. The results reveal several key insights into the practical safety concerns in human-robot collaboration. \begin{table}
\begin{tabular}{c c c c} \hline
**Risk Factor** & **Frequency of** **Mention** & **Main Content** & **Characteristics** \\ \hline Collision & 30–35 & Collisions with workers and equipment, sudden encounters at blind spots & Low height of robots; difficult to perceive due to low noise \\ Path deviation & 20–25 & Invasion of work areas, failure to avoid obstacles, unexpected route changes & Issues with recognizing existing safety \\ Battery discharge & 5–10 & Work interruptions due to battery discharge during operation, long charging time issues & Difficulty in moving robots when batteries are discharged \\ \hline \end{tabular}
\end{table} 
Table 2: Table of survey results for those with experience of collaborative working. Collision emerged as the most frequently mentioned risk factor (30-35% of the responses), characterized by concerns about potential impacts on workers or equipment, particularly in blind spots. This high level of concern likely stems from the unique characteristics of quadruped robots--their low height profile and quiet operation make them less noticeable than traditional mobile robots. Unlike wheeled robots that follow more predictable paths, quadruped robots' leg-based locomotion can create more complex movement patterns, potentially increasing collision risks in confined spaces. Path deviation was the second most cited concern (20-25%), with workers specifically noting issues with work area invasions and unexpected route changes. This heightened awareness of path deviation risks reflects the challenging nature of the factory environment, where robots must navigate through dense pipeline networks and narrow spaces. The concern about robots failing to recognize existing safety devices like traffic cones suggests a need for better integration of traditional safety measures with new robotic systems. Three factors--explosion prevention performance, sensor malfunction, and work environment issues--each received 15-20% of the mentions. A similar frequency of these concerns indicates a balanced awareness of both technical and environmental risks. The emphasis on explosion prevention performance is particularly noteworthy given the industrial setting, suggesting that workers are highly conscious of the potentially severe consequences of technical failures in hazardous areas. Battery discharge (5-10%) and other factors, including psychological burden and emergency response capabilities, were also identified. While these received fewer mentions, they highlight important aspects of human-robot collaboration that extend beyond the immediate physical safety concerns. The psychological impact on workers, for instance, indicates the need for comprehensive safety strategies that address both technical and human factors. Notably, unauthorized access and external acceleration received relatively few mentions (<5%). This lower frequency might suggest that existing security measures are perceived as adequate or that these issues are less visible in day-to-day operations. However, given the potential severity of security breaches or stability issues, these factors warrant careful consideration in safety planning despite their lower mention rates. An important context for interpreting these results is that no actual accidents occurred during the two-year operation period. Therefore, these risk perceptions reflect anticipated rather than experienced hazards. This proactive risk awareness among operators provides valuable insights for preventive safety measures while also suggesting a potential gap between perceived and actual risks that merit further investigation.