In recent years, autonomous mobile robots have increasingly been used in logistics and service industries to transport and deliver packages. However, it has not yet been fully understood what distances or movement patterns make people feel comfortable and safe when working in the same space with robots. In particular, when a robot approaches a person to receive a package, its movement trajectory and stopping position may greatly influence how the person perceives comfort and behaves. Against this background, the present study aimed to clarify the behavioral characteristics and subjective comfort of humans when they face and approach an autonomous robot to hand over a package. To achieve this, the researchers conducted three psychophysical experiments.

In the first experiment, the team examined how people’s walking behavior changes depending on how closely the robot approaches. The results showed that when the robot came within a short distance, participants tended to walk more cautiously and often hesitated, sometimes stopping momentarily. In the second experiment, the researchers investigated how the weight of the package influences perceived comfort. They found that participants felt more comfortable when the robot approached closely, especially when the package was heavy. In contrast, when the robot remained stationary at a distance, participants tended to feel uncomfortable. In the final experiment, the study compared people who were familiar with robots with those who were not. No significant differences in comfort ratings were found between the two groups.

Taken together, these findings suggest that humans may perceive a robot’s approach not merely as mechanical motion, but as a cooperative action to help receive the package. In other words, by appropriately designing a robot’s approach distance and motion patterns, it may be possible to create robot behaviors that provide people with a greater sense of comfort and reassurance. This study provides fundamental insights for realizing a society in which humans and robots can collaborate safely and comfortably.

Assistant Professor Hideki Tamura, one of the study’s co-first authors from the Department of Computer Science and Engineering, explained: “Autonomous mobile robots are increasingly being used in various applications such as logistics, food delivery, and serving in restaurants. For these robots to become more familiar and accepted in our daily lives, their movements must be designed to feel natural and comfortable to people. We believe that by incorporating human cognitive and behavioral characteristics into robot motion design, it will be possible to achieve more comfortable coexistence between humans and robots.”

In the future, the research team plans to conduct further investigations in more realistic settings to examine how various factors—such as the robot’s appearance, size, emitted sounds, speed, and direction of movement—affect human perception and comfort. Based on these findings, the researchers aim to establish a foundational framework for designing robot behaviors that enable safe and comfortable collaboration between humans and robots in diverse contexts, including logistics and service environments. These efforts are expected to contribute to the realization of a society in which robots are more naturally accepted as part of our living environments and can work alongside people in everyday life.