%0 Journal Article
%T UHF-Band Wireless Power Transfer System for Structural Health Monitoring Sensor Network
%A Tansheng Li
%A Kikuzo Sawada
%A Harutoshi Ogai
%A Wa Si
%J Smart Materials Research
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/496492
%X For detecting and measuring health conditions of bridges, wireless sensor networks are used in these days. However, battery life is critically restricting the application and maintenance cost of sensor network systems. To extend life time, a wireless power transfer system at UHF band is introduced to supply the current wireless sensor network. This power transfer system is based on electric wave at 950£¿MHz. This power transfer system is redesigned for tiny power transmission, including a combination of a rectenna and a Cockcroft-Walton boost converter, battery board, and a control board. Also, current wireless sensor network is redesigned for power transfer system. The working flow of sensor network is modified to bottom-to-top to save power of sensor modules which are the power bottleneck of this sensor system. As a result, the system is able to support a sensor module continuously with received power of £¿14£¿dBmW, when the transmitting antenna is 30£¿dBmW at 10 meters distance. 1. Introduction In Japan, most landforms are rugged by mountains and rivers. Therefore, bridges played a critical role in daily transports. However, the average age of bridges in Japan is over 20 years, and due to rapid nature disasters, bridge health monitoring techniques have become an important field. Recently, in the field of bridge health monitoring, wired sensor networks and wireless sensor networks are both used. However, a wired sensor network system usually costs much more than a wireless one. In a previous research on Donghai Bridge, optical fiber and GPS servers are implied to transmit data [1]. Although it is the optimal method to monitor one of the longest bridges in the world, price of this system is unacceptable for most of bridges in Japan, because each module costs over 10,000£¿USD. To monitor and detect the bridges¡¯ health condition, several health-monitoring systems (Figure 1) based on wireless sensor networks are developed worldwide including our original system [2]. In this sketch, S stands for sensor, R stands for router, and C stands for data collection device. Figure 1: Basic sketch of wireless sensor network bridge health monitoring system. In this system, sensors are used to acquire bridge vibration. After measurement, sensor modules transfer their data to the data collection device via routers. The data collection device is able to transfer data to a computer via USB cable or to the Internet via a network module. However, a problem still occurred in this system. Under a current measurement plan, the sensor network activates for 15 seconds per day to
%U http://www.hindawi.com/journals/smr/2013/496492/