说明：  此文件是用于智能小车的自动调速，通过PWM波形来改变脉冲占空比，从而该变电机两边的电压，又P=UI的，电机的功率改变，从而达到电机的调速。
(This file is automatically used for the smart s speed through the PWM duty cycle waveform to change the pulse so that the variable voltage motor on both sides, and P = UI of, electrical power to change, so as to achieve the speed control motor.)