Study on a Sensor Network System with a Self-Maintenance Function for Plant Monitoring System

This paper presents a new network-based concept of real-time plant monitoring based on the wireless sensor network. The wireless sensor network is a novel technology to perform distributed sensing tasks, especially for applications such as environmental monitoring, smart spaces, medical systems and etc. The advances in MEMS technology, sensing technology and wireless communications have enabled the development of real time, detailed, wide-range, lowcost, low-power and multifunctional wireless sensor network. On the other hand, semiconductor devices like ICs suffer from radiation damage. We must consider this effect for applying wireless sensor network devices to nuclear power plants. Radiation may produce one-time noise signals in the sensor network, or it may damage the wireless sensor network device. Therefore monitoring system will be unreliable for nuclear power plants in ordinary way of composing wireless sensor networks. In this study, we develop a new concept of a robust wireless sensor network, that has a tolerance against both the partial node’s failure and packet errors; realized by a Self-Maintenance function. The Self-maintenance function is a function that enables an artifact to find, diagnosis and fix the trouble automatically and maintain itself. So far some approaches have been tried to realize robust monitoring system by applying the idea of multiplex system, based on “2 out of 3”, but this requires a large amount of the hardware and is not suitable for sensor network systems. Here, we designed a sensor network system with Self-Maintenance function based on qualitative reasoning technique for robust wireless sensor network system, and an instrument network based on ZigBee has been set up for investigations. It is found that ZigBee-based instrument networks are robust but susceptible to interference from traditional way of sensing.