The key motivation of this study is for a style of the sensor arrangement to have an effect on the localization performance of mobile robots in case of using sonar sensors. In general robot platforms with sonar sensors, sonar sensors are supposed to be radially arranged on their rotational axis of mobile robots. However, relevant limits to several functions required for their autonomous navigation occur unexpectedly, because a sonar sensor generally has the negative nature of its wide beam width together with the specular reflection. We present a new strategy of the sonar sensor arrangement capable of enhancing the localization performance. Sonar sensors are intended to be arranged nonradially (twistedly expressed in this paper) on their rotational axis. The localization scheme called STARER: Sonar-Twisted ARrangement localizER is based on the extended Kalman filter (EKF) with occupancy grid maps. Experimental results demonstrate the validity and robustness of the proposed method for the localization of mobile robots.

At a zone of operations or underwater mine warfare, it's very critical for warship to be damaged by underwater mine. In order to increase survival rate of warship from threat of mine, specific signal of warship is measured. And then specific signal is treated and calibrated below the baseline. The sensors that measured the signal are installed under the sea to exactly measure. It's difficult for maintenance men to approach the underwater equipment compared with the ground equipment. It needs long time for maintaining, demands support equipments and handling equipment. And it needs people who maintain the equipment under the water. So, it's important to analysis accurate reliability and estimate maintenance period. This paper present the reliability analysis method about array sensors under the water. The analysis object, array sensors, is set bounds to a warship signal measurement facility. At First, this study established procedure of reliability analysis about array sensors under the water and analyzed the structure of array sensors. It decided number of sensors which was depended on size of warship and selected reliability model through considering the structure and operational concept. Finally, it calculated MTBF(Mean Time Between Failures) of array sensors under the water.