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This paper shows a system composed of multiple robots which cooperate each other through local communications, in order to search a goal of a given maze. Though a diameter of an each robot is 40 mm and it equips with a very simple algorithm, each robot plays a part to find the goal of an unknown maze as a whole system. In this study, a computer simulator has been also developed in order to examine the validity of designed algorithms.

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Monitoring of the skin vibration is disturbed little by environmental noise. Therefore, the skin vibration is more relevant than bruit on the skin by means of monitoring the fistular blood flow. Frequency analysis of the skin vibration generated by an internal arteriovenous fistula indicated two peaks of power spectral density (PSD), one in the frequency range of 4-10 Hz and the other from 100-300 Hz. The analysis of the skin vibration generated by an external fistula, however, showed only one peak in the range of 4-10 Hz and a moderate flat PSD level in the range of 100-300 Hz. The PSD level in the range of 100-300 Hz decreased dramatically or disappeared when the fistular blood flow diminshed or ceased. Therefore, the optimal frequency for monitoring skin vibration may be the range of 100-300 Hz.