Stepper motor is an open-loop control component which converts electric pulse signal into angular displacement or linear displacement. In the case of no overload, the speed and stop position of the motor only depend on the frequency and number of pulses of the pulse signal, and are not affected by the change of load, that is, a pulse signal is added to the motor, and the motor turns a step angle. The existence of this linear relationship, coupled with the stepper motor only periodic error and no cumulative error, makes its control speed and position very simple. The difference between stepper motor and ordinary DC motor or AC motor in use is that it can not be directly connected to the power supply, but must be used in the control system composed of double ring pulse signal and power drive circuit.