Behavioral expression by an expressive mobile robot-expressing vividness, mental distance, and attention

This paper proposes an idea that it is possible for a mobile robot to display behavioral expressions by its motion. Behavioral expressions are expressions of vividness, sense of distance and attention. To confirm the idea concretely, an expressive mobile robot has been designed and implemented to display the behavioral expressions. Utilizing the robot, psychological experiments have been conducted to evaluate impressions on three items: 1) velocity changing pattern, 2) distance between human and the robot, and 3) various poses. The experimental results indicate: firstly, there is a proper speed pattern for expression of vividness, the pattern being triangular along the time axis; secondly, there is a proper distance range between human and robot for expression of mental distance between them, its average value being about 2.5 m; thirdly, when the robot faces the human, the impression of attention is increased where the robot puts its head on one side or raises its hands. The implemented expressive mobile robot is puppy-sized and has 2 DOFs for motion, 2 DOFs for two swingable arms and 3 DOFs for pan, tilt and yaw of its head. The experimental results prove feasibility of the proposed idea of the behavioral expression by the robot.