大规模控制节点群管理系统设计

发布时间：2018-08-10 21:58

【摘要】：为突破传统RS485串行总线对可接入节点数量的限制,本文基于RS485总线提出了一种大型嵌入式节点集群的架构方式,将最大可接入节点数量扩展到2.7万个。针对该网络特点,对Modbus协议进行扩展,建立集群节点通讯及控制的通讯协议,实现集群节点的有效管理及可靠控制。在此基础上,构建完整的信息传递策略,最终完成地理测绘信息从主控器到各个终端节点的正确映射。首先建立合理的物理链路,并设计出一套与之相适应的通信协议。通过在主控器与叶子节点间加入中继器,实现RS485总线支持节点数的扩展,建立一对多控制的嵌入式节点集群。通过对Modbus协议进行扩展,增加了中继层规约。与传统单纯增加物理地址长度的方式不同,新扩展协议采用局部寻址方式,打破了Modbus地址长度对子节点数的限制,并引入节点扫描和差错反馈机制,从而实现了主控器对各网络节点的可靠控制。其次设计地理测绘信息的传递策略。利用GDAL库,使用UTM结合正方位投影方法对获取到的遥感地理数据进行投影变换,并提取其坐标和高程信息。以原点为参考,以终端模块能接受的最大数据量为标准,将数据矩阵划分成块,并与底层终端位置一一对应,再按中继层规约依次将高程信息封装传送。由于仅传递高程信息,坐标已经隐含其中,因此减小了网络的数据量,提升了传输效率。实验检测了系统在拓扑结构变化时的性能。在采用扩展协议时,一层中继器的引入导致周转延迟增加5.6%,而两层中继器则将延迟率增加了36.51%,并使总延迟较原始Modbus系统增加1.94倍左右,但实际中的应用的两层中继系统将平均延迟控制在了100ms左右。而传输可达性测试显示,系统信息帧的送达率高达99%。结果表明,该方案在牺牲一定系统实时性能的前提下,实现了嵌入式节点的集群化管理。同时,控制协议和物理链路不但保持了简单性,还具有易移植、可扩展的特点,能及时适应集群拓扑结构的变化,并保证了地理信息的精确映射和传递。
[Abstract]:In order to break through the limitation of traditional RS485 serial bus on the number of access nodes, this paper proposes a large embedded node cluster architecture based on RS485 bus, which extends the maximum number of access nodes to 27000. According to the characteristics of the network, the Modbus protocol is extended, and the communication protocol of communication and control of cluster nodes is established to realize the effective management and reliable control of cluster nodes. On this basis, a complete information transfer strategy is constructed, and the correct mapping of geographic mapping information from master controller to each terminal node is finally completed. Firstly, a reasonable physical link is established and a corresponding communication protocol is designed. By adding repeater between the main controller and the leaf node, the RS485 bus can support the expansion of the number of nodes, and the embedded node cluster with one-to-many control is established. By extending the Modbus protocol, the relay layer protocol is added. Different from the traditional way of simply increasing physical address length, the new extension protocol adopts local addressing method, which breaks the limit of Modbus address length on the number of sub-nodes, and introduces node scanning and error feedback mechanism. Thus, the reliable control of each network node by the master controller is realized. Secondly, the transfer strategy of geographic mapping information is designed. By using GDAL library and UTM combined with orthographic projection method, the remote sensing geographic data are projected and transformed, and the coordinates and elevation information are extracted. Taking the origin as reference and the maximum amount of data acceptable to the terminal module as the standard, the data matrix is divided into blocks, corresponding to the bottom terminal position one by one, and then the elevation information is encapsulated and transmitted according to the relay layer protocol. Because only the elevation information is transferred, the coordinates are implied, so the data volume of the network is reduced and the transmission efficiency is improved. The performance of the system is tested when the topology changes. When the extended protocol is adopted, the introduction of the first layer repeater increases the turnover delay by 5.6, while the two layers increase the delay rate by 36.51, and increase the total delay by about 1.94 times compared with the original Modbus system. But in the practical application of two-layer relay system, the average delay is controlled around 100ms. The transmission reachability test shows that the delivery rate of system information frames is as high as 99g. The results show that the scheme realizes the cluster management of embedded nodes at the expense of real-time performance. At the same time, the control protocol and the physical link not only keep the simplicity, but also have the characteristics of easy transplantation and extensibility, which can adapt to the change of the cluster topology in time, and ensure the accurate mapping and transmission of the geographic information.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TP273;TP315

【相似文献】