附录ARemote Monitoring System of Pumping Unit Based on Wireless Sensor NetworksMeijuanGao, Jin Xu, and Jingwen TianDepartment of Automatic Control, Beijing Union University School of Information Science, Beijing University of Chemical Technology Beijing, ChinaI. INTRODUCTIONAs wireless communication technology continues to improve, it is an important development direction to implement the remote monitoring system of pumping unit using wireless networks. Now in this field the application is mainly GPRS wireless network, but the network base station is costly, with coverage blind spot, and oil exploitation is usually in the areas where the communication signals cant cover, the paper introduces a remote monitoring system of pumping unit based on ZigBee 1-2. ZigBee is a new wireless networking technology, it is a technical proposal between Bluetooth technology and the wireless marker, with low power, low cost and short time-delay characteristics. ZigBee is the set of specs built around the IEEE 802.15.4 wireless protocol, using ZigBee, devices in a network can communicate at speeds of up to 250 Kbps while physically separated by distances of up to 50 meters in typical circumstances and greater distances in an ideal environment. Based on ZigBee network communication technology and microprocessor technology, the system can deal with the various operating parameters of the remote transmission, real-time data collection and real-time load monitoring. The significance is: By monitoring the functioning of the pumping unit, when failure or abnormal operation take place, it can give an alarm quickly, reduce downtime and ensure oil pumps operate safely, provide a reliable guarantee for oilfield. II. SYSTEM DESIGNThe main design thinking of the system is: Monitoring the three-phase power, temperature, rotational speed and flow of pumping unit by sensors. When abnormal operation take place, it can cut off the power of the oil pump and give an alarm, at the same time the monitored data can be transmitted through the ZigBee network. The worker can understand the oil pump work state at control centre, and implement the monitoring of pumping unit informatization and automation, the purpose is to protect normal pumping units, reduce downtime, improve efficiency and achieve economic efficiency. A. Network Design of System The system is made up of data collection monitoring module, wireless module and control centres. Its structure is shown in Fig.1.In the blind area of the mobile communication system, as the distribution of oil wells are non-uniform, we can set up a relay node in several neighboring collection points. The data collected by each nodes can be sent to relay nodes firstly, then each relay node send the data to the network coordination, at the same time, when the works abnormally of oil pump is detected by collection node, the power of oil pump can be cut off timely. The information is transmitted to the control centre PC by network coordinator, workers can know the working condition of oil pump in time through PC. When we need long-distance transmission in the area where the communication signals cant cover, there will be a number of ZigBee wireless nodes to transfer data in relay ways, and then connect to communication network when there are communication signals. This will not only solve the problem of blind spots in mobile communications networks, but also achieve a long-distance transmission, and save cost.BMesh NetworksMesh networks are regularly distributed networks that generally allow transmission only to a nodes nearest neighbors. The nodes in these networks are generally identical, so that mesh nets are also referred to as peer-to-peer (see below) nets. Mesh nets can be good models for large-scale networks of wireless sensors that are distributed over a geographic region, e.g. personnel or vehicle security surveillance systems. Note that the regular structure reflects the communications topology; the actual geographic distribution of the nodes need not be a regular mesh. Since there are generally multiple routing paths between nodes, these nets are robust to failure of individual nodes or links. An advantage of mesh nets is that, although all nodes may be identical and have the same computing and transmission capabilities, certain nodes can be designated as group leaders that take on additional functions. If a group leader is disabled, another node can then take over these duties. All nodes of the star topology are connected to a single hub node. The hub requires greater message handling, routing, and decision-making capabilities than the other nodes. If a communication link is cut, it only affects one node. However, if the hub is incapacitated the network is destroyed. In the ring topology all nodes perform the same function and there is no leader node. Messages generally travel around the ring in a single direction. However, if the ring is cut, all communication is l