The Design And Implementation Of Dry Powder Preparation System Based On S7-200 PLC

Solving the problem of sewage discharge in the process of industrial production has been brought to the country’s attention,it is also a long-term research task. Dry powder, take polymer flocculant PAM for instance, the molecular weight of PAM product in China has reached more than 10 million, which can be used in sewage treatment, papermaking, textile, coal washing and other fields effectively.This design is based on "dry powder formulation device" of Prominent Fluid Control(Dalian) Co, Ltd, design and improve a set of high-performance, high-reliability automatic control system of dry powder preparation. This system takes PLC as the core, through the industrial control touch screen, sensors etc, achieve to control stirrer, solenoid valve, frequency converter, level switch and other equipments, and complete the preparation of a given concentration of PAM automatically.The main work of the project are as follows:(1) Design the hardware of the automatic control system for the dry powder preparation, and use AutoCAD software to draw the electrical principle diagram of system;(2) Complete the design of matched PLC control program and industrial control touch screen human-machine interface by the Step7 software and the DOPSoft software;(3) In the traditional preparation system, there is no clear function relationship between the output frequency and the output quality of dry powder, this paper uses the cftool toolbox under the MATLAB platform to obtain function relationship between the two with the method of curve fitting, and apply to the PLC formula program;(4) With the respect to the false alarm, which is caused by the instability of reservoirtank level during the process of solution preparation, and the actual water flow is too small to read the accurate water flow, through improving the PLC program and adding PID control to make the concentration of preparation solution more accurate;(5) For the designed automatic control system of the dry powder formulation does on-site commissioning and discusses the typical issues during the commissioning process, and give some appropriate solutions;(6) For the stirrer motor fault of dry powder preparation system during practical use, with wavelet analysis method to collected motor vibration data for feature extraction, and for subsequent agitator motor fault diagnosis provides references.Through the design of hardware and software, system can realize manual control, remote automatic control, achieve the purpose of centralized monitoring and distributed control.