PID demonstrater and experiment (no lua)

PID controller is a common-used control device in current industry. In this case, the PID controller is used to lock the DC motor at a certain angle.
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Control:
Z: Target angle
F: Power on/off
G/H/J: P/I/D subsystem on/off
X/C/V: P/I/D subsystem coefficient
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P (proportional) means that the control power is proportional and opposed to the difference between current angle and target angle.
I (integral) means the controller will try to fix the error have made.
D (differential) means that system will calculate the current change rate and use it to predict the future change to fix.