通過三、四兩篇文章，基本上已經弄清楚了PID控制算法的最常規的表達方法。在普通PID控制中，引入積分環節的目的，主要是爲了消除靜差，提高控制精度。但是在啓動、結束或大幅度增減設定時，短時間內系統輸出有很大的偏差，會造成PID運算的積分積累，導致控制量超過執行機構可能允許的最大動作範圍對應極限控制量，從而引起較大的超調，甚至是震盪，這是絕對不允許的。
爲了克服這一問題，引入了積分分離的概念，其基本思路是 當被控量與設定值偏差較大時，取消積分作用; 當被控量接近給定值時，引入積分控制，以消除靜差，提高精度。其具體實現代碼如下：
pid.Kp=0.2;
pid.Ki=0.04;
pid.Kd=0.2; //初始化過程
if(abs(pid.err)>200)
{
index=0;
}else{
index=1;
pid.integral+=pid.err;
}
pid.voltage=pid.Kp*pid.err+index*pid.Ki*pid.integral+pid.Kd*(pid.err-pid.err_last); //算法具體實現過程
其它部分的代碼參見《PID控制算法的C語言實現三》中的講解，不再贅述。同樣採集1000個量，會發現，系統到199所有的時間是原來時間的1/2,系統的快速性得到了提高。
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