说明：  数据采集卡采集拉力值，与预先设定的拉力值进行比较，然后PID运算，控制相应的PWM占空比输出，最终控制电机的速度
(The data acquisition card collects the pull value and compares it with the pre-set pull value. Then the PID arithmetic is used to control the output of the corresponding PWM duty cycle, and finally the speed of the motor is controlled.)