Pseudorandom Tag Arrangement for Accurate RFID based Mobile Robot Localization

Abstract

The localization of a mobile robot is one key ingredient for autonomous navigation, along with map building and obstacle detection/ avoidance (Borenstein, J., et al., 1996). Several sensors have long been used for mobile robot localization, but all of them are confronted with their own inherent limitations. Encoder suffers from error accumulation, ultrasonic/ laser sensor demands the line of sight, camera expends complicated processing, and GPS works at low resolution. To cope with these problems of typical sensors, new attempts have been made, which use the RFID system consisting of tags, antenna, and reader for mobile robot localization (Finkenzeller, K., 2000). There have been two different research groups of working on the RFID based mobile robot localization. Both groups assume that a set of tags storing the absolute positional information are deployed throughout a navigation environment. In one group, either active or passive tags are installed along the wall and they are used as beacons or landmarks to guide the navigation of a mobile robot (Kubitz, O., et al., 1997; Kantor, G., et al., 2002; Hahnel, D., et al., 2004; Kulyukin, V., et al., 2004; Penttila, K., et al., 2004; Yamano, K., et al., 2004; Kim, B.K., et al., 2006; Vorst, P., et al., 2008). However, in the other group, passive tags are installed on the floor and they are used to indicate the current position of a mobile robot (Bohn, J., et al., 2004; Choi, J., et al., 2006; Kim, B.K., et al., 2006; Han, S., et al., 2007; Kodaka, K., et al., 2008). This paper belongs to the latter group. When an antenna senses a tag on the floor, there involves the positional uncertainty within the sensing range, which degrades the performance of RFID based mobile robot localization. One simple way of alleviating such a limitation may be to increase the tag distribution density on the floor. If more than one tag is sensed by an antenna at one instant, the current position of a mobile robot can be estimated more accurately by utilizing multiple tag readings (Han, S., et al., 2007; Kodaka, K., et al., 2008). However, the increased tag distribution density may be accompanied by the economical problem of high tag installation cost and the technical problem of incorrect tag readings. For a given tag distribution density, the performance of RFID based mobile robot localization is affected by how a set of tags are arranged over the floor. There have been a variety of tag arrangements considered so far, which can be categorized into three repetitive arrangements, including square, parallelogram, and tilted square. Depending on the