Fuzzy Controlled PAD Emotional State of a NAO Robot

Various Emotion Models (e.g. Circumplex Model [1], Vector Model [2], PANA (Positive Activation - Negative Activation) Model [3], PAD (Pleasure Arousal Dominance) Model [4], etc...) can be used to represent the different emotional states of a robot. In this paper we chose to use a PAD Emotional Space [5] to simulate the emotional state of a NAO Robot (NAO is the name of a humanoid robot developed and commercialized by Aldebaran Robotics). But one difficulty is to write an algorithm that makes evolve the emotional state according to external and internal stimuli. Simulating a coherent Emotional State over the time is a real challenge for designing a virtual personality. As human emotions are fuzzy by nature, many researchers explored using Fuzzy State Machine [6], [7] or Fuzzy Logic [8], [9], [10], [11], [12] to control the emotions of a virtual character or robot. Following the same approach, in this paper we propose to use a Fuzzy Control System [13] to control the emotional state of a NAO robot by injecting attractors in his PAD Emotional Space. Fuzzy Control Systems are usually good controller of uncertainty and easy to write thanks to their syntax close to the human language. The result of our experiments showed that the evolution of the Emotional State of our NAO robot was smooth and coherent with the situation met when interacting with humans. Moreover with different set of rules it becomes easy to switch the personality of the robot (meaning the robot can react differently to the same stimuli according to the different set of rules used).