Research Of Boiler Water Temperature Control System Based On LabVIEW

Present every domain of industrial control shows us that electric boiler control systems are widespread used. However, our electric boilers are applied in industry later than other countries, and exist following problems, such as low control level,algorithm rough simple,the function is not good enough,easy appear vibrations when output,the overshoot is big. So, research the electric boiler control system is very important.The article takes electric boiler as research target, by using experiments, find out a best control method, and achieving these goals of stable system, short control time and small overshoot. And designing boiler water temperature control system based on PLC and the LabVIEW, generally speaking, this hardware architecture of system includes two parts, that's lower position machine and the superior machine.The lower position machine, takes PLC as core, heated by thyristor. The signal of temperature feedback after transformed by A/D, sent into PLC for processing, then comparing the boiler water temperature value by measuring equipment and the setting value in PLC, and using PID module to adjustment. If the water temperature value by measured surpasses the setting water temperature over 1℃, the lower position machine delivers the conditioning signal to the frequency changer to adjustment through PID module of PLC, adjusts the water pump current capacity, to achieve the goal of changing the water temperature value in real-time boiler, realizes the boiler water temperature control. In this part also emphatically introduces correspondence between the MM420 frequency changer and S7-200PLC.The superior machine takes diagram language of LabVIEW as monitor software, designs man-machine contact surface, and realizes correspondence between the superior machine and the lower position machine, realizes to the controlled member signal and equipment's centralized management and the monitoring, which can demonstrate the temperature observed value, the given value, the value of exports as well as the PID parameter value, realizes monitor to the boiler system temperature. In this part, this article introduces correspondence method between LabVIEW and VISA serial port module in detail.Takes PLC as the lower position machine, and LabVIEW as the superior machine development platform, uses the LabVIEW's formidable data operation ability and analysis ability, and through LabVIEW and PLC serial port correspondence, composition a real-time monitoring graphical display platform. Debugging result indicates that this system has the good contact surface, reliable movement characteristics, simplify operation, and so on.