The respective characteristics of pid control laws

P (proportion: proportional regulation):

1, will inevitably make the system there is a steady-state error (because only the deviation signal is not zero when the regulator has an output, if the deviation signal is zero, the regulator output will also be zero, at this time the loss of the regulatory role, so the proportional regulator is the use of deviation to achieve control).

2, the steady state error decreases as the proportional gain increases, increasing the proportional gain can also speed up the system response, but the larger the proportional gain, the worse the stability of the system, easy to fluctuate up and down.

3, it is suitable for differential tracking of a system where the given value is unchanged, and is not applicable to a system where the given value changes with time.

I (integral: integral regulation):

1, can improve the system without difference, that is, to improve the system's steady state control accuracy.

2, shortcomings: integral regulation of the transition process is relatively slow, the stability of the system deterioration, so generally not used alone, usually with proportional regulation (PI regulation), and PI regulation and pure proportional regulation compared to the stability of the relative deterioration.

3, the shortcomings of two: as long as the deviation is not zero, the regulator will not keep integrating to increase the output, resulting in the regulator output into the depth of saturation, the regulator to lose the role of regulation.

D (differential: differential regulation):

1, can predict the deviation in advance, for preventing the system to be adjusted by the amount of large dynamic deviation is favorable.

2, two-sided: differential time is small, increase the differential time can reduce the deviation, shorten the response time, reduce the degree of oscillation, thus can improve the quality of the system; but when the differential time is large, on the one hand, there is the possibility of amplifying the measurement noise, on the other hand, may also be the response of the system to generate oscillation.

3, the differential regulator alone can not work, it is often combined with proportional regulation (PD regulation) or proportional integral regulation (PID regulation).

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