we often say that the stepper motor is a special motor control, so it certainly is natural to rotate in a fixed point of view, we often say this is the step angle, is not what the accumulated error, so it is quite good, so this place is very natural to use many, most of them are open loop control.
There is a stepper motor is the pulse signal directly into electrical pulses to the angular displacement of the actuator, we understand that a point is the stepper driver receives the pulse signal, then he will be in accordance with the requirements to drive the stepper motor rotation corresponding.