The main purpose of this study is to apply the mechanism of human weight perception to multimedia applications. When a start and the goal points are given in the human motion, the velocity profile has a unimodal profile including the acceleration and deceleration zones. In such case, it is widely said that the motion control becomes more accurate in the deceleration zone for the final approach. Hence, it is assumed that the sensing ability also improves. This study challenges to confirm the hypothesis with weight stimuli generated by a force display device. As a preliminary experiment, this study confirms that our device enables the evaluation of human perception by tracing Weber's experiment in virtual reality; the obtained difference threshold (DL: Differenz Limen) almost agrees with the previous results. The difference threshold is a very important factor, which means perceptual threshold for weight changes. We further attempt to clarify the mechanism of the human weight perception for sudden weight changes during the lifting process. Based on individual lifting profiles, this study suddenly changes the load force in the two zones, and examines the difference thresholds of each subject. The results demonstrate that the human weight perception tends to become more sensitive in the deceleration zone during the lifting process. These results also imply the effectiveness of force display devices for physical experiments.

In this paper, by focusing on weight perception, we attempted to clarify a perceptual mechanism using functions of the haptic interface. We especially examined the weight perceptual mechanism when the weight of an object suddenly changed, which does not take place in our natural life. This experimental condition can only be realized by using the advantage of the haptic interface. The results show the difference in the perceptual threshold due to addition and reduction of the weight. Moreover, the results indicate that subjects can also correct the supporting force corresponding to the sudden change in the weight when they could not sense the change. Namely, it implies that subjects adjust the supporting force under an imperceptible state, which may indicate an interesting muscular motion under a state of unconsciousness.

Recently, the haptic interface system (one of a variety of force display devices) has attracted great interest as a new virtual reality technology, stimulating vigorous research. Most reports deal with methods of constructing a haptic interface system or the development of new devices having with a particular mechanism, and the various methods suitable for force display. However, it is also necessary to clarify the relationship between the virtual dynamics characteristics of a system and a human being's feelings in order to present the accurate force sensation from virtual environment. In this paper, we evaluate the force sensations experienced by human beings with the psychological experiments that examine perceptual illusion phenomena, including the horizontal-vertical illusion and the size-weight illusion. These results show that perceptual illusions occurring in a real environment can be also reappeared in a virtual environment. Therefore, perceptual illusions may have the potential for application to virtual reality. Moreover, the characteristics of perceptual illusions can be examined by changing the virtual dynamics parameters of the haptic interface. Finally, this paper shows that the haptic interface is a very effective tool for the investigation of perceptual illusions.