Mitsuhisa Yamashita

A motion rule for human-friendly robots based on electrodermal activity investigations and its application to mobile robot

This paper investigates impressions on the robot motion based on EDA experiments, deduces a motion rule for human-friendly robots from the investigations, and applies it to a mobile robot experimental apparatus. In our previous work, it was suggested that actuation noise come from the robots tended to raise the sympathetic nerve system (SNS) response of the heart rate variability. In another experiment it is observed that blocking out either the sound or the sight attenuated the electrodermal activity (EDA), which reflects the SNS, to the robot motion. In the present work, the experiment was designed not so as to avoid the influence of the habituation differently from the previous experiments, which was the significant factor contributing to reducing the EDA responses. As a result of statistical analysis, it was concluded that the present work supported the result of the previous work. Based on these investigations, we deduced the motion rule for human-friendly robots from this investigation, that robots must reduce their motion speed in the immediate vicinity of humans. We constructed the experimental setup that a mobile robot approached human with its speed decreased in conformity with the rule. To estimate the distance from the human, the skin color detection and depth-from-focus techniques were applied to a monocular color video camera system with pan/tilt/zoom operation. The experimental result showed that a proper choice of commands could perform the robot motion to reduce its speed in the immediate vicinity of the human.

Influence of auditory and visual modalities on skin potential response to robot motions

This paper addresses the issue of investigating the relationship between skin potential response (SPR) and robot motion from the aspect of auditory and visual modalities. The motion of the robotic devices primarily gave stimulus to the human through the auditory and visual modalities. Our previous work indicated that actuation noise caused from the robots tended to raise the sympathetic nerve system response of the heart rate variability. However, it was difficult to evaluate instantaneous response corresponding to a specific stimulus using the HRV. The SPR is possible to reflect the instantaneous response to the stimulus. In the experiment, we controlled the conditions of the visual and/or auditory modalities by blocking out the sound and sight from the robot, a manipulator with 5 D.O.F. We also changed the position of the robot around subjects for stimuli variety. As the result, it is shown that the SPR magnitudes, under the condition of blocking out not only the sound but also the sight from the robot, tended to be significantly lower than without blocking.

Further Experiments to Investigate the Influence of Robot Motions on Human Impressions

This paper investigates human impressions of the robots reaching motion based on psychophysiological experiments. There has been an increasing development of robots that move in the immediate vicinity of humans. It is important to ensure the security and relief of humans in the presence of robots. In our previous works, we employed heart rate variabilities, skin potential responses, and skin conductance responses (SCR) to investigate the influence of robot motion on human impressions. The results of several experiments showed that there was a modality effect, that is, the blocking out of the actuation noise and sight coming from robots tended to decrease the sympathetic nerve system (SNS) response. In this paper, we performed further experiments to investigate the modality effect and the long-term effect on human impressions based on SCR analysis and subjective ratings. The long-term effect implied a variation of response to robot motion over a long period. When the same stimuli are presented to humans, their responses to the stimuli tend to attenuate gradually. This phenomenon is known as habituation. In our experimentation (Hanajima et al., 2005), the subjects were asked to engage in two successive sets of the experiment for two months. We found two kinds of habituation in the data, the variation in a day and the variation between days. We defined the short-term variation as the former and the long-term variation as the latter. By comparing them, the long-term effect was investigated. As a result, we confirmed the same modality effect as illustrated in previous works. We also observed significant differences in the short-term and long-term variation from the SCR analysis. In the analysis of subjective ratings, the significant difference in the long-term variation was observed in more subjects than in the short-term variation. This suggested that the negative mental impression of the subjects to robot motion decreased as time passed

DESIGN OF VARIABLE STRUCTURE CONTROL SYSTEMS WITH INTERNAL MODELS

A design method for variable structure control systems with internal models is proposed for a class of nonlinear systems. The structure which satisfies the internal model principle is given. The switching hyperplane which stabilizes the variable structure control system together with a dynamic compensator is introduced. It is shown that the dynamic compensators are easily derived for servomechanisms and repetitive control systems. The repetitive control system effectively reduces the tracking error if the same pattern is periodically repeated in the reference signal. The robustness property is still valid for the variable structure control systems derived by the proposed design method. The design and simulation results are given for the repetitive control of a robot manipulator, in order to illustrate the effectiveness of the proposed design method.

Design of Variable Structure Control Systems with Internal Models

Abstract A design method for variable structure control systems with internal models is proposed for a class of nonlinear systems. The structure which satisfies the internal model principle is given. The switching hyperplane which stabilizes the variable structure control system together with a dynamic compensator is introduced. It is shown that the dynamic compensators are easily derived for servomechanisms and repetitive control systems. The repetitive control system effectively reduces the tracking error if the same pattern is periodically repeated in the reference signal. The robustness property is still valid for the variable structure control systems derived by the proposed design method. The design and simulation results are given for the repetitive control of a robot manipulator, in order to illustrate the effectiveness of the proposed design method

Model-following repetitive control.

A design method for a new type of repetitive control system is proposed. By considering a reference signal generator to be a model which a controlled system should track in a typical repetitive control system, a model-following structure is derived. It is shown that state feedback can further be added in this repetitive control system without affecting the repetitive control. The tracking error of the proposed repetitive control system can be made extremely small by adjusting the gains in the feedback loop. In case that there are inaccessible state variables, a minimal order observer is useful to construct the repetitive control system although the observer does not estimate the exact states of the system due to disturbances.