Research Of Intelligent Valve Positioner Based On PROFIBUS-DP

With the continuous advancing of society, highly requirements were proposed about control effect and routine maintenance in industrial process control equipments. Pneumatic valve was extensively used in process control region for its special characteristics. Valve locator, the master control unit of pneumatic valve, could improve the control accuracy and response speed of the valve to a large degree, and meliorate dynamic characteristics of the valve significantly.PROFIBUS-DP bus was widely used in process control region for its unique advantage and was evolved as the machinery industry standard in our country in 2001. The smart valve positioner being researched internal are mostly based on HART protocol, while the PROFIBUS-DP bus was adopted more in process control region in our country. According to this, there is greater significance in researching smart valve positioner based on PROFIBUS-DP bus.The smart valve positioner being studied in this paper adopted two-wire power supply. The overall locator was analyzed and researched in this paper by embedded design techniques, which focus on the structure of hardware system. The mainly work are as follows:1. The smart valve positioner in and abroad was analyzed and researched in this paper, referring to relevant documents and literatures. Advantages and disadvantages of valve positioners with different type and structure were analyzed in the basis of structure, working principle and function. At the same time, the protocol architecture, communication model and functional characteristic of PROFIBUS-DP field-bus were analyzed and studied. Also the design method of PROFIBUS-DP intelligent node was proposed.2. The inner mechanism of pneumatic valve control system was studied. The flow characteristics mathematical model of valve, piezoelectric valve PWM control signal and valve position mathematical model and valve position feedback signal conversion mathematical model were all proposed in this paper. 3. Various components of the smart valve positioner system were analyzed and studied deeply with the modular analyzing and study method. The overall program of smart valve positioner system was structured based on MPU S3C44B0, in the basis of comparing the differences of various design methods. And the desired design goals were proposed.4. The hardware system of smart valve positioner was analyzed and researched in this paper. The main core circuits of the positioner such as power circuits, sampling circuits, I/P converting unit, feedback circuits and communication circuits were analyzed and studied in the basis of two-wire power supply design by embedded design techniques. Also the design projects were proposed.5. Overall planning was designed for software components of the smart valve positioner. The overall design of software system was proposed at first. And then the signal sampling process, master control program, communicate program and man-machine interface program were analyzed and designed in the basis of software with the modular programming method.