As a common electrical actuator, stepper motor is widely applied in automatic control field. Stepper motor needs to be equipped with a special drive power the output of which is controlled by external pulse signal and direction signal. Each pulse signal can make stepper motor rotate a fixed angle, which is called step angle. Total angle and speed of rotation respectively depend on the number and frequency of pulse. The direction of rotation depends on direction signal. For a equipment with a known transmission ratio, the movement distance and speed of its parts can be controlled by controlling the number and frequency of pulse without the requirements for the feedback of distance and speed signals; and direction signal can control moving direction. Therefore, open loop control is a simple and economic electronic control technical scheme.