Fuzzy-PID Control's Application On Cement Process Control System Based On PCS7

As the cement enterprises are becoming larger and more grouping, the control systems should be changed, so as to provide a unified technological environment for automation syetem and achieve a unified configuration, data management and data communication. Siemens SIMATIC PCS7 is a new generation of process control system, which is modular and based on fieldbus. It combines advantages of the traditional PLC and DCS control system, functions of which are combined as well. In PCS7 system, the hardware is based on a unified hardware platform, software is fully integrated into the SIMATIC program Manager, and there is also a unified software platform. As its high control performance and good stability, the PCS7 is widely used in large cement production line control system.The actual complex industrial process is often highly nonlinear, strongly coupled, time-varying characteristics of uncertainty, it is difficult to obtain satisfactory control quality by traditional control strategies and control methods. Such as PID control, it is difficult to meet the needs of field control if we set the same parameters, which causes much inconvenience to the actual project. At present, a number of advanced control theories are gradually introduced into process control, fuzzy control is one of them. Fuzzy control has good robustness and is not sensitive to the pure delay and changes of objects 'parameters, but it usually causes steady-state error due to its rough control rules. The fuzzy-PID hybrid control not only maintains advantages of PID control's small steady-state error and good stability, but also owns the fuzzy control's adaptive and fast-regulation characteristics. It achieves good control effect when it is used in complex process control system which is nonlinear and large delay.This paper firstly analyzes the newly dry cement production craft and characteristics of modern cement production line's control system, combining design requirements of cement production line's control system, based on PCS7, does research on control system's hardware configurations, network configuration, automation programming and control interface configuration etc. And then taking packing substation for instance, taking level of silo into studying object, this paper proposes the strategy of fuzzy-PID hybrid control, and does simulation on Matlab. The result of simulation shows that the control effect of fuzzy-PID hybrid control is superior to PID control and pure fuzzy control. In the meantime, based on PCS7 software platform, using the combination of CFC and modular programming method, this paper successfully designs fuzzy-PID control module and does research on PCS7 simulation system, named as PLCSIM. From the result we can see that, it is feasible to achieve fuzzy-PID hybrid control in PCS7 software platform, which has some reference value to its application in other complex process control.