Hart Protocol Applied Research In The Hydraulic System

The thesis introduces the technological characteristic, the background and trend of fieldbus technology and the domestic and international general situation of the application of fieldbus to the hydraulic control system. It points out the necessity and importance of introducing fieldbus technology in the hydraulic control system.HART communication protocol is researched on the basis of probing into fieldbus technology by analyzing network model and data communication. HART communication protocol, as a simple digital communication protocol, is compatible with the former 4~20mA analog signals while realizing digital communication. There are realistic meanings to study it because of the existing of a large number of analog signal transmission in the industrial control system. The DD of HART communication protocol offers possibility for the mutual operation of instruments on the spot. After studying HART communication protocol, the thesis designs and realizes the intelligent pump/valve based on HART communication protocol. It adopts MPU as central processing unit. It uses AD7714 chip to realize the input of the signals and AD421 chip to the output with the electric current of 4~20mA. The thesis describes the realization of HART communication module especially, including physics layer, data link layer and application layer of HART communication protocol. Based on Bell 202 FSK standard, it compares the performance of HT2012 chip with SYM20C15 chip and use SYM20C15 chip to modulate and demodulate in the realization of physics layer of HART communication protocol. It realizes data link layer and application layer of HART communication protocol by programming. Finally, the thesis compares the performance of the intelligent pump/valve based on HART communication protocol with the former pump/valve.