in the PID controller, the proportional part produces the output signal proportional to the deviation in order to eliminate the deviation; the integral part produces the output signal proportional to the integral value of the deviation in order to eliminate the static error of the system; and the differential part produces the deviation. The rate of change of deviation is proportional to the output signal in order to speed up the adjustment rate of the controller, shorten the excessive time and reduce the overshoot. If these three parts fit properly, they can be adjusted quickly, smoothly and accurately