Imitative Interactions with Sony humanoid robot

Experimental studies of the imitative interactions (Ito & Tani, 2004) between robots and humans were conducted by using the Sony humanoid robot QRIO SDR-4XII (see Figure 1). As the first step, adaptation of the robot was examined in the context of imitation by synchronization. The later experiment examines the case of mutual interactions. In this experiment, the robot learns multiple movement patterns shown by a user’s hand movements in the learning phase. The RNNPB shown in Figure 2 (a) learns to predict how the positions of both the user’s hands change in time in terms of the sensory mapping from st to st+1 and also it learns how to change the motor outputs correspondingly in supervised ways. The positions of the user’s hands are sensed by tracking colored balls in his hands. In the interaction phase, when one of the learned movement patterns is demonstrated by the user, the robot arms are expected to move by following the pattern. When the hand movement patten is switched from one to another, the robot arm movement pattern should switch correspondingly. This sort of on-line adaptation can be done by conducting the generation and the recognition processes simultaneously as a mirror system (see Figure 2 (b)). When the prediction of the user‘s hand movement generates error, the PB vector is updated to minimize the error in real time while the motor outputs are generated depending on the current PB values. The results of the experiment are plotted in Figure 3. It is observed that when the user hand movement pattern is switched from one of the learned patterns to another, the patterns in the sensory prediction and the motor outputs are also switched correspondingly by accompanying substantial shifts in the PB vector. Although the synchronization between the user hand movement pattern and the robot movement pattern is lost once during the transitions, the robot movement pattern is re-synchronized to the user hand movement pattern within several steps. The experiments also showed that once the patterns were synchronized they were preserved robustly against slight perturbations in the repetitions of the user’s hand movements. Our further analysis concluded that the attractor dynamics system, with its bifurcation mechanism via the