说明：  人为数字给定直流电机转速，与霍尔测速得到的直流电机转速（反馈量）进行比较，其差值经过PID运算，将得到控制量并产生PWM脉冲，通过驱动电路控制直流电机的转动，构成直流电机闭环调速控制系统。
(For digital dc motor speed, given with hall speed of dc motor speed (feedback) comparison, the difference through the PID arithmetic, will get control and generating PWM pulse, through driving circuit control dc motor rotation, constitute a closed loop dc motor speed control system. )