The Research And Design Of Digital PID Control Module Based On Mod Bus Protocol

The PID controller is widely used in the industrial control field, lie in its simple structure, strong robustness, good stability and easy operation. In industry, most of PID controller are customized for different situation and environment, with high cost and poor generality. According to the principle of PID control and the structure of control system, a general digital PID control module,which is applied to acquire standardized analog signal and output the control signal, is developed in this paper. As the module communicate with computer based on Mod Bus protocol, the operator can manage the industry control system centralized, and adjust the best control effect by select the PID algorithms and configure the parameters.Firstly, the research on current status of the development and the trendency at home and abroad is introduced. Driven by the development of industrial integration, the digitized proceeding of PID controller and the necessary of communication function to PIDcontroller is an inexorable trend.Then, Mod Bus Protocol are introduced in detail including the principle of Mod Bus, the transmission mode and data verification. The principle of PID control and the structure of control system are presented, and the design scheme and structure of module are determined.The module are divided into seven parts, including processing unit based on single-chip system, data acquisition unit, singal output unit, serial communication unit, power unit, indication unit and download unit. With the core of ADu C848, the control system are designed in detail both in hardware and software. The interface programmed by Visual Basic6.0 on computer are introduced briefly, which can data exchange with the module by RS485 bus. Through the debugging and testing for the whole system, the module make a good performence in the experiment that control the input voltage to set point, it can make a control accuracy of 0.2% in the end of this paper.The digital PID control module has small volume, light weight, low power dissipation and strong versatility, it has a certain worthiness on pratice.