调节pwm，通过程序，控制pwm的占空比，可以实现控制电压，或小车的速度。-Regulating pwm, through procedures, control pwm duty cycle control voltage can be achieved, or the speed of the car.

基于STC51单片机的智能小车前进后退的测试c程序-STC51 MCU-based smart car forward and back test c program