Localization of wireless sensor networks for industrial applications

ABSTRACT: In new generation manufacturing systems, Wireless Sensor Networks have become an important technology because of the various ameliorations in comparison with common sensors, such as power consumption, connection to base station, data processing and etc. In order to obtain all these capabilities in sensor nodes, some difficulties may be encountered such as power resource, data transmission and localization for each sensor node. The objective of this study is to investigate a localization of the distributed wireless sensor networks in the manufacturing domain with utilizing Trilateration algorithm and received signal strength Indicator (RSSI) as distance based measurement. In experimental part of this study, an Assumption Based Coordinates (ABC) algorithm is proposed to define the location of a node with unknown position through utilizing the Trilateration method. This part is composed of two different methods. Both of these methods are distance based, and Received Signal Strength Indicator (RSSI) is used as a measurement factor. Friss transmission equation is the base of the theoretical part of this study and the results obtained by experimental methods are compared with the theoretical results related to this equation. The first experimental part was done in a simple environment without any manufacturing machines and equipments. Sensors were deployed in that area and RSSI was measured in different distance for several times. Because the simulation of Terilateration method is the aim of this experiment, the graph that shows the relationship between the measured RSSI and distance was obtained to use as data resource to calculating the distance for one hundred random RSSI. Nevill algorithm is a mathematical solution to change this graph to be data recourse for the distances those related to one node to use as input data for Trilateration method. In the second experimental method some unknown nodes are assumed in a coordinate system and their distances to each reference node was calculated. By utilizing the Friis equation the related RSSI for each distance was measured. The theoretical RSSI was changed by adding 40 percent white Gaussian noise (AWGN) and then imported again to the Friis equation to obtain the distances related to each RSSI. Finally, the locations of unknown nodes were obtained with the Trilateration method. The proposed localization methods were considered on two different manufacturing environments as industrial application of WSN. The first one is EMU mechanical engineering workshop which houses different types of machines and manufacturing equipments and the second one in gas distillation columns used in oil and gas refineries. Comparison of the theoretical location of unknown node with the location obtained by experimental methods shows the errors and deviations are depend on many factors. These factors are environmental condition, available machines or equipments in sensor field, computational errors of the written program for Trilateration or Nevill algorithm and etc. Keywords: Wireless sensor network, Manufacturing, Localization, Trilateration, RSSI, Distance. …………………………………………………………………………………………………………………………