基于西门子PLC温控调速系统的设计

The Design of Temperature Controlling Speed System Based on Siemens PLC

以西门子PLC，S7-300，CPU313C-2DP-V2.6作为控制中心,运用模拟量输入输出模块334-0ke00-0ab0，作为温度传感器热电阻Pt100的输入端：输出的模拟量作为三晶变频器频率控制的输入电压，其范围是0~10V。温度控制具有明显的大滞后特性，当过程值偏离设定值较大时调节过程过于缓慢，而接近设定值时又容易出现较大超调。存在上诉两种问题，温度控制必须满足在偏差超过一定的范围时，输出最大或者最小的调节量，让温度值快速回到一个小的范围中，以缩短调节时间：在设定值附近时，越靠近设定值，调节量应越小，以防止超调。为此，在OB35中调用FB58时，设计控制带功能。当过程值大于设定值,且偏差绝对值超过控制带,则以输出下限作为输出值。当过程值小于设定值，且偏差绝对值超过控制带,则以输出上限作为输出值。如果偏差的绝对值小于控制带，则以实际PID的计算结果作为输出，即变频输出。

The controlling center of the design is Siemens PLC S7-300, CPU313C-2DP-V2.6.Analog input/output module 334-0ke00-0ab0 is used.The input port is connected by the thermal resistance Pt100 temperature sensor, and port is connected by the SANJ inverter .The input voltage of the inverter is 0 ~ 10 v.The obvious characteristic of temperature controlling is hysteretic quality.When the processing value is deviating from the setting value, the adjustment process is too slow.On the other hand,when the processing value os approaching the setting value, the adjustment process appears larger overshoot.For the two problems, when the error range goes beyond a certain value,the output is maximum or minimum value for minishing the error and reducing working hours. When the output value is near the set value, the adjust value should be small for decreasing the overshoot. On the purpose, when the FB58 in the OB35 are used,controlling zone function is designed. When the processing value is greater than the setting value, output bottoming is used. When the processing value is less than the setting value, the output upper limit is used. If the error is less than the controlling zone value, the practical results of PID is used.