Stepper motor dislocation that is out of step, out of step and the step into lost step. When the stepping motor is working properly, when it receives a control pulse on every move a step angle, namely forward. If the continuous input stepper motor control pulse, the motor will rotate continuously kept accordingly.When the lost step, the number of steps to advance the rotor is less than the number of pulses; when more step, a few steps ahead of its rotor is greater than the number of pulses. Once lost step or the step of the step number that is equal to an integer multiple of the number of run shot. When the throw serious step, the rotor will stay in one position or location around a vibration, the more serious step, drag structure will overshoot. Stepper motors are open-loop system is an important part, is to provide solutions to its stall reason reference：

    1．Rotor acceleration is slower than the rotating magnetic field of the stepping motor

　　N When the force is slower than the speed of the rotor rotating magnetic field of the stepping motor, which is below the commutation rate, the stepping motor will produce stall. This is because of lack of power input of the motor, synchronous torque generated in the stepping motor can not follow the rotational speed of the rotor speed of the stator magnetic field, causing a stall. Due to the dynamic output torque of the stepper motor run continuously with increasing frequency decreases, and thus, all higher than the frequency of the operating frequency will have lost step. This step-described torque stepping motor is insufficient, drag lack of capacity.Solving methods: ① electromagnetic torque stepping motor itself increases. This could be due to increase in the nominal current range drive current; in the high frequency range torque is insufficient, may be appropriate to raise the driving voltage of the driving circuit; instead torque stepper motors. ② stepping motor to overcome the torque decreases. This could be due to lower motor operating frequency in order to increase the output torque of the motor; set longer acceleration time, in order to get enough energy rotor.

    2．The average speed is higher than the average rotor rotational speed of the stator magnetic field

　　The average speed is higher than the average rotor rotational speed of the stator magnetic field, then the excitation of the stator is energized longer, greater than the time required for the rotor step further, the rotor gained too much energy in the step process, so that the stepping motor generating the output torque is increased, so that the step motor. When those stepping motor drive the load, under the action of agencies, more likely to have more step phenomenon, it is because the downward movement of the load, the motor torque required is reduced. Workaround: Reduce the stepping motor drive current to reduce the output torque of the stepper motor.

    3．Stepping motor and the load carried by inertia

　　As the stepper motor and the load carried by its own inertia, so that the motor can immediately start and stop during operation, but appeared lost at the starting step, occurs when the step is stopped. Workaround: a acceleration and deceleration, which start at a low speed, then gradually accelerate to a speed run, and then gradually slow down until it stops. Reasonable, smooth acceleration and deceleration control is to ensure the stepper drive system is reliable, efficient and accurate key operation.

    4．Stepper motor resonance

　　One reason for the loss is caused by resonance step. When the stepping motor is in continuous operation, if the frequency of the pulses is equal to the natural frequency of the stepping motor control, and will have resonance. In a control pulse period, the vibration can not be sufficiently attenuated pulse came next, and thus in the vicinity of the resonance frequency of maximum dynamic error and will lead to a stepping motor stall. Workaround: appropriate to reduce the stepping motor drive current; subdivision driving method; damping methods, including mechanical damping law. The above method can effectively eliminate motor oscillation, avoid out of step phenomenon.