低压铸造控制系统中模糊PID在PLC中的实现

Realization of Fuzzy-PID in PLC for Low Pressure Casting Control System

在基于PLC的低压铸造控制系统中,西门子S7-200PLC中的PID运算功能,在具有传统PID算法静态性能好、无静差等优点的同时,也继承了其动态响应品质差、容易超调等缺点。通过对控制过程中的偏差和偏差变化的模糊化处理,设计出了能够对PID的3个参数KP、KI和KD进行在线调节的模糊PID控制算法,并采用间接寻址的方法,将其在PLC中进行了实现。

When it is applied in the PLC-based control system for low pressure casting,the PID function in S7-200 PLC which was produced by the Siemens,not only has the advantages of good static performance,no steady-state error,but also has the disadvantages of poor dynamic response and being easy to overshoot.By fuzzification for error and error change during the control progress,the fuzzy-PID algorithm,which could adjust three parameters KP,KI and KD in PID algorithm online,was established.The new control algorithm was realized in PLC by indirect addressing.The production application shows that it exhibits desirable controlling effects.