Research Of Distributed Measurement And Control Network System Based On P-NET Fieldbus

With the continuous development of automation technology,the fieldbus technology has become a hotspot problem and research direction of automation control technology.The P-NET fieldbus as a bus standard,has been widely used in the field of automation.However we are still relatively unfamiliar with this bus standard. The research and application of the P-NET fieldbus is still at the primarystage.This paper set in the agricultural greenhouse, according to the characteristics of the P-NET fieldbus,designed and bulided a distributed measurement and control network system based on P-NET field bus. This paper starting from the P-NET fieldbus protocol standard, analyzing the current situation of agricultural greenhouse, eventually completed the design and implementation of the hardware and software of the ommunication platform based on the agricultural greenhouse system.This paper first mainly studied the data link layer protocol of the P-NET fieldbus and analysied the multi master communication process based on the virtual token. Then analysing the agricultural greenhouse, designed and gived the structure chart of the agricultural greenhouse system based on the P-NET fieldbus. Finally, according to the diagram of greenhouse system structure,I respectively completed the desien and implementation of the hardware and software of the host computer,the main station and the substation.The host cmmputer is mainly used to monitor and manager the greenhouse system;the main station is mainly used to manager the different single greenhouse and store the environmental condition data;the substation as a intelligent instrument,mainly used to measure the environment state data in the greenhouse.