Investigating Emotional Expressivity in Robots Wearing Light-Emitting Clothing
Authors: Sugiyama Takashi , Kanoh Masayoshi 
Published: October 2023

People communicate smoothly through emotional expressions. Therefore, we consider that emotional expression by robots is necessary for human-robot coexistence as well. Various studies have been conducted on emotional expression by robots. In our previous study, we created a robot named "Tilting Robot" that tilts back and forward, and investigated the effect of the color of the clothing worn by the robot on its emotional expression. The results showed that the intensity of the emotional expression may change depending on the color of the clothing and the speed of the robot's motion. In this paper, we investigate the effect of using light-emitting EL sheets as a material for the robot's clothing. Many robots have been developed that express emotional expression by emitting light from their eyes and cheeks, but there is no research on emotional expression by emitting light from clothing. In addition, light-emitting clothing is easy to implement and does not cause discomfort when worn by a robot, so if light-emitting clothing is effective in emotional expression, it has great potential for application. In the experiment, the robot's clothing was colored red, green, blue, and white, and a light-emitting material (EL sheet) and a non-light-emitting material (felt) were prepared for each of the four colors. Also, for the light-emitting material, two conditions were set: one was to emit light continuously during the robot's motion (constant light-emitting condition), and the other was to emit light in the middle of the robot's motion (midway light-emitting condition). Therefore, there are three conditions for the clothing: the felt condition, the constant light-emitting condition, and the midway light-emitting condition. The robot made a total of five motions, including back and forward tilting motions, fast and slow motions, and no motion while in an upright posture. Subjects observed a total of 60 materials that were a combination of all conditions and motions on a monitor, and evaluated each material.The results of the experiment showed that, first of all, when the robot leaned backward quickly, subjects expressed an emotional expression of surprise, regardless of the type of clothing. In addition, when the motion was slow, the robot also expressed surprise in the mid-lighting condition. These results indicate that the intensity of instantaneous emotional expressions such as surprise depends on the speed of motion, and that the midway light may be used to express the emotion. In addition, it was found that the forward-tilting motion can express the emotional expression of sadness regardless of the type of clothing.Next, when we focused on the color of the clothing, we found that the color red evoked an emotional expression of anger, and that the two luminous conditions evoked anger more strongly than the felt condition, in which no luminescence was emitted. The blue color showed the same level of emotional expression of sadness in all clothing conditions. These results indicate that emotional expression can be achieved by changing the color of clothing, as in previous studies, but that the luminescence of the clothing may make it more pronounced.