Pid is an important parameter in the control system, which refers to the control mode and the response mode between output and input. As the name implies, proportion means that the output and input are carried out in proportion, and the speed can be adjusted, usually changing the feedback. Integration is the integration of output and input, which is accumulation. When the input changes greatly, the output only changes according to the length of time, which plays a filtering role, also called hysteresis, which is equivalent to connecting a capacitor in parallel at the input end. Differential means that the output is only sensitive to the change of input, especially when the input is sharp, but the input is unchanged, no matter how big it is, the output is zero. Therefore, it is also called lead adjustment, which plays an accelerating role, which is equivalent to connecting a capacitor in series.

By applying force to an object for analogy, proportion is like the magnitude of force, integration is like giving an object a constantly balanced thrust, and differentiation is like hitting an object with a hammer.

PID can be adjusted by hardware or mathematical algorithm. Intelligent devices make most of them use mathematical algorithms without manual adjustment, such as self-adaptation, self-correction and fuzzy algorithms.