直流电动机双极性可逆PWM系统，其中电流PI调节控制中，根据转向标志DIRECTION来决定输出极限：正转时，输出范围是0-250，反转时是250-5-DC motor reversible bipolar PWM system, current PI regulator control, according to signs DIRECTION decision to limit exports : being transferred, the output range is 0-250, w