| With the continuous advancement of computer control technology and wireless communication technology,Networked Control System(NCS)have also developed rapidly.At present,China's industrial enterprises are gradually adopting intelligent terminal equipment with wireless communication capabilities to replace traditional instruments on the purpose of reducing the limitation of traditional transmission media and overcoming the field devices moving with wired situation,and solving possible bad environment of the scene that makes people unable to reach.In this paper,in order to improve product quality,expand market scale and reduce development costs,an instrumentation automation company commissioned the lab where the researcher of this paper belongs to develop a low cost,small scale ZigBee Network Control System.The ZigBee Network Control system can quickly and accurately complete the networking,configuration,and online polling functions and meet the needs of practical applications.Based on inheriting the existing achievements,this paper develops a new network system topology design for the ZigBee Network Control System and a new multichannel cluster technology,enhancing the ability to work in parallel and synchronously of the master-slave communication between the coordinator and each cluster-head node and internal node of the token cluster implicit token communication.It also enhances communication efficiency,expands the number of access devices polled by the Network Control System in mode of online polling,establishs application-oriented fault tolerance and health diagnosis mechanisms.It improves the Robustness of the Network Control System.The main content of the paper is as follows:1)System design.The Network Control System is composed of a host computer software,a coordinator gateway,and token clusters,and designs system frame scheme based on the technical idea of multichannel clustering.The host computer software communicates with the coordinator through Industrial Ethernet,and the coordinator communicate with the token cluster through the ZigBee wireless module.The token cluster structure includes a cluster-head node and multiple intra-cluster nodes.The cluster-head node is configured with two ZigBee modules,which work on different channels,respectively,to distinguish between intra-cluster communication and inter-cluster communication without interfering with each other.The coordinator and the clusters use fixed channel communication,and strictly follow the master-slave polling communication;in a single network cluster,the only data communication channel in the entire network is allocated by token communication.The key idea of the token-cluster is that the nodes in the cluster forms the network protocol,transforming the communication mechanism into an invisible token transmission mechanism.The nodes in the cluster receive the polling request command to occupy the token,and obtain the rights of channel use in the cluster,and package the sampled data and the request command as a new token to pass it to the next designated node in the cluster,completing the node data in the cluster one by one,and releasing the rights of the token use.Clusters adopt the invisible token communication mechanism,compared with the point-to-point master-slave communication to reduce the number of data communication transfers,removing redundant headers and tails to improve the utilization of network bandwidth resources;intra-cluster and inter-cluster communication are independent and synchronized without affective each other.Combined with the Network Control System token-cluster technology,the corresponding fault tolerance and health diagnosis mechanism is designed.When a node in the token cluster fails and the response times out,the next designated node in the cluster uses the self-designed protocol frame as a token to trigger regularly and actively upload.It avoids nodes of cluster failures to network failures and ensures system robustness.2)Hardware design.The paper completes the cluster-head node hardware solution design,which can make the multi-channel Network Control System token cluster communication operate normally.In order to meet the working performance of the cluster-head node and the token-clustering network,and base on power consumption and cost considerations,STM32F072 is selected as the MCU main control chip;designing the minimum system circuit of the cluster-head node as the network control system multi-channel clustering technology can work The basis for implementation;design hardware interface circuits for ZigBee,USART serial communication and USB serial debugging for communication and online debugging functions;in order to improve data sampling speed,accuracy and data accuracy,use off-chip ADC chips and design corresponding peripheral circuits;Use the MCU's on-chip flash storage capabilities for cluster membership and data management of the network control system token cluster.3)Software development.The paper completes the programming and implementation of the various functional modules of the network control system multi-channel resource allocation and token clustering.It mainly includes the coordinator node protocol conversion and data forwarding,the formulation and implementation of data communication sending and receiving protocols for nodes in the token cluster;with the coordinator protocol forwarding function,the host computer software configures the network configuration parameters of the nodes in the token cluster;according to the data in real-time designing and implementing communication scheduling strategies with different real-time priorities;designing the fault tolerance mechanism within the token cluster;customizing the invisible tokens established by the protocol and the range of healthy node ID values recorded in the protocol frame header to achieve system health diagnosis,The design idea of timing trigger and active uploading is used to solve the problem that subsequent nodes cannot upload data due to node damage.4)Experimental verification.A complete experimental platform is constructed by coordinating the host computer software with the coordinator gateway and token clusters,and completing system joint debugging,testing,and system operation test improvement on the platform on purpose of completing the project development;The designed multi-channel cluster and network fault-tolerance mechanism and health diagnosis are tested,and the experimental results are analyzed to verify the correctness and effectiveness of various functions of the ZigBee multichannel Network Control System,which can meet the actual needs and have better performance. |
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