当执行机构需要的不是控制量的绝对值，而是控制量的增量（例如去驱动步进电动机）时，需要用PID的“增量算法”。-When the executing agency need is not the absolute amount of control, but to control the amount of the increment (for example, to drive stepper motors), the need to use PID' s " incremental algorithm."