The Research Of Pneumatic Valve Positioner Based On Foundation Fieldbus

Integrating the open communication and process control abilities, the FOUNDATION Fieldbus (FF) is the best fieldbus for process automation area. The project is intended to develop the pneumatic valve positioner based on FF, on base of which to study the developing scheme and method of the Fieldbus device.The scheme of developing fildbus device by direct method and OEM method is first presented, depending on the analysis and compare of different developing methods. In view of the available situation, the later one is selected and the overall design is made comprised of two CPU. The work is accordingly divided into two parts: software & hardware development of Device Card and software development of Round Card. The MCS51 CPU is the kernel of Device Card, performing the functions like I/O signal processing, HMI interface, control algorithm. It tries to achieve multi-function, simple in structure and low in power consumption. Round Card software includes the communication software with network and with Device Card, and Function Block algorithm. This is realized using the Round Card, commnication stack software and Function Block SHELL in the development kits of NI Corp. By means of the serial communication between the two cards and communication to the fildbus by Round Card, the valve positioner is equipped with the FF field device function. Further, HART protocol is made full use of in the project.The experiment indicates that the two cards can communicate with each other, the whole device can run on the fieldbus and interact with the system. This approves the feasibility of the overall design scheme andmethod. The original study of how to develop a fieldbus device provides some advisable clues for future study; gains much experience in using the development kits, specially in using the Function Block Shell; the result is of some instructing value for developping intelligent valve positioner based on FF, and other fieldbus devices as well.