双极性pid 单极性就是输出只有整数没有负数，双极性有负数，比如一个温度控制系统，只有加热或者只有制冷，这就是单极性，又有加热也有制冷这就是双极性-Bipolar pid integer not only unipolar output is negative, bipolar have a negative, such as a temperature control system, only heating or only cooling, which is unipolar, there