Attempts to put robots to practical use have been increasing, as robot becomes more human-friendly. In the human-robot interaction field, main issues are how variously the robot can express its emotion and how much the expression is socially acceptable. This paper proposes a robot's expression generation method based on the context information and combination of behavior database for emotional interactive service. Our goal is to generate synchronized multimodal expressions automatically using a few of pre-defined database and the context information inputs. Overall procedure is separated by offline task using a GUI-based editing toolkit and online task using an automatic generation method. In the offline task, behavior database is formulated corresponding to types of sentences and robot's emotional state. For automatic generation, we propose primitive database based on parameters and organizing behavior database. In the online task, using context information inputs, robot generates new expression automatically. Proposed generation method is to combine pre-defined behavior database using parameters of the primitive database and interpolation method. Finally, generated synchronized multimodal expressions are refined according to a robot's hardware.

In the field of HRI, to take advantage of people’s innate ability of communication, researchers have thus far concentrated on facial expression in facilitating human robot communication. However, for the robot to express emotional intensity, other modalities such as gestures, movement, sound, and color are also needed. This paper suggests that the intensity of emotion can be expressed with color and blinking, which are applicable on robots via LED. Although color and emotion have certain relations, it is difficult to implement the findings of previous research in this area due to a lack of quantitative data. In this paper, we determined RGB values of color and blinking period to effectively express intensities of six basic emotions based on quantitative data. Color and blinking are implemented on an avatar and the intensities of emotions are evaluated through surveys with the avatar. It was found that color and blinking helped the avatar express emotional intensity of surprise, happiness, disgust, and anger. For fear, and sadness, the color and blinking did not play a significant role.

Recently, in the field of HRI, multimodal expression has been an issue. Synchronizing modalities and determining what modality to use are important aspect of multimodal expression. For example, when robots express emotional states, they may use only facial expressions or facial expressions with gestures, neck motions, sounds, etc. In this paper, emotional boundaries are proposed for multimodal expression in a three-dimensional affect space. The simultaneous expression of facial expression and gestures was demonstrated using proposed emotional boundaries on a simulator.

This paper introduces an emotion interaction system for a service robot. The purpose of emotion interaction systems in service robots is to make people feel that the robot is not a mere machine, but reliable living assistant in the home. The emotion interaction system is composed of the emotion recognition, generation, and expression systems. A user's emotion is recognized by multi-modality, such as voice, dialogue, and touch. The robot's emotion is generated according to a psychological theory about emotion: OCC (Ortony, Clore, and Collins) model, which focuses on the user's emotional state and the information about environment and the robot itself. The generated emotion is expressed by facial expression, gesture, and the musical sound of the robot. Because the proposed system is composed of all the three components that are necessary for a full emotional interaction cycle, it can be implemented in the real robot system and be tested. Even though the multi- modality in emotion recognition and expression is still in its rudimentary stages, the proposed system is shown to be extremely useful in service robot applications. Furthermore, the proposed framework can be a cornerstone for the design of emotion interaction and generation systems for robots.

It is expected that robots will be widely exposed to humans in the near future. Emotional communication is very important in human-robot interaction, as well as human- human interaction. Facial expression is an emotional expression method between humans, and it also enables human to recognize a robot's emotional state. Although there are lots of previous research regarding facial expressions, it is not easily applicable to different shapes of robot faces, if the number and types of the robot's control points are varied. In addition, the natural connection between emotions has not been considered or has been inefficiently implemented in previous research. In this paper, we propose a linear dynamic affect-expression model for continuous change of expression and diversifying characteristics of expressional changes. Therefore, the proposed model allows a robot's facial expression and expression changes to more closely resemble those of humans, and this model is applicable to various mascot-type robots irrespective of the number and types of robot's control points.

A robot's face is its symbolic feature, and its facial expressions are the best method for interacting with people with emotional information. Moreover, a robot's facial expressions play an important role in human-robot emotional interactions. This paper proposes a general rule for the design and realization of expressions when some mascot-type facial robots are developed. Mascot-type facial robots are developed to enable friendly human feelings. The number and type of control points for six basic expressions or emotions were determined through a questionnaire. A linear affect-expression space model is provided to realize continuous and various expressions effectively, and the effects of the proposed method are shown through experiments using a simulator and an actual robot system.